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Ian Harrison

Hi Gerry

 Here’s the info on tyre circumferance and height.


33 ½” (on 125mm/5″ wide rims) = 850.9mm, Ride Height = 135.4mm

33″ (on 150mm/6″ wide rims) = 838.2mm, Ride Height = 133.4mm

Tolerance: +/- 3.2mm on front tyres circumference


34 ¾” (on 200mm/8″ wide rims) = 882.65mm, Ride Height = 140.5mm

34 1/4″ (on 230mm/9″ wide rims) = 869.95mm, Ride Height = 138.5mm

Tolerance: +/- 6.4mm on rear tyre circumference

Ride heights are calcualted from circumferance measurement and are from centre of axle to O/D of unloaded tyre. Of course the actual ride height will vary from this figure dependant on tyre pressure and load, but it will give you an idea.

The difference in ride height from 5″ to 6″ wide front rims and 8″ to 9″ rear rims is 2mm (4mm on diameter).

I was thinking more about why Hoosier recommended the 6″ front and it was probably due to them carrying out an awful lot of the initial testing with Erik Frank, who ran a PVP chassis, which like Aussie Brian Stockman’s Stockman MR2 chassis and the UK made Formula 1 chassis seem to work better with a 6″ wide front rim.

Best Regards

Ian :-)