The dreaded drag radial wobble

[kevinlc]

Looking for pointers on how to fix my issue. 68 dart with stock front suspension and four link rear. BB motor with 821hp and a 727. The tires are Goodyear 31.5 x 31 x 15 with 18psi. Car makes it to the 1/8th mile then the steering wheel starts moving left and right and the car wobbles really bad. Ran bias tires for years and no issues. Switched to radials and adjusted the shocks and this happened. Any thoughts on how to fix this. Thanks for the advice.

[dragracerray]

How much caster do you have? Ray

[Mark Howes]

No Fun!

Having been there and done that with different cars over the years I can tell you that many answers are found in the front end not the rear.

The lower psi of the bias ply masks underlying issues already in play. I have seen the following cause radial wobble....
* Bad front shock
* Bad rear shock
* Loose Idler arm
* Cracked steering box mount

Hope you find it easily

[novassdude]

do you have radials front and back? Mixing them made my car drive terrible on the top end.

[Mike Pearson]

Anti roll bar might help with the 4 link. Try running the same pressure in the radial as the bias for a staring point. I run mine a 12 psi and have minimal problems with the wobble. Make sure everything is tight in the suspension and no slop or loose bolts. Radials need to dead hook. No wheel speed as some call it.

[kevinlc]

I do have bias front tires. There on a four inch wide wheel and an anti roll bar in the rear. Front end was setup for racing but that was a long time ago and I don’t remember the specifics.

[Roy Kinslow]

Originally Posted by kevinlc

Looking for pointers on how to fix my issue. 68 dart with stock front suspension and four link rear. BB motor with 821hp and a 727. The tires are Goodyear 31.5 x 31 x 15 with 18psi. Car makes it to the 1/8th mile then the steering wheel starts moving left and right and the car wobbles really bad. Ran bias tires for years and no issues. Switched to radials and adjusted the shocks and this happened. Any thoughts on how to fix this. Thanks for the advice.

I am not a radial expert but I have worn out a few sets of similar sized Hoosier radials. I will offer what I do and don't do. I only have about 600 hp first of all. I think radials are more sensitive to track temp and prep. I never run more than 13 lbs of air, at 18lbs the outside 2 inches of tread doesn't contact the track. Maybe you are running about 5 or 6 lbs too much air pressure ,that's a lot. I have a four link , no anti roll bar, bias ply front tires and I routinely switch from radials to bias ply with basically no change other than air pressure. I would consider where your four link is also ,perhaps shorten it up some so it keeps the tire planted and a shorter setting has more triangulation and thus less roll tendency. I believe that as the tire unloads and slips is when this problem happens. Most of the cars with lots of gear and weight transfer seem to work fine. Good luck!