Landracing Forum

Tech Information => Technical Discussion => Topic started by: 38flattie on August 17, 2012, 07:38:58 PM

Title: Narrow speed rated tires?
Post by: 38flattie on August 17, 2012, 07:38:58 PM
What are the narrowest 23" tires available, rated for the salt? I'm running the Goodyear Frontrunners, on a 3800lb car, but would like something narrower, if possible.

Thanks in advance!
Title: Re: Narrow speed rated tires?
Post by: Bob Drury on August 18, 2012, 12:02:43 AM
  Why?  At two tons I don't think you want or need a narrower tire.
  If its a matter of spining the rear tires, you need either more weight or to change the weight bias.
  If the car is darting the same holds true.  
  With the high cg of your car, catching a rut with a narrower tire will be much easier and I can't think of a single good thing to help handling if that is your problem.
  What I would advise, is if you don't allready have one, convert to a Vega cross steer which will take a lot of wiggle and shake out of most any front end.
  If you are running 14 to 20 degrees of caster, zero degrees of camber, 3/16th of a inch toe in, you have checked your rear axle for zero toe in/toe out, your steering box and tie rods are tight, the chassis has been string lined and the wheelbase cross measured, the only thing left is that you have forgotten to match tire roll out side to side.  This important item can usually by fixed by tire pressure and without it you can chase your tail for years .............  
  If you still have a problem, start the sequence over and stick with the 4 1/2 or 5 inch tread.
Title: Re: Narrow speed rated tires?
Post by: Tman on August 18, 2012, 12:19:04 AM
What pressures Buddy?

We ran higher than last year and are kinda in the same boat weight vs speed
Title: Re: Narrow speed rated tires?
Post by: 38flattie on August 18, 2012, 12:22:49 AM
Guys, the car handled like it's on a string-no issues there!

I'm simply trying to lose every little bit of extra drag that I can.
Title: Re: Narrow speed rated tires?
Post by: PatMc on August 18, 2012, 01:10:48 AM
Opinion Page:

There is no free lunch.  I can weigh a car with a piece of paper, a pencil and a tire gauge.  Contact patch is a function of PSI and weight, nothing more.  However, narrow tires made a long flat area, which is bad for high speed.

Let's say you wildly overinflate drag tires to 100psi.  The contact patch will be 1 sq in per 100lb.  So if your front tire weighs 1000lb, it will make a pattern of 10 square inches.  But it will be pretty flat sided.

AFAIK, there are no rules about running dangerously overloaded tires, it's up to the driver to figure that out.  But that deflection will have it's consequences.  As the tire speed rises, it will first make a second flat area, then a third, and so on until the whole circumference is a polygon.  When the last two sides touch, the tire grenades.  I really need to dig up those home movies when I get time.  It's why we switched tires.  

The good news is a front blowout normally handles a lot better.  Bad news is at 100mph a tire becomes a deadly weapon when it grenades.  If you don't have armor in the front, you could be killed.  On just a street car at 55mph, I had the whole steel bed crumple like it was paper.  That had to take several hundred lbs of force.  People think someone hit me broadside at an intersection.

You could test it though.  Standard Testing Labs (http://www.stllabs.com/) is who I use to test tires.  You will want to overload the tires, since you don't know if your car generates lift or downforce.  I overload 20%.  This is how you get videos of what happens.

If you are serious about pushing a tire past it's design limits, I'd test it first.  It's a lot cheaper than testing on the freeway or a racetrack.
Title: Re: Narrow speed rated tires?
Post by: Tman on August 18, 2012, 01:41:00 AM
What he said^^^^^^^^^^ Talk to Tom Burkland about what tires can and can't do. Heis a willing mentor.
Title: Re: Narrow speed rated tires?
Post by: 38flattie on August 18, 2012, 07:50:22 AM
Guys, thanks for the info and concern!

Like the title says, I'm looking for speed rated tires-something proven. I'm not looking to over-inflate the tires, or use something questionable$