S8 rear brake upgrade
07-25-2004, 05:14 PM
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S8 rear brake upgrade
This weekend, I upgraded my rear brakes to the 2003 S8 setup, based on
information from these posts:
<a href="https://forums.audiworld.com/s4/msgs/739012.phtml">The post that got me excited: Don Istook uses S8 rotors on his racing S4s!</a>
<a href="https://forums.audiworld.com/s4/msgs/1444571.phtml">Matt's info may have come from the ETKA, which is a little vague. S8's have 280mm rotors, A8's have 269mm rotors; see my response.</a>
<a href="https://www.audiworld.com/tech/wheel1.shtml">Great tech article, but lists A8 parts not S8 parts.</a>
Unfortunately, the S8 part numbers were a little hard to come by (my response to Matt was actually posted <b><i>today</i></b>, to save future upgraders some pain). Because of this, I initially got the A8 parts and ended up doing most of the installation before <a href="https://forums.audiworld.com/s4/msgs/1707837.phtml">aborting due to fitment issues</a>. It turns out that the A8/269mm setup would have worked just fine, but at the time of this post, the caliper mounting bolts were not tightened all the way (I was test-fitting). The caliper lines up correctly once the caliper mounting bolts are torqued down... The red lines in the carrier comparison pic are a actually red herrings
.
Anyway, here's my S8 rear brake upgrade install pics. Enjoy.
Where we start, the stock rear brakes:
<img src="http://pictureposter.audiworld.com/2123/stock_brakes.jpg">
The S8 part numbers again (rotor: 8E0 615 301B, ($80.84 list); carrier: 4D0 615 425C, ($146.60 list)):
<img src="http://pictureposter.audiworld.com/2123/part_numbers.jpg">
The S8 parts (bigger and shinier) compared to stock:
<img src="http://pictureposter.audiworld.com/2123/carriers_side_by_side.jpg">
Note the venting on the S8 rotor:
<img src="http://pictureposter.audiworld.com/2123/rotors_side_by_side.jpg">
The S8 parts are a little heavier (weights are of the carrier and rotor together):
<img src="http://pictureposter.audiworld.com/2123/weight_stock_rotor_and_carrier.jpg">
<img src="http://pictureposter.audiworld.com/2123/weight_s8_rotor_and_carrier.jpg">
Here, you can see that the S8 rotor (left) runs a couple of millimeters farther outboard than the stock rotor (right):
<img src="http://pictureposter.audiworld.com/2123/rotors_side_by_side_edge_on.jpg">
The different "offset" of the S8 rotor leads to clearance issues with the carrier when mounted on the S4 knuckle (the carrier touches the caliper on its outboard surface):
<img src="http://pictureposter.audiworld.com/2123/clearance_without_washers.jpg">
A couple of 2mm washers between the carrier and the knuckle does the trick:
<img src="http://pictureposter.audiworld.com/2123/washers.jpg">
Split the difference?:
<img src="http://pictureposter.audiworld.com/2123/rotors_side_by_side_edge_on_washer.jpg">
No more touching:
<img src="http://pictureposter.audiworld.com/2123/clearance_with_washers.jpg">
I'm getting ahead of myself, though. First you need to remove the caliper, remove the pads, remove the carrier, then remove the stock rotor:
<img src="http://pictureposter.audiworld.com/2123/poor_mans_gear_puller.jpg">
<b><i>Don't laugh</i></b>, it works... I actually used the above setup and a heat gun to get the passenger side rotor off the first time. $40 at Sears gets you the real solution:
<img src="http://pictureposter.audiworld.com/2123/gear_puller.jpg">
To mount the S8 carriers, the S4 knuckle has to have a little bump ground off the rear knuckle:
<img src="http://pictureposter.audiworld.com/2123/bump_on_knuckle.jpg">
If you don't do this, the carrier won't line up correctly. I used a Dremel, takes about 3 minutes:
<img src="http://pictureposter.audiworld.com/2123/bump_on_knuckle_ground_down.jpg">
Then, mount the new rotor.
Install the S8 carriers using the aforementioned washers between the knuckle and the carrier:
<img src="http://pictureposter.audiworld.com/2123/washer_in_situ.jpg">
Re-mount the pads, compress the caliper (you have a thicker new rotor):
<img src="http://pictureposter.audiworld.com/2123/poor_mans_caliper_compressor.jpg">
Don't laugh, it works..
Remount the caliper, and voilą:
<img src="http://pictureposter.audiworld.com/2123/s8_brakes.jpg">
Those sharp of eye among you might notice that the splash guard has been deleted. I removed mine because I wasn't satisfied with the clearance I obtained by bending it back inboard. I removed my front ones too, (I run StopTechs) because tight clearances when cold led to rubbing when hot.
-Rob
information from these posts:
<a href="https://forums.audiworld.com/s4/msgs/739012.phtml">The post that got me excited: Don Istook uses S8 rotors on his racing S4s!</a>
<a href="https://forums.audiworld.com/s4/msgs/1444571.phtml">Matt's info may have come from the ETKA, which is a little vague. S8's have 280mm rotors, A8's have 269mm rotors; see my response.</a>
<a href="https://www.audiworld.com/tech/wheel1.shtml">Great tech article, but lists A8 parts not S8 parts.</a>
Unfortunately, the S8 part numbers were a little hard to come by (my response to Matt was actually posted <b><i>today</i></b>, to save future upgraders some pain). Because of this, I initially got the A8 parts and ended up doing most of the installation before <a href="https://forums.audiworld.com/s4/msgs/1707837.phtml">aborting due to fitment issues</a>. It turns out that the A8/269mm setup would have worked just fine, but at the time of this post, the caliper mounting bolts were not tightened all the way (I was test-fitting). The caliper lines up correctly once the caliper mounting bolts are torqued down... The red lines in the carrier comparison pic are a actually red herrings
.Anyway, here's my S8 rear brake upgrade install pics. Enjoy.
Where we start, the stock rear brakes:
<img src="http://pictureposter.audiworld.com/2123/stock_brakes.jpg">
The S8 part numbers again (rotor: 8E0 615 301B, ($80.84 list); carrier: 4D0 615 425C, ($146.60 list)):
<img src="http://pictureposter.audiworld.com/2123/part_numbers.jpg">
The S8 parts (bigger and shinier) compared to stock:
<img src="http://pictureposter.audiworld.com/2123/carriers_side_by_side.jpg">
Note the venting on the S8 rotor:
<img src="http://pictureposter.audiworld.com/2123/rotors_side_by_side.jpg">
The S8 parts are a little heavier (weights are of the carrier and rotor together):
<img src="http://pictureposter.audiworld.com/2123/weight_stock_rotor_and_carrier.jpg">
<img src="http://pictureposter.audiworld.com/2123/weight_s8_rotor_and_carrier.jpg">
Here, you can see that the S8 rotor (left) runs a couple of millimeters farther outboard than the stock rotor (right):
<img src="http://pictureposter.audiworld.com/2123/rotors_side_by_side_edge_on.jpg">
The different "offset" of the S8 rotor leads to clearance issues with the carrier when mounted on the S4 knuckle (the carrier touches the caliper on its outboard surface):
<img src="http://pictureposter.audiworld.com/2123/clearance_without_washers.jpg">
A couple of 2mm washers between the carrier and the knuckle does the trick:
<img src="http://pictureposter.audiworld.com/2123/washers.jpg">
Split the difference?:
<img src="http://pictureposter.audiworld.com/2123/rotors_side_by_side_edge_on_washer.jpg">
No more touching:
<img src="http://pictureposter.audiworld.com/2123/clearance_with_washers.jpg">
I'm getting ahead of myself, though. First you need to remove the caliper, remove the pads, remove the carrier, then remove the stock rotor:
<img src="http://pictureposter.audiworld.com/2123/poor_mans_gear_puller.jpg">
<b><i>Don't laugh</i></b>, it works... I actually used the above setup and a heat gun to get the passenger side rotor off the first time. $40 at Sears gets you the real solution:
<img src="http://pictureposter.audiworld.com/2123/gear_puller.jpg">
To mount the S8 carriers, the S4 knuckle has to have a little bump ground off the rear knuckle:
<img src="http://pictureposter.audiworld.com/2123/bump_on_knuckle.jpg">
If you don't do this, the carrier won't line up correctly. I used a Dremel, takes about 3 minutes:
<img src="http://pictureposter.audiworld.com/2123/bump_on_knuckle_ground_down.jpg">
Then, mount the new rotor.
Install the S8 carriers using the aforementioned washers between the knuckle and the carrier:
<img src="http://pictureposter.audiworld.com/2123/washer_in_situ.jpg">
Re-mount the pads, compress the caliper (you have a thicker new rotor):
<img src="http://pictureposter.audiworld.com/2123/poor_mans_caliper_compressor.jpg">
Don't laugh, it works..
Remount the caliper, and voilą:
<img src="http://pictureposter.audiworld.com/2123/s8_brakes.jpg">
Those sharp of eye among you might notice that the splash guard has been deleted. I removed mine because I wasn't satisfied with the clearance I obtained by bending it back inboard. I removed my front ones too, (I run StopTechs) because tight clearances when cold led to rubbing when hot.
-Rob
07-25-2004, 05:43 PM
#7
Increases rear bias by a factor of ~9.375%.
280mm/256mm = 1.09375. So now the 355mm kit probably has the effective bias of the 332mm kit, and the 332mm kit moves more rearward to about the point on the graph (i.e., to the right about the same distance as the distance between the 355 and 332 points) in the linked post where it changes direction and starts heading upward again.<ul><li><a href="https://forums.audiworld.com/s4/msgs/1273466.phtml">https://forums.audiworld.com/s4/msgs/1273466.phtml</a</li></ul>
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07-25-2004, 05:44 PM
#8
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The brakes are still in the pre-bed stage....
...where the old pads re-shape to the new rotors. Another day or 2 of normal driving and I can bed them in.
The S8 wheels have been great, except for the annoyance of the spacers (clumsy to mount, tire shops can't deal with them). I'm planning to mount the spacers to the wheels permanently to fix this, though.
-Rob
The S8 wheels have been great, except for the annoyance of the spacers (clumsy to mount, tire shops can't deal with them). I'm planning to mount the spacers to the wheels permanently to fix this, though.
-Rob
