Larrfry - Not to flame, but a big part of the reason for the existence of forums such as this one is to discuss the effects and effectiveness of various mods. And this discussion has always been about a mod, even though tire pressure doesn't have to cost you anything (at least not if you use the "break out the bicycle pump & get some exercise" method).

Like any hardware mod, it's an individual choice to "tinker with" the car in this manner to better suit it to him/her. For some of us, this means enjoying more nimble handling and more neutral behavior at higher cornering speeds. Consequently greater weighting is given to such characteristics than Nissan was willing to do at the OE design/manufacturing level for the entire spectrum of their target Maxima population. The only caveat is that we should understand what may be involved when we perform these mods.

I don't presume to make any blanket statement regarding universal and unquestioning acceptance of my personal tire pressure choices for every Maxima loading condition or even for every Maxima owner with the 225/50-17 tire package who only drives with a front-seat passenger. What I will do is take off the blinders re the OE recommendation, do a little research, and act/post accordingly including statement of my basis and/or other reasoning behind my position.

Re loading vs load capacity: I found those tables I mentioned earlier. Given the 225/50-17's rating of 1433 lbs @ 35 psi, at the OE recommended inflation pressure of 32 psi it's good for 1360 lbs (give or take a few lbs), and at 28 psi it's still 1260 lbs. So on the light end of my car I've given away about 200 lbs of tire rated load capacity, but with my specific normal loading condition being in the neighborhood of 400 lbs less at that end I'm well within the safe operating envelope of my tires. Do you still think I've done something stupid?

Remember, it would be a very short-lived bb if everybody simply agreed to "leave it stock because the mfr provided it that way".



Phuong – It's not that a 2 psi difference can't be felt in a Maxima (see my earlier discussion of tire pressure experimentation on the '87); rather it's a situation where 34/32 does not feel or behave much different from 32/32. Sure, that's an acceptable combination, but it isn't as nimble as I prefer. FWIW, 34/32 is close to where I started this time around in tuning pressures (actually it was 35/32). And about those crappy all-season air containers destined for Buicks – don't you mean to say that those tires work at higher slip angles than do performance tires?


Norm

 

smartire?

 

Nope, that's what I meant. Street tires are more forgiving than R compound and high performance tires when driven at or above the limit of cornering forces(stickier tires break away more abruptly.. harder compounds break away more smoothly). I don't have a scanner but I've got a good graph that has cornering forces on the Y axis and slip angle on the X axis, comparing the R compound vs. high perf. vs all season tires that explains what I'm relaying here.

 

(snip). Street tires are more forgiving than R compound and high performance tires when driven at or above the limit of cornering forces(stickier tires break away more abruptly.. harder compounds break away more smoothly).
The "more forgiving" description of the behavior of all-season tires is the flip side of the more linear behavior of the performance oriented rubber as you approach the point of peak cornering force and the associated slip angle. It's that last few % of grip that's more difficult to consistently take full advantage of with a "peaky" curve because it occurs within such a narrow range of slip angle, and because it's relatively easier to go too far beyond the peak grip point. Progressive drop-off of grip that starts well before the peak point results in a more gradual curve that doesn't nose over and fall as rapidly and which will provide more warning and be easier to hold at near-peak cornering force levels. But to produce the same cornering force (and hence lateral acceleration) it seems that more slip angle would be required rather than less.

I'm interested in seeing that graph and compare it with other similar info that I already have (but which isn't handy here in the office). Watch for e-mail.

Norm

 

Fair point Norm:

Certainly to explore beyond the recommendations of Nissan, Inc is a worthy goal. I remain VERY concerned that others look for a simplistic answer to the "ultimate tire pressure answer".

You can review all the tire loading charts you want but they rarely also consider high speeds where things can get considerably worse. Nor is that the only issue or the central issue.

Frankly, I don't consider loading to be the main issue (although it is important). Rather the balance of the car - front to rear, I think is even more important! The balance of the car is greatly affected by small changes in tire pressures. Another post sums it up well, 2 psi changes things very dramatically but ---- if you don't race you may never notice it. What I'd add, beyond what that post said, is you may never notice it until things go very wrong and you can't pull out of a bad situation.

Certainly, lets explore, but we need to be mindful of people looking for simplistic solutions.

We have a great forum!!!!!!!!!!

 

Couldn't agree more!!!!!!!!!! I certainly don't mean to flame anybody and if I had all the answers - I won't be visiting the forum, but Rice has it right --- 2psi really changes things. I've seen it routinely! If we are NOT talking about the "limit" - what's the point of the discussion - any pressures should do?

I think what is NOT appreciated is that you can change your presures and enjoy your everday commute and, then, even post them for others - yet - they are not optimum, and, may, in fact, be dangerous.

 

OK, Larrfry. Maybe we're not so far apart after all.

