wheels & tyres

derek

Well Known and Active Forum User
VOC Member
I have decided to fit road rider universal tyres to my Comet, which has 19" rims , I think wm2 both front and back? How do I check wether wm1 or wm2, is it the width of rim?
What would be acceptable sizes, I have been told front 90/90 & rear 100/90, what do these figures mean?, and are they the best ratio:
 

b'knighted

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VOC Member
As I understand it, or maybe misunderstand it, the figures are width in mm/height in percentage of width so 90/90 would be 90 mm wide but only 81mm high, 100/90 would be 100mm wide and 90mm high. Take into account that a lower profile will alter gearing to some extent and while I would worry about this on the back you should be aware of the increased inaccuracy of the speedo. I believe they were accurate with a 3.00x21 and a little optimistic with a standard 3.00x20 as its circumference has dropped by more than 3 inches. It was generally said that fitting a 19" front had little detrimental effect on accuracy as a slightly wider 19" tyre would have about the same rolling circumference. This will not be true with a low profile as the circumference will drop by another 2 inches. This will make it out by one in forty - should we worry?
 

derek

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VOC Member
I have now found the answer.
Rims. WM1 = 1.60" WM2 = 1.85" WM3 = 2.15"
However, you can use a 1.85" rim were 2.15" is recomended and a 1.60" were a 1.85" is recomended.:)
 
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