libertyforall1776

iTrader: (2)

From a suspension/handling performance perspective, is there any negative to an 18" wheel 9.5" wide on a 4th Gen for daily driving, HPDE, and AutoX? Positives? I know there was never any OEM size bigger than a 17" wheel 9" wide... What kind of tire size would be ideal on this size rim? 275s?

I am considering these:
http://www.factoryreproductions.com/...Chrome-c82.htm

TIA

02TransAm/Batmobile

iTrader: (32)

I think the larger diameter of the 18" wheel would be preferred since there is less sidewall deflection (if you stay at stock tire height).

A negative is that tire prices are much more expensive!

libertyforall1776

iTrader: (2)

I guess the other negative is when you goto a 35 sidewall 18" tire, they become much more susceptible to pothole damage & it becomes a firmer ride, I care more about the first point though since the car is primarily a street car...

99Bluz28

iTrader: (35)

You could go with a 285/35/18 tire.

2QuikTA

I run 275 up front and 295 in back on my 19x9.5

99Bluz28

iTrader: (35)

I've been running 275/35/18s on my DD over 10yrs, just get a good set of tires(don't cheap-out)and your ride shouldn't change much at all.
Now as far as running a 295 on a 9.5" wide wheel that's your choice, but there's a good reason the tire manufactures recommend a set wheel size range; to offer the best possible performance from their tires. IMO, your only short changing yourself when mount you tires on wheels outside the recommend size range.

Paul Huryk

A lower profile sidewall increases the effective spring rate of the suspension - whether the car feels better or not.

There have been tests where a car has been fitted with several different wheel sizes and it seems that at the 25" to 26" tire height, the 17" gives the best times on the track and the 18" "feels" best (but is usually a bit slower). As a 3rd gen owner, there is an inflection point at the 17" size - 16" can't give the grip, and 18" is too stiff - 4th gens are similar in that respect.

trans_am7935

iTrader: (15)

one big benefit to 18's is you can run bigger brakes like the 5th gen Camaro brakes or the CTS-V brakes. that is where i am regretting getting 17's, cant fit the bigger brakes i want now. moving to 18's shortly.

Cap'n Pete

iTrader: (2)

From a ride/performance/economics perspective, it's hard to beat the 17's, however, I don't think you're giving up much moving up to the 18's.

As for big brakes, yes, you can fit BIG brakes under the 18's, but you can still go to C5 brakes under the 17's.

libertyforall1776

iTrader: (2)

Well I added the rims in the OP (18X9.5 5X4.75 +40); I guess the untold advantage of 18" wheels in a 4th Gen is the ability to run Michelin Pilot Super Sport tires that I bought (275/35/18), no 16" or 17" options for 4th Gens on these tires. Consumer Reports rates the PSS 90 of 100 -- the tops in their Ultra High Performance tires category, and the highest rating ever give to a tire! Next closest rates 82 of 100...

http://consumerreports.org/cro/cars/...s-overview.htm

Perhaps this tire can help wipe out any some negatives of a bigger rim? Michelin's 30k mi. tread warranty appeals as well.
http://www.roadandtrack.com/special-...er-sport-tires