Re: simplistic answers. I guess I naively assumed that people would read the whole post and not just look for a magic number or two (hey, I'm an engineer, not knowing why is almost the same as not knowing at all, and that's the way I evaluate nearly everything technical that I read). So I'll admit to having difficulty understanding why anybody willing to spend the time posting and presumably re-checking this thread would then develop a case of selective blindness with respect to the alphabetic characters in the responses.

I'm aware of some inflation pressure increases and/or loading decreases at extremely high speeds (>150 mph) and tires above "V" rating. I think that part of meeting the various speed ratings is a test at rated speed under rated load, but I'm not sure of the duration of such testing.

I've included within my basis more than just tire loading charts here, although it's apparent that there's far greater margin at the rear than up front. Slip angles and front/rear balance has been at the heart of my part in this discussion right from the beginning. Believe me, I know what "loose" feels like, and also believe me when I say that I wouldn't even post a "loose" combination of pressures. FWIW, I've run at these pressures for a period of at least 8 months, in good weather and in the wet, around town, and on long highway trips. With cornering up into the mid 0.7g range, conditions permitting. And the occasional hard braking, enough to get into the ABS once or twice. Yes, I have inspected the patterns of tread scuffing a few times after taking some hard turns (similar to the shoe polish trick). I'm getting similar amounts front and rear and not down past the point of the shoulder either. I'm not the only driver; my wife drives it regularly, although not as hard as I do. So you could consider our experience with these pressures an extended test that, so far, has produced satisfactory results. All that's left is to see how it behaves in the snow.

Left to themselves, Nissan's engineers probably would have liked to have pushed the 5th gen Maxima a bit further in the direction of sport sedan a la the previous generation of BMW's M3 (I'm referring to the 240 hp US model here). But that was really unlikely to have happened. Since the Maxima is really a mass-market vehicle at ~100,000 sales/year rather than a truly hard-core enthusiast niche model, Nissan has to idiot-proof its handling so that anybody with a pulse and $25k can drive off the lot in one, i.e. with more understeer than is really necessary.

I suppose I should have considered those who drive for extended periods of time at speeds in excess of 100. My fault, I guess, for underestimating that sort of "enthusiasm". I'd probably run somewhat different pressures too, if that was within my normal driving, but here in NJ things are a bit too congested for that kind of driving and I'm not in quite that much of a hurry any more anyway.

If I were to auto-x or on-track the Max, I'm sure I'd have to experiment some more. And I'm equally sure that I'd end up tuning to within 1 psi at each end. But since this isn't supposed to be a race-only forum . . .

And when (if?) I add a RSB, I fully expect to crank at least a couple more psi back into those rears to cope with the additional rear lateral weight transfer and change in slip angle.

Late-breaking thought, Larrfry: You've got the dedicated facility and a 5th gen Max. When the opportunity arises, just give it a shot and post or e-mail me your take. Meantime I'll measure camber to make sure that the issue isn't getting muddied by that.

Norm

 

My 2000 Maxima is seven days old and I tried to get test time at my facility but it wasn't available. I've since mounted studded Nokian "Hap 1" snow tires so no testing until the spring.

Frankly -- I just don't know how anyone sets up their tires, short of track time. What I can't figure is how anyone can recommend pressures until they push to the limit and a tiny bit beyond. I'm looking for balance (and I think everyone else is) and a few psi do really change things. In everday driving you get VERY VERY crude indications of what's right, but until you really test it ---- I just don't know how anybody has more than a vague clue (at best), about what is right. I guess that is the essence of my posts. I guess that also sums up my belief in not messing with stock pressures despite all the compromises by Nissan, that may have been involved.

I've seen plenty of drivers trying to create oversteer at low speeds, but if they actually succeeded in creating that oversteer at low speeds (that they so desperately desired) -I'm sure they'd scare themselves silly in a fifty MPH turn (taken at the limit) with the same degree of oversteer. One question we need to ask ---- how many posts are just looking at combating low - speed understeer with no appreciation of the effects at higher speeds?

Moving onto tire-loading and Peterson's well reasoned posts. I thought tire loading degraded with speed far below 150mph but, then again, it's not an area I claim expertise. My impression was as speed increased, loading decreased. I certainly would like to learn more, although it is not central to my arguments. From a technical point of view it would be useful if Peterson could analyze it for ALL of us.

Also , I think there MAY be more 100mph+ commuters than any of us may imagine and our pressure recommendations should account for that.

This is a good debate. Thanks for all the thoughtful replys.

 

if anyone in the central PA wants to lend me their Maxima, I'd be more than willing to flog their car around the autocross course (for the greater good of Maxima.org, of course ). Don't worry, I'll be gentle. Worry not for I am experienced

http://www.eatricezone.com/miata/ext/m25.jpg

 

The more I think about this, the more I question that speed does not HAVE A VERY SIGNIFICANT EFFECT on tire loading. I question whether the tables Norm is referring to aren't based on a constant speed and FAIL to analyze the degradation of loading versus speed. Most car enthusiasts are familiar with popular tire speed ratings like "S", "H", and "V", etc. In essence these ratings verify that a particular tire will not fail at the rated speed even under continuous operation, within it's load range. What I question is that as pressures drop, not only does the load carrying ability of the tire decrease but ALSO the maximum safe continuous speed rating of the tire.

