Learn me slicks

So, I found bias ply circle track slicks in an equivalent size to the 235/60/15 radials on the challenge car. American Tire out of Pennsylvania. I know Dave easty is running this brand on his hillclimb car, which is how I found out about them.

The tires are ~$100 each. With is what replacement radials would cost. There are no r-comps. Or really any performance tires in this size. Closest thing is cooper cobras.

So, anyway, the slicks were measured on an 8 inch wheel. Ours are 7 inch. I know on a radial that it would be slightly pinched, but not badly. What about with a bias ply slick?

Next: I've seen references that chassis setup is different for radial Street tires vs bias ply slicks. What exactly needs changing?

Also, the manufacturer offers a soft, medium, and hard compound. We'd like to buy one set, and run the season of autocross before the challenge. My thought is buy the medium, run the season, put some of the good that makes slicks stickier before the challenge, and finish them off down in Gainesville. Thoughts?

Also, how to these kinds of slicks hook on the dragstrip?

I've never owned or driven on slicks, so I'm way out of my comfort zone.

Interested for answer too!

I've been running bias road race slicks on the Camaro. Here is what I can tell you about them. This is on a CP car, so there may be some differences to what you are running.

Bias slicks move around more side to side, so it can be a strange feeling at first until you get used to it. As for rim width, the manufacturer has rim recommendations, so if your wheels are in that range, you are good. The taller the sidewall, the more forgiving they are of rim width changes.

Compound wise, I would go with the softest you can. Harder compounds take more to get heat into them for grip. Medium compound could be a good choice for both grip and longevity. Granted they won't last as long as R-comps or street tires. You will know when they are done, grip tends to go away noticeably.

As for drag racing, they just don't grip on launch very well. It takes a bit of throttle modulation to get going.

When you increase grip with R-comps the lateral forces acting on the car will go up. This means more body roll in the corners. Generally you want to raise spring rates and increase sway bar size to counter this.

235 on a 7" rim will be a bit pinchy. Are wider wheels a possibility?

Call Burgett Tires and see what they offer in a take-off Hoosier. His prices are pretty aggressive.

A 235/60 has enough sidewall that it should work alright on a 7" wheel (you'll definitely feel some flex though), but wider would definitely be better if possible.

I'd love to go wider, but at this point, don't know if we have the budget.

We are building to c prepared rules, just so the car has a purpose after the challenge.

Sway bars are already the biggest available, and spring rates and shocks have not been finalized.

Are there any alignment differences between the slicks and radials?

And, on the same subject, Circle track vs autocross slicks: what's the functional difference?

What else an I not asking or thinking of?

The bias ply's need less camber, change shape based on pressure, and often have measurements based on tread width instead of sidewall to sidewall. If you can't find section width information somewhere I would assume a section width 2" greater than tread width.

Dusterbd13 wrote: And, on the same subject, Circle track vs autocross slicks: what's the functional difference?

The autocross slicks are just the softest compound road race slicks you can get. Mine say "Road Race" right on them. As for differences between circle track and road race, this article goes into what tires Nascar uses at each track: http://www.roadandtrack.com/motorsports/news/a27475/more-than-you-ever-want-to-know-about-nascar-tires/

Other than the stagger they run on ovals, I would believe the circle track and road race tires are fairly similar.

I used to run a set of Hoosier slicks on my Mini in GP. One thing I found is that they liked a lot lower tire pressures than my street tires (Yokohama A008 or A048. Mine were meant to be F500 front tires - I ran them on 6" wide 10" wheels. Not sure if that is a universal truth, but I ran something close to 22# IIRC.

I ran mine at 24# front, 20# rear, so they do like less pressure.

There is some good info here on slicks, both bias and radial: https://www.rsracing.com/TechTire.aspx

Bias slicks run much less camber than radials. On my sports racer - 20.0 x 7.5x13 F 22.0x9.0x13 R Hoosier mediums on 7" and 10" wheels - I'm at -1.3 deg F, 1/16"/side toe out and -.5 deg R, 1/16"/side toe in.

I go out at about 12/13#F and 13/14#R to come off at 18F/19R hot.

They used to be good for heat cycles 2-8, but now that the car is closer to 1200# down from last years 1300# minimum, they look to maybe be good for 9 or 10.

I ran 20x9.5x13 Goodyear Formula Atlantic fronts on my 1275lb (1435 with me in it) Locost, on 10" wide rims. Bias slicks in R175 compound. I ran them around 13psi cold. Ran maybe a degree of camber.

When the tires were new and fresh, I felt like a driving god among men. It was unbeberkelyinglievably awesome. Despite not really getting them hot enough (135° was the hottest I could get them).

My co-driver and I had a ball. For about 15 minutes of runs (maybe 4 or 5 events?). And then it was like "something's wrong with the car, it just doesn't turn." We ran them for another two years anyway, just to get the money's worth.

Then I bought some used Hoosier R25 (or was it R35??) in 20.5x7x13 on 13x7" rims. I soaked them with 50%Xyelene/50%Toluene to soften them. They felt just like the 9.5's did.

I will echo what other people say; bias ply tires run much less camber.

On the Datsun, I used Hoosier TDs (tread slick really) and run -1.2 degrees of camber. Tire pressure is 24 psi all the way around.

On the F500 I'm running -1.5 of camber and 10 psi front 11 rear.

Radials have lots of windup and do not slip a whole lot. Bias plys move around a lot and if you're not comfortable with a car the moves around a bunch you may find it disconcerting.

Tom