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famoroso famoroso is online now
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Join Date: May 2015
Location: San Francisco & San Diego CA
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Quote:
Originally Posted by Bill Verburg View Post
The thing that determines s/r wrt the wheel is it's ET, higher numerical ET = lower s/r

a 911 w/ 7ET23.3 has a s/r of 52.4mm

a 930 w/ the 21mm spacer, whether from the o/s hub on late 930 or the 21mm spacer of early 930, has a s/r of 73.4mm

use a wider wheel like the early 911 Ruf 8s w/ ET 30 and the s/r goes down by the difference in Ets

the early Ruf 9 w/ ET17.7 would raise the s/r compared to a 7 ET23.3

RSR w/ the 21mm spacer and w/ 9ET3 has a s/r of 72.7mm

similarly track changes w/ ET changes, a 930 w/ 7ET23.3 wheels has a front track of 1432mm, 60mm wider than a 911 w/ the same wheel

the Ruf 8ET17.7 would reduce track by 35.4mm
Thanks Bill, I appreciate the explanation. I'll go an whiteboard a visualization.

If I do Ruf 9&10 x 17 wheels on a 930 / M491, what are the recommended tire sizes? I assume there are a few pairing options? What are the aggressive, middle and conservative sizing options? I'm not a teenager anymore, so would prefer to avoid fitment issues.
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Frank Amoroso
911 M491 / M470 coupes:
1987 GP Wht / Blk "Apollo"
1987 Gemini Blue / Blk "Gemini"
1989 GP Wht / Blk "Vents"
Old 06-22-2025, 06:44 AM
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