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Would chaning your wheel offsets have affect on scrub radius?

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Would chaning your wheel offsets have affect on scrub radius?

Old 10-25-03, 08:04 PM
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Would chaning your wheel offsets have affect on scrub radius?

Just was wondering, if you moved up to bling bling wheels and they wheel offsets were different... say +32 mm or +35 mm instead of + 40 mm on a stock FC.

Would this change the scrub radius enough to affect performance?
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Old 10-25-03, 08:26 PM
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I once read a post on a Miata forum where one member related an increase in steering effort with lower offset wheels (miatas use something crazy like +50, oh wait the FD uses that same offset).

So what is scrub radius? That is a technical term that I haven't learned yet.
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Old 10-25-03, 09:33 PM
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Scrub radius is the difference in distance between the center of the tire contact patch and a line extending through the center of the kingpin axis to the ground. If these two points are the same then you have zero scrub radius.

If the kingpin axis does not intersect the center of the contact patch, then you have scrub. It is called this because as the steering wheel is turned the tire must literally scrub or roll about an axis that is not in the center of the contact patch, thus "scrubbing" the tire across the pavement. Keep in mind all this is when viewed from the front, and is not to be confused with "trail" which has the same description but is viewed from the side. Trail works like a castor and helps the steering self center.

Increased scrub radius results in higher steering effort and a much stronger tendency for the steering wheel to kick back when the grip at the front tires is not perfectly balanced. Scrub radius and trail work together to give the car its steering "feel".

So to answer the question, maybe. If half the difference of the new rim width compared with the old is added to the offset, then scrub radius will remain the same. Anything else will change the scrub radius.

Last edited by DamonB; 10-25-03 at 09:45 PM.
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