Originally posted by sjwau2xr6
Just remenber that for every 10mm wider go 5 lower on profile.
This keeps the overall diameter correct.
Ummm, sorry to be so pedantic but no it doesn't.
What you are saying is take 10% of the section width
(ie. your 5% lower on profile, noting that there is section width at the top and bottom of the tyre) regardless of the section width for every 1" (25.4mm) change in wheel diamter.
It only works at a constant 254mm section width.
Try the maths;
((section width)x(aspect ratio)/100x2) + ((wheel dia. in inches)x25.4)
which gives the theoretical diameter in mm.
For example, if these sizes existed;
they all would have a theoretical 635mm overall diameter, which would be OK on a Falcon, although a bit shorter than standard.