Is wheel offset measured in mm, eg: A wheel with a offset of ET30 would need 5mm spacers to increase to ET35, is that right & are their any problems encountered using spacers ?

Simon.

 

adding a 5mm spacer will bring the offset down to et25.

 

As above, because offset is a negative number for most cars.

 

Thats really confusing because i have a set of wheels with ET35 that stick out further (fill the arches more) on a 3dr & are 7.5J wide. My other set are 8j & are ET30 & they don't fill the arches as much they sit further in not a lot though. Whats the right offset for a 3dr ?

Simon.

 

ET30 and 8" will sit out further

 

Maybe the info on the wheel is incorrect because the 8j ET30 do not sit out as much & they also sit nearer the strut & the brake caliper, maybe its just the style of wheel, is their anything wrong with using spacers to bring them out a bit more.

Simon.

 

I suppose as the wheels in question are secondhand it is possible that at some point they may have been machined to a higher offset to fit on another model ?

Simon.

 

yes its possible they have been machined.

 

Spacers are ok up to a point , they do put quite a lot of additional strain on Wheel bearings . Dont suppose they are old gpA wheels are they ?

 

this pic might help.....

 

ok thanks, no their not grp A wheels. just bought some spacers & going to have a play

Simon.

 

also, the further out the wheels sit, the more that car will tramline...

unless other suspension mods are done to counteract it.