We all know that big meats on the back of our ponies look kick-***, but do they really have a significant effect on the performance? Do they result in better acceleration? Handling? etc?

Would the same car with 285s out back get up and going faster than one with 255s ? I currently have 255s all around and want to know if it's worth it to beef up the back for a reason other than looks.

thanks

 

More sidewall (and presumably more flexible, too), and a wider contact patch, is much better for forward acceleration traction. The rubber compound is also important. For example, my new M&H tires are narrower than my previous Nittos, but slightly taller, and much softer. They hook dramatically better than the Nittos ever did. But, they wouldn't be all that great for corner carving.

 

don,
any chance for a ride a long at the q to experience your fast car?

 

It's about traction.

 

Are you talking solely forward thrust or are you including the twisties as well? If you make no other change than to add 285's to the rear (with I might add, the proper sized rim - none of that fitting anything over a 255 to the stock rims crap) you will increase understeer as well, which will need to be balanced out with some suspension tuning if your inclined to do so.

 

I can't run it all out with a passenger in the car. Anything quicker than 8.50, and they cut your armband and fine you $50. My wife already did that once... d'oh.

 

Bob, what would be the proper wheel size for a 285? Would a 18 x 9 or 18 x 9.5 fit the bill?

 

I have 18x10s for my 285s, and I think it looks perfect. However, I believe the shelby GT500 uses a 18x9.5 at all 4 corners w/ 255s in front and 285s in back. The 18x9 rim works great for the front 255s.

 

Its all about contact patch. More improves braking, accelleration and cornering. Depending on power, staggerd size may or may not do you any good. Higher powered cars neen more contact patch on the drive wheels. Other limitations are front and rear wheel well obstructions.

For BFG G-Force P285/40R18 recommended rim width is 9.5 - 11.0. For other manufacturers of this size, very likely the same rim width recommendation

 

Still depends on the tread pattern and compound too.

 

18x9.5 to 18x11 (285/40R18)

http://www.bfgoodrichtires.com/catalog/tuner/14.html

Since BFG does alot of tuner sizes and the tire data is pretty standard for most manufacturers (except probably max pressure and max load) the spec tables can be pretty handy when determing wheel size. The notes below the table also has some good info (like the effect that rim width has on tread width and proper inflation pressures for high speed driving as well as the resulting loss in load carrying capacity)