Any advantages to having larger rear tires?

[Seraphitia102]

I see many performance cars with larger tires on the back (i.e. fronts: 255/35/ZR18 and rear: 295/35/ZR18). Is there any functional advantage to having larger tires on the back? I have 245/40/ZR18's all the way around because I wanted to rotate my tires (since performance tires cost like $200 a tire). Also, if I did get larger rear tires, is there a calculator out there that can tell me how much my speedometer will be off by?

Thanks

 

[triggz]

A wider rear tire will give you more traction, simply. Plus they look really good. Wide tires on the front will cause 'tracking', make your car follow all the imperfections in the road and such.

When you go wider, typically the aspect ratio (the second #) goes down, so the tire maintains the same overall height.

Heres a calculator though
http://www.dakota-truck.net/TIRECALC/tirecalc.html

 

[Seraphitia102]

Thanks do you know what impact larger rear tires have on the quarter mile?

 

[chicks-dig-it]

Thanks do you know what impact larger rear tires have on the quarter mile?

I wasn't able to get a quarter mile time when I had the stock tires, but the added unsprung weight has definitly made a SOTP difference for the worse. Still, the launch is perfect with the added traction. The G's I can pull in a corner is just scary, too.

 

[_jb_]

Thanks do you know what impact larger rear tires have on the quarter mile?

It depends. If you go from a 185/XX/XX to a 315/XX/XX there will be a difference. On my 88 I went from 205 to 255 and it made a difference. Don't know if it was the width difference or because I bought a better tire.
The wider the tires the more rubber is on the road, so the more the better.

 

[triggz]

I brought down my 60' times about .05 - .08 going from 245 to 275s. Doesnt sound like much, but a tenth at the 60' is usually worth 2 tenths at the traps.

 

[tomustang]

wow i'm tired amnit: (non drag racing prospective )

Basically, the cars from the factory with wider tires, their suspensions are designed around the (wider back) configuration by having more oversteer, corrected by adding a larger rear tire you are balancing out the steer. In a mustang they are built with minor understeer (for safty reasons) something you can easily balance out or make more oversteer ie: stiffer srings in the rear, adjustable swaybar etc.

When it comes down to it, and I know from experence that when you have a stiff suspension with a live axle on the street small bumps and bad roads can cause your rear end to kick out right from under you and having a wider tire in the rear would give you alot more grip when it does. Alot of people who own mustangs do NOT push their car to the limit where understeer is a factor.

 

[triggz]

wow i'm tired amnit: (non drag racing prospective )

booooo

 

[tomustang]

booooo