etchhead

I picked up some take off and have just gotten around to getting them mounted but am concerned the delta in height may be too big..

245/645-18 = 25.5" dia
305/680-18 = 26.9" dia

My plan was install them today, but wanted to check first- what do you guys think?

Car- 7.1GT3 track alignment > -3degrees. Wheels CCW 9" & 12"

flyingpenguin

I can tell first hand that these are great tires, especially if you got them at JPH's great price of $500-600 for the set.

The rear diameter is almost a full inch bigger than stock, which is likely to affect you TC, but I run with it off anyways. Bigger concern is the fact that it increases the rake of the car by 10-12mm which is rather significant. You have to deal with a lot more tail happiness, which can be (partially) neutralized by stiffening front sway and loosening the rear.

Ideally you would want the car's set-up redone (so lower rear suspension and corner balance / align again). I am still driving the car on the street quite a bit, so not ready to make that drastic of a change yet though.

paver

I've never tried them but I wonder if the 305/660 wouldn't be better matched

etchhead

Prob a better match, but looked like they wanted an 11" rim

powdrhound

Anyone have contact info for JPH?

surlynkid

305 MPSC rear on 997.2 GT3 shows specs as belonging on an 11" rim yet P puts it on a 12". It actually shows max as like 11.5. P puts it on an even wider wheel completely ignoring Michelin recommendations, so what do we know.

etchhead

Will send you his eml. That's where I got mine.

RSRanger

Okay to be totally up front, we get what we get with "scrubbed slicks".
I bought "scrubbed" Michelin and Yoko slicks from JP. Sold as 3/4 or better tread.
The tires looks pretty good on arrival. There was prominent rubber build up on them.
At Sebring in one 30 min DE session the rear Yoko's were down to the cords.
I have a strong car but I drive like a grandma.
The Michelin's held up well but I picked up something and the right front was focally cut to the cords.

I am sure JP offers the best tires he can but IMHO it's always a crap shoot.

I do not disagree for a second that using "scubbed" slicks can satisfy DE drivers considering the price of new Michelin and Pirelli slicks. You have to sell one of your offsprings to afford them.

Ranger

mooty

i am not so sure 680 works on street gt's. usually 650

CRex

Those sizes will work and I've seen them run on a 7-3. I'm familiar with the same tire in 255/650-19 and 305/690-19 and they're VERY fast. Just dont run with TC on--but if you need TC you really shouldn't be going on slicks.

I don't know the condition of your scrubs but the DH compound can easily handle competitive pace through 3-5 HCs from new and another 5 at very good pace.