DIY: B7 RS4 Rear Brake Swap to B6/B7 S4 Full Write Up

[CHECKERED]

This is a DIY guide for upgrading your rear B6/B7 S4 brakes to B7 RS4

Table of Contents:

Difficulty

Benefits

Drawbacks

Why you shouldn’t do this swap

Needed tools and hardware

Installation instructions

Answer to: Are oem RS4 lines SS braided?

Difficulty:

I would rate this as 4 out of 5, you need special tools and rare sockets, this requires the removal of a hub/wheel bearing for clearance to drill the spindle, outside machine work is required, this is not something you can accomplish in your garage over the weekend, this is by no means a bolt on swap like the fronts, not for your average mechanic or even your average performance shop. This has been the hardest brake swap I have ever done, and I have a Frankenstein BBK on my altima; Infiniti G35S calipers with BMW 840 pads, Wilwood friction rings and aluminum hats that were machined out of forged aluminum blocks …that kit was a piece of cake, also under my belt; several BBK installs, RS4 front conversion, drum to disk conversions, brake conversions that required entire spindle and rear end swaps, do not take this swap lightly, this guide makes it look easier then it is.

Benefits:

The main benefit to this swap compared with any aftermarket kit is you get to keep your hand brake, and maintain a ‘none flashy’ low profile setup, I realize that’s a benefit to me but for everyone.

The Caliper:

The piston size is the same utilizing the same exact pad, however the caliper and carrier are beefier. A bigger caliper acts as a better heat sink then a smaller one, reducing the temperate of the brake system. Also a beefier caliper is stiffer, meaning that more hydraulic power is transferred to the rotor rather than spent flexing the caliper, in other words: the efficiency of braking system is increased.



The Rotor:

The OEM S4 is a traditional cast iron 300mm (11.8") diameter with a thickness of 22mm and a weight of 13lb.
The RS4 is a cross drilled 325mm (12.8") semi floating rotor (neither a full floating rotor nor a cast iron, it is somewhere in between) same thickness as OEM at 22mm but with a weight of 14lb, The advantage is being bigger by a full inch while only gaining 1lb. The bigger size allows the pad to bite into a faster spinning rotor creating more friction and allowing the caliper to apply more torque/leverage.

Drawbacks:

This swap requires some safety compromises, like the risk of the rotor not sitting flush with the centric ring on the hub which might cause wobbling and vibrations, it also requires removing some support structure from the carrier which might not be safe.

Cost: all new parts + machine work will cost around $2500, that’s only $500 away from a no-hassle bolt-on 4 piston rear Brembo kit. Obviously used parts is the way to go, you can also save $700-800 by reusing your S4 calipers with the RS4 rotors and carriers, more on that later.
Maintenance cost: oem rotors are a bargain at $65-75 bucks while the RS4 are wallet draining $300-350 each...or 600-700 per pair.

When you move un-sprung weight further away from the axel you end up "loosing hp" or you will put less power to the ground. So pound for pound, the farther the weight is from the axel the bigger the loss. This has to do with moment of Inertia, because the RS4 rear rotors are both heavier and bigger, you will end up with slower acceleration, If the 1/4 mile time is very important to you and you are doing this swap you must get true light weight floating rotors.

Why you shouldn’t do this swap:

If you want better rear brakes, buy quality OEM replacement rotors, performance pads, SS lines and use good fluid, if your mind is set on a BBK, buy a Brembo, this swap is not for the faint of heart. My reasons for doing it are probably different from yours, I got my rear RS4 setup for nothing when I bought my fronts, and all my cost was one new carrier ($200) new guide pin ($8) shipping on used rotors ($35), SS lines ($90) spacers ($55) and machine work ($370) = $758 minus a couple hundred for my S4 setup.

I was told this swap is impossible or too risky: I had something to prove. I had a buyer lined up for my oem S4 brakes, and couldn’t just back out because this swap is “hard”

Lastly, my car would inch forward when brake boosting on the line, I needed bigger rear rotors to prevent that.
So if you are crazy enough to do this swap and you are a hardcore DI-Yourselfer, continue reading.

Needed tools and hardware:

Time:

There is about 4 hours worth of work per side which includes, removing the hub, drilling, trimming the carrier, bleeding the system, doesn’t include outside machine work.

Tools:

Jack and jack stands, small secondary jack recommended

Flat head screw driver

Various torque wrenches and extensions.

