rollout

We've had an issue with our fc driving to the left, and we've been thinking it's a driver issue, but we measured the tires, and the right tire was 1/2" bigger. Is that enough to move the car? If I put 1/2 pound more in the left, it evened them out.

On a sidenote, we thought the front tires were driving left a little bit, and staightened them out, and it appeared to fix the problem, but now I don't know.

thanks
bryan

 

What my father always had me do when two tires measure differently was fill the smaller one with excess air. for example maybe 10 or 15 pounds in the outside verses the 4 or 5 that we ran. Leaving the tire like this for a few minutes maybe 5 or so then reduce the pressure back to opperating pressure and remeasure. Do this until the two tires are the same circumference at the same pressure. You dont want to race with the two tires at different pressure or different circumferences.

nick

 

I thought of that. Also heard of filling them up, and setting it in the sun to allow it to heat and stretch, but how much pressure can you put in the outside(50lb in tube)? I assume it would shrink back, I guess we'd have to watch it closely, and periodically stretch it.
thanks
bryan

 

If the driver "feels" the car pulling to the left and everyhing is mechanically ok (nd if you have adjustable front spindle)then take the left front spingle and place it higher 1/16 at a time (takes bite away from right side) .

But before all this make sure the driver is looking at the "right place on the track" , if availabe on a parking space , place driver on the seat , full gear on and push car for about 50' with him driving toward a cone or drum in front of car (150' out)when he feels he is lined up visually check he is pointing the car straight to the cone .

Hope this helps because sometimes the driver helmet will be croked and he will drive to one side without thinking. good luck.

 

We were thinking he was looking out left of the hat, but after adjusting the steering wheel, it seemed to fix it, so that could've been wrong. He's been driving a long time, and this problem has seemed to come up relatively recently. Now I'm just wondering if by adjusting the steering wheel, we crutched the real problem (rollout), and now the car will go right if the rollout's the same on both tires

bryan

 

Well after driving 6 years the same car I jumped into a new one,right. The car would leave very straight (wheels in the air for 150,) and everything would be fine until 400-500' out when I would get to close to the center if on left lane or wall on the right. Turns out my new Nitro Helmet is diferent than my old RX4 so I wouldn't stay centered on cage pads . After performing what I described and a "better" pading the car will run like an arrow. Now I always check (with one eye closed!) where i'm looking down track !

 

Usually with a new set of tires we will over inflate them to 20-30 psi and leave them in the sun for a while. This seems to even the tires out then we deflate them to 5 psi and ck the rollout. Since the actual pressure that we use at the track fluctuates based on track condition we always ck the rollout at 5 psi. keep in mind though, that I use beadlocks (pro mod car) so the funny car guys with inner liners may have a different way of doing it.

 

Everyone here sounds like they are on the right track to a point....Once a new set of tires has been run (USUALLY AFTER 1 BURNOUT) you cannot change the rollout of race tires. They are made from nylon fabric(among other things) that have a "memory". Putting race tires (new or used) in the sun to try to correct rollout issues will usually only compound the problem. If you catch it before they are run, you stand a chance of correcting a "rollout" issue...once run though, they never will stay. On the other hand, 1/2" rollout on a F/C is not completely unheard of. Not to say it's not good, but usually not enough to create an extreme "pulling" effect. You can contact me if you have any more questions with tire tech at .... jboyd@smileysracing.com or 972-289-7223.

 

1/2 inch doesn't sound like much, and the problem went away when fixing the wheel, but I'm gonna start checking it often. At what point is the difference to much, and they need to be changed? 1", 1 1/2"? I really don't feel comfortable running 1/2 lb more in one tire, or is that a reasonable thing to do? I think I should stick to what we've been doing, and watch the rollout closely.
thanks
bryan

 

On a tire that has 110" or 112" rollout, 1 inch is too much. I have heard of guys with that much on their car and still running the tires but would not recommend it. When we mount tires here we try our best to make them even but we cannot control what happens once they leave our trailer/store.

As far as running increased air in a tire vs the opposite side..... I would not recommend that either. Air pressure in a tire is (in relative terms) the spring rate of a tire. More air....more spring rate. You want your air to be equal right vs left. One thing to always remember...NEW tires require as much care as a new puppy. If one is in the sun....both need to be. If one is inside the trailer....both need to be. If one tire equalizes and gets hit with 25# of air...do that very same thing to the other.Always remember....whatever you do to one...do to the other. Hope this helps......J