ACR-X : Rear end slow to heat up

[schulmann]

We have a problem here with an ACR-X.
The rear end is slow to heat up on a given track. We ride this track in 3rd upto 6000rpm.
This is a very technical race track on concrete (Old Mirabel airport).


This is a "stock" ACR-X with Micheling slicks.
It is very well balanced and predictable.

Rear & front hot psi: 27

Didn't measure the tires temperature but by touching with my hands it was around 90-100F.

The front is very stable, holds and drivers like if it was following rails.
After 1-2 laps the front is ready: Brakes and Tires.


However the rear with the Michelins is "unstable" mainly because it takes 4-7 laps before the tires heat up so they get sticky.
Even after the rear tends to spin out in 3rd gear.

Is there an alignment for the rear so it gets more stable ?
What can be done to get the tires up to the right temperature ?

[daytonprowler]

Contact Jim Stout. I'll PM you his email address.

[TrackAire]

Are the rear tires older and or do you know how many heat cycles they've been put through?

Stout will probably be able to answer this question very quickly....wouldn't be surprised if the hot tire pressures actually need to be lower with the slicks. Let us know what you find out.

[XSnake]

I've never run the Michelin slicks but 27 hot seems low to me, my Hoosiers like about 31 hot. You could also add a little more wing angle which should put more pressure on the rear tires. I'm guessing most of your situation can be solved with a good alignment. I'd have Archer do it if you are anywhere near them

[schulmann]

The car is a late 2010 production. From 2010 to 2013 it was sitting in a warehouse.
In june 2013 it was put on track for the first time.
In qualifying it fishined 3rd but was involed in an accident on first lap (too cold tires ...) So it was rebuilt during this winter.
Since june 2013 it was not running.

Nbr heat cycles ? 10 ?

The front is 10/10, rear is very stable, tail breaking is amazing, the entire car is well balanced.

After 3 years are the Michelins too old ?

Are the michelins very sensitive to 1-2 psi pressure change ?

[RedTanRT/10]

Reach out to Tom Francis at viper race HQ he has a wealth of knowldege and support; tom.francis@viperracehq.com

Those Michelins are really great tires, but deteriorate (loose grip) real quick. I was with Michael VonQ at Spring Mountain a couple of weeks ago (he ran 2 X cars in the series), he told me how many sets he was using per weekend, how great they are and how they quickly their done. Best wishes, Mike

[mjorgensen]

We have a local X that we set up and the rear camber with the Michelins is set at -1.7 and the front is maxed out for camber. Hot pressures for him are 28-29 psi and yes the tires heat cycle very quickly so yours are probably past their useful life.

[bluesrt]

those tires have been heat cycled and then sat for some time, I would start off with a fresh set of tires front and rear. once they are heat cycled and then sit,they tend to crystlize and not heat up to par grip as they would when new,and figure on turns,the back end does not have the heavy force that the front has,especially on tight turns...

[schulmann]

I was wrong, the tires are from 2013, the old one were thrown out.