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Effect on handling of changing offset
aka Keith - 8/9/11 at 04:20 PM

I am looking to go from a 7 inch with a 35 et offset wheel to a 6 inch with a 19 et offset.

I have done my calculations and it looks like to out side of the wheel will be just about in the same place, whilst the inside of the wheen will be further from the hub face.

Before I commit , I would like to know from the collective if there will be any detrimental effect on the handling from this change?

cheers
Craig

phelpsa - 8/9/11 at 06:40 PM

It's really difficult to say without knowing other geometry. The main effect that it will have is to increase the scrub radius of the front wheels, which can lead to generally lighter steering but with a greater tendency to transmit forces through the steering. Plus there are effects due to increased track and a few other things.

But at the end of the day, most people use wheels of around ET19 with no issues

v8kid - 8/9/11 at 07:03 PM

Hmm I would have thought it would make the steering marginally heavier but nothing to worry about. It will also change the camber recovery characteristics and the roll centre migration slightly but it would not bother me if I were in your shoes so to speak

Cheers!

phelpsa - 8/9/11 at 07:51 PM

quote:
Originally posted by v8kid
Hmm I would have thought it would make the steering marginally heavier but nothing to worry about. It will also change the camber recovery characteristics and the roll centre migration slightly but it would not bother me if I were in your shoes so to speak

Cheers!


You would think that steering would weight up as you are moving the wheel further, which when stationary is true. My experience (admittedly mostly of FWD hatches) has shown that infact a reduction in actual tyre scrub causes the steering to become lighter but other forces transmitted forces have a greater effect (if that makes sense). Obviously if you go too far things get a bit different....

[Edited on 8-9-11 by phelpsa]

Fred W B - 9/9/11 at 06:51 AM

I would have thought that as he is keeping the outside face of the wheel in the same place, and moving the inner face inwards (due to wider wheel), as he states, then the track and scrub radius would both decrease. This as the centre line of the wheel is moved inwards.

Cheers

Fred W B

[Edited on 9/9/11 by Fred W B]

[Edited on 9/9/11 by Fred W B]

scudderfish - 9/9/11 at 07:22 AM

His width is reducing, so the centre line will move out and increase the scrub radius.

Fred W B - 9/9/11 at 07:37 AM

Ah, missed that, thought he was going wider, not narrower.

I stand corrected

Cheers

Fred W B

aka Keith - 9/9/11 at 08:23 AM

Thanks everyone, it would appear that it will not be too dramatic an effect on handling, the reason I am looking to do it, is so that I can go down to 13 inch rims from the current 15 and many of the 13x6 wheels have a reduced offset ie 19 rather than my current 35.

cheers
Craig