higher grade tires are normally mounted on wider wheels, and also are sometimes lower profile than normal road going tires.

I think it would be nice to see a bit wider tires on the road cars when you swap to road supers, and also maybe a bit less sidewall.

Tire compound, width, and sidewall height are all separate tire characteristics that do not affect one another.

Having a wider contact patch will (probably, but not definitely) provide more grip. Big deal. The compound does that alone. No need to start changing the size of the tire to get even more when all the cars are the same anyway.

I think you'll find what you're looking for here: http://forzamotorsport.net/

wow that was rather harsh of a response :/

pretty misplaced towards me as well, but I'll move on

According to lfs tweak the rear tire of the xrt is 229/40/17

I went to tirerack and punched in 225/40/17

I got no results, but its a very uncommon size, so I went to a 45 sidewall and there were pleanty of choices for tire selection.

I think it would be interesting to see a different wheel choice and tire dimensions with the road super compound like you would commonly see at an autocross or track day event.

heh so there you have it, the XRT has a lower profile tire as you have asked.

Last time I checked the XRT was wearing:
225/45/17 up front
245/40/17 at the rear

It's possible they have changed recently but I thought it was only the FXO that had that happen.

Yea but the sidewalls are still single ply and designed to run at 32PSI nominal. How many performance tires in a 245mm/40%/17" size do you see that have such excessive side wall flex?

if you underinflate them as much as you don in lfs... quite a few id imagine

Quote from Gimpster :

Yea but the sidewalls are still single ply and designed to run at 32PSI nominal. How many performance tires in a 245mm/40%/17" size do you see that have such excessive side wall flex?

They all do, watch any car going round a roundabout too fast and even with road pressures the flex is very obvious.

I thaught they would flex alot less untill recently. But after looking into it and actualy handeling a tire with 30 sidewalls (305/30 R19), they are actualy a bit thinner and almost as loose as a tire with a 45 sidewall.
They flex almost as much.

I'd imagine that running any tires at less than 25psi would be quite harmful to the sidewalls. I've seen the inside of a tire that was run under inflated many times, the whole inside of the tire always turns into little flakes.
Haven't ever handeled full on racing tires, so I woulden't know about them, but I'd imagine you can't go much lower.

It's odd you didn't find tires at 225/40 R17, you get a nice set of racing tires when you punch that into tire rack, you don't get any road car tires though, if thats what you meant.
You can go as low as 35 on tire rack and get a rediculous set of summer road tires at 225/35R17, 3.1 inches of sidewall is mental.


Edit: I can't see the XRT needing any size bigger than it's already got.

this made a whole lot more sense until I found that the xrt was actually on decent sized tires.

there isn't really much point for this topic anymore :P