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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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How to work out required offset?
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Sun, 06 June 2004 06:20
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Now that I have my diff ready for my Celica, I need to get some wheels to suit.
Whats the best way of working out what offset I need?
Also when I go looking for some second hand wheels, is the offset specified on them? All wheels I have looked at so far have something like 15x7J. Is the "J" the offset?
Thanks
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Location:
On your mum!
Registered:
May 2002
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Re: How to work out required offset?
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Sun, 06 June 2004 07:28
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J is something to do with the rim width. I have always just run a straight edge off the wheel flange and then measured to the inner guard/leaf spring and then to the the lip on the guard.
This gives a pretty good picture for you to work out where the rim will need to be in relation to the flange. Note - the tyres can afford to be nearer the guard because of the slight bulge in the tyre means that it needs to move further before contact is made (also when the body rolls to one side, the guard has a tendency to be move away from the tyre).
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Location:
Terrigal
Registered:
May 2002
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Re: How to work out required offset?
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Sun, 06 June 2004 08:52
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Howdy, offset will usually be measured in MM. eg 30mm .
The more postive offset means the track width will decrease. whereas a negative offset will increase the track.
For example I had +20 on my RA28, then put a wider diff in and the wheels scrubed the guards badly (almost sat outside of the guards), so put +32mm wheels on and now just sit inside the guards.
That doesn't really help you decide what you need though 
Cheers
Joel
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: How to work out required offset?
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Sun, 06 June 2004 08:57
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| TurboRA28 wrote on Sun, 06 June 2004 18:52 |
Howdy, offset will usually be measured in MM. eg 30mm .
The more postive offset means the track width will decrease. whereas a negative offset will increase the track.
For example I had +20 on my RA28, then put a wider diff in and the wheels scrubed the guards badly (almost sat outside of the guards), so put +32mm wheels on and now just sit inside the guards.
That doesn't really help you decide what you need though
Cheers
Joel
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Thats interesting. Thanks
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: How to work out required offset?
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Sun, 06 June 2004 14:11
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http://forums.toymods.org.au/index.php?t=msg&t h=36672&rid=1976&S=560e5f54859a57836bb70ce 47eebcef2&pl_view=&start=0#msg_330572
for actual offset working out (of rim) google for "offset yokohama" (iirc)
best bet is borrow rims and try them (preferably with the same size tyres you want and same rim width), and then go from there...
btw, i think J is the bead profile of the rim.....
oh, as for second hand wheels.. if you know the width, measure the 'backspace' this is the important measurement anyways...
so take ruler and measure from the mounting face to the inner flat face of the rim (just below the bead)
ie 6" rim = 150mm wide. if the backspace (brake side) is 90mm, then the other side is 60mm. (90-60)/2 = +15 offset.
if you want to go from 6" to 7" rims then you still need backspace to be the same (give or take for sidewall differences)
Cya, Stewart
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