Simply put Norm suggests that the tire design (load rating) and tire pressures are the TWO design principles that interact and I believe that tire design (load rating), tire pressure, and the continuous speed the tire is exposed to - represent the THREE principles that interact.

In the end, this is a technical debate and assumming the above principles are correctly applied - that is the STARTING POINT for establishing safe parimeters in which balancing tire pressures can be done, based on track experiences.

 

I can buy into that. Maybe we can take it one step further at this point.

Perhaps the most extreme tire failure mode is the end result of the development of a standing wave in the tread. I've got a technical tire book (~800 pages) with some pictures of this; take my word for it, they're scary and you don't want it happening underneath you.

Tire deflection as a function of load and inflation pressure is important here, since that's the initial basis for the tire's deformed shape. Whatever natural frequencies and damping that exist in the tire's tread (and probably there's some effect due coupling of sidewall frequencies) either amplify or isolate, depending on mostly on speed vs stiffness. Hence the generally stiffer construction of higher speed-rated tires.

I also agree completely with the idea that you can't come up with a valid set of pressures tuned for minimizing understeer by just moseying around the 25 mph neighborhood streets or taking a short interstate highway drive. You need to be able to have hard cornering of sufficient time duration for the effects to show up. You need to see what happens if you back out of the throttle or brake. For any change in the cornering maneuver that you can think of that might happen, you have to satisfy yourself that you aren't going to find yourself faced with a nasty surprise that might not have been there previously. Yes, track experience is probably the safest, particularly with regard to things like license suspensions and bigger insurance premiums, but it's the experience at cornering levels above 0.7g or so that's necessary. Learning to drive smoothly, not yet mentioned in this thread, is also important. Cutting this short; I've got an appointment to get a windshield replaced (that somebody else's insurance company is paying for).

Norm

 

Months ago, this thread started and then ended. As mentioned in my previous posts, I'd attempt to document the effects of tire pressures on the handling characteristics of the 5th generation Maxima when I gained access to a facility suitable for testing. Here are my inconclusive results. (Testing continues).

My 2000 Maxima, shod with Dunlops (very worn at the front), was tested with various tire pressures. The manufacturer's recommended tire pressures were 29 (front) / 29 (rear). I tested various combinations starting at 37/37 AND LOWER. The tests I used were a very abrupt lane change manuever at about 45 mph and also driving at the limit in a constant radius circle at a lower speed.

What first became apparent was that "cold tire pressures" were not constant. Depending on the oudoor temperature on a given day I saw cold pressures vary by a 1 to 1 1/2 pounds per tire. This was apparent in ONLY a week of testing!!!!!!!!!!!!!!!! I checked cold pressures after more than 12 hours of NOT driving yet I observed these differences! . SO WE START WITH A SOMEWHAT VARIABLE BASELINE FOR TESTING!

NEXT - I looked at pressure increases due to normal/ non-aggressive driving driving. Over the course of a 2 hour commute pressures increased by 3 to 4 psi. More at the front, less at the rear. I had the same results after only an hour of very non-aggressive driving.



Results with testing: Using both a very abrupt lane change manuver and a constant radius turn (a circle) I felt the following with the Dunlops on my 2000 Maxima. To repeat -recommended manufacturer's tire pressures were 29/29 (front to rear).

High rear pressures (37psi) decreased handling. I worked my way down in pressures and I now believe somewhere between the 29 psi (recommonded by the manufacturer for my Maxima 2000) and possibly as high as 31 psi) make sense for rear pressures with the Dunlops. The rears are lightly loaded in the Maxima and in fact, with the lane change manuever, the Maxima was oversteering and fairly dangerous. In short -- not well balanced. Actually I now view 30 psi as a maximum!!!!!!!!

With front pressures, I played with everything from 37psi cold down to 29psi cold (manufacturer's recommendations). Here it was harder to tell. The Maxima, like all FWD, wants to understeer. It improved with higher pressures to a point but then seemed to worsen. Somewhere between 33 -35 psi cold seemed best BUT IT"S HARD TO TELL.

AS I drove the car in testing, tire temperatures increased. In addition, No one's memory is perfect so it is hard to compare results in an absolute manner. As I abused the front tires it was hard to determine whether tire pressure or tire temperature (due to abuse) changed the handling for better or worse.
Over time and considerable absuse 39 psi HOT seemed to produce Worse results but that was HOT with my Dunlops!

The only firm conclusions I can make are stick to stock pressures (or marginally higher) and secondly BEWARE: the Maxima is unstable (meaning marginally handling) in turns because the rear unloaded tire lifts off the ground producing very unpleasant effects.

