Tireshake 4link setup

I had this problem for a while know. 7.5 Steelchassie. Alcy 540Cui, HighH kobelco 8-71 about 20Psi, powerglide, gear 4.34. I´m having tireshake 9-10 passes.. tried a retard controller this weekend and knocked off 10 degree 1.5 sek and had a 60f 1.18 without shaking the tires, but it came back when we went to 8 degree. we run 6 psi tire pressure my 4link IC length is about 55inches and height about 4inches. Any ideas? What happens if you put your IC higher?

 

raising the instant center will load the rear tire harder. What RPM do you leave at? It is hard to tell exactly what your car is doing and what steps can be taken to remedy the problem without seeing a video or a data graph. With that being said, I will say that tire shake can be caused from not enough wheel speed which wont allow the car to get 'up on the tire'.

 

I start at idle and it start shake at startline or a couple of feet down, adjusting shocks doesn´t do anything. How do I get more wheelspeed? It get´s even worse with more power..

 

shake

Tireshake is the whole deal with a convertor car. The window between going fast and shaking can be small. 2 degrees on the hit can make/break the setup. My experience says you can't shake it with low hp. You had a soft setup that worked. Give it a little more of what it wants and improve the 60ft. Rear shocks need stiff valving and launching from idle probably won't work.
I can run 1.03 60 ft on a good track or soften it all the way to a 1.15 with the timing and blower overdrive. I launch at 3200-4000 on a 2 step.
I've shook the tires at high and low wheelspeeds but it's always from being too agressive.
Mike

 

Tire shake

I can make my car shake so bad just by dropping the top bars, did it once just to see what would happen and I did it before the rear tire hit the 60 ft cones. Personally I think its in the rear suspension. Soften the hit a bit with the rear bars and then sneek back up on it. We went with a rear 4-link software and it became much easier.

Corey

 

We run quite a similar set up in an altered and found anywhere 6 psi or lower shakes the tire. We always run 6.5 to 7 psi and it helped alot. Just my 2 cents.

 

Comax racing, what do you mean by dropping the top bars? Lower the IC?

Overkill69, I thought It would be a softer launch at idle? but I never tried anything else.

 

4-link setup

Sorry, I guess I should have said "moving the bars" not "dropping the top bars". I meant it as more of a general term not a specific tuning manuever. I can look at my notes to see what I did exactly. Basically I was trying to say that I have been able to tune tire shake out with the rear suspension.

Sorry to confuse anyone.

Corey

 

tire shake

we had problems with tire shake when he had 2.20 gear in the lenco and 4.56 in the diff.
we went to a 1.80 in the 3 speed and the car calmed right down!!

 

shake

You didn't say what tire you run but your gearing is good for 33.5to 34.5 tires. You have the timing control so you don't need to soften it launching at idle. Just dump the timing to calm it down. I could never get a reaction time or decent 60ft from idle.
The 4 link IC can make it more shake prone. I think you're in the ball park but you'll have to give a lot more chassis details. Promodzone.com might give more info.
My chassis originally was setup for a clutch and it shook easily with a powerglide. I lengthened and lower the IC slightly and it seemed to take some bite out of it. It still shakes easily but i'm throwing a lot of power at it and it's heavy.


Mike