stretching tires on scales

[hughesracing9]

Ive read something on this a while back but cant find it

Heres the scenario:

Lets say youre scaling the car, you need 1/2" taller tire on the rf. Now, for this example, lets assume you have THAT exact tire in your trailer, same offset and all, but just dont want to change it on scales.

So you air it up to the psi needed for the 1/2" growth. Yay or Nay?
My brother said he does that, during my speech about not doing it i started questioning myself.
I know you scale it like you race it, but if the car is just sitting there, does it make a difference?

[charcoal01]

Yes because air pressure changes spring rate in that tire. You up the air, you change the spring rate, you change the scale number. You ever recorded your corner weights, then put 5 lbs more air in that tire? Try it out.

[johnny v]

your just changing the size of the tire on the scales.... spring rate of the tire applies on the track....just like the air pressure affects grip on the track.... doing it on the front will affect ride height, not the rear ( because of how you measure) .... I play with air on the scales to see what happens to the numbers like going from a heat race setting to a feature setting on air....

I agree with the brother who is doing it..

[RRR_Products]

Statically I couldn't see it changing drastically. I know every 1 psi is 3-5lbs per corner on scale. As for how much the tire changes on the scale I think it would vary rears vs front especially when camber is involved. Try it out with 2 different tires and let us know and front vs rear.

[jsf74]

just do it right and be done with it.

[MM90]

I got an old set of tires I use for scaling only. Put some innertubes in them so they don't loose any air. Some of the tires were old enough that I had to fudge the psi "no more than 2 psi" to get the size compared to where I normally run my tire psi at when I race. If you scale it the same way every time you shouldn't have a problem.

[Anonymous24]

just do it right and be done with it.I agree 100%. If you do things half assed, you get half assed results.