The One THing that was evident in my limited testing is that The 2000 Maxima was unstable and unpredictable when entering a turn. Meaning this: In the lane change manuever --- the Maxima always broke loose into aggressive oversteer when negotiating that exercise- the result of the unloaded rear tire actually lifting off the pavement which produced a period of instability, then the rear tire finally touched the ground again which finally provided a period of stability, i.e, - a reasonably predictable car, once that rear tire touched down, but unpredictable prior to that. In the constant radius circle you again have a period of instability, (rear tire off the ground) and then a contstant but predictable state of understeer when the rear tire finally touches down again. A difficult car to drive at the limit!!! In short, a poorly balanced car!!!!!!!!!!


Finally, for your information (I will bring this up in another forum when my tests are complete) but the Maxima's power steeering "locks up" in aggressive steering as in the "lane change manuever" I performed. The steering wheel almost ripped out of my hand during these testing phases ON EVERY RUN!!! If my dealer can't fix it - I will be bring it up to the federal level (NTSB). It is a serious flaw but probably never noticed in a crash investigation. Wnat I need to know is this a defect limited to my car or is it more generic? A few months from now I should have a better idea.



Larrfry

 

i cant believe this thread is still going on..i started it a LONG time ago....lol

albert

 

It is worth pursueing!!!!!!!!!!!!!!!


Larrfry

 

(snip)
What first became apparent was that "cold tire pressures" were not constant. Depending on the oudoor temperature on a given day I saw cold pressures vary by a 1 to 1 1/2 pounds per tire. This was apparent in a week of testing!!!!!!!!!!!!!!!! I checked cold pressures after more than 12 hours of NOT driving yet I observed these differences! . SO WE START WITH A SOMEWHAT VARIABLE BASELINE FOR TESTING!

Not at all unusual if ambient temperatures vary widely. 1 psi per 10 degF keeps coming to mind.


NEXT - I looked at pressure increases due to normal/ non-aggressive driving driving. Over the course of a 2 hour commute pressures increased by 3 to 4 psi. More at the front, less at the rear. I had the same results after only an hour of very non-aggressive driving.

Your results are approximately the same as mine here. Even 15 minutes of easy driving from dead cold pressure will give you practically the same increase.


High rear pressures (37psi) decreased handling. I worked my way down in pressures and I now believe somewhere between the 29 psi (recommonded by the manufacturer for my Maxima 2000) and possibly as high as 31 psi) make sense for rear pressures with the Dunlops. The rears are lightly loaded in the Maxima and in fact, with the lane change manuever, the Maxima was oversteering and fairly dangerous. In short -- not well balanced. Actually I now view 30 psi as a maximum!!!!!!!!

With front pressures, I played with everything from 37psi cold down to 29psi cold (manufacturer's recommendations). Here it was harder to tell. The Maxima, like all FWD, wants to understeer. It improved with higher pressures to a point but then seemed to worsen. Somewhere between 33 -35 psi cold seemed best BUT IT"S HARD TO TELL.

I guess that I can take that as at least lukewarm support for the pressures that I posted a couple of pages ago (and continue to use).


As I drove the car in testing, tire temperatures increased. In addition, No one's memory is perfect so it is hard to compare results. As I abused the front tires it was hard to determine whether tire pressure or tire temperature (due to abuse) changed the handling for better or worse.
Over time and considerable absuse 39 psi HOT seemed to produce Worse results but that was HOT with Dunlops!

It takes only a few seconds of really hard running to send tire temps soaring. Since this thread was left idle a few months ago I've started auto-Xing the Malibu. Gaining 3 psi in each tire on the first run - about 40 to 50 seconds duration - is easily possible.

FWIW, that's why hot inflation pressure is more useful for the auto-X venue. That's in contrast to the better basis cold pressure gives you for normal street driving (or whatever slightly higher pressure you might have following less than 1 mile of easy driving).

Regarding the lifting of a rear tire by a FWD car in a turn, I've seen plenty of that at the auto-Xes. What's out of balance is rear roll center height (too high) and rear roll rate vs rear weight. Too much of the former, not enough of the latter, at least during extreme cornering.

Smoothness counts. You don't want to generate so much pitch and roll momentum that the car "overshoots" its steady-state attitude and then gets pushed back by the overcompressed springs and overtorqued a-r bars. Shock condition matters, but can only do so much. These see-saw motions (as seen in side view for pitch and in rear view for roll) will show up as an "unsettled" feel, because what is happening at the contact patches is being substantially affected by things not under the driver's direct control.

Getting your braking done in a straight line helps by not pitching one rear corner up in the air and running you out of suspension travel. So does getting slightly back on the gas once the car has started to turn in, as this generates a little front to rear weight transfer, though it's important to note that this technique may not always be available to you on the street.


(snip)
Finally, for your information (I will bring this up in another forum) but the Maxima's power steeering "locks up" in aggressive steering as in the "lane change manuever" I performed in testing tire pressures. The steering wheel almost ripped out of my hand during these testing phases ON EVERY RUN!!! If my dealer can't fix it - I will be bring it up to the federal level (NTSB). It is a serious flaw that I suspect will be only recognized too late.

