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Help with wheel offsets

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Hi.

Can anyone tell me what offset ET I need to look for, for a rim (16") that is 4" from the outer bead area to the nave plate? i.e. deep dish.

I'm pretty sure a standard Discovery 5 spoke steel rim has an ET of 33 and is approx 2" from bead to nave plate. So I want to know the ET to make the wheel stick out further/wider track.

Thanks.

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You need to be a bit more specific in what you want to do. A popular choice is the Modular wheel, which has an offset of 8mm. From a disco wheel with 33 mm offset, this will move the tyre out 25 mm. It is a bit pointless measuring the outer bead to the nave plate alone because where your tyre sits depends on the position of the inner bead as well.

So what tyres are you trying to fit to which car is what we need to know basically.

Daan

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You need to be a bit more specific in what you want to do. A popular choice is the Modular wheel, which has an offset of 8mm. From a disco wheel with 33 mm offset, this will move the tyre out 25 mm. It is a bit pointless measuring the outer bead to the nave plate alone because where your tyre sits depends on the position of the inner bead as well.

So what tyres are you trying to fit to which car is what we need to know basically.

Daan

Hi Daan,

Thanks for the reply.

Not meaning to be vague, although I thought I was being fairly specific. Not fussed about the inner bead or tyre sizes, I know what size fits. I'm just struggling to find the right wheels for sale as most places list offset in ET and I'm having a hard time working out what ET equates to the dish depth I'm after. :)

For certain RTV competition the maximum offset in the regs is 4" from the outer bead area to the naive plate. So this is what I have to work with.

Disco rims are great on the back as they tuck the wheels inside the body. As per my op a standard steel Disco rim is 2" from outer bead area to the naive plate. I've read this = an offset ET33.

On the front I want rims to give the widest track possible as this then gives maximum lock and the smallest turning circle. But I can't go any wider than 4" from the outer bead to the naive plate. I just don't know what this would be in ET?

The rims would likely be 16x7.

For example:

IMG_5031Medium.jpg

This 90 has Disco rims on the back and the 8 spokes on the front have a 4" dish from outer bead to naive plate.

This 90 (harder to see):

IMG_4905Medium.jpg

Also has 4" dish rims on the front, but the rears only have a 3" dish from outer bead to naive plate.

The blue 90 has a slightly tighter turning circle.

I've seen some 8 spoke (16x7) for sale listed as ET08, but I don't know if this means they'll be 3" or 4" from the outer bead to the naive plate. If they aren't, what ET should I be looking for?

Hope this makes sense.

Thank you.

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If you understand what the offset means, you can simply work it out for yourself.

an offset of 8mm, means the wheel hub mounting face, is 8mm further outboard than the centreline of the wheel.

See here:

WheelsFAQ-diagram.gif

If you take a 16x7 and 16x8 both with an offset of 8mm, then the 7" rim has a "dish" of around 3" (exactly 7" divided by two, minus 8mm, minus thickness of the wheel mounting face) and the 8" has a dish of around 3.5" (8" divided by two, minus 8mm, minus wheel mounting face)

The "dish" measurement alone that your looking for wont tell you what turning circle you'll end up with. The offset however is a closer approximation.

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Can you not ' turn' some disco rims to give the desired offset?

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If you understand what the offset means, you can simply work it out for yourself.

an offset of 8mm, means the wheel hub mounting face, is 8mm further outboard than the centreline of the wheel.

See here:

WheelsFAQ-diagram.gif

If you take a 16x7 and 16x8 both with an offset of 8mm, then the 7" rim has a "dish" of around 3" (exactly 7" divided by two, minus 8mm, minus thickness of the wheel mounting face) and the 8" has a dish of around 3.5" (8" divided by two, minus 8mm, minus wheel mounting face)

The "dish" measurement alone that your looking for wont tell you what turning circle you'll end up with. The offset however is a closer approximation.

Thanks.

I guess I was just getting puggled with the numbers.

So am I correct in saying for a 16x7 rim to achieve a 4" deep dish I would need an ET of -17?

My logic path has been, a Disco 16x7 has an ET of 33 and a 2" dish. So 33 - 2" (50mm)

Any idea where I can buy some steel rims (pref 8 spoke) with this off set?

Thanks.

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Can you not ' turn' some disco rims to give the desired offset?

Yes and I have some I want to do this for, sadly it's beyond my own personally ability though, so waiting on others. :)

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You need to be a bit more specific in what you want to do. A popular choice is the Modular wheel, which has an offset of 8mm. From a disco wheel with 33 mm offset, this will move the tyre out 25 mm. It is a bit pointless measuring the outer bead to the nave plate alone because where your tyre sits depends on the position of the inner bead as well.

So what tyres are you trying to fit to which car is what we need to know basically.

Daan

Erm, I don't understand. Could you explain that again? A Disco wheel has an offset of 33mm, so when choosing a modular with an offset of 8mm the net result is 25mm of outward movement in the wheel/tyre combination. So, are all offsets measured relative to a standard wheel (the Disco steel in this case?). And, why does an offset of 8mm result in a -8mm difference? Shouldn't the offset therefore be "-8mm"?

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Offsets are measured from the centre point of the wheel to the mounting face where it bolts to the hub, I know it's very confusing!

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Hmm, well it explains why my mud tyres on Disco steels don't foul the body under compression but my AT's on modulars do!

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Offsets are measured from the centre point of the wheel to the mounting face where it bolts to the hub, I know it's very confusing!

It can be a bit confusing, if you look at aragorns picture, the bigger the offset, the narrower the track is going to be. smaller offset will give a wider track, 0 mm will make your wheels stick out of the arches, depending on how wide the tyres are. Negative offset means it will be even wider.

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OK, so in my case (and I'm sorry, I don't mean to be stealing the thread!) modulars with an offset of 8mm push the wheel/tyre out by 25mm relative to the standard wheels because the originals were 33mm offset and so tucked the wheel & tyre in under the arches. Got it ;)

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