Ess8

I have a S8 with 255/45/18 tires on the stock wheels. I want to move the wheels outward so as to give the car a more agressive stance from the wider track.

Can anyone reccomend what thickness spacers I could use to move the rims out as far as possible without the tires rubbing on the fenders?

Also, will doing this put too much leverage on the wheel bearings?

Thank you, Ed

ex-a8drifter

I believe OE S8 wheels are ET48

My replicas are ET35. I think you have like 13mm to play with there. My wheels come flush with the fenders.

I have 18x8 wheels 245/45 18 rubber.

So a rough width of your tires are 255mm (255/45-18), so you are about 10mm wider, so divide by half so 5mm wider (but I dont think its straight forward width though). So subtract 4-5 mm from the play, and you have between 8-9mm spacer range.

I'd even say that you'd be OK with a 10mm spacer all around. For fender clearance anyways.

I think this is right.....

ryoung

For the last 5 years, the summer tires on my S8 have been 255/35-20 on 9" ET 39 wheels. From this alone, a 9 mm (48-39) spacer would be OK. In addition, an 8" wheel width would pull the sidewalls in somewhat and result in a bit more clearance.

Here's the result with 255/35-20 on an 20x9 ET39 wheel. They've never rubbed.

<img src="http://pictureposter.audiworld.com/17157/right_front_aw.jpg">

Jkay

H&amp;R sells 5mm and 15mm spacers for us.

newfinish

HERE that's 8.5" 18" 35 offset
with 255 45 18
and I think a 10 mm would be very close if not touch the sidewall<ul><li><a href="http://i69.photobucket.com/albums/i76/AUDIA8MAN/avendre007.jpg">http://i69.photobucket.com/albums/i76/AUDIA8MAN/avendre007.jpg</a</li></ul>

BrianC72gt

Imagine you are sitting on the ground in front of the car on the driver's side looking straight back at the front suspension with your x-ray vision.

The scrub radius is the distance between the center of the tire's contact patch and the imaginary line that passes through the upper and lower ball joint pivots.

When looking at the car from the front with the wheels straight ahead, you want that imaginary line to pass through the center of the tire's contact patch. The distance between the center of the tire and this imaginary line is the Scrub Radius. You want a scrub radius as close to zero as possible. An increased scrub radius increases the effort needed to turn the wheels. It also increases the side load on the wheel bearings. The trick with installing wider wheels is to ensure that they are properly offset to minimize scrub.


If you ran a larger wheel, it would move the intersection point further out which would allow the use of back spacers. I've got no specs on the suspension to tell you how well Audi did in the factory setup, but I would expect they aimed for something close to Zero.

ryoung

The pic shows a positive scrub radius. With a negative scrub radius, the steering (kingpin) axis intersects outside the centerline of the tire. One advantage of negative kingpin offset is that the steering wheel or car doesn't pull one way or the other when braking with a flat tire.

I don't know whether the A8/S8 suspension uses negative kingpin offset; but if so, wheel spacers could reduce scrub radius to zero.

<img src="http://campus.umr.edu/fsae/library/sae_paper/fg2.jpg">

BrianC72gt

Love the drawing, but I would make one change, the upper balljoint is typically inboard of the lower one and the spindle has an ear to keep the hub face vertical at rest. This gives you a 5 to 7 degree outward tilt to the "kingpin Angle" (btw, my MGB still has kingpins instead of ball joints so this makes sense to me). The result is that changes in wheel diameter also have an effect on scrub radius (albeitnot a very big one - but some). That's why I mentioned a larger wheel also allows you to run it a little wider necessitating a spacer to keep the scrub at or close to zero.

Ess8

For all of your responses and help. It seems that I should give the 10mm spacers a shot. Now I just need to find some....

Regards, Ed