EH 15inch wheel offsets

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EH 15inch wheel offsets

by Joe Irvine » Thu Jan 14, 2021 6:40 pm

Hi All, new to the group.Currently putting a 253 into my eh and have an enquiry regarding wheel offsets.The eh has modified hr front end the hq disks and the rear is a shortened borg warner with hq drums.The diff is the same width as the original diff.I have no idea how to work out what the offsets should be if running 15inch rims.I was hoping 6inch front and 8inch back.Does anyone know.Cheers Joe
 
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Re: EH 15inch wheel offsets

by Harv » Fri Jan 15, 2021 7:47 am

G’day Joe,

It’s a complex question, as clearance to things like steering arms, tie rods, caliper/drums, ball joint grease nipples etc make a big difference to how much offset you can run.

There are rules around track increase and tyre width that you will need to meet. As an example, 6/8” wheels on an EH meet NCOP requirements, though are limited to a 205 tyre. Best to check with whoever is certifying the vehicle (probably an engineer given the changes already made). The rules are guidance, and each certifier interprets them differently. As an example, some engineers set track limits based on the EH diff spec, others use the BW diff spec. Either way meets the rules... just interpreted differently.

If it was me:
a) contact engineer, work out what rules/limits they want you to meet.
b) buy a cheap 15” steel wheel from the wreckers and mock it up. Use washers to space the wheel in/out until you have clearance and still meet the rules.
c) measure the offset from your mock-up and buy your new wheels.

Cheers,
Harv
 
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Re: EH 15inch wheel offsets

by claysummers » Sat Jan 30, 2021 11:35 am

Hi Joe,
Can I suggest sevens on the rear is more realistic target? Not saying it can’t be done but with a maximum 205 tyre width the sevens would possibly work out better. Six inch on the front is realistic. Any more and the track will be too wide to meet spec. There are good reasons behind the track increase limit. By the way I think the hq discs will push the track out compared to original. So rims will need to compensate.

So practically speaking you are looking at 185 tyres front and 205 rear. This combo looks good and runs very well on six and seven inch rims. My 2c worth mate.
Cheers
Clay


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