Offsets and et numbers - help I'm confused

[richiep]

I agree with Hot66.

After the help I have recieved off this forum and from a local alloy wheel shop, I'm pretty sure how it all works now. Its people's interpretation of what is a positive or negative offset that led me to start this thread in the first place. Kinda comforting to know that other people have differing views on it. Anyway, after talknig to the wheel shop, I will have a go at explaining the whole positive-negative thing. Positive refers to the et number being a positive number, et25 for example. Negative refers to the et being a negative value, eg. et -25.

How this relates to the dimensions of the wheel has been explained before in this thread but I'll have a go aswell (just to make sure I fully understand it now!)


Imagine you have a 6inch alloy wheel with no tyre on it sitting in front of you with the shiny side to your right and the crappy brake dust covered side to your left . If the wheel had a zero offset (et0) then the mounting face of the wheel would be bang on in the centre, 3 inches from either rim edge. Now if the mounting edge is moved (offset) right (towards the shiny side of the wheel) by 20mm, the wheel is deemed to have a positive offset of 20mm (et 20). If the mounting face is moved to the left of the wheel by 20mm from centre - (towards the crappy side), then the wheel is said to have a negative offset of 20mm (et -20). I don't know why offsetting toward the shiny side is known as positive and dirty side is known as negative - it just is.

So a wheel with a positive offset will tuck under the wheel arch (fender) more than a wheel with a negative offset if they both have the same width.

I understand that positive sounds like sticky outy and negative should mean tucky undery - but this is wrong.

Oh, btw I have chosen to go for 5.5 x 15 fuchs alloys with a 42mm offset. Should just get 175 55 15 on the front with those.

If I can't source any of these, Pedrini's or Mahle alloys from a 914 have the same offset but I will have to change my disks (rotors) to standard VW pattern to fit these.