BIG torque wrench with 1/2” drive



2-3 foot cheater/breaker bar recommended

T-30 and T-25 torx wrench or bit

10mm socket

13mm socket

18mm socket

Two 21mm sockets

11mm open ended wrench

13mm open ended wrench

15mm open ended wrench or thin pliers

8mm allen/Hex bit (an allen key will not work)



17mm allen/hex bit with 1/2” drive (for the axel to hub bolt, rare I had to buy online)

12mm triple square bit (had to buy online)



Audi/VW Rear caliper piston retraction tool, universal once will not work

A minimum of 0.5 liter brake fluid (1 liter recommended and a power bleeder highly highly recommended)

Drill (corded and variable speed preferred)

Heavy duty 1/2” drill bit (for metal)

2+ foot crow bar

Grinding wheel (a good dermal can work)




Hardware: (I included factory part numbers for reference)

RS4 Rotors 8E06986HODQ
RS4 Left Rear Caliper 8E0 615 423E
RS4 Right Rear Caliper 8E0 615 424E
RS4 Caliper carrier 8E0615425K (you need 2)
RS4 Carrier to spindle bolts: N91126801 (you need 4)
RS4 Pads 4B3698451A
RS4 Brake Lines 8E0611707H (two of theses)

Installation instructions

It’s a good idea to only do the swap on one side first, then drive around confirming there is no rubbing, vibrations, or unusual noises, if you did both at once it would be harder to pin point which side is responsible.

1.
a. Pull the parking brake

b. remove the center cap to expose the axel to hub bolt



using an 17mm Allen/Hex bit and the biggest torque wrench/break bar you can muster, loosen this bolt (don’t remove completely) if this bolt has never been removed before you can spray WD-40 the night before the help loosen it.



2.Loosen (do not remove) the lug nuts.

3.a. Jack up the car and place it on jack stands.

b. remove lug nuts.

c. remove wheel.

d. remove the T30 bolt that holds the rotor.



4. Release the parking brake.

5. Remove the fender liner it is held together by T25 bolts (the passenger side also has a 10mm bolt)

6. Using a small secondary jack, raise the spindle just a tad to alleviate strain from the shock.



7. Disconnect the shock at the base using 2-21mm sockets on both sides, you will need 2 wrenches and a combination of extensions, hold the main bolt and loosed the nut. The bolt should slide out fairly easily, raise or lower the spindle as necessary. If you are having trouble, you can gently hit the bolt with a mallet to get it started.



8.
a. Using a 15mm open ended wrench hold the guide pin and with a 13mm socket remove the caliper to carrier bolts, if you don’t have a 15mm ended wrench, you can place an Allen key as shown in the picture to stop the guide pin from spinning.



Due to clearance I had to use a 13mm open ended wrench to remove the lower bolt.



b. Slide the caliper out. (if it doesn’t slide out your parking brake is on, see step 4) Place it on a box or tie it to the control arm so there is no strain on the brake line.



c. Remove brake pads

9. a. Remove both carrier to spindle bolts using an 8mm hex bit and wrench





an Allen Key will not work, there is thread locker from the factory, you will need an actual wrench to loosen these bolts. This is why you had to disconnect the shocks’ lower bolt it sits directly in front of the lower carrier bolt.



b. Remove the carrier.



10. Place something under and in front of the rotor to catch it, (a extension cord spool, garden hose)

Place anything resembling a crow-bar behind the rotor and in front of the spindle and pull towards you, (do not hit it with a hammer you will just damage it) in the picture I have my jack handle however that didn’t work, I had to get a 2 foot prying bar to actually remove the rotor.


11. Using a T30 wrench or bit remove the 4 bolts that hold the dust shield.



Notice how you don’t get a straight shot to the spindle-carrier mounting location.



in this thread, the guy grinded down his hub for clearance do NOT do this, you risk unbalancing the hub.

http://audisrs.com/about481



12. Remove the axel bolt, and place it away from your working area so it doesn’t get dirty.



13. a. Push the axel inward and tilt it out of the way, first down, to get clearance for the upper hub bolts, then tilt the axel up or to the side for the lower hub bolts.





b. Using a 12mm triple square bit, remove the 4 rear bolts that hold the hub/wheel bearing inside the spindle, these are very hard to remove, keep trying, take a break, try again, I needed both hands and all my strength to break these loose, ones loose they can be removed by hand.

c. Slide the hub out. And place it away from the working area to reduce dust/dirt/metal shavings getting in there.


With the hub out, you have clearance to drill.

14. a. place tape over the hub opening to prevent metal shavings getting inside and on the axel.



b. Using a heavy duty 1/2” (metal specific) drill bit, enlarge the openings to accept the larger 12mm RS4 carrier to spindle bolts. A 1/2” drill bit will give you 12.7mm hole, while a notch smaller 15/32 drill bit will give you a 11.9mm opening which will be too small. The slightly large opening is not a problem, the OE opening is just slightly larger than the bolt by design to allow for expansion/contraction.

c. I first put the drill in reverse and with some pressure created a crater bore at the opening for easier drilling,
drill slowly and most importantly strait. The spindle looks like it’s made from cast aluminum so the metal is not super hard.

