: Has anyone put 245s on front & 255s rear?



g50
04-17-05, 01:09 PM
maybe goodyear gsd3.

CVP33
04-17-05, 01:34 PM
I remember a post from whitelighting or someone who tried 255's all around. Claimed there was no rub. Also saw another post with "slight" rub. I just picked up a set of tires off ebay "cheap cheap" that are 255's. My guess is they'll fit. We'll see in about 6 months. Sorry I can't be of more help.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=7967138161&sspagename=STRK%3AMEWN%3AIT

At $100 bucks a tire, I just couldn't refuse. I know I'll probably give up some bite and turn in, but the 360 treadwear is a trade off I wanted to try.

urbanski
04-17-05, 01:35 PM
nobody has done this.
the problem lies in sizes front to back here.
255/35, 255/40, and 255/45 are all over 1% difference in diameter compared to the stock 245/45 size. This may throw off stablitrack/ABS, and you don't want to go there.

use a calcualtor before you buy anything
http://www.1010tires.com/TireSizeCalculator.asp?action=submit

CVP33
04-17-05, 02:18 PM
I can't believe that stabilitrak won't compensate for a .4" variance in diameter. It would seem to me that over and under inflation of the tires could cause a similar variance. I'm not saying you're wrong here Urb, just saying it's hard to believe.

urbanski
04-17-05, 02:53 PM
it's cool :)
let's see what Dreamin has to say, he knows his tires...
he's worried a 0.3" difference in the Toyos I ordered may be a problem.

wildwhl
04-17-05, 03:33 PM
Makes one wonder how the Stabilitrak handles the bald rears after only 4,000 miles or so on most V's. Never measured, but I'd imagine they were about 1% smaller in diamter or more when mine came off the car :lildevil:

Yes, Dreamin knows his tires, and now he also knows how my modded V drives compared to his. I also had the chance to drive a stocker again - I'm NEVER going back :bouncy:

CVP33
04-17-05, 03:42 PM
I'm not a math whiz by any means, but maybe someone can help me with this:

Key Assumptions:

Stock Diameter = 26.6 inches
New Tread Depth = 10/32nds
Worn Tread Depth = 2/32nds

Diameter = 2 times Radius
Circumference = 2 (Pi) Radius

Worn tires have lost 8/32nds or .25" when worn. This amount taken times two on the diameter would reduce diameter by .5 inches. I have to believe that stabilitrak can compensate for an increase of .4 inches in diameter if in fact it can compensate for a 1/2 inch decrease due to worn tires.

Am I missing something? :hmm:

g50
04-17-05, 10:54 PM
nobody has done this.
the problem lies in sizes front to back here.
255/35, 255/40, and 255/45 are all over 1% difference in diameter compared to the stock 245/45 size. This may throw off stablitrack/ABS, and you don't want to go there.

use a calcualtor before you buy anything
http://www.1010tires.com/TireSizeCalculator.asp?action=submit

I did not think of the diameter difference. I would think, the 255/45 not only being taller but also wider would cause more understeer. 255/40 might balance out just fine but at this point I might just stay with 245s.

CTSV05
04-17-05, 11:51 PM
I would suggest you be very careful up front, as there is minimal clearance between the tire and the suspension.

Is there a 255-18 tire with the same overall diameter?

g50
04-18-05, 12:04 AM
I would suggest you be very careful up front, as there is minimal clearance between the tire and the suspension.

Is there a 255-18 tire with the same overall diameter?


I do not want to change the fronts, just 255s on the rear.
Thanks

Dreamin
04-18-05, 12:16 AM
g50: You need to keep the front and rear diameter the same... as close to the same as possible. There will be no real benefit to run 255/45... get 9" or wider rims in the rear and run 275/40/18s!

CVP: Your math is correct. My info is directly from GM and Katech... GM tried to reprogram the Katech V's PCM (BCM actually) to get 255/35/19 and 275/35/19 tires to work, they could not (0.6" diameter differance). They had to go with 245/40 and 275/35. So maybe 0.5" is the limit before the PCM freaks-out? Maybe they were testing "worst-case", using your math, bald fronts and full rears, which would be 1.1" difference in diameter.
...just playing messenger here...

Dreamin
04-18-05, 12:20 AM
Yes, Dreamin knows his tires, and now he also knows how my modded V drives compared to his. I also had the chance to drive a stocker again - I'm NEVER going back

Dayyym dude... rub it in why dont you... ;)

BTW, from our discussion yesterday about wider rear tires... The car is perfectly balanced for 400fwhp; it wont be at 500fwhp.

So i'm back thinking about widened stock rims with 275s... Not so much for traction off the line... but to handle power-on oversteer... like how i almost got the tail to come around on your car at 30% throttle in 1st going around that corner onto the freeway :bonkers:

wildwhl
04-18-05, 12:45 AM
Dreamin -

I know you're right...but I'm just wondering how much more meat can hit the road before my rear diff implodes.

We need to figure out a plan...and widening isn't out of the question. I'm sure I can burn off these F1's (didn't put the GSD3's back on today, ran out of time) by the end of May or so :lildevil:

Then we'll have 4 rims to ship out and have widened before powdercoating :hmm: