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Wheel Offset Question
Dave Bailey - 4/5/09 at 07:29 PM

Have I got this correct? I have a 7" width rear wheel with offset 35. The wheel does not sit in the arch correctly by about 15mm... Would a 6" with the same offset be 12.5mm further inside the arch than the 7"?

thanks
Dave B

CRAIGR - 4/5/09 at 07:40 PM

Useful link

http://www.1010tires.com/WheelOffsetCalculator.asp

[Edited on 4/5/09 by CRAIGR]

SPYDER - 4/5/09 at 08:09 PM

In a word, yes. The outer edge of the 6" wheel will be half an inch further in, all other things being equal.
However, the edge of the tyre, given that you intend to fit the same tyres, won't be any further in at all as you aren't moving the centreline of the wheel/ tyre combo.
If you are going to buy a different set of wheels why not buy ones with the correct offset right from the start.
Might even be cheaper to fit wider arches.
As for fitting different diameter drums as per the previous post I can't see the thickness of the drum mating flange being much thinner or thicker no matter what diameter they are. Certainly no more than a millimetre or two, and certainly not the 15mm that you are looking for. The diameter of the drum won't make any difference to the offset at all, obviously.
Geoff.

Dave Bailey - 4/5/09 at 08:33 PM

Thanks everyone... The web site link is very usefull..... I have rear disks so cannot go the rear drum route....

thanks
Dave Bailey

SPYDER - 4/5/09 at 08:37 PM

quote:
Originally posted by Paul TigerB6
quote:
Originally posted by SPYDER
As for fitting different diameter drums as per the previous post I can't see the thickness of the drum mating flange being much thinner or thicker no matter what diameter they are. Certainly no more than a millimetre or two, and certainly not the 15mm that you are looking for. The diameter of the drum won't make any difference to the offset at all, obviously.
Geoff.



The 8" drums are narrower (by 18mm) as well as smaller diameter and so the wheels are moved inwards by the difference in width. I'll dig out the figures and link now.

8" drums - 203mm dia x 46mm width
9" drums - 229mm dia x 64mm width

Brakeparts.co.uk

Hope this helps

[Edited on 4/5/09 by Paul TigerB6]


Hi Paul.
The width of the drum makes no difference.
It is merely acting as a spacer between the hub face and the wheel as far as the wheel is concerned. The drum is probably around 6mm thick or so at the hub face, no matter what it's diameter or width.
Now if you have to fit different hubs along with your different drums, and the hub faces are further in then you have a point.
Geoff.