15. Put the hub/wheel bearing back together and install the hub to CV axel bolt, tighten to 90-100 ft/lb only so it’s snug.



16. In order for the RS4 carrier to mount on the S4 spindle you will need to shave 2-3mm off the bottom. This is easily done with a grinding wheel, a dermal will take a while and you will most likely go thru several grinding stones.

[CHECKERED]

17. Now the hard part, mount the rotor on the hub (use 2 lug nuts just to hold it in place, do not tighten) mount the caliper carrier with the RS4 bolts (18mm socket), once the RS4 rotor and carrier are mounted to the S4 spindle you will notice that the offset of the rotor is different, my offset came out to be 7mm, yours might be slightly different, so please measure to confirm.

To measure hold the rotor so it sits in the middle of the carrier (you might need a helper on this step) then insert anything thin thru the lug nut opening until it touches the hub, mark the distance between the hub and the inner opening of the lug nut in the rotor, that is the offset you need to correct. Or you can do what I did with the wheel spacers for the front RS4 kit:



buy shims and with tape place a few over the lug openings, mount the rotor and carrier, increase the number of shims needed to center the rotor, measure their thickness that is your number, repeat this a few times to make sure you get the same number.
In order to have the caliper and rotor mounted properly you will either need to push out the rotor by 7mm or machine 7mm off the caliper carrier mounting location, but there is a problem with both.

If you were to machine 7mm off the carrier you are losing two thirds of the supporting structure, this is considered unsafe. On the other hand putting a 7mm aluminum spacer, might create other issues, like caliper to wheel clearance, different expansion rates: steel hub|aluminum spacer|steel rotor| aluminum wheel also balance issues it will be harder to center the rotor with such a large spacer…the compromise I came up with is to shave 3mm of the carrier and use a 3mm steel spacer, (I know that’s not 7mm so the rotor sits slightly inward)

17. a. This is where machine work comes in, you will first need to have a machine shop shave 3-4mm (depending on your measurements) off the carrier and be perfectly flat, this has to be done precisely not something you can do in your garage even if you have a fancy bench drill.





For this to be done correctly, you will need your machine shop build a Jig to hold the carrier perfectly flat, they should then confirm this by putting in on a bench with an articulating measuring arm.



17. b. For spacers I got a ECS 3mm steel wheel spacer and had the diameter reduced from 138mm to 128mm, the end result should be gap of 1mm but no more than 1.5mm between the outer lug nut holes and the outer edge.



The opening was increased from 57mm to 77mm, take your own measurements especially if you get aluminum spacers or a different brand.





Looking back the safer (but more expensive) way would be to make a custom spacer, by bringing the hub and rotor to the machine shop, have them take measurements, so they can build a spacer with a hub centric ring so that the RS4 rotor sits flush and centered on the hub.

18. Once you have the carrier machined down, mount it on your spindle (without the rotor) and verify clearance, on mine the top edge had to be gridded down.



remove carrier, and make necessary adjustments, repeat until there is clearance.

19. a. Reinstall the dust shield. The S4 dust shield clears the larger RS4 rotor without any modification, the use of RS4 specific dust shields isn’t necessary.



b. install the rotor with the spacer behind it, a drop of glue or a very thin layer of JB weld can hold the spacer on the hub, for a more permanent solution you can spot weld it to the hub.



20. Install the RS4 carrier again and verify clearance, my carrier and caliper ended up sitting about 2mm closer to the hub, this is evident by the gap between the pad and rotor, on the RS4 the pad sits directly in the middle creating a rusty ring on the top(outer) and bottom (inner) of the friction surface, but once mounted on the S4 spindle, the pad sits flush on the bottom but with a larger gap at the top.



So the outer edge of the rotor might rub against the carrier, my driver side did, but passenger side did not, I’m guessing this is because the way the spindle was drilled. You have two choices here: drive like hell with the hand brake on to heat the rotor to red hot, as the rotor expands it will act as a gridding wheel and shave off the necessary gap, once contracted it will never rub again unless you managed to heat it up even further then your shake down run, I realize this is easy but unsafe. OR the gridding wheel way would be to drive around the block, park, take everything apart note where there is rubbing and shaving off those areas, then repeat until no more rubbing.

21. Once the carrier is mounted, install the brake pads.

22. You have two choices here: Route ‘A’ or ‘B’

Route A: Use the oem S4 caliper:
A23. it does fit and will work fine, remember that the thickness of the rotor is the same for both cars (22mm) although you lose the added stiffness of the RS4 caliper. Mount the OEM caliper to the carrier, if the piston expanded and won’t fit, in order to push it in, open the bleeder valve and with a special rear piston tool push in and turn clockwise. (under no circumstance should you rewind the piston while it is connected to the hard line and the bleