I'd like some personal experiences here.

I wonder which of the following factors are most important to members when they upgrade their wheels & tires: looks, dry handling, wet handling, road noise, rolling resistance, speed rating, temperature rating, unsprung weight, or tread life.

Are gas mileage and acceleration a consideration?

I realize that gas mileage and acceleration are, in part, a function of these other factors, but I would really like to know how much gas mileage and acceleration times are affected as a direct result of a size change, such as going from stock wheels & tires (15" or 16") to 17" or 18" (or higher).

I know that going up to larger wheels will reduce your low-end acceleration, but what about high-end acceleration and MPG?

Thanks.

It all depends on what size rim you have and offset what kind of tire. some wheels maybe heavier (Chrome) but then you can get light weight wheels which will cut weight on your car which would somewhat improve your gas miledge. the bigger the rim the heavier it will be and you have to worry about rubbing to.

i don't really care for looks as much as i do for MPG and handling. i got the steelies on mine and i can careless as long as they're light (opposed to chrome) and as long as i can drive in the rain without worrying too much about skidding and hydroplaning.

what kind of tires are you looking at.

when i get some money after my system, i forgot the name but my a lot of my friends have it, they say the handling on it is ridiculous. i think its eagle f1's?

i would get 17s... some 17s look like 18s anyway... better performance than looks

wheels dont give your perforamnce tires do. if your talking about light wheels then yes that cuts weight like i said before. BF Goodrich is good so is Toyo or Yokohoma. those are my opinions in good tires some people may disagree.

Going up in rim size will slow your acceleration. You're moving weight toward the outside of the wheel, and the total wheel weight usually increases also, so both of those factors slow down your punch off the line. Pay sharp attention to wheel weight - similar looking wheel designs of the same size may be as much as 30% different in weight. That's huge.

You can have quiet tires, but they won't do too well in the rain or snow. You can have great rain/dry tires (summer tires) but they will be treacherous in snow or ice. Decent all-season tires will be pretty loud.

The more grip you want (performance) the shorter the set will probably last. Longer lasting tires are cheaper and offer less grip all around.

Wider tires will give more grip on the dry, less grip in rain and snow, more steering feedback and tramlining, be more sensitive to camber setting, cost more and weigh more.

Gas mileage should be almost completely unaffected, assuming you keep your total wheel diameter the same. Be careful with wheel diameter - run the calculations to make sure it doesn't change more than a percent or two.

Low profile tires will ride rougher, tramline more, and absorb bumps less than a stock sized tire. The low profile tire does not provide more grip.

The whole low profile/larger wheel phenomenon was born of the idea that for track use, the typical street car needs bigger brakes. The larger brakes required a larger wheel and shorter tire. The extra weight was the tradeoff made to avoid fading the brakes. Somehow that became associated with a 'tuned' car, and now everyone buys the wheels that way because it looks more aggressive than stock sized wheels.

Dave

dgeesaman's is a great summary. Here is a set of calculated sizes for 4G.

Width Aspect ratio Wheel dia Tire dia
mm percent inch mm
205 65 15 647.5 Standard

225 60 15 651 1%
245 55 15 650.5 0%
265 50 15 646 0%
215 55 16 642.9 -1%
225 55 16 653.9 1%
245 50 16 651.4 1%
195 55 17 646.3 0%
215 50 17 646.8 0%
235 45 17 643.3 -1%

These numbers have not been checked for fit. The last number in percent is the speedo error for each size. Probably anything more than 20mm wider than standard will cause rubbing. I have a set of 16 inch wheels from a 5G I35 that I will try next.

If I ever do go with aftermarket rims they will not be any bigger than 17", at least 8" wide, and no more that 17lbs per rim. Tires, well I'll keep putting winter tires on the stockers while performance tires go on the aftermarket rims. Dry traction and performance will be mos important for those...

Wheel weight is important, but people don't realize that tire weight is actually MORE important. The tire is pretty much entirely further away from the wheel rotating axis than the wheel is, and affects the moment of inertia pound-for-pound much more. Of course, there are many other things to take into account when purchasing tires.

I'm planning on going from 16s to wider 17s this summer (not sure if it'll happen or not) and will decrease my wheel/tire weight by about 5lbs per corner.

Also keep in mind that lower offset wheels will increase your scrub radius. This means that your tie rods will be doing more work, the steering wheel will feel heavier in general and your wheel bearings will be worn out slightly faster.

Your current 16s must be pig-heavy.

I'm guessing your current 16's are at least 19+ lbs..

Good info...I was thinking about upping my tire/rim size too (from 15" to 17 or 18")

Don't low profile tires provide better cornering, due to less sidewall flex?

I replaced my Michelin Energy 16's with Kumho Ecsta SPT's and the difference in both wet and dry grip is phenomenal, but they're downright scary in the snow. Might as well put skids on the car.

I thought about "upgrading" to 17's, but after reading about the wheel weight issue, I figured the difference wasn't really worth it for heavier rims and more expensive tires.

Here is the calculated result for 18 inch rims. Bear in mind the torque robbing issue dgeesaman mentioned above.

Width Aspect ratio Wheel dia Tire dia
mm percent inch mm
205 65 15 647.5 Standard

195 50 18 652.2 1%
205 45 18 641.7 -1%

Last number in percent is the speedo error. 1% at 50MPH is 0.5 mile faster or slower.

About 20-21lbs apiece. I wouldn't call that pig-heavy by any means, especially for OEM wheels.

You don't see these low profile tires on F1 and Indy cars?

The Tonga Royal Prince and Princess died in a roll over this year on US101 near Palo Alto, CA. The car got side swiped and the driver over corrected. The rim dug into the pavement and caused a roll over.

If you want to drive aggressively and still be safe, leave plenty of side wall on the rim.

You see low profile tires on touring cars, rally cars in tarmac trim, and pretty much every other form of road racing. What's your point?

I agree that leaving sidewall is better for performance for a few different reasons, but your logic is flawed. Strange though, I used to live in Palo Alto, I don't remember hearing that news.

Manufacturers put these tires on to sell cars. This is what consumers demand today. But taken to the extreme like 20 inch has no benefit.

I have done the 1+, 2+ for many cars as seen in my tire size calculator. But taken to the extreme like 20 inch has no benefit. As it is, I just replaced a set of 17 inch and they cost way too much for a wear item. God forbid when I have to replace the 18 inch tires.

It was a 20 year old girl in the other car and she was racing when she hit the Royals. This girl is in hot water right now.

No.

If you focus purely on dry pavement grip, the game of gaining traction comes from three things:
- bigger contact patch on the road (wider tires)
- more sticky rubber
- better balance of load across all four corners

It's the last one where low profile tires underperform in many cases. When going through a corner the weight shifts hard onto two of the wheels. The job of the suspension is to keep that balanced across all four corners as best as possible, and when the tire offers no compliance it becomes more difficult.

55+ profile tires inflated to the proper pressure have no problem grabbing and throwing the car around a corner if set up properly. Sure, the sidewalls deflect some, but it still holds up the car just fine. Take NASCAR wheels for example, and remember that they run on fairly smooth and bump-free pavement. Simply put, for racing and performance, having more flex in the tire and less flex in the suspension pays some real benefits.

The real problem with low profile tires on the street is that they are extremely sensitive to tire pressure. I will bet a dollar that the Tonga royalty crash was related in some way to an underinflated tire. You see these super thin tires on expensive touring cars for appearance. In fact they always put one of those fancy pressure monitoring systems in there with those wheels because it's a lot more work to keep on top of the tire pressure. (As if some rich lawyer is going to check his tire pressure monthly - hah!). If you let the pressure get 5psi low then you're already on the verge of rolling the bead, bending the rim, or just plain losing traction.

Dave

what is tramline?

Yes, my wife shredded a 17 inch likely due to under inflation. Luckily it was a run flat tire and only 2 rubber rings remain attached to the rim. The 18 inch has pressure sensors set at 28 psi. Now I have those ugly looking indicator caps that show a green band above 28 psi.

Wider tires DO NOT increase contact patch, it changes the SHAPE of it.

The whole low-profile phenomenon is not related to performance at all, it's tuner-crowd driven. There is an article floating around (Motor Trend or R&T, cant' recall) that quoted BMW engineers lamenting the demise of higher profile/lighter rims. They complain about the sacrifices in ride & handling they had to make in order to give the public what they want. Having said that, 17's on a lowered Max looks quite good

As noted above, F1 cars run 15" wheels & high profile tires...you'd think those dumb engineers would learn by now eh?

When you're driving on a bumpy or wavy road and the car gets steered around by it. I think of it as overresponsive steering.

Also, I didn't use F1 as an example because they have regulated wheel sizes. I think most race classes do. But race classes are generally not regulated in a way to make tires less grippy, less forgiving, or less durable. They usually choose a very good size for their mandates.

As for the issue that the contact patch changes shape but not size when going wider - it's partly true. But analyzing the grip produced by a tire shape using theory alone gets pretty wild. I find it sufficient that in general a wider tire produces a little more grip, because the real-world results prove it.

Dave

A wider tire provides more lateral grip because the contact patch is stretched width-wise as opposed to longitudinally (if you can picture it). Not arguing with you, actually agreeing , technically it's correct to say "shape" rather than "bigger". I'm no expert, I read about this somewhere & initially I was taken aback, but it all makes sense.

since I got my 17" 350z rims on my car, the punch off the line is slower and it seems that my MPG has gone down also. Am I just imagining it, or does the wider Z rims/tires decrease my MPG?

The rims are in my sig.

Read post #8 above.

I said wheel size doesn't affect fuel economy, which is true, but it can affect the driver.

If you're accustomed to a certain amount of accleration off the line, putting heavier wheels on will slow you down and have you using more throttle and burning more gas to compensate.

Dave

Wheel weight does increase fuel economy. I went from 50+lb/corner 18's, then went to 37.5lb/corner 17's and saw a consistent 12-15% increase in fuel economy, 90% highway. 77-82 MPH avg. speed.

As a Rule of Thumb, and assuming that wheel diameter is kept constant, the lower the aspect ratio, the higher the tire width needs to be in order to maintain the OEM diameter of the tire+wheel combo.

Which brings me to this question:

With performance (e.g., lateral and straight-line acceleration and g-forces) and not looks being the primary factor for upgrading from OEM, and given that the standard wheel size is 205/65 x 15, what combination of wheel size, tire width and aspect ratio would produce the best overall performance while keeping the overall diameter within 3% of stock?

From the Dgeesaman's post, I think it depends on your driving style. If you are doing mostly off the line acceleration, use the stock rims or lighter rims. If you are doing lots of high speed, sweeping turns, gong up in rim size should be ok. If you have a mixed acceleration and quick turns, going up an inch or two and lighter rims should be ok.

If you have poor roads with potholes and high expansion joints, stock rim will be better. I added a few more calculated 18 inch sizes for you (without consideration for fit):

Width Aspect ratio Wheel dia Tire dia
mm percent inch mm
205 65 15 647.5 Standard

195 50 18 652.2 1%
205 45 18 641.7 -1%
215 45 18 650.7 0%
225 40 18 637.2 -2%

My bent is toward autocrossing and track events. Autocrossing is about getting the widest tire allowed in your class, diameter doesn't matter since they're race tires.

For track use, where acceleration isn't as critical as lateral grip, and you have larger than stock brakes, I would think a 17" wheel should be fine to fit over a good BBK without adding too much bulk. Again, wider tires for more grip. Unfortunately that's as specific as I can be since the Maxima really isn't a performance car and I've not spent any effort studying how to improve it's on-track characteristics.

If you want performance, focus on tires, not wheels. If the wheel is as light as reasonable for your needs, then you can forget about it and focus on optimizing the tires. For a street driven car that sees *any* snow in winter, I suggest two sets of wheels so you can have at least all-season tires in winter. Then you can put some really aggressive tires on for summer. Be careful applying race tires to street use - too grippy becomes dangerous in rain and won't do well on the gravel and dirt found on streets.

Dave

I just upgraded to the following

A33 I30/I35 16 inch rims
215/55-16 Michelin Primacy MXV4

These A33 rims are not particularly lighter compared to the original A32 I30 rims. So virtually no effect on the acceleration.

The 215/55-16 Primacy MXV4 is slightly wider and lower profile than the 205/65-15 Energy MXV4+ so it now feels more secure in the curves.

The relatively new KYB GR-2 are not performance shocks but does a good job in controlling body movement compare to the worn out factory struts that were on the car until recently.

Having lighter rims WILL increase fuel economy, all other things the same. It has the EXACT same effect that lightening up your car will have.

Actually, my main concern here is handling in wet weather. Would a tire with a wider patch do a better job of avoiding hydroplaning, all things considered?

I've got a set of 60-series 15" Fuzions that handled great in the rain for the first 60% of their tread life. Now, with 40% of tread left, they are starting to hydroplane a lot. So, i'm at the decision point of "Do I stick with my stock wheels and get better tires, or do I go up one or two wheel sizes in addition to getting better tires?"

My rationale for going up in wheel sizes is to be able to get wider tires, like 235/50 x 16 or 235/45 x 17. Both of these sizes are less than 1% different from stock.

Hydroplaning is a different issue entirely. Wide tires will tend to hydroplane more, since the contact pressure is reduced a bit and the water has to be channelled further to allow the rubber in contact with the road.

A tire defends against hydroplaning by using deep, sweeping channels in the tread that push water to the outside of the tire. So tire selection is absolutely critical to getting maximum rain performance. While it's not a bible, I find the tirerack ratings to be helpful in assessing rain performance. You will be very pleased if you get a summer performance tire with a very high wet performance rating. I've had excellent success with Goodyear Eagle F1 GS-D3s.

Losing hydroplaning resistance as you described is perfectly normal. As the tire wears and the channels get shallower, the hydroplaning resistance goes down. I personally try to avoid using tires all the way to the end of their legal tread life, since they become downright dangerous in rain by that point. Time to slow down in rain or buy new tires.

Dave

I put on 200 miles on my new rims and tires today. Here is my feeling on the new and old. Just to recap:

Old: 15x6.5inch rims, 205/65-15 Michelin Energy MXV4+
New: 16x6.5inch rims, 215/55-16 Michelin Primacy MXV4

On asphalt the new tires are silky smooth at speeds up to about 85 mph. On concrete at same speeds there is this light shimmer like the tires are slightly out of balance. The old tires didn't have this difference on asphalt and concrete.

Both have 2 polyester, 2 steel and 1 polyamide plies in the tread but the older tire has 1 polyster ply and the new tire has 2 polyster plies in the sidewall.

So this could lead to a stiff sidewall and caused the slight shimmer on concrete or the shorter sidewall may caused it also?

Do your new wheels have the correct center bore size? Most aftermarket rims have a center bore of 73mm as apposed to the nissan 66mm (or 67 i forget). If you have a center bore mismatch then you should purchase some center bore locators (or hub rings as i've heard them called) to ensure that you put the wheel on straight.

Also after about 100 miles or so you should re-torque your wheel nuts.

The new rims are standard rims from a 2000/2001 I30. I will torque them as you suggested.