Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

and or for street racing down in... Mexico.... I recently had to get new tires for my IROC. I just got the replacement 245s on all fours. While watching random F-Body YouTube videos, I notice a lot of street built third gens have slightly bigger tires perhaps 255 or maybe even 265s in the rear. It looks cool but does it help with traction at all in the 1/8th mile or on the street?

In a couple of months my IROC will no longer be my daily driver as I am getting either a late model Maverick or Renegade. I would like to start putting some money into my IROC and turn it into a mild street machine. (Before anyone says anything, it already has headers, y-pipe and muffler as well as the airfoil and the HVAC piping in the ram air).

Re: Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

A little wider tire would obviously have a larger contact patch and therefore the potential for more traction. You need to take into account your overall rear gear ratio as well. If you already had 3:23 gears AND you put on Wider tires (which are also usually taller) it might actually make your takeoff WORSE!

Re: Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

My car actually has the 3.70 gears. I'm assuming those with wider tires might make my takeoff worse?

Re: Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

Width affects the likelihood of wheelspin. Tire height / diameter affects the effective gear ratio. They are not in a fixed relationship, which is why tires are sold by width and aspect ratio.

Re: Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

Not necessarily, but you DO need to take the overall diameter into consideration. This will help you SEE the difference of different tire sizes.

Tire Size Comparison

Re: Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

I appreciate it. Thanks.

Re: Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

The type of rubber is the number one factor for traction on a stock 16x8 rim. The lower the tread wear the stickier the rubber.

There aren't very many choices of tires that will fit a stock rim. 245 vs 255 just comes down to which one is available in the kind of tire you want. Basically you get what you get, you won't have a choice.

Re: Do Larger Street Tires on the Rear Make a Difference for the 1/8th Mile
 

The larger tire isn't likely to offer any better traction on the street or track. This is larger in a width sense while keeping the overall diameter equal.
I've run all manner of 26" diameter tires on the back. 245/50/16, 255/50/16 (both BFG Comp 2) and also MT ET Street bias DOT slicks in a 26x10 and prehistoric McCreary Road Star treaded dirt track tires. Once you're at a certain power level, none of the above will provide traction on the street. Just different looking tire marks left on the pavement. There was some advantage with the racing tire but overall all traction was limited.

The track is different. The street tires such as the Comp 2's won't hold worth a lick regardless of the width. The track specific tires with a different compound (as QwkTrip stated above) than that of conventional street tire is where you'll start to see the advantage. And wider is typically better although there are many factors that come into play when testing at the dragstrip. Track prep being a big player here. As well as tire construction as in radial vs bias ply.

Case in point: After breaking a rear gear set when making my 1st pass in the 12's (many years ago) a change from the 3.70 gear (BW 9-bolt) to a 3.27 netted a quicker 60' time. This was largely due to the reduced torque seen at the rear tire and thus less wheel spin. You could feel and hear the difference in traction. Same tire (the McCreary's mentioned above).
Back to a 3.73 gear (Dana 44) and a change to the ET bias slicks was now just as quick. However after a few years of minimal racing the tires started to show their age and the 60' went away gradually, season by season.