It sounds like the PS pump wasn't keeping up with your steering demands. A band-aid for your testing might be to keep it in a lower gear so the pump is at least spinning faster. I haven't heard, overheard, or seen evidence of this complaint from an auto-Xer in the events I've recently attended, which have been almost exclusively 2nd gear affairs.

Norm

 

It would be worth knowing what Nissan recommends for tire pressures for all 5th generations.


According to my 2000 manual --- 29psi BOTH front and back is what is recommended FOR ALL TIRE SIZE/WHEEL COMBINATIONS.

If I have figured what NORM said correctly - it seems for 2001, Nissan recommends 31 psi front and back.

For 2002 - who knows. Anyone care to enlighten us?

 

. . . If I have figured what NORM said correctly - it seems for 2001, Nissan recommends 31 psi front and back.

For 2002 - who knows. Anyone care to enlighten us?

Close. 32/32, for a 20th Anniversary Edition with 225/50-17's.

Norm

 

I wonder if that is an effect of the Max's "speed variable assist" power steering? IIRC, the assist decreases at higher highway speeds. Maybe there's an effect where the assist suddenly decreases to zero, making it feel like it locked up but actually it's just very hard to turn the wheel.

BuddyWh

 

It could well be a result of the variable assist although frankly I'm not sure whether the 2000 Maxima has it or not. My test speeds were at about 45mph give or take 5mph - not highway speeds.

Regarding whether the steering "locked up" or was just "very hard to turn" - in practical terms - the effect was the same - the wheel almost ripped out of my hands and my ability to turn the wheel as rapidly as I wished -- was limited - albeit momentarily.

Larrfry

 

Had my tires rotated yesterday. The guy doing the work is an avid street racer of musclecars and since we were talking about hard driving he recommended 35 psi. So, driving around with 35 psi yesterday produced plenty of squeals. I didn't lose control but turns that I can take at ~65 at 38psi with the tires just starting to squeal produced squeals at 55mph with the tires at 35psi. I consider 35psi to be the low point and will keep mine set between that and 38psi.
I've tried 40psi and it tends to get a bit bouncy. Max psi is 45 on the AE rims.

 

Norm: Does Nissan recommend other tire pressures for other tire/wheel combinations for 2001?

 

Mike:


One point I've been trying to make is that these generic suggestions about tire pressures are SIMPLY STUPID!!!

The guy at the tire store may be experienced in "street racing" and may know a little bit more than the man on the street BUT he is still an infant in the world of cars. Whether you follow Nascar, F1, or simply SCCA racing - a few psi changes how a car handles and getting the "balance" right between front and back is a struggle for any car and racer!!!!

No ONE with any meaningful experience would EVER consider recommending tire pressures for a car without having driven THAT SPECIFIC CAR AT THE LIMIT!!!!!!!!!!

Your testing of this street racing "expert's" recommendations produced negative results. You mention squealing on turns. What you need to identify is whether the front or back of the car is producing this result! Are the fronts too low? Are the fronts too high? Are the rears too low? Are the rears too high? All would produce squealing!!!!!!!!!!!!!!!!!!!!!!!

Your current pressures seem better and may be from what Mr. Street Expert recommended. I don't know. But better than what? Better than a guy who street races and offers easy and dumb suggestions. Your pressures may STILL BE FAR FROM OPTIMUM.

I said it months ago and I really stand by it - without a test facility or track time I DON'T KNOW HOW ANYBODY SETS UP TIRE PRESSURES.

STICK WITH MANUFACTURER'S RECOMMENDATIONS or possibly a few (1 to 3) psi higher. I've never driven a street car that was off by more than that. I will add that sometimes the manufacturer, in the owners manual, will note an alternative tire pressure for speeds above (eg) 85 mph. I've always used that recommendation, if present.

Final note: I would NOT be testing on a public road at 55 - 65 mph. What if things go wrong? Can't you find an empty lot for lower speed tests?

What is missing in your tests/suggestions is an understanding of balance. The KEY component to car handling ---- bar none!!!!!!!. If the pressures you recommend produce a grossly under or over-steering car, you have created one UNSAFE vehicle.


Larrfry

 

Hi Larrfry --

I'd like to come off topic for just a moment. As you can see from my sig, I've (erroneously) earned the title of Master of All Things Rubber. That's because of the hard stance I've taken against running tires that are out-of-spec for the rims on which they're mounted. Specifically, a running debate exists on the org about whether or not it's safe to mount 235/45R17 and 245/45R17 tires on the stock 5th Gen OEM rims. The OEM rims are 7.0" wide. However, the Tire & Rim Association as well as every manufacturer of tires in those sizes states that 7.5" is the minimum acceptable rim width. (The T&RA contour tables are posted on page 5 of the FAQs if you want to take a look at them.)

