S4 big brakes - new wheels won't fit

[Grant Lenahan]

Let's start with the basics.  Changing offset may be OK, but it is not 
desireable. It changes both steering and suspension geometry, and 
unless you think Audi made a terrible mistake that you are correcting, 
not for the better. You'll get lots of incorrect advice, mostly from 
wheel shops, that you can and should change offset to clear brakes and 
other obsticles.  That said, small changes - on the order of 5-10mm, 
should not have a big negative effect, but I have felt it, and it will 
- minimally - increase kickback, increase strain on all suspension 
mounting points, decrease the effective springing and damping, and 
increase scrub radius and thus scrub. If you are wondering, do a mind 
experiment and place the wheels at the end of 5 foot spacers.  Think 
abou;t how they would travel, especially when the steering knuckle 
turned on a pivot point 5 feet inboard of the wheel center.  Extreme? 
Yes, but exactly what is happening on a smaller scale.  Do the math.  
'nuf said on that topic.

Spacers are simply a means of changing offset.  They have the added 
problems of doubling the opportunity to get an eccentric mounting and 
create balance and runout issues. Plus it weakens the mounting.

But if you are intent on proceeding, at least get the facts.  Your S4 
should have an offset of -45mm, regardless of wheel size (again, 
despite what you will hear, since its measured from the centerline).  
What is the offset of the ones you got?  They may be offset less (more 
negative, say -50mm) or, more likely, they will already have added to 
your offset by 5-10mm, since -35mm was a popular offset for the larger 
Audis, such as the S6, A6 2.7t and others.  So if you were to space 
that out, you would be adding the spacer width to the 10mm 
(-35mm-(-45mm)) = 10mm you might ALREADY be offset.

Generally its best to solve these problems with wheels that have a 
spoke shape that accomodates big brakes.

Grant

On Aug 20, 2006, at 1:57 PM, Lincoln Rutledge wrote:

> My friend upgraded his S4 brakes, he calls them Big Reds.  I'm sorry, I
> don't much about them.  I believe it's a 2002 model.
>
> Anyway he got some new 18" wheels, I believe off a newer car (A6
> maybe?).  When we went to bolt them on, the face of the caliper hits 
> the
> inside of the spokes of the wheel.
>
> Now he is thinking spacers.
>
> Is that a good idea?
>
> Does anyone have an idea how big they should be?
>
> Will they make the tire hit the wheel well on the lip?
>
> I can get more specifics.
>
> Linc
>
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