Originally posted by JAG Racing
RR - explain that please... (1st part)
Using the 22T pulley instead of the stock 23T pulley alters the front pulley drive ratio and gives front overdrive i.e. front wheels rotate more times than the rear for a certain amount of engine rotation.
The rear part of the car will have a stock pulley drive ratio of 2.421 while the front will have a pulley drive ratio altered to 2.316 with the 22T front side pulley.
If you run equal front and rear tires with this 22T side pulley, the front will have more tire rollout than the rear i.e. you get front overdrive or in layman's terms the front pulling the rear. Some like to drive the car like this in low traction and tight tracks but sometimes too much will make the rear end loose. Front belt also gets strained more.
In order to run equal front and rear rollout i.e. 1:1 overdrive, you need to use about 2.5 mm smaller front tire diameter than the rear. Say if you use 60 mm for the front tires, you need to use about 62.5 mm for the rears...
Using smaller front tires in a split like this has it's benefits. Firstly, the front rollcenter gets slightly higher than before at the same ride height which makes the car more nimble at a given steering input. Secondly, smaller tires solves traction rolling problems and tire chunking. Thirdly, it still gives you adequate tire rollout (top speed) at the back of the straight and at the same time permitting you to run smaller front tires.