Nadine

Hiya,

What would be the ideal offset for 19 inch rims for the S4?

I have these rims below and there is a choice of offsets from 50mm to 67mm.

Can someone please recommend as need to place an order tomorrow as still do not understand all this offset thingy majig %?/%^?

Thanks

Nadine

Jim bailey - 928 International

This explains it pretty well..tirerack.com/wheels/tech/offset.htm - but simply stated more of the wheels need to be sticking in than out so the more offset the less lip you see on the outside and the less likely to have the tire hit the fender lip. As you use a wider rim and tire even more must stick to the inside. GT for the front used a 65 MM on a 7.5 inch rim . Rear was a 52 mm on a 9 inch rim.

Glenn Evans

The issue with the wheel diameter is to make sure that the overall diameter (OD) of the wheel and tyre is close enough to the stock OD to be within any limit mandated by your registration authority. The OD of the rear wheels will affect the accuracy of your speedometer and odometer.

IMHO you shouldn't go much wider than 255s on the rear, unless you can get a profile lower than 30. 255/30R19 on the rear has a nominal OD of 635,6mm; 1.4 per cent greater than the S4's stock 626.9mm, so your speedo will read less than before for the same actual road speed.

The 928 front suspension was designed to use wheels of 65mm offset.

Offset is the distance between the mounting face (where the inside of the wheel mates to the hub) and the centreline of the wheel. 65mm is a large offset compared to that used on nearly every other car. This is why The centres of the 928's stock front wheels appear to bulge outward because their mounting face is further outboard (away from the centreline of the car) than nearly every other wheel you see. Compare stock 928 front wheels with your stock rears (52.7mm offset); or those of Boxster fronts (55mm offset) or 911 fronts (most are 47mm, I believe; but don't take that as gospel). These wheels look "dished" or concave compared to a stock 928 front wheel.

If your new front wheels are WIDER than stock, you certainly cannot use a smaller than stock offset or your tyres will not clear the guards. If I recall correctly, Kim Crumb once posted that he recommended using a 70mm offset if 9 inch wide front wheels were fitted.

Why is the 65mm offset for the 928's front wheels important? I happened to write this for another forum last night:

The 928 front suspension was designed to have a negative scrub
radius, which means that the line through the steering axis hits the
ground OUTBOARD of the centreline of the wheel; -16mm for MY78 to 85,
and -10.2mm for MY86+ (MY86.5+ for the US). To achieve this scrub radius, all 928 front
wheels had an offset of 65mm (except for the forged Clubsport wheels on
the MY88 Clubsport and MY89 GT, which had 60mm, which gave these a
-5.2mm scrub radius.

The benefit of negative scrub radius is that, when there is uneven drag
on the front wheels - for example, if one is going through water or mud,
and the other isn't; or one has low pressure, and the other doesn't; or
the ABS is releasing one front wheel and not the other - the wheel with
the greater drag will be turned inward, countering the greater drag on
that side of the car ie the steering is self-correcting, to some extent.
If the scrub radius is positive, greater drag will turn the wheel
outward, adding to the tendency for the car to pull in that direction.

You should not fit a front wheel with a small enough offset to give you
a positive scrub radius. A 55mm offset front wheel on an MY86+ car will
give zero scrub radius, which is the absolute minimum you should go;
even that is not recommended. Boxster front wheels have an offset of 55mm, so they are candidates if you are prepared to tolerate the reduced scrub radius.

Glenn Evans

This may help:

Stromius

Also very useful is http://928registry.org/928-wheels.htm.
Good luck...also search the forums for 'offset'

RyanPerrella

I have 19 x 8 front with 57mm offset

19 x 11 rear with 51mm offset and dont use spacers. They fit perfectly!

drnick

nadine, i am jealous! those are the new turbo rims and they look wicked. dont worry about the outside diameter of the wheel too much, i have found that it makes the speedo more accurate when it is increased. 19s on a 928 look great i have the same style as ryan as picured above.

Nadine

I now have the sizes:

8.5 x 19 with ET 56 and 235/35/19
11 x 19 with ET 65 and 315/35/19

Will these fit my S4 ?

Thanks

Nadine

Vilhuer

19" diameter do not change ET requirement in any way what so ever.

This means 8.5" wide with ET 56mm will fit but it will stick out too much for some people. This means 225 or 235 is widest rubber which can be used with them. Even 235 can be problematic if suspension is lowered and fender isn't rolled. '90-91 MY S4 had rolled fenders from factory IIRR.

11" wide at rear is very picky about ET value as is 315 wide tire. On slightly rolled fender '87 S4 10.5" and 315 wide had only few mm space on both sides. This means ET must be just right for 11" to work even with rolled fender. I can't remember what ET was exactly but it was close to 65mm. Problem is that being just 5mm off will create fairly serious problems which can be unsolvable without using large hammer.

Art_Z

my rears are 67mm and i needed a 1" spacer to get them to fit in the rear. prob can go a little smaller, maybe 21mm