Right I am at the end of my tether with this... I have a track 996 RWD Turbo weighing just under 3000lb and have been running Pirelli Slicks, 645 fronts / 650 rears, the probem I have is the rears start going off and the car starts squirming bigtime. My understanding is that the 650 (most 650's) just do not perform well and a lot of heat is generated through the tire thus leading to poor performance. I have gone into detail with Geoffrey, Rad (NJ-GT), Keith and Rick (thanks again guys) with this and it just doesn't look like I can run the size of a 680 Michelin under the rear end without removing liners and all Intercooler ducting work, TBH I heard this before but thought it would maybe just squeeze, but it is now extremely doubtful.

So I am back to my original plan... Someone tell me a 650 rear that is out there that will perform well... Rad has strongly advised against the Michelin 650 as it does not perform well, Rick has mentioned the Yoko works ok, but I want to hear more options before I spend more money.

 

I have heard and read the same thing as the 650 are more of a front tire. As for the Yokos, the specs specifically warn against using the 650 as a rear tire unless on a fairly flat track. Might be worth a try. May try a slightly harder compound than you were using to handle the extra heat so they don't go away faster than the front.

FWIW

 

Thanks Gasser... what about Hoosier Slicks anyone any experience with these?

The new R100 series

 

I have used 320/650 hoosier R100s on the rear of my early chassis car (approx 350 rwhp) and they work fairly well. I run a 12" rear wheel.

 

Clay, your car is pretty light is it not? BTW thanks for the wing help. Car ran as predicted 2 secs a lap faster with the wing and wider track. This was after one 20min session so there is more time with some tuning.

 

Thanks Clay... how do these new Hoosiers compare against the likes of the Michelins?

 

Guys, please get your facts correct..!

Yoko specificly says the 280/650/18 tire was designed as a front tire and should not be used as a rear...NOT THE ENTIRE 650 Lineup..!

The 320/650/18 was built as a rear and works really well in this situation. It comes in a hard compound and will do the job very well.

Hoosier is another really good choice....I've had really good luck with them in other sizes....

 

Guys... I am not completely ruling out the 650 Michelin Tire, I know Rad was against it but I was talking with one of the team members from here http://gt3europe.com/teambio.php?countkey=1 and he tells me the only real issues they had (but most had) was Monza as it is hard on tires anyway.

Look at the specs of the jaguar above, using 650's all round and weighing in around GT3 weight

 

I've used the S8C compound Michelin tire for years and can tell you they fall far short of the modern compounds in the Hoosier or Yoko.... Have you looked at Dunlop??

 

Now your messing with me mind Rick

I have had a couple of others telling me the Michelins (not Cup Spec) are pretty good, obviously not as good as Cup Spec but still up there.

decisions, decisions, decisions

 

Try the Dunlop.. I used them exclusively with my heavily track prepped 996 GT2... Was able to get power Dow keep traction for over 30 min.. Yokos were gone in 20 min dropping a quite a bit of time per lap!!! Don't know much about the new Hoosiers .. Have heard a lot of good about .. Buy I know the dunlops really do the trick

 

I do understand that the tt need lil different tire than the NA

 

Sorry to confuse you..

I raced last year on the 31/71/18 and the 27/65/18 Michelin in the S8 and S9 compounds. They are OK, not great.....

I think you can do much better on the Yoko or Dunlop. I would consider the 300/650 or the 300/660 Dunlop if it fits. I would say the Dunlop is a Far better tire than the Michelin S8/9 tires and the a little better than the Yoko...

But I would seriously consider the Hoosier First..!! The 320/650/18 looks like a good one.

Hows that for confusion...

 

Now I have heard of some mixing tire compounds but this is takin' the ****

FL Michelin
RL Yoko
FR Dunlop
RR Hoosier

 

A 320/650 slick definitely has a higher load support than a 270/64 or 285/65 tire. Running low profile slicks on flat tracks should be fine but you're pushing the limits. Moving to tracks with elevation changes or high bankings puts more stress on the tires. A RWD 996TT puts more torque and power to the rear wheels than a GT3 Cup. Porsche has been using 680 rear tires in the factory GT3 Cups since 1998 (same chassis as a 996TT), and even taller 31/71 on the faster race cars (993 GT2, GT3 RSR). Even the lightweight F430 Challenge uses a 680 slick.

Michelin makes a 300/650 for the front of the RS Spyder. Check with the tire manufacturer whether your tire choice is suitable for a 1000 lbs/corner static weight, high downforce (add another 500 lbs per corner at speed), high power, RWD 996 TT. I think somehwere on RL there is a video of a tire blowout with a 996TT running low profile race tires in the back. The 996 TT with a GT3 Cup style wing, on a high bankings track on corner exit can easily put in excess of 3000 lbs on one rear tire, or over 4,000 lbs if there are bumps.

If you want a low profile tire, fit the widest tire available, so there is enough load support, and get the endorsement from the tire manufacturer. You have already experienced the Pirelli going off when you push the car on fresh tires (650 profile). My 997 GT3 RS with the 24/64-27/68 slicks was very gentle on the four tires, of course this was not a powerful car, but it was heavy (3,300 lbs) and with some fair downforce in the rear.

I would rather go with a taller rear tire, updating the electronics and running a 680. A 650 could be fine for light 911 cars with lower power, less downforce, on flat tracks.