Do you have a position with respect to this issue? In other words, do you believe it's safe to exceed manufacturer specifications with respect to acceptable rim/tire combinations? If so, would be good enough to share your view with us?

Thanks.

BTW, just between us girls, there's nothing I love better than a Newbie who knows their ****!

 

Unfortunately I don't know anybody who has one with the 16" wheel/tire package (or have a service manual). I think the owner's manual simply refers you to the sticker under the console lid.

Mike - As regards the advice of the musclecar driver I'll suggest that his area of expertise is mostly bigger tires and lower pressures than we're dealing with here. And probably with somewhat milder cornering in mind, particularly if he's of the "front skinnies and rear fatties" straight line camp.

Norm

 

I must say your suggestion makes good sense: it is generaly safer to stay close to the vehicle manufacturer's recommendations unless you know the desired handling effect you're after and how to adjust for it.

I added "generally" because there is one situation where one should always increase pressure well above the vehicle manufacturer's recommended: when the vehicle is heavily loaded. A vehicle's GVWR is based, in part on the tire's load rating and the tire's load rating is given at the tire's max pressure on the sidewall, well over the data plate pressure recommendation. If your vehicle is heavily loaded (four adults w/luggage will fully load a Max, probably overload it), always increase tire pressure (especially rear) to the max pressure to be safe at highway speeds.

It's not a handling thing, just a safety thing. But kinda important to always keep in mind.

BuddyWh

 

I'm not positive but I believe a manufacturer does envision maximum loading in their tire pressure recommendations. However, Nissan could easily underestimate or UNDERSTATE the "maximum" load for legal reasons.

In my view - a post worth reading

 

Using a track to test tires isn't going to prove what you should set them at on the road. I don't drive on a track and the road surfaces I drive on change constantly. That's why you have to do on street testing to find out what pressure works best. I'm not talking about street racing a Maxima - it wasn't designed for it. I'm talking about finding a pressure that sets the car up properly for long distance driving on various roads at the posted speed limits. I've found that 38psi works best. The temperature never gets near the maximum pressure of 45psi and the ride is not harsh. Nor does the car squeal like a pig when going around curves or on-ramps at the posted speed limit.
The manufacturer sets the pressure low so people will be happy with the soft ride of their car. An old shop trick is to simply lower the pressure of a customers tires if they complain of noise, ride, or balance problems. The negative side affect of setting them low can cause problems as seen in the Ford Explorer. I'm also wondering what a low pressure would do to gas mileage and longevity of the tires. I'm interested in hearing from other people who run at other pressures. If you are getting better than 23mpg in rush hour traffic (Austin's version) and it looks like your tires are going to last longer than 39,000 miles then post your setup.
I'm not advocating that everyone inflate their tires the same way I do. You don't drive on the same streets I do and might not even have the same brand of tires.

 

Mike,

While a test track may not tell you specifically what tire pressures to run on the street it at least gives you a safe place to find out what pressures not to use. And FWIW, I'm uneasy with the idea of 38 psi in the rear from the center-tread wear and oversteer points of view. Especially with mid-corner bumps causing the grip at both rear wheels to be compromised, courtesy of that beam axle.

As far as tire life vs inflation pressure, at some point you get into the land of diminishing returns and eventually the curve noses over and drops, giving you shorter life with that last psi.

Actually, I have less issue with you telling me 38 psi and knowing that you specifically have Maxima experience than I do with the musclecar guy's 35 which on the face of things does not suggest either FWD or cornering experience.

Norm

 

Not necessarily, and very doubtful. I have Avid V4's on my max and the Max's GVWR is well over the tire's load rating at the data plate pressure... the tire's max load rating is only achieved at about 44psi.

IIRC, as load is increased on a tire the pressure in the tire does not increase comensurately. What happens is the carcass distorts to allow the contact patch to "fatten" and spread the load over a wider area. It is that carcass distortion that leads to overheating and tire failure at highway speed. You have to increase pressure, up to the max pressure on the sidewall, to return the carcass to it's correct shape.

I think it would be very safe to say that if the tire can't be returned to it's normal shape, without exceeding the max pressure, then the tire is overloaded!

BuddyWh

 

Sorry, I disagree. Road surfaces can change but the balance of the car does NOT, no matter how much "grip" the surface may/or may not have - the balance of the car remains the same. Track time allows you to test at the limit --- safely. How can that be done on the street???

What you have failed to understand is that any driver's goal is to achieve a car that is balanced - which means neither the front tires or the back tires are overworked and prone to skidding unduly. I don't know how you can experiment with tire pressures except in a test area (assumming you have the expertise). Fooling around on public roads is dangerous, there is little room for errors, and simply unwise. I repeat an earlier point - how anyone deviates from manufacturer's tire pressures without test time in an appropriate facility is a mystery to me.

Certainly you can increase pressures to the point that wear is significantly decreased. The car may be unsafe but you will have longer tire wear. Doesn't seem a wise trade-off to me.

