tire shake ideas?

[cad500justin]

a friend of mine is battling tire shake issues. Here's a good slo-mo viddy. They've tried different tire compounds and pressures, but no luck. blown alky sbc, 7.60 index, glide, leaving flat on the converter. If they hop up the motor to beat the shake, the car runs too fast for the index.
They're talking about stiffer sidewall tires.
i keep thinking just raising the tire pressure until it quits, but i've never dealt with this problem either.
wonder what lowering the launch rpm or a higher stall converter?
Maybe using a pneumatic throttle controller like what Greg has?

[gregm784]

I believe this is a tire issue.  i think it can be made to work (more timing, more run at converter, to get tire speed)

[32bantam]

Longer...lower wheelie bar would help (single wheel). It is jumping up at the hit...on the wheelie bar...then the bar slams it back down ect.
Not sure where you are with tire pressure....but 10 lbs might fix it...you NEED wheel speed, not spinning...just not wadding the tire up.
If 10 fixes it...try 9.5...then 9 until the problem comes back, then you know your tire pressure for those tires on that car.

[Draw 3D]

I'm no expert but looks to me that the wheelie bar is too low and too much air pressure

[dusterdave173]

I am no expert but my friends car was acting similar with blower they upped leave RPM to pretty high RPM and it quit shaking and started running great  I mean it was like high maybe 4000 but car settled down and started really showing out
also bar may be too low
a good leave is a balance between leave RPM--tire pressure--and bar height
If my car is driven right it is perfect--if any of the three is off it can look awful
Tire pressure on mine seems to be the item that makes the least diff
bar height Critical then leave RPM
I have had several pals go from injected to blower and high leave RPM fixed them all after many trials

[225digger]

im no expert either...but the rear engine car i had yrs ago it liked less air, it had a 632 that ran low 7's ... anything over 5.5 it shook i think the sweet spot was around 4.75-5psi to get it perfect...... think i left around 4800.  it was a big hoosier tire i ran cant remember the numbers but it was a very popular tire around 2009.... couple times i was solo and got strapped in and had to wait to run and couldn't check psi and i know they got hot, instant shake..... those bars do look like they hit so that could be upsetting it

[fuel749]

Some other info might help.  Trans low gear?  Rear gear? What is that RPM flat on the converter?  Are you saying the problem goes away when the car is hopped up? 

[Curly1]

Okay, I am not sure on this but here is my two cents and what I would do. I would lower the wheelie bar so it slows the wheelie down before it unloads the rear tires. regardless the rear tires are spinning then hooking hard.
I am curious, what is the rear gear ratio and converter stall?
Is it a hardtail?
Also what tire pressure are you running? May need less but hard to tell with it unloading rear tires.

[wideopen231]

OK I will follow the no expert thing,tire shake wise few are. I will say anytime I have tuned on a car with tire shake,more tire speed was answer. On our funny car if shake a hit more rpm was answer and we left at 6500 to 7000 as was.If shaking thru gear more clutch got rid of it. Now you can go oppisite direction and get rid of it some times and at times that better approach.More than likely you will loose performance backing down and go quicker being aggressive.

 How yo get more tire speed? More rpm,suspenion. wheelie bar and or pressure. While less pressure by reason would mean more hook .I have been told and found true that most of the time less will allow more slippage,but like most thing depends on setup of other factors.

From video I would say car has more than enough tire speed and shake starts as car is unloading tires from wheelie bar hit. In your case I would approach wheelie bar first while leaving launch alone then pressure.