Tire Size and Pinion Question
 

As the tire size gets smaller (foams), which way should I go with the pinion? More or less teeth? I got about 50 minutes on my tires and I noticed i was really getting beat on the low end the last few runs, top end was only a little slower. I can see my car is really dirty so I know the foams have gotten smaller. I run a JRX-S with CO27 motor. Tires started at 63mm and I was runing 21/96 with great results. I run a a freshly paved blacktop track if that matters.
Thanks

A larger pinion will spin the tires faster and make up for their smaller diameter. The change in circumferance will determine the ratio change. Circumferance is diameter x 3.14. Going up to a 22 pinion will be a 4.7% change. Did the diameter of the tire change that much?

Tire wear is a huge factor running foam on asphalt, for rollout, ride height, and "tweak"

I was running today and was losing about 1mm in a 5 min qual. I started the day with 61mm nitro shoes in 19 turn and after 4 runs ended up with 57mm tires!

I had to make gearing adjustments after every run. I suggest to start using rollout even if you are just "bashing" to keep the motor from over or under reving.

If you are running rubber you just need to know what pinion runs best with your motor.

I check the tires and now they are all different sizes. LF=61, RF=63, LR=60, RR=59.

What is wierd is the RF tires has almost no wear at all. Car handled great, if it wer not touching the ground I would think I would have had a hard time driving it.

That would be because of the loads on the tyres are different at each corner.

If you were to rotate your tyres L to R and run the car again you would find that the tyres would all be almost equal in size L to R