CantHookUp

I have been testing different tire pressures for BF Goodrich G-Force Drag Radials 315/18's and I found that too low of a pressures will leave a gap in the middle of two black marks ... like they are riding on the rims and too much pressure leaves a narrow strip from the middle of the tire.

Anyone figured this out yet.

pro1955

On my super gas car, we would do the burn out to heat the tires up then look at the contact patch at the launch, you already are going in the right direction. Start in the middle of the two pressures you know don't work, another mistake some racers make is running too wide a tire for the rim.

MR1911

What I have always done is , on a clean FLAT cement surface , roll the wheels through water and look at the pattern on the cement. I try to make sure the car is at the basic weight that I run it too, say 1/2 to 3/4 full of gas .

Yes this takes time to do but it works for me

CantHookUp

Thanks ... The empty gap in the middle was on 315's and 10.5's rims at 24psi ... 36 psi left 3/4" on each side after the chalk test. But I cant tell a difference 27 and 33psi. Is this crazy. I must be nuts ... I guess 30 psi is the number .... I was hoping there was someone more crazy than me

Black 79

I run 40 with run flats.
David.

Evil-Twin

If you are talking about a burn out and you have a gap in the middle of your tires you have some serious problems...When you spin the tires they rotate close to the red line... with all this momentum and heat all tires grow tremendously in the middle.. this is why you run drag tires low...and doing a burn out does the same thing...A visual look at a dragster withh show just how this effect works...but on a smaller scale
There are other issues on launch... front lifts air get under the car and lifts it.. these are all non conventional driving habits.. meaning this is not what the car sees 98 % of the time..
As a qualified expert on this subject, I do not let my tires get above 30/31 psi "HOT"... Many members follow my guideline and are seeing 45,000 to 49,000 miles...with no center wear. I won't debate this in open forum... do a search under my name and you will see hundreds of posts, fact and input gathered from several NASCAR crew chiefs.Road conditions and road temperature play a big part in the "right psi"... looking at Cold setting does nothing but give you a reference for Hot conditions.. when its 90+ outside in the summer, I run 25 psi to give me 30/31 psi when out on the hot road surface.

pro1955

Its just a damn good thing we have a qualified expert like you Evil.

chanderson

I run nitrogen in all four tires at 31psi. No fluctuation in pressure with nitrogen hot or cold.

Black 79

I have never heard that before! Where do you fill-up?
David.

FourG63 97GST

I do also in my street tires. but I'll be running M/T Street ETs for the track. should I run nitrogen in them also and just set them at the pressure I want?

CantHookUp

I agree. the marks are just from a little punch on the pavement 10 feet or so. No burn outs are being done. I dont' want to go through a set of tires just to figure the pressure out. However, when I do make a run at the track I will do a longer burn-out to prep. What I am talking about is the best for the street. I never get to do a burn out before I catch someone wanting to play.

Evil-Twin

Nitrogen is ok, but all gases expand an contract, just mot at the same rates...
getting air from a compressor already has 78 to 80 % nitogen anyway, there is oxegen and traces of argon and bad breath and water vapor, and dioxide. While it is true that wat6er vapor expands and contrats at a great rate than pure nitrogen... unless it is free, its hardly worth it... Ive seen places charge ten dollars a tire for nitrogen..
To say that pressure doesnt increase with Nitrogen tires in just not true..
put Nitogen filled tires @ 30 pounds cold and put that tire on a Hot Georgia ashault highway @ 140/150 F and that tire will grow, about half as much as a compressed air tire will.

Black 79

Thanks Evil.