I went to great lengths, in my personal testing, to document and minimize the changes produced by repeated testing. In racing or even autocross, tire temperatures and pressures escalate rapidly - thus results differ quite a bit from everyday driving. Hence my very inconclusive results. I can't tell you the number of times I did a "first run" and then recorded my results in my testing log just because I was looking for a good balance for the Maxima "on the street"!

What bothers me is you had no trouble posting tire pressures in this forum based FIRST - on some guy you met in a garage who was a "street racer of muscle cars" --- that was your expert -- and then later complained his tire pressure suggestions didn't work out - AFTER YOU HAD POSTED THEM!!!! Now, because Mr. Street racer's suggestions didn't work out we should now believe you know what you are talking about because your haphazard recommendations seem better? This is unbelieveable.

Norm has it right, as do others - I believe your rears are way too high based on MY car and MY Dunlops. I also believe you have little basis to suggest your views. I wish you had answered me when I asked you if your fronts or rears were squealing but I'm beginning to believe you don't have a clue.

It really bothers me, that opinions like yours, are so readilly offered to an unsuspecting public.

 

Could not agree more!!!!!!!!!!!!!

 

I read Mike's posting as adjusting pressures to his liking... and I read your posts as finding optimal pressures for racing. I don't think either of you are wrong, just talking about different things.

You state the goal of any driver is balanced handling, but you fail to note the goal of the manufacturer is something else, i.e., safety. Strong understeer bias is generaly considered much safer for untrained drivers. High-performance racers, as I recall, prefer oversteer. Neither is balanced, i.e., neither understeer nor oversteer.

I would prefer your method: but we can't all get track time to try out pressure adjustments at the limits. The manufacturer's recommendations were (probably) conservatively set to facilitate understeer and yet allow maximum fuel economy. But then... we all change tires, maybe +1 the size, and that changes everything from what the mfr. anticipated in his recommendations.

How do you suggest we go about finding the correct new pressure, if not experiment a little, even on "public streets". Testing it out on the street here doesn't mean trying for maximum time around a closed course laid out in a school zone or a crowded freeway, I do mean an isolated street with no traffic performing sane "street" maneauvers and guaging the feel for myself.

BuddyWh

 

I have the ability to watch the tire pressure rise while driving on the C5 as it has pressure monitors and in the cooler weather it is + 2>3 lbs and in the summer (WI) it is 3>5.
Too little is bad as they squirm and too much is bad as they reduce patch.
On the Max mine was deliverd with 45 lbs all around and I did not realize it for a month but it really torque steered. Normal presurure no torque steer!

 

A good reply. However I was NOT trying to find pressures for racing!!
No way - I'll never race the Maxima nor would want to. If you read my post I used a lane change maneuver at about 45mph - typical of a kid running out in front of a car (and the driver trying to avoid him) and a Low Speed constant radius circle to give me a feel for the balance of the car. Hardly racing stuff. I may have been unclear but I really worried about the effects of repeated testing which would elevate tire pressures (and temperatures) and produce results not appropriate for the street but more typical of racing! My personal goals were to produce a vehicle as safe as I could for everyday driving!!!!!!!!!!!!!!!!!!!!.

Regarding manufacturer's tire pressure recommendations - well I think it is Mostly an Urban Legend that Manufacturer's tire pressures are way off. Meaning this - manufacturer's probably (probably - being the key word) do balance handling, comfort, full load considerations and a desire for understeer in their recommendations BUT - no proof exists to prove that point, the logic however is appealing. Secondly, my limited experience says the manufacturer's are not far off. In an admittiedly small number of cars I've owned - the tire pressures recommended by the manufacturer are close to being right for me.


The final question being asked is how do I determine what is right for Me? The answer is as simple as it gets - unless you have the expertise to analyze car handling and access to a facility - stick to the recommended pressures.

 

I wasn't looking for a set of pressures for racing use, only looking for a little more nimble feel and a little less understeer, with due consideration for the way I drive (pretty hard on occasion, conditions permitting) and for the load that my car normally carries. Finding pressures for a road course would take a different approach, using extensive tire temperature measurements. Auto-X you can set using chalk or by careful observation of where the scuffing ends.

But I can't imagine being happy with 38 psi in the rear tires on a beam axle. Especially when under 40% of the weight is normally carried there. I'm assuming some sanity here, to the extent that the hardest driving is not done while heavily loaded. I don't seem to have any problem with my tires squealing using f/r pressures below and well below 38 respectively, so Mike's problem at 35 psi may be a function of cranking the steering wheel over at a rate more consistent with auto-X driving than street driving. I wouldn't run my street pressures on course either.

You state the goal of any driver is balanced handling, but you fail to note the goal of the manufacturer is something else, i.e., safety. Strong understeer bias is generaly considered much safer for untrained drivers. High-performance racers, as I recall, prefer oversteer. Neither is balanced, i.e., neither understeer nor oversteer.

