WM3 Tyre size

[DaveH]

Hi. Can i have some suggestions for tyre sizes for WM3 18 rear rim. 4.00 18? Is 90/90 18 the modern equivalent?
Any help appreciated.

Thanks,  Dave.

[DAVE BRADY]

Hi Dave,

You can get a 400x18 in a modern tyre or the equivalent is a 110/90x18.  A 90/90 is only a 3.25 and a 100/90 a 3.50.  I would think that the 400 or the 110/90 is right for a WM3.
I use Avon RoadRiders.

Dave.

[DaveH]

Thanks for that Dave. I'm somewhat confused as 4" = 101.6mm so it must be the 90 profile that changes the equation?
Cheers,  Dave

[idie]

I think that tires given in inches are 100% in profile, so the height and width are the same. When you have a different figure 90 for instance it means the profile is 90% of the width. This means that the rolling diameter is lower, this in turn will lower the gearing slightly.

[DaveH]

Brilliant. Thought their must be some simple formula.
Thanks for the enlightenment.

Cheers,  Dave

[Mike Farmer]

 

Very good explanation. If anyone wishes to read it up in greater depth I suggest that you look up "Tyre Sizes Explained".

Mike