Front Wheel Wobble

I Was Watching The Funny Cars At Seattle And Saw One Of Them Get A Front End Wobble Right After The Burnout And Have Seen Some Alcohol Cars Do It Also What Causes This. And How Do You Stop IT. Once It Starts Do You Just Let The Car Settle Down Or Does The Braking Cause It-- Just Curious Thanks Jamie

 

I have had this happen a couple of times in my alcohol funny car. It seems to happen to me if the burnout RPM is too low. You can try tightening the steering damper to help prevent it. Once it starts you have to get the car stopped as quickly as possible because you have no steering control.

It just plain sucks!!!

Scott

 

Yea Mike, just like the front wheels of the shopping carts we all push, a low speed wobble because of the postive caster. I see the dragster do it while backing up to fast, knock on wood! I don't know how many racers have lost because of trying to get a hold of the wheel and set off the parachutes while backing up, from Top Fuel to Top Alcohol dragster inculding Big Daddy.
One more good reason to have the levers instead of air buttons on the wheel.
I just never looked at the funny car really close untill lately. That was way cool to see the tires dance under the front of those funny car bodies. And Mikes right you just get it stopped asap, and start over again especially backing.
Andrew

 

I cant rember who makes it ,but there is a shimmy damper just for this problem. some one jump in here and spill the beans, Scotty Mac, i think Mikey or Victor has one on there car?? P/S i think if you run 10 degrees or less plus caster you wont have that problem.

 

We've never had that problem with any of the cars we have ever built, mainly because when we build the a-arms we don't lay the front pins back very far. I've never understood why they lay them back so far in the first place...maybe someone can enlighten me?

 

the more positive caster you put in a car causes it to just about straighten the wheels by themselves going forward at speed. i think the mormal is 7-10 degrees positive. the problem with alot of caster is when going slow or sitting still is that when you turn and go past center the wheels will drop to the side you are turning . like pushing something over a hill. once you reach the top, it takes off on its own. my old, old car had 12 degrees and when backing up you had to have a gorilla grip on the wheel and back up slow. if you turned to much backing up the front would take off to the left and right. all you could do is let go of the wheel and grab the brake as hars as you can to stop the car. then start backing up again. if you try to hold the wheel it will brake your wrists.

 

Positive caster makes the car go straight, unfortunately when backing up the car now has negative caster, witch makes the car shimmy,

 

I guess that makes sense...but now I ask, when in a FC do you ever have the steering wheel straight?! lol.

 

When you put it in the trailer.

 

VW has a damper for real short money (under 20 bucks)

 

Victor does have a damper on the car and I haven't seen it shimmy since I've been crewing the car. I don't remember who makes it but S&W rings a bell. I'll try to confirm who makes it and post my findings.

 

Jamie,
We had the same problem earlier this year, EXCEPT it happened on the burnout, no problem, then at the end of the run, on a solo pass thank GOD, and at about 100 mph!!! Fortunately, the car was going straight and I was able to stop it without incident. We installed the S&W steering dampner and check front rotor runout, .014" and promptly installed new rotors. NO problems now. Hope this helps...Keith

 

the one from s&w is simply a damper off a motorcycle.

 

We had this problem, even with the dampner, and had to add a second one. Haven't had a problem since. I just went to a local motorcycle shop, and they were able to get one. Just remember to get one that's adjustable, or it will be hard to turn the wheels when you're not moving.

bryan

 

I had that shimmy a few times when I was stopping after a burnout. I looked the car over head to toe and found a loose caliper in the rear. When I tightened that it never did it again. I don't use a lot of brakes at the top end. So I never noticed it there.

 

We had the same thing happen to our blown altered but it only happened in the braking area after the run, we thought it seemed to be related to weight transfer, we fitted the S&W dampner kit and never had a problem since

Marc