tire sizing...

[sota]

can someone give me a detailed explaination as to the pros and cons of the various size slicks out there? For example how do you decide between 24.5" and 26" tall slicks? When is shorter better? When is taller better?

Thanks!

[blackbird]

There's a bunch of factors to consider. As their name implies, 24.5 and 26" slicks have two different diameters. Because of that you can think of the two sizes as similar to altering the final drive. The engine and transmission are still turning at the same speed (dictated by rpm and gear ratios) but the taller tire will move the car further for the same number of turns than the shorter tire.

There are other differences as well. The short tire will have less sidewall and many times won't be able to "crinkle" and "give" as much to deform and help maintain the contact patch and therefore traction. Then again on a stock suspension or without coil-over's you might be able to run a wider 24.5x8" slick where you'd be limited to a 26x6" due to the spring perch on the strut and wheel offset limitations.

Optimal size for traction is generally as big and wide as will physically fit. If you have coil-over's on the car that's about a 26x8" for the SRT-4 without a lot of rubbing and having to perform other modifications. But you should still take into consideration the effective gearing differences. Also on lower powered cars the extra rotating massing sucks up more power.

Here's just a few quick links I came up with that might help making some calculations:

http://www.izook.com/gearcalc.htm
http://www.csgnetwork.com/gearratcalc.html
http://www.csgnetwork.com/multirpmtirecalc.html
http://www.f-body.org/gears/

[sota]

Thanks Eric!

I've been trying to figure out what to do since my car is still bone stock. My last track day last year a guy loaned me a set of slicks (which I think were 24.5") that cut my ET down by .3, but dropped my mph by 3-4 at the top end of the track. Problem is i'm only in the 100mph range and a 14.00 dead flat ET on street tires. You can see that I'm *just* having to grab 4th for like maybe a second which is wasting ALOT of time but i doubt I could get a tall enough tire to get my in-car indicated mph down to 90 as I cross the finish without having to grab 3rd.

Guess the better solution is... MAKE MORE POWER so I need to grab 4th sooner. :rofl:

[punkrokdood]

lemme tell you... if you try to run 26x8 slicks, an aftermarket clutch is a good idea :lol:

and your experience sounds about right... the 24.5" slick is slightly shorter than stock, which helps acceleration, but lowers your top speed