cdbmathews

Can anyone help me wit the offsets and backspacing specs for a standard body C6 racing in SCCA T1 trim?

I believe the rim sizes are Front 18x10 and Rear 18x11, but I need the offsets and backspacing specs.

I understand the tire of choice for T1 is Hoosier A 315.

Thanks in advance,
Chuck.

C&M Racing

Check the SCCA web site. There may be some wheel changes soon. Current rules allow up to 18" wheels. Fronts are max of 10" with rears max of 11". Offset or backspace is not specified but how far they can protrude is. If you follow the data on the web site GCR you will be fine.

cdbmathews

Thanks! I am familiar with the GCR. But, when trying to purchase new/used rims I will need the offset/backspacing measurements. I assume the T1 racers have figured out the numbers?

gkmccready

Pretty much all the wheel vendors know the backspacing necessary to fit the T1 sizes on the car. The CCW guys will probably even just tell you if you ask, but I bet they just calculated it from the stock sizes... stock C6 is 18x8.5 6.53" backspacing 58mm offset, and 19x10 8.11" backspacing 79mm backspacing. My CCW C140 18x10 fronts (just C6 fronts, not T1 specific) have a 7.75" backspacing, I don't seem to have my rear measurements for the 18x11 handy, though.

naschmitz

My CCW C14s for the standard C6 (18x10f, 18x11r) have 7.75" and 9.25" backspacing (+57mm and +83mm offset).

cdbmathews

Again, thanks. What size tires are you running (315s, 285s or ?) on those rims. I assume no tire rub? Can anyone else confirm those numbers?

I am looking at a set of used rim and don't want to end up $1,500 later with something I can't use.

Regards,
Chuck.

SIK02SS

Chuck, whoever you order through, make sure to clarify the wheels need to clear a BBK and cant protrude more than i think 1/2" measured by the rolling width (roll car through chalk, see where chalk line ends and measure that distance)...our negative camber obviously greatly helps us when the tire visibly protrudes ~1/2" from wheel well

naschmitz

You get slight rub at full lock.

Pirelli D2 GrandAm Slicks 285/645 305/660
Hoosier Rs. 295/30 315/30
Kumho V710s 305/30 315/35

cdbmathews

Good points, thanks Chris.

cdbmathews

Forgeline gave me 18x10+61f, 18x11+65r. The front numbers differ by 4mm, but the rear is differering by a more significant 18mm?