Subw00er

FYI, the Goodyear DOT tires are no long available in 2007 and are just about sold out everywhere. I actually found and bought a set of the GS-SC F1 tires leftover from 2006. The bad part is that they look old because they have cracking along the grooves, so I'll be returning them.

So I've started looking at other options and have pretty much narrowed it down to the Kumho V710's or the Hooser R6 track tires. I have a question about sizing...

It looks like the V710's are available in 275/40-17 and 315/35-18
It looks like the Hoosier R6's are available in 275/40-17 and 295/30-18

Are these the accepted sizes to use on OEM Speedline rims? I see that the Hoosier also has a 315/30-18 but I'm a little concerned here with sidewall flexing. I'm also concerned with going down a series to 30 on the rear (instead of 35) because I do use competition mode at the track and I've heard changing to a different series tire can throw off the traction control computer.

Can anyone comment here? I've done some searches but havent been able to find this info.

John Shiels

look at overall diameter of the tire not the 30/35. I run the same size front and rear with no problem and many others here do also.

Subw00er

John, so you run Hoosiers on stock rims? Would you mind telling me which sizes they are? I jsut want to be clear as I'm a r-compound tire newb.

AU N EGL

Soundlike Sub it is time for another set of wheels, so you have more tire choices.

XGRANDSPORTX

Not looking to hijack the thread and I know it has been discussed before but which combination is better 17 inch rims all around 18 inch all around or stock size.

Alan

AU N EGL

Alan

The SCCA T1 races for C5s are required to tun 17 all around. a 17" wheel is lighter, rotates quicker, and tires are relatively not that expesive. Plus there are a fair number of scubb tires that you can get from racers for a good price

18" wheels are a nice comprmise to price and weight. 19" are out of the question as they weight tooooooo much, not to mention the cost of tires

So either 17 or 18s would be fine.

XGRANDSPORTX

Dont do organized racing only HPDE, so I can use any size I want. Just trying to get the best bang for the buck if I buy new rims. . Thanks for the info.

Alan

Subw00er

I just bought these oem rims. I didnt realize they were so non standard. I guess I'll research more next time. Perhaps I should justget another set of 17" stockers..

UstaB-GS549

A lot of people run same diameter front and rears without any problem. My track wheels are all 17's. 275/40 and 315/35 are same O.D.

Subw00er

Do you use active handling or comp mode at all? It seems like an inch diameter would be enough to throw the cpu off.

UstaB-GS549

I usually run with everything ON for early morning practice sessions. It's like having a free instructor along dragging rear brakes when you overcook a corner or try to roll into the gas too soon. I switch to either COMP mode or ALL OFF for timed runs depending on track conditions and amount of runoff room. The car is faster with everything off, but you have to be smooth.

I did have a problem driving on the interstate one time, going to an event with same size race tires front and rear, but I think it had something to do with electrical connections as it seemed to be triggered by pavement heaves. It happend also during a practice session that morning and went away later in the day. If it was diameter dependant it wouldn't have come and gone. It has not happened since.

I have never seen any documentation to back up the urban legend about percentages and tire diameters. You could have totally bald rears and new fronts and get a few percentage points differnce using stock tires. I can't believe the computer looks at much other than rates of deceleration and wheel lock-up... but that is just my pet theory.