I am pushing the car so hard that on Dunlop slicks I now only get 3 track sessions.

Session #1 - tires are awesome
Session #2 - tires are very good ( .5 seconds slower)

Session #3 - tires are not bad (1.0 seconds slower)

Session #4 - car will no longer handle at my normaly operating range (2.5 seconds slower)

After that the car is terrible to drive at speed. When I say terrible, the turn in has virtually all but disappeared. So I have total understeer at that point.
I can turn the wheel and virtually nothing happens; so I use the throttle to rotate the car, which is fun, but very slow. The front tires are like driving on ice after that.

Background -

Alignment good
Tire temps good
Tire pressure cold & hot good
Tire wear even

Front tires medium-soft compound
Rear tires medium

Locked rear spool (ie.. no diff - the car came that way)...

For the first 2 sessions, the car is a blast to drive. After that the fun quotient starts falling off...

This compound setup is the recommendation from all the Dunlop teams I have spoken with and the Dunlop engineers.

Even after 3 sessions, the rear grip is still pretty good. The front is just gone.

So I have been thinking about trying medium compounds on the front to see if they will last like the rears appear to be.

The balance of the car will not be as good if I do that, but it may not be all that noticable.

Additionally, the car may just be setup to have way more understeer. I could work on improving the mechanical grip in the front while reducing a little of the rear, but I like how it handles with good tires.

Yes, I could slow down on the subsequent sessions, but that is no fun.

I would like to come up with a more cost effective solution that still provides near the same performance.

One possible idea is run 2 sets of new fronts for every set of rears. But that means 1.5 sets per weekend; which I would rather not do.

I am thinking about trying Pirelli which are quite a bit less expensive to see how their performance and longevity compares. Yok & Michelin are also quite a bit less expensive. But it appears I can run the same alignment settings for Dunlop & Pirelli, and the sizes are about the same...

I do have 1 more event @ VIR in a few weeks, so I need to get tires for that event. It is a DE, so I can do more tire testing without worrying about qualifying...

Any ideas ?

Now I know why the IMSA teams dont use the tires more than 2 stints...

TIA,
Norm

 

I think the Pirellis will give you the same issues. My car wears out fronts much quicker than rears too. I was running D6 (hardest) up front and D4 in the rear.

I've just tried out a set of used Hoosier "endurance" slicks that are run in the Grand Am Cup SGS class. I am guessing that they had about 2/3 life left in them when I mounted them. I put 5 sessions on them last weekend. They are quite a bit harder than the Pirellis and I had to adjust my driving style to compensate. In my first session out, I was very surprised to find that I could get wheel spin coming out of every corner. My pressures were a bit high but not enough to account for the wheel spin. I attributed this to the hardness of the compound. I adjusted by being more judicious when getting on the gas and everything seemed to work out OK. I also had to adjust my braking as they were easier to lock up. When I forgot, it got interesting quickly! The relative grip from front to rear was pretty good...I wasn't under/oversteering too badly. As for overall wear, I didn't get a chance to evaluate the tires before I had to load up and go home...that will have to wait until I get the car into the garage next weekend.

 

Glenn, thanks for the info. Isnt D6 the softest not the hardest (I have not used Pirelli so I am not sure).

Performance is key but I would like to add longevity. Those 2 may be mutually exclusive and I might have to rethink and try some harder compounds...

Norm

 

Glenn,

According to :

http://www.bobwoodmantires.com/pirelli/pzeroslick.htm

D3 is the hardest and D6 the softest. I just want to find out what is correct since I may try them...

Thanks,
Norm

 

Glenn:

Did you change the set up on your car after you changed to the Hoosiers? I am under the impression that the car needs to have a different set for the different slicks that are out there. I had purchased a set of Yokes for my MY01 Cup car from Woodman and was told the tire has a different camber than the Pirellis it was originally set up for. I think he was right since the laps times on new Yokes were about 1.5 slower than the Pirellis.

 

Jim,

Why did you stop using the Pirellis ?

Also, how well did they last ?

Norm

 

Sorry Norm...I meant D4 in the front and D6 in the rear.

Jim...I did not change the setup and that may account for some of the problems I experienced. I have no guidelines to use for setup so I'm going to have to figure it out over time. If you've got a starting point, I'd be willing to try it!

 

I only used Yokes for the one race, I changed back to Pirellis. The Pirelli is a great tire, but tends get greasy quick.

 

You may want to reduce downforce in the rear before You chase the rest. Unless the push is only in low speed reducing wing in the rear can significantly aid front bite in mid to high speed turns.

 

Glen, thanks for the ideas.

To further clarify - Once the tires go away, the understeer is both slow speed and high speed turns. Mostly entry turn-in to apex... once the fronts go away, it seems I just linearly lose the grip through the whole operating range....

Thx,
Norm

 

You have your work cut out for you trying to keep front tires in shape with a spool and wide rubber in the rear. I never liked pirellis, sure they were fast for the first couple sessions, but after that they were down right treacherous if you wanted to go fast. It was like you running two brands of tire; new pirelli (less than 3 sessions) and old pirelli. New pirelli was both swaybars full stiff; old pirelli was front full soft and rear full stiff to get rid of understeer. I also had trouble getting the front end to "bite" at turn-in even with D6's in the front. I love yokohamas, they fall off gradually, they break away much smoother, and they remedied the low speed understeer problem we were having.

 

Phil,

Your experience with Pirelli is pretty much the same as mine with Dunlop. Even with the sway bar settings.

Has anyone tried Michelin slicks ? How do they compare ?

Norm

 

Norm,
You just need to slow down! Seriously, talk to John Wright and see what his customer's 993GT2's are using. I thought they had changed to Michelin's from the Dunlops but not 100% positive.

 

Gregg,

Will do. Thanks,
Norm

 

ngoldrich:

A suggestion, have you tried "scrubbing" each set of tires before using them hard?

Scrubbing is mounting a new set, going on track and do 1 or 2 slow laps (about 50% speed) then take tires off the car, leave for 3-4 hours.

I have been told that it helps "cure" the tire. Call it what ever you like, in my experience, MOST tires "stay good" for 1 or 2 more heat cycles.