Perhaps it would be better to think of it as the search for an individually preferred handling balance. It's a range within the handling spectrum rather than a discrete point. If you were to somehow precisely obtain neutral steer under some set of driving conditions you could push that into either understeer or oversteer by use of a different amount of brake or accelerator. No argument here about the OE tuning criteria, they're pretty much stuck with considering the entire spectrum of driving ability. I only have to be mindful of a mere handful of people, just two on any regular basis and half a dozen at most, of which I do know something regarding driving experience and ability.

I would prefer your method: but we can't all get track time to try out pressure adjustments at the limits. The manufacturer's recommendations were (probably) conservatively set to facilitate understeer and yet allow maximum fuel economy. But then... we all change tires, maybe +1 the size, and that changes everything from what the mfr. anticipated in his recommendations.

Some track or auto-X experience helps in developing your own pressures, and is probably necessary if only to give you a peek at what might happen. So does an understanding of the physics of it all. Behavior as the tires approach their limit cannot be linearly extrapolated from moderate driving. Even driving that would be considered quite hard (by normal driving standards, anyway) may not reveal everything. What you have never experienced and can't see (or feel) from driving at relatively easy levels you just plain won't see coming at you until you find yourself driving harder and it's suddenly staring you in the face.

I'd guess that "moderate" is representative of the upper limit of linear tire response, somewhere around 0.4g if you want a ballpark number, and is probably about as hard as the average driver ever intentionally pushes it. Various degrees of "hard driving" can be associated with the transitional portion of the tire's response, where the response is no longer linear but before appreciable sliding occurs.

FWIW, I have wondered from time to time if any of the people who have plus-sized their wheels/tires paid any attention to this.

Norm

 

I think something is very wrong in your analysis. Otherwise Nissian is making a massive engineering error and also creating a huge opportunity for lawsuits. That's NOT the case, I believe, here's why.

Remember - first the GVWR (for non-techies that means the weight of the Maxima plus the weight of 4/5 average passengers and their luggage) is the maximum design specification. In my 2000 it is 4333 pounds. That's the absolute total weight for the vehicle with passengers and luggage. HOWEVER, that weight is shared over FOUR tires - not one!!!!!!!!!!! I think you made that mistake in your analysis - correct me if I am wrong. I don't want to get overly technical but on the label you are referring to it also lists maximum front end weight because this is a front wheel drive car with most of the mechanicals up front and therefore most of the weight. Again, even if you look at maximum loading at the front - this is divided by two. I think you'll find none of the tires are close to being overloaded at stock presures but I don't have the charts for your tires to confirm that. But I bet there is excess reserve in abundance!!!!!!.

Finally, maximum tire pressure as embossed on the sidewall of the tire refers to HOT, ABSOLUTE MAXIMUM PRESSURE - not cold. I'd refer you to Road and Track, June 2002, pages 155 to 157


Larrfry

 

I don't I like the look of my GLE wheels better that the 17s beside mine came with better tires. .....but cornering wise yeah 17s kick ****. I have 16s and probably no one cares what perssure I'm running, but here goes. I run 34psi all round.

 

You know, that's the most important observation made so far, IMO, and cannot be emphasized enough. And it is true of any vehicle on the road.

I've read there are very few drivers on the road who know how their vehicles behave at the limits and, as you note above, that behaviour probably has little to do with the way it behaves in the regimes we mostly drive.

This leads me to draw a controversial conclusion: what difference does it make how it behaves? so what if a tire pressure change has altered it "for the worse"? I can't deal with it (at the limits) even if it were at it's best... it's a given I would probably loose it as I am just not trained to deal with it. What I should do instead is optimize within the areas I do drive, and focus on staying out of the regimes in which I don't drive.

By the way, oil change guy left tire pressure at about 40psi once... I hated it... too "lively" and the car followed every line in the road. Very "uncertain" handling, felt like the rear wanted to come around in even moderate turns. Maybe that wasn't an indication how it would handle at the limits, though... maybe the car would be very predictable and break away only after giving me lots of (such) notice. In a sense that would be good from a safety perspective even if cornering speed was lower. I didn't care to explore the "limits" though, and it made me nervous enough I dropped it back to the 31-33 range I like as soon as I could.

By the way, I found a very interesting article at:

http://www.turnfast.com/tech_handlin...pressure.lasso

Which talks at length on this subject. Pretty interesting, and has a section devoted to front wheel drive autos in particular.

But then, I read another article that actually advocates leaving pressures at around 35-38 PSI (if normal is 31-33). Why? it's a safety thing again: so many people neglect checking pressure for so long, the idea is to delay when the pressure drops to into the extreme hazardous range of the teens that much longer. Go figure!

BuddyWh

 

You are right --- no one cares. But they(your rims) are a thing of rare beauty and I'm sure your 17" (bigger is better - right?) are Formula One in handling. Thanks for informing us. I'm sure they kick "****", whatever that means, and I'll change my pressures immediately!

Another intelligent post from the members of Maxima.org. God help us

 

An article well worth reading --- sorry I ignored it initially!!!!!!!!!