SonnyinVA

i saw an ad in vette magazine for some 20" x 10.5" Z06 wheels.

i only want to know if they'll fit, and what mods are necessary, if any. unfortunately, i do not have the backspacing info.

if anybody has pics of any 20" wheels on a C4, i would like to see those too.

please do not comment on style or size as far as personal opinions go and whether or not you would put them on your car. i would like to keep this post about technical info.
thanks in advance!
Sonny

scorp508

Will they fit? Yes, as the overall diameter will be approximately the same as other combinations and we can fit 11.5" wide rims before tubbing. My 17x11" rims and 315/35-17 tires have pleeeeeenty of clearence with its proper backspacing.

SonnyinVA

i believe a 20" wheel/tire will be 1.5" taller than most 17" combos...

considering the sidewall is probably about the same height (if running the same profile series tire, i.e. 35 with a similar width), but the wheel is 1.5 inches taller on either side of the axle... right?

in other words... a 20" wheel, with a 295/35/20 should be approximately 1.5 inches taller than a 17" wheel with a 295/35/17, right??

SonnyinVA

ummm... ok, i re-read my post... what i meant was the 295/35/20 will be 1.5" further up in the wheelwell (1.5" radius). overall diameter will be 3" difference.
basically, so i should need at least 1.5 " of clearance around my 295/35/17 in order for the 20" combo to fit??
TIA
:cheers:

scorp508

Do they even make 20s in a "performance" tire 295/35?

SonnyinVA

not exaclty sure, but i was just using that as a reference point...

SonnyinVA

ok, i found pirelli p-zeros in a 315/35/20... so that should be a better comparison. the sidewall should be 110.25 mm tall... same as your 315/35/17. which is 4.3 inches.

my 20" wheel will have a 1.5 inch greater radius, so 10" plus aproximately 4.3 inches of sidewall... so 14.3 radius for wheel/tire. 28.6" diameter.

would you mind measuring the diameter of your tire/wheel combo?
theoretically, it should be... 17" plus 8.6"... equals 25.6". so radius is 12.8".
how does that compare to actual height of your combo??

right now i have the 285/40/17, so my radius should be about the same as yours (sidewall is the almost the same... 114mm vs. 110mm)

so i need at least 1.5 inches of clearance around my tire to fit the 20" combo???
of course this doesn't include the difference in depth... hmmm...

Alchemist

I also have 315/35/17s (on 11" GS rims). Tire height is 25 3/8"...So you're calculations are pretty close.

SonnyinVA

ty alchemist...
i wish i could find somebody that has already put 20" on their car... hello? anybody?
i only know one person, and that is scott rowland, but i can't remember his screen name.

chaos on wheels

If you go up in rim diameter, you have to reduce the sidewall height to keep the overall diameter the same. Less section width or aspect ratio (or combination of the two) will reduce sidewall height.

There's a Michellin Pilot Sport A/S that's 295/25R20 with an overall diameter of 25.8".

Continenal has a 305/25R20 summer tire with an O/D of 26".

There is a larger variety of tires in the 285/30R20 size, but the O/D is listed as 26.8".

I've never run any of these sizes, I just started inputting different sizes into the Tire Rack's website (search by tire size).


[Modified by chaos on wheels, 11:08 AM 10/27/2003]

SonnyinVA

that's very good info, and i appreciate the links.

i'll have to find some kind of happy medium cuz for obvious reasons i don't want to reduce the section width, and i'd like to go wider, actually.
and i really don't want to decrease the sidewall too much cuz then i'll get the bad ride characteristics that give big wheels a bad name.

:cheers:

bogus

my bigger concerns will be wheel & tire survival and wheel weight.

You will see some drop off's of performance thanks to the added weight. Wheel weight, or, unsprung weight, are killers.

you have that much wheel, with that small a tire, gee... one good pot hole, and they exist here in large numbers in the Northeast, and your new 20 is a 19"....

Zix

I've seen a C4 with 20" rims and it just looked wrong, not becuause I didn't like the rims, but simply because they looked too big for the car. It looked like it was going to be used for off-roading because it was jacked up too high.

jsquared94

I hate paying for 285/40/17 tires. The thought makes me cringe. You wanna buy 20's? You're NUTS!!! :crazy: (Or incredibly wealthy...)

Jared :flag

BAM92

I have seen a few c4's around here with 20's. They are just a little too big for the car. I am considering the 19" motorsport zo6's my self that are on ebay in a 19x11 rear. I have the 17x11's now. 18's look great and I think 19's still will be OK but 20's. Too much. I have 20's on my truck. But it is your money and your car so go for it. As will they fit I am trying to find out too. Have to check the offsets. :thumbs:


[Modified by BAM92, 7:07 PM 10/27/2003]

nonnivett

Here are 19"

35th

A friend of mine has those 20" Z06 rims on the rear of his C4. I don't know what tire size he has but they will fit. :yesnod:

SonnyinVA

those 19's look good...

35th, do you think you could find out what tires size he has, and possibly take a picture? find out what he has in the front too...
thanks guys!

86_RedRider

:lurk:

i've got to see 20's, because those 19's are huge.

TA

Man, I wouldn't want to hit a bump too hard with those things :crazy: