Tire Shake Problem

[Longo]

Im have a problem with tire shake, but not off the hit, about 30' out! The car # 3220 with 52% front 48% rear, its a ladder link car with a 22" lower bar and a 10.5 spread a rear bars, double adjustable KONI rear shocks ( Top setting at 8 clicks bottom at 6 clicks ) and 110 pound springs, strut front shocks ( at about half setting ) with 3" of travel, 31x13.5 Hoosier Quick Time Pro with 9.75 psi, 2 speed with a 1.69 first and 4.30 rear, 400 hp hit off the trans brake with a 3100 rpm 2 step. Ive put tubes in tires and even had the conv. loosened up for more wheel speed with no help! Ive tried to pull timing 5 deg. at 6100 to 6700 ( where it shakes ) and tried to add timing with no help! Best et 7.80 with a 1.13 short but with tire shake! Any help would be great!

[Pegasus]

I am looking forward to some knowledgeable answers to your question.

This past weekend I had the same problem. I left good then went into shake. I short shifted to high my 2nd stage of NOS is on a button I would go on and off the button. Still nothing did help. I really cannt explain how bad this was I couldnt hardly see. Anyone with any smarts would have shut it off I have never been accused of being smart. It shook the full 1/8 mile up to 152 MPH.

I dont run tubes or beadlocks. I now see why others do.

My trouble is the new tires I bought were non S tires and I think my help dropped the tire pressure to low. The non S tire is 2lbs lighter thats 4lbs of rotating weight. It didnt work. My new tires will be 10.5 S.

[John_Heard]

Never had the issue myself, but I have heard many people talk about air pressure when dealing with shake, also the clutch being too aggressive/locking up too soon. Sounds to me the first thing to try would be whatever stiffens the sidewall - air pressure, tubes, stiff sidewall, etc.

[Longo]

Don't get me wronge the tubes did help a little but people told me that, that would be the fix and it was not! The conv. got lossened up thinking like a clutch ( coming in to soon ) it also help a little but shake is still there!

[John_Heard]

Don did you have that kind of issue before you changed tires and went to the non-s sidewall?

Longo maybe try a different set of rear shocks? You got a buddy with a set of Stiff Valved Afco's or Santhuffs you could borrow to see it that makes a difference?

[Pegasus]

Just once. It was nothing like this. It was in elims at the first race eveytime I hit the second stage it would shake. I think after they ground the track it hooks alot better on the big end. Last year at this point my car would spin.

I have been around fast cars its normaly to much clutch or down on power. I run over 150 MPH in the 1/8 so I dont think im down on power.

Im sure new 29.5-10.5-S-15 MTs and more air will fix my car.

[Longo]

I guess im on my own with this one, not even the experts want to touch this one!!

[aitch o]

Add air.

[want-a-be]

Add air.

I agree with more air pressure. Start at around 11 psi. Adjust 1 half pound from there. As the car sets right now....how many wrinkles are in the side walls?

Don

[John_Heard]

Some reading material...

http://wediditforlove.com/techtalk19.html

http://www.frankhawley.com/pdf/Article07.pdf

I like the part about Big Daddy having a list covering his whole trailer door on what causes it...

[Longo]

Don if you go to www.dragracinginc.smugmug.com there is a picture of the car on page 18 of a 84 Camaro ( Longo Racing on hood ) Canada day June 27-28 OSCA Thanks Tell me what you think!

[want-a-be]

John,

This article, http://wediditforlove.com/techtalk19.html is a great read. Anyone one who is battling tire shake ought to take the time to read it over.

I've hung around a well known Pro Stock Team, Now retired, for years. Most of what I, Think I know, comes from their teachings. I was always told that the car needed to leave up on the tires with just a bit of spin. If it does it always MPHed better. Hook always sounds like the way to go. But too much of it and your bogging the engine or risking going into tire shake. MOre air pressure is a way to fine tune the " too much hook " issue. If thats not enough then a change on IC length or height may be needed.

Longo,

The way I was always taught to seek the initial tire pressure like this. Air the tire up just enough so there are no wrinkles in the side walls. Make sure both tires are the same pressure at this time. Let the air out 1 to ­1/2 pound of pressure at a time until you can just make out 1 wrinkle in the side wall. Start tuning from there.

I'm sure you're well aware of this. But not all gauges will read the same. I have seen the same manufacturers gauges not read the same. Some won't even repeat their readings on back to back tests. This is one of the reasons the guys who taught me about this stuff use what I've mentioned above.

Hope this helps out.

Don

[want-a-be]

Car looks good. How long is it on the wheelie bars? How hard do the wheelie bars hit? When the car sets the front wheels down,...is it a slow smooth or a fast transition? When the they do come down,....how much time after this event do you go into tire shake?

As you can tell by my last post. I'm not talking about wrinkles in the side wall as your leaving the line. But as the car is setting still on a flat even surface. I've seen some cars that didn't need much of a wrinkle at all.

Send me a pic, or post one here, of a rear tire set at the pressure you mormally run an also as I asked you to try to set it up as. I'd like to know what pressure both tires are at when you've taken the pictures. Remember that I, we, will need to be able to make out how the wrinkles in the side walls look. So you may need to play around with some angles for the picture to get what I'm wanting to see.

Hope this helps out.

Don

[Longo]

Don, first of all I would like to thank you for taking the time to help me out! Thanks! Now as far as the wheelie bars go they barely hit, it just lightly take the caulk of the wheels, its on the bar for about 2 to 3 feet out. The car does not get higher then the picture shows off the line! As far as the front end goes, it seams to come down smooth and the shake happens shortly after that! I will try to get some pic. of the tire at our shop on the ground as soon as I can!

[want-a-be]

You're very welcome. This is a very good forum to hang out in. Lots of good guys more the willing to help out.

Sent you my contact information as well. But forgot to add an e-mail if you wanted it.

Don