dr-rjp

iTrader: (4)

I started this thread in the 4th Gen forum because I wanted the responses to take into consideration what I drive.

Of course, someone had to chime in with "There is a forum for this" smak. So, I am coming here to see if the responses I get are more helpful than that one.

Here's my question:

Forget about looks if you can for a second, and think about what would be the ideal tire/wheel combination that would get you the best possible gas mileage without sacrificing performance, or spending more for the rims and tires than you did for the car.

So far, a number of respondents have said to use the smallest wheels possible, or keep the stock 15" wheels, or use the lightest rims possible (no larger than 17" in diameter).

These have all been helpfui, although I need something more specific enough for me to make a choice among the myriad of choices.

Some other considerations regarding which rims and tires to buy might be:

1. ride comfort
2. noise level
3. rim durability
4. tread longevity
5. wet handling
6. dry handling
7. cornering stability
8. stopping distance


and so forth.

Of all these additional factors, what is most important to me is wet handling. I live in Florida, and rain rather than snow is our major weather hazard.

Has anyone done a direct comparison of several wheel/tire combinations using the same car? I know where to find tire comparisons, but not wheel/tire combos.

Your help will be greatly appreciated.

02theMax

iTrader: (2)

I think what your asking has no real bearing on what you're looking for. Even if someone chimes in and says a certain wheel/tire combo is the best way to go that is nothing more than a personal opinion. If I were in your position I would start with the wheels (rims) first, how much do they weigh? Are they forged? How good do they look? Once you find something that appeals to YOU then go for the tires. There have been many threads about tires on these forums but www.tirerack.com was a big help for me. I just can't see you finding the ultimate wheel/tire combo that is performance driven at a cost that is suitable to you, or even me for that matter. Good luck with your search just be patient. By the way I'm very happy with my 19" G35 wheel/tire setup with Bridgestone Potenza RE050A's and I was happy with the cost as well.

dr-rjp

iTrader: (4)

OK...personal opinions are valuable, too, like yours listed above.


Except, that I bet you have more to add than just your opinion.

For example, did you originally drive your car with a different setup than what you have now? Yes? Well, then what was your MPG before and after? What was your acceleration times before and after. See...as long as you have that information, why not share it with me along with your opinion?

02theMax

iTrader: (2)

I didn't go that far in depth when buying my rims. I do how ever see your point. My MPG is almost the same as stock, slightly less, and acceleration is almost the same as well most likely due to the the rim/tire package being almost equal in weight as stock. HTH, good luck.

dr-rjp

iTrader: (4)

Tire diameter will also have an effect on a vehicle's final drive ratio. As tire diameter changes, so will engine rpm at a given speed. We can demonstrate this with the simplified formula: rpm = (mph x final gear ratio x 336*) / tire diameter (*see "Formulas for Success" sidebar). For example, given 65 mph, a tire diameter of 30 inches, and a final gear ratio of 4.10, the engine speed will be approximately 2,984 rpm--(65 mph x 4.10 final gear ratio x 336) / 30-inch diameter tire. If we reduce the tire diameter to 25 inches, the engine speed increases to 3,581 rpm. By installing shorter tires, the vehicle will accelerate as though it has a 4.73 (higher numerically) gear without the expense of gear swapping.

From http://www.chevyhiperformance.com/te...148_0208_gear/

dr-rjp

iTrader: (4)

So, if I interpret the above correctly, the smaller the tire, the larger the final gear ratio, and the higher the RPM's for a given speed. A large final gear ratio would be good for acceleration, but poor for gas mileage.

Conversely, larger tires would yield a lower final ratio, fewer RPMs per MPH, and thereforee better gas mileage.

Am I correct?

MorpheusZero

iTrader: (10)

Yes.

10char

NisMoN00B

iTrader: (2)

I'm no math scientist, but for the *best* MPG I'm sticking to the recommended manufacturer specifications (for now, at least, 17" OEM + 225/50/17 Kumho Ecsta ASX). I'm now getting 25-26mpg combined city/highway after I hit 90k...which is weird. I used to only get 23-24mpg.

DrKlop

iTrader: (3)

This is only true when you are cruising at a constant speed. Smaller outer diameter makes it easier for the car to accelerate, thus less effort and less fuel is required to accelerate the car. So, I would say tires with smaller outer diameter will result in better fuel economy unless you are driving like 100 miles a day non-stop with your cruise control always on.

Larger diameter tires (given the rims is the same size,) however, will result in a better ride, obviously better rim durability and longer thread wear.

Wider tires (given the rims is the same size) will result in higher noise level, better dry traction, better rim durability, less hydroplaning resistance and lower steering precision.

Lighter rims/tires result in better ride, better acceleration & stopping, higher cornering traction, better fuel economy and less wear and tear.

Very high profile tires result in a sluggish steering responses, lower cornering traction, cornering instability, but better acceleration, fuel economy and ride.

Very low profile tires result in crisp steering responses but low cornering traction, cornering instability, low fuel economy and acceleration..

Profile that is just right will result is good traction & cornering stability and obviously adequate acceleration, fuel economy and steering responses.

dr-rjp

iTrader: (4)

LESS ROLLING RESISTANCE

dr-rjp

iTrader: (4)

I'm leaning to getting a set of 17" wheels/tires, so I have another question:

I found a tire diameter calculator on the Net (actually I found a few), that let's you compare up to 5 tire sets at a time.

From what I calculated the 225/45/17 are the closest match-- the stock 205/60/15 are 24.7" in diameter, while the 225/45/17 are 25" in diameter.

Now, I read somewhere that getting tires/wheels that had more than 5% difference in diameter was bad for the car's brkes, and possibly unsafe.

Have you (or anyone else) heard about this?

Also, what would be the largest 17" tire I could put on my 98 I30 assuming that I get the speedo recalibrated to match the change in gear ratios?

DrKlop

iTrader: (3)

it is harder to stow down with larger wheels, thus your brakes have to work harder to stop the car.

how exactly are you planning to do that?

dr-rjp

iTrader: (4)

We have an awful lot of people buying really large
diameter rims with low profile tires for their cars and then wondering why their gas mileage is not as good as it used to be.

DrKlop

iTrader: (3)

Is that a question or confirmation of what I said? lol

motocross416

iTrader: (6)

If you want 17s, just stick with 225/45-17 tires, I don't know if it is possible to get our speedometer recalibrated. With those size tires my 4th gen's speedo reads 1mph high at 60mph according to those radar units that sit on the side of the road

dr-rjp

iTrader: (4)

From what I've calibrated, 235's would be a closer match...only off by 0.67%

95bluse

iTrader: (1)

Agreed, that's what I have on my '95. Wheels are 17x7.5 & tires are 235/45/17.

Be aware that you should get at least 7.5 width to run 235-series tires.