Hoosier Radials
 

Curious as to what kind of air pressure some of you run in your radial slicks. We have a set of 31.5/13.5 R 15'S and are running them at 14 lb's. It feels like the wheels are rocking back and forth in the sidewalls at the finish line. Someone suggested 21 lb's ? Thanks.

Re: Hoosier Radials
 

I typically run 21-23 psi in my 30×9 Hoosier radicals. Have had as much as 28. I would suggest 18 and go up from there until you find a comfortable setting.

Re: Hoosier Radials
 

I run Hoosier's 32.0/13.5-15 radials. If I get close to 15 lbs, I get a radial wobble. Years ago I tried more pressure, but only made it worse. Seems like the smaller tires can take way more pressure and not show any wiggles. Maybe it's the greater lbs of weight per square inch on the surface area with the small tire. Don't know

Re: Hoosier Radials
 

Thanks , so do you run less than 15 or more to get away from the wobble?

Re: Hoosier Radials
 

21 is a number we have been hearing. Right now it wobbles bad enough that you can see it from the fence.

Re: Hoosier Radials
 

I run under 15 lbs all the time. My rule of thumb is....increase the tire pressure until you subject yourself with radial tire wobble....then go lower in psi.

Re: Hoosier Radials
 

radial wobble has nothing to due with air pressure and everything to due with track prep and chassis setup.

Oh and I run 21 psi my 32/13.5 radials. ;)

http://classracer.com/classforum/pic...pictureid=6316

Re: Hoosier Radials
 

I think that going from 14 -21 would have to help...no? Only been out three times and this last week was the first for the wobble.

Re: Hoosier Radials
 

I posted this photo for a reason. My car was killer at this track/at this race and IIRC, I ran five, 5.60s in a row, won the boggie race too.

Then once the sun went down and the track cooled, it was a different car and I had radial wobble every pass and had this not been an 1/8th mile race, I would have had to lift.

Point being it was the track not my car.

Left that track, made no changes and the car was right back to perfect launches, passes where ever I raced it.

BTW, that was the last time my car has had radial wobble and that was 7 years ago this November.

Re: Hoosier Radials
 

Ok. makes sense as that was the same for us. This past week was the first night time passes and that's when we started having trouble. Thanks for the help.

Re: Hoosier Radials
 

I don't know what width wheels you have. I found my 13X31" Hoosiers hooked harder, and felt more stable on wider wheels. Went from 12" to 14" wide wheels, no more wobble at all.
Then, I bought a second set of 14" wheels & bought a pair of MT tires, same size. A-B-A testing during a track rental showed the MTs 5 hun quicker, close to one MPH faster. I use 13 to 15 psi to help corrrect my lights. Both dead hooked, I'm thinking the time differences were maybe sidewall design?
Been so long, I don't remember how much air in the Hoosiers. Have run the Mickeys as low as 12, still no wobble on the 14" wheels. Both brands of tires left better foot prints on 14" wheels.

Re: Hoosier Radials
 

I've experienced radial wobble, and as a result, studied it intensively, looking for a cause. Much as I hate to say it, Ed Bigley is probably the closest to what I've learned. The prevailing theory is that the car does not come down from the wheelstand entirely evenly (i.e. one front wheel touches before the other) and that sets off the rocking motion, which gets worse as you progress down the track. Here are other things that affect, but do not eliminate it: shock settings (tighter shocks on the rear tend to reduce it); track prep (as Ed mentioned), but for me, it had a VERY minor effect; and finally, tires themselves. Hoosiers are "credited" with being the most susceptible to wobble, Mickeys are supposedly better and Phoenix allegedly won't wobble at all. The tire pressure everybody talks about for a relatively big tire is 18-22 psi.

Re: Hoosier Radials
 

Mine does some kinda big wheel stands at times, and neither that, nor different (or lack of) track prep, ever effected the "Hoosier wobble". Wider wheels stopped it all anyway. Before I had it back-halved at EastTexas Race Cars I ran 9" tires on 10" wheels. Then mini-tubed it to run 10.5" tires. Those liked 12' wheels. I loaned my 13" Hoosiers on 14" wheels to a friend that was having "the wobble", and it stopped his too. He now has wider wheels & no wobble. He still uses Hoosiers.

Re: Hoosier Radials
 

That's great information, Ed (Wright). I experienced absolutely nothing in the way of wobble on my previous Cavalier, but this one is prone to it. I have 14-inch wheels as you suggest, but hate the condition so much that I've given up on Hoosiers and switched to Phoenix radials.

Re: Hoosier Radials
 

Thanks for all the info. I'll measure the wheel width tonight so we know what that is. It's a Chevy II so it gets up a little. We also raised the launch rpm by 600 to 3800. All of this including the wobble happened after that. I will pay attention to how the car lands as well. VERY helpful and thanks to all.

Re: Hoosier Radials
 

14" wheels and 4200 launch RPM.

and I've been running radial slicks longer than most everyone posting on the net as well I have logged far more runs than anyone on them.

Re: Hoosier Radials
 

Bet your better looking, with a bigger Willie too. LMAO!