Hey guys have a couple of questions. I put new Hoosiers 29.5x10.50x15 slicks on my car took it to the track and have a issue of the car swaying back an fourth slightly past the 1/8th mile mark. I have 12.5 psi in both tires. The car ran 110 mph/1/8th and 125 mph in the1/4 on motor. I was going to spray my single stage 350 shot but did not want to take the change on wrecking the car, so ran it on nitrous 6.01@116 1/8th. The car had the same issue. I have check all 4 shocks, front and rear suspension I can't find any issues. Is it possible there is not enough air psi in the rear tires? I have 30 passes on then car never had this issue and the only things I changed was rear tires, had MT ET streets with tubes and now Hoosiers slicks with tubes and these are not stiff sidewall tires. Any Ideas? Thanks Matt

Are these radials or bias ply slicks?
If radials probably their to low on the pressure, if not radials I would call Hoosiers west (559-405(maybe 408?)4612 or Hoosier factory 574784-3152) and ask them about their recommendations
Are the new tires on the same wheels as the M/T where on? If not look closely at the new wheels and their fitment to the axles and brake drums also as well as the pressures

Hi, these are bias ply slicks, brand new . I did call Hoosier tech line and he said to try 12 psi! These tires are on the same rims the MT were on.

hold the steering wheel still, let the rear end waggle back and forth, and enjoy the ride!

that's how slicks are


You can start with 15 psi and work your way to lower pressure if they spin at that high of pressure.

btw I run 20 psi in the 9x29 slicks on my altered wheelbase chevy. Hooks ok, and less waggling

Sounds like you have radials on the front

How much does the car weigh? The only times I ever had that happen was when I went too low on air pressure in the rear tires. If this is basically stock weight, I wouldn't go down on pressure. You will probably end up between 13 and 15 to get you back to where a stiff sidewall worked.

As other have stated, go up in air pressure. Sometimes after your slicks get a good many runs on them the car will start to feel different, its because the sidewalls are getting weak. Going up in air pressure is an easy fix. The Hoosiers you got might be a softer sidewall than the MT thus the reasoning you need to go up in air pressure.

Curious as to what tires you run up front ? On my 63 street car I run a 215/70-15 radial tire up front. Its not as fast as its a 10.70 car on good days but I used to run Hoosier QTP tires on the rear that were 29 x 10.5 and they are a bias tire. I also would get some sway/walking in the traps. So one day I tried 30 x 9 Hoosier radial slicks and what a difference. Heck now and can let go of the steering wheel in the traps as the car goes nice and straight with no walk or sway. And I believe it was from me mixing a front radial tire to a rear bias. Now I run about 18 psi in the radial slicks and I love them because the car hooks good on them and goes nice and straight. Ron

Thanks guys for the info, front tires are MT 26x7.50x15 bias tires which are the 8 ply version with 35 psi. Car weighs 3400 pounds with me. I use comp engineering 3 way shocks set to 90/10. What would be a better shock to run? Would it be better with shock set at 70/30 or 60/40? My 60ft that I just ran was 1.35 on nitrous with the 12.5 psi in those new Hoosiers! Thanks for the help!Matt

Did you measure the circumference of the tires? If they are more than 1/4" different you will get some swaying.

the only way to find out what works best on YOUR car is to test each of those settings AKA aside you may need to change the shock settings(front and back) depending on track conditions
I have

Check the diameter on each tire

Check both tires one measures 96.0 and the other 95 7/8! Hoosiers advertises 96.0. this is at 13 psi.

Tires aside, the 110 mph 1/8 doesn't jive with the 125 mph 1/4. Might want to find out why before you spay through a 1/4.

Put some more air in them. I'd bet 14.0-15.0. Smaller the tire the more air. I run 13.5-14.0 in my 10.5Wx31.
Doug

Many measuring tools don't read exactly the same like every other tool of the same type and even the same brand
I don't loan out my air pressure gauges, torque wrenches, micrometer and many other tools like that after having three low pressure Moroso tire gauges ruined by people I loaned them to at the track
I don't learn quickly on some things, huh
My message is use your tire gauge only to find out what pressures the new tires like on your car

The swaying is typical of bias ply slicks, regardless of the type of tire is on the front. The only time mine has swayed bad on bias plies was when the pressure was too low.
On a heavy car, you'll probably be around 14-15 psi for them to be happy.

So your car only picks up 15 mph on the back half N/A? And then only gained 6 mph at the 1/8 on a 350 hit???? You have some issues going on here.

I agree as I do remember my low 12 high 11 car from the 70's walking some in the traps and I had bias slicks and bias up front. But I have seen mixing radial and bias make it seem even worse as I know it did on my car. Course radial slicks also run more pressure then bias also which can help. I know my 63 is much better with the radial slicks then the bias were and I do run radials up front. But I think you are right as even if I had bias tires up front I believe it would still have walked some in the traps. Because as you stated it is typical some of the bias slick from what I have seen and heard. Ron