Couple of pics regarding ET and top balljoint

[silverbullet]

There seem to be a few "will these rims fit?" questions being asked again so here is an example to illustrate the situation for the uninitiated.
6.5x15" ET30 SA "Starburst" alloys, the widest production rim fitted to any T3, along with late type PAS uprights etc.
Here is what goes on round the back, showing how close things start to get between top balljoint and tyre. With 16" rims it gets worse, 17" are better iirc.


Hopefully this will help anyone getting confused with the wheel fitment thing

PS the ET dimension is negative offset i.e. how much the centreline of the rim is set towards the middle of the vehicle. Bigger ET, more rim set into the arch and more chance of a wider rim/tyre fouling the suspension.
As rims get wider, so the ET must necessarily reduce in order to maintain clearance.
Period aftermarket 7x15" alloys like Pentas and ARCs were all ET 21 for this very reason.

[Jiminez]

Very useful post Silverbullet!
If the aftermarket 7x15 Pentas with an ET of 21 fit, could you tell me if a wheel of 6Jx15" with offset of 22 would fit? From reading the various posts previously, I thought the ET had to be somewhere between 33-38 ish? So an ET 40+ needs a spacer to bring it back down to the 30 range. So confused if these Pentas at ET21 fit, then would the ones I've seen with above dimensions fit?

[silverbullet]

Thanks. There is so much confusion and BS talked on this subject its not.true.
Engineer talk first:
The ET or German for negative offset or "inward offset" or however you want to describe it on a T3, is just a means to measure how the wheel rim and tyre poaition relates to the steering axis (an imaginary line drawn through the centres of the top & bottom balljoints) and how this should pass down through the contact patch of the tyre on the tarmac under all suspension movement and steering angles, or as near to this as is mechanically possible.
This is essential for safe, predictable handling and good road manners.
It also a means to get the corner weight and cornering/braking loads on the wheelbearings balanced, for long service life.
Too much outward offset will make the steering "kick back" and make a vehicle heavy to steer, along with causing premature bearing failure through uneven loading.

Whether a particular rim will fit or not depends on the particular van.
Measure the gaps that you already have on your existing rims when fitted, add half the width increase and then allow for the change in ET and the larger rim diameter, to work out where the inner rim will sit and if it will foul the upright or top balljoint.

Smaller ET means that the rim moves outwards. Its that simple.

[silverbullet]

PS a 6 x 15" will have approx. half an inch more clearance on the inner rim than a 7 x 15" of the same ET

[California Dreamin]

Just to re-enforce just how close things are.....when I first fitted my standard 14 inch VW Carat alloy wheels with common 185R14C tyres, I balanced them using clipon weights (these are one way of balancing alloys without using traditional knock on weights that damage the rims). The only trouble was that the 5mm or so that the weights stuck out from the rim was enough to hit the uprights (California with power steering uprights)
I ended up re-balancing the front wheels with stick on weights...lesson learned.
I too was very surprised at the very small clearance.

Martin