Wm Rose

Here's my plan: I have a base C7 with the 18/19 wheels. I want to get aftermarket wheels in the same size as the Z51's, which is 19x8.5 and 20x10......I like the idea, and ride quality of the taller tires on my base, which is 245/40/18 and 285/35/19. My understanding is, the 40 and 35 in those tire sizes, is the height.

The factory Z51 tires have 35(front) and 30(rear) as the height. I want to put taller ALL SEASON tires 40(front) and 35(rear) on the new 19" and 20" wheels. I used a tire calculator on a tire site, and bottom line is, the taller tires would increase the overall diameter of both front and rear wheels by 1 inch. That really means only 1/2" closer to the inner fenders. Am I missing something, or should this be a simple change, other than throwing the speedometer off a hair.

Z51: stock size front wheels -245/35/19 changed to 245/40/19 for new front wheels.

Z51: stock size rear wheels- 285/30/20 changed to 285/35/20 for new rear wheels.

I don't track the car. I'm more interested in filling the wheel wells a bit more, and more tire height for a softer ride, like I have now with the base wheels......Thoughts?

sl33p3r15

I would say you would be fine with the taller tires. As you said; the taller sidewall on the 20" rim will fill the wheel well by an extra 1/2". Plus, it will possibly soften the ride a little, but that will largely depend more on the tire compound than the extra 1/2" sidewall height.

Zymurgy

The difference in "ride quality" due only to the difference in the sidewall height of the stock Michelin run flats is very minimal. Run flats have very rigid sidewalls. The "ride quality" is much more dependent on the suspension components. Switching to non-run flats will have a greater impact on softening the ride than will the greater sidewall height.

Your speedometer error will be a little more than 4%.

Walt White Coupe

I like that idea also but I think the problem right now is that there aren't any "All Season" 285/35/20 sized tires that are available for the rear. Have you found any?

Wm Rose

Yes Walt... I looked into that. Michelin makes an A/S tire in that size, but they're not run flats.
http://www.tirerack.com/tires/tires....SAS3&tab=Specs

alienranch

And to clarify, the first number (285) is the width of the tire in mm. The second number (30) is the percentage of the height to the width (30% of 285mm). So a wider tire might show a smaller height percentage, but actually be the same height in mm.

Wm Rose

Ok, I got the new wheels and the slightly taller tires on the C7. The wheels are 19's & 20's... the tires are Pilot Sport A/S 3's....The tires are one size taller, front-245/40/19..rear-285/35/20. I gained a half inch in ride height, and also filled out the wheel well a bit, without lowering the car. I need the stock height to get in my garage, so no lowering. There is no rubbing, although the front tires are only about 1/4" from the inner wheel well when it's turned completely to one side. I love the new look.. Here's a shot of the new set-up.

JerryU

Ride quality is more proportional to aspect ratio than diameter.
I see folks with 22 and 24+ inch tires on cars and what look like rubber bands for tires. They must ride like solid rubber!
Also 1 inch taller is 4% larger according to TireRack and your info (suggest you use TireRack actual diameter vaklues for the tires you're planning rather than some "generic formula" as tire bands are different to some degree) so your speedometer will read ~4% low.

halt00

Great solution to the wheel well gap vs. lowered driving problems debate!

1776DAVE

I like it !
When I need tires on my z51 I will go larger also!

Tulsaeasyrider

It looks really good and if you're not rubbing when you hit bumps, or turning sharply, you are good to go. Your math is correct in that you gained 1 inch in overall height for both front and rear tire/wheel combos. Stock front 18" tires were 25.7" tall and rear 19" was 26.85". Your new fronts are 26.7" and rear is 27.85". My all season fronts are (275/35/19) 26.57" and the rears are (295/30/20) 27.6" which is slightly less than your current diameters. I have no problems with the fronts, but, occasionally, I can hear the rears rub when encountering bumps or abrupt dips in the road. Hence, my thought that you could observe some rubbing. Or course, it could be my wider (+0.41" over stock) rear tires that are responsible. If that's the case, I'm glad I couldn't find any 305's or 315's. Enjoy!

Walt White Coupe

Wm Rose,

Nice information and something I would like to do when it comes to new tires. Please let us know if you have any rubbing issues after you put some more miles on the setup.

Thanks.

Wm Rose

After a weekend of beautiful weather and a 100 miles or so of driving the Vette with the new wheels, I'm very happy with the new set-up. I had no rubbing anywhere. The tires are 1" bigger in diameter, which is really only 1/2" on each side of the wheel. The aspect ratio is the same as the factory 18/19 base wheels. The ride isn't much different than with the factory tires, but they aren't as sticky which is what I wanted. A lot of thought went into picking this size, as I couldn't find anyone who had tried it before me. Here's a few more shots of the wheel/tire combo.

Walt White Coupe

Very nice, thanks.

AmmoVet

[QUOTE=Wm Rose;1592075292]After a weekend of beautiful weather and a 100 miles or so of driving the Vette with the new wheels, I'm very happy with the new set-up. I had no rubbing anywhere. The tires are 1" bigger in diameter, which is really only 1/2" on each side of the wheel. The aspect ratio is the same as the factory 18/19 base wheels. The ride isn't much different than with the factory tires, but they aren't as sticky which is what I wanted. A lot of thought went into picking this size, as I couldn't find anyone who had tried it before me. Here's a few more shots of the wheel/tire combo.

How is the ride. I'm trying to get a similar setup. I want a softer ride for the spouse and plan to keep two sets of wheels and tires. The stock items on my 2016 will become my autocross tires and the new ones I want for day to day road trips. Open to all suggestions and I'm leaning toward Bridgestone.

Wm Rose

I didn't notice much of a difference in the ride. The tire aspect ratio on the new tires is the same as the factory tires, so that didn't change. Only the diameter of the wheel/tire combo increased by 1 inch....The new tires are A/S 3 +, and I've read reports that they ride softer, but I did notice it much. It still handles like a new Vette on rails.

DickieDoo

So they are non-runflats ? and you did not notice an improvement in ride? interesting....

Wm Rose

See post#16

Dif

Yeah, I thought non run flats ride so much better than run flats.
At least that's what I keep hearing

L8ter

Looks good!