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8.5 and 9.5 width rims question.

M

muzy67

Guest
I have two 8.5 and two 9.5 width rims on a 86 conv. Will this affect handling and does it matter if they are on front or back?
 
R

RubyDropTop

Guest
Yes to both of your questions...

Yes, it will effect handling and yes, it matters if they are front or back.

In '92 GM placed 9.5" rims all the way around, in '93 they changed that to 8.5" in the front and 9.5" in the back. The reasoning being an increase in handling performance.
 
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I thought the reason was for better drivability... the super wide tires on the front are not great for going in a straight line... especially on the highway when there are ruts in the road from big trucks.... I thought chevy put the smaller tires on the front so vettes would have a stance similar to a regular car, so it would drive better (i also thought that was why they didn't change the offset of the smaller rim to match the larger one) Also, the high performance Z51 package came with a full set of 9.5 inch wide tires... to increase handling (and looks in my opinion)
 
R

RubyDropTop

Guest
Doesn't it have to do with unsprung weight as well? Wouln't a smaller tire/lighter rim on the front play a role in unsprung weight as far as road contact? Is that what you mean?

Maybe I did not explain myself too well.
 

Spiderman

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Gorgeous White '91 Coupe
Bringing the width of the front rims down to 8.5" most likely didn't have much to do with increasing the cars performance. The car is designed to carve it up in the twisties. Reducing the rim size on the front simply made the rear wheels look larger than the previous years models. This probably had more to do with the accounting department than the performance characteristics. "If has big tires it must be fast" :gap "Is that one of those ZR1's? It sure has big tires on it." quotes: Joe Public

Just my $ .02

Spiderman :w
 
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yeah... i think chevy figured out that the cost of the smaller front wheel and tire package = less money... the difference in a 255/50/17 tire, and a 275/40/17 tire, for some reason, is a lot of money... I was able to get goodyear F1's for the front of my 93 for 300.... the rears were 400... I think their engineering excuse was the drivability of the cars...

The unsprung weight thing.... I bet the weight is almost the same between the tires... on top of that, the engine isn't spinning the front tires, they are just along for the ride... the rotational weight issue only seems to make a real difference on the tires that the engine turns
 
V

vettepilot

Guest
Chevy learned a lot over the C4 years about handling, and ride control.
In mid-1983 when the 1984 C4 debuted the wheels were 16x8.5 all around on the base suspension, the Z-51 got 16x8.5 on the front and 16x9.5 on the rear. Due to a shortage of 8.5 wheels late in the model year some base suspension cars recieved 9.5 wheels. Wheels sizes remained pretty much the same until 1988, then 17x9.5 wheels were offered on the Z-51 and Z-52 suspensions. In 1989 17 inch wheels were standard on all suspensions.
When the ZR-1 came out in 1990, the tire/wheel combination was 17x9.5 wheels and 275-40/17 front and 17x11 315-35/17 on the rear. The standard Corvette still had 17x9.5 wheels with 275-40/17 Gatorbacks.
This remained so through 1991 model year.
In 1993 the lessons learned from the ZR-1 suspension were brought to bear on the standard suspension, placing 17x8.5 rims on the front on which were mounted 255-50 tires and 17x9.5 rims with 285-40 tires on the rear (except for the RPO ZO7 which had 17x9.5/ 275-40 all around). This combination ensured that base suspension cars would always have terminal understeer, and provided improved handling on the street.
This technology remained the same to the 1996 model year. That year saw the Grand Sport Coupes get the ZR-1 size wheel/tire treatment once again.
I'll end here with the end of the C4 era technology, but I think you get the picture.
The C5 takes tire/wheel/chassis technology to a whole new level, and I'm sure the C6 will astound us with even more fantastic handling / ride control technology.
vettepilot
 

WhalePirot

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Good explanation VettePilot

My '84 Z-51 has the 'mixed' wheel sizes. I drive aggessively, at times, on the street and have always rotated the Gatorbacks. I found no difference in handling, in my application, regardless of whether the 9.5s were fore or aft.

I did find that switching to 17" Epsilons solved the wheel balance problem, as many of the made-in-Mexico wheels were drilled off center slightly! Balance jobs lasted about 10k miles. I believe this drilling issue was resolved, which should make mine rare and very collectible, right???? LOL
 

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