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Changing Shift Speeds With Tire Diameter

Gearing With Tires
Posted July 22 2008 08:06 AM by MilesSpeed 
Filed under: Hard Driving

tire compare

This is not the most ideal way to get your rpms where you would like them at the track and on the street, but not all of us can afford to change gear sets all the time.  


drag radial
bfg r1

My recent trip to California Speedway let me know my gearing was way wrong for that track. It seemed like I was letting off to keep off the rev-limiter in 3rd gear trying to avoid shifting into high gear because of the lack of engine braking. I would have liked to be able to stay in 3rd nearly the whole course (minus the 150mph straight and oval). I am currently running a 245/40-17, when before I used 245/45-17, and I can really tell the. Right now I am shopping for a taller tire to allow me some more speed per gear. I recently put my drag radials on the rear for the street that are nearly 2-inches taller and it felt like I had an overdrive on the freeway.

You can help your traction issues by running a taller tire as well since it acts like a lower (numerically) gear. One thing drag racers try and do is calculate the speed they need to go through the traps at, and between tire diameter and gear ratio, they make their high-gear red line at that speed.

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