I Recently Put Z06 Riveted Rims On My 01 Coupe.now I've Been Told I Need To Change My Tire Size To Fit The Rims Correctly.is This Correct??thanks.JESSE. p.s. what will the diff.be in speedo reading?will programming,like diablo,correct the diff.??

 

Need you to post the size of the wheels and the size of the tires.

 

stock run flats GY,AND the aftermarket rims which are the same size as the stock rims.17x9.5 front,and 18x10.5 rear.

 

Stock wheel size for a coupe is 17x8.5 and 18x9.5. So your stock tires would be too narrow for the wider Z06 wheels.

 

...but, you can still use your old tires w/o problems.

 

A 245 on a 9.5 wheel and a 275 on a 10.5 wheel? Awful narrow tires for those wheels. I'd step up to at LEAST 265 and 295s minimum.

 

Not according to the guys at tirerack.com. Give them a call to verify - they will give you a definite answer.

PS: I'm running Z06-size rear tires (Michelin Pilot Sports) 295/35-18s on 18x9.5 rims. Tires have approximately 8k miles with no abnormal wear across the tread.

 

My point EXACTLY. You're running a 295 on a 9.5 wheel and recommending that someone run a 275 on a 10.5 inch wheel? What am I missing here?

BTW, go back to TireRack.com and see what tire size they recommend for Z06 wheels.

 

The tread should be approximately an inch wider than the wheel. 245 divided by 25.4mm is 9.64" on a stock 8.5" rim. Likewise a 275 is 10.83" on a 9.5 inch rim. If you're going to use Z06 rims you need at least the stock Z06 tire sizes. You can go that far without any adverse affects but you won't be getting optimum performance. You can use the Z06 tire sizes without any problems to your speedometer too. According to my calculations the Z06 rear tire is less than 2% larger diameter. This means that when your speedometer reads 50, you'll really be going 49, or 98 when it says 100 etc.

Tire sizes are numbered in millimeters. A 275/40 is 275mm wide. The 40 means the height is 40% of the width. In this case, 275/25.4 is 10.83" wide x .40 is 4.33" tall x 2 + 18" rim = a tire diameter of 26.66". The Z06 is 295/25.4 =11.61" x .35 = 4.06" tall x 2 + 18" rim = a tire diameter of 26.13". Finally 26.13/26.66 = .98012 - 1 = 1.988%

 

Thank you for very useful info.....your math is good too

 

Thanks For The Info People.to The Person W/the Math Going On...thanks,i Appreciate The Breakdown,but In Simple Terms,what Size Tire Is That???265's And 295's Will Work?

 

Yes. If you are using the Z06 rims, you'll want to use the Z06 tire sizes. 265/40/17 front and 295/35/18 rear. Your speedo will be minimally affected as stated because the tire diameter will remain almost the same.

 

almost got it all right. the first number is not the tread width. it's the section width. that's the widest point from sidewall to sidewall. the tread width will vary from one manufacturer to another. in the ultra high performance market, the tread width to section width will range from 90% - 96%. what i look for is that the tread width doesn't exceed the rim width. if it does, the tire will start to fold, or bend, at the tread section. oh and the 275/40-18 will work on a rim width of 9"-11".

look at all the different brands and compare the tread width. you'll notice the tread width vary. also look at the rim width measured on. that has an effect on section and tread width.
here's a quick compare

tire brand ----- approved rim - measured rim - sec width - tread width
potenza s0-2A -- 8.5-10.5 -------- 9 --------- 10.6 ----- 9.4
potenza s0-3 --- 10-11 ----------- 9.5 ------- 11.1 ----- 8.5
eagle F1 GS-D3 - 9.5-11 ---------- 10 -------- 11.3 ----- 9.2
yokohama AVS -- 9-11 ------------ 9.5 ------- 11.3 ----- 10.1

when it comes to tires. i look for the ones with the most tread width. that's what touches the ground. all of those are 275/40-18 and the yokohama in this compare has the most tread width.

 

You may be right about the 275mm being section or tread width. The design of the shoulder will have a lot to do with the actual tread width. A rounder shoulder will have a slightly narrower contact patch and a more square shoulder will be wider. But I believe they actually start at the full 275. However, I don't know where you got those numbers from because I have a brand new set of GS-D3's sitting right here and there's no way to measure it without getting at least 10" on my ruler. There's no way I can cheat the number to show only 9.2". Additionally, as the tread wears down the rounded shoulders, it would gradually be slightly wider. I'm not being combative, nor am I a tire expert, I'm just curious. Where do you get those numbers? It's obvious to me they are not accurate but that's judging only by the Goodyears. Thanks

 

I forgot to ad that 275mm is 10.83" and you also show the section width as being 11.3. The section would also be different depending on the rim width to I find it hard to believe those numbers nor the claim that the section width would be the one that is specified. ????

 

got all those numbers right off tire rack's site. http://www.tirerack.com/tires/Compar...ark=1&x=13&y=2

by each tire on the right side click SPECS. it'll show you all the specs. these specs are from the manufacturer.

 

if you notice, each tire has a specific rim width the manufacturer measures their tire with. as i said above, each manufacturer decides how much tread width to section width they think is appropriate for their tire. that's why when you look at two tires identical in size (275/40-18) one will 'look' wider than the other. it's the tread width that you see. i worked with BFGoodrich for 5 years. then Firestone for 2 years. i currently my business (suspension/alignment shop) is co-located with Goodyear/Wingfoot here locally. been here for 4 years.

 

Well you're right about where the numbers are but they don't make any sense to me. I have the tires and the ruler right in front of me. If you're a Goodyear dealer, pull out a set of GS-D3's and tell me what YOU get. I'm sure there's some kind of voodoo going on at the mfr level with the specs but a ruler is a ruler.

THanks

 

it's a mystery to me. but they measure on a particular rim size at a given inflation pressure. and i'm sure wheel and tire isn't mounted to car. they might be measuring from where the tread ends on each side for tread width. and for section width it's the widest point of the sidewalls on both sides. a vernier caliper would be a better tool to use.