Please Explain Offset to me.

[qwerty]

Basically I have some 7" wide ET0 Steel wheels. Iwould like to get them banded to 9" Wide. If I get 2" added to the back of the wheel what off set will this make them?

This is how I thought it out in my head and then realised I must be wrong.

Original ET is 0 so if I add 1" or 25mm to the back that would make the ET25(?) So if I add 2" that would make the offset ET50(?)

So I thought add an Inch to the front and to the back......but then that would just keep it as ET0. Would adding say 1.5" to the back and 0.5" to the back work?

Anyway any help and guidance would be appreciated!

Have some VIP Japanese cars.







Can't help but look at these and think Rover 600:

[TwincamGTi]

Edited as incredibly offensive.

[Garry]

Dec 17, 2010 17:53:47 GMT TwincamGTi said:

Something very offensive

What the hell? I'm speechless at that post. Incredible.

Edit - couldn't leave it at that negaitivity.

Had a look on Google, it looks like as you increase the width of the rim, the offset goes down because the centre of the wheel is moving in relation to the width.

www.edition38.com/forums/index.php?showtopic=128740

[dude]

A member since '05 and thinks the thousands of "vip" cars out there are photoshopped?

And about your question, play with willtheyfit.com until you figure it out
And does it really matter what offset they are?

[Eidolon]

Dec 17, 2010 17:53:47 GMT TwincamGTi said:

DELETED'

Dude, you need to leave this forum.

Now.

For Good.

[Eidolon]

Dec 17, 2010 17:30:13 GMT qwerty said:

Basically I have some 7" wide ET0 Steel wheels. Iwould like to get them banded to 9" Wide. If I get 2" added to the back of the wheel what off set will this make them?

This is how I thought it out in my head and then realised I must be wrong.

Original ET is 0 so if I add 1" or 25mm to the back that would make the ET25(?) So if I add 2" that would make the offset ET50(?)

So I thought add an Inch to the front and to the back......but then that would just keep it as ET0. Would adding say 1.5" to the back and 0.5" to the back work?

You are right in all you say. It's all about the movement of the mounting face of the wheel, in relation to the centrepoint between the front and rear tyre bead faces.

If you add equal amounts both front and rear of the mounting face, the ET will remain the same. Adding more in front of the mounting face will reduce ET, adding more to the rear will increase ET.

A 7" wide rim at ET0, with a 2" band inserted in front of the mounting face, will give you a 9" rim with ET-50.

In your example of adding 1.5" to the front and 0.5" to the rear, the 'difference' is 1", which is in front of the mounting face, therefore the ET reduces by 25(.4)mm, giving a wheel with ET-25.

[HARDCORE]

Dec 17, 2010 17:53:47 GMT TwincamGTi said:

Something very offensive

I've deleted your unbelievably offensive and frankly absurd post - please expect a PM from Admin.

Remember your report button folks - it makes it much harder to remove this sort of stupidity if people quote it in their replies.

[RobinJI]

if you add 2" to the back of an et0 wheel you will end up with an offset of +25mm.

The mounting face has moved 2" in relation to the back of the wheel, but it's only moved 1" in relation to the centreline of the wheel, as by adding only to the back, you have moved the centreline rearward by an inch.

Basically, if you only add to the rear of the wheel, add half the extra width to the offset. If you only add to the front, then subtract half the extra width from the offset. If you add to the back and the front, then just do one and then the other.

For your examples:

7" et0, 2" added to backspace: offset = 0 + 50.8/2 = 25.4mm

7" et0, 2" added to the front edge: offset = 0 - 50.8/2 = -25.4mm

7" et0, 1" added to back and 1" added to front: offset = 0 + 25.4/2 - 25.4/2 = 0mm

7" et0, 1.5" added to back and 0.5" added to front: offset = 0 + 38.1/2 - 12.7/2 = 12.7mm

I hope that makes sense.

[qwerty]

Missed the negative post so sorry to anyone who was offended by anything my topic might have sparked.

Thanks for all your help guys! I'm hoping ET25 will be perfect. I'll have muck about on the fantastc willtheyfit.

[ben711200]

Dec 17, 2010 19:57:45 GMT RobinJI said:

if you add 2" to the back of an et0 wheel you will end up with an offset of +25mm.

The mounting face has moved 2" in relation to the back of the wheel, but it's only moved 1" in relation to the centreline of the wheel, as by adding only to the back, you have moved the centreline rearward by an inch.

Basically, if you only add to the rear of the wheel, add half the extra width to the offset. If you only add to the front, then subtract half the extra width from the offset. If you add to the back and the front, then just do one and then the other.

For your examples:

7" et0, 2" added to backspace: offset = 0 + 50.8/2 = 25.4mm

7" et0, 2" added to the front edge: offset = 0 - 50.8/2 = -25.4mm

7" et0, 1" added to back and 1" added to front: offset = 0 + 25.4/2 - 25.4/2 = 0mm

7" et0, 1.5" added to back and 0.5" added to front: offset = 0 + 38.1/2 - 12.7/2 = 12.7mm

I hope that makes sense.

I tried typing out a reply to say exactly that but I just couldn't do it without pointing at stuff and scribbling with a Sharpie on the back of an envelope to prove what I was saying ;D

[RobinJI]

Haha, I know the feeling Ben. If you can't explain it with numbers, then I have to resort to dodgy sketched diagrams and pointing at things. The guys at work are getting used to finding random drawings all over anything that's left of the desk.

[tri]

*bookmarked to read when my brain is enabled*

..also hugely curious as to what was so offensive!

[qwerty]

Dec 18, 2010 0:24:15 GMT tri said:

*bookmarked to read when my brain is enabled*

..also hugely curious as to what was so offensive!

+1

I don't really understand how this thread could evoke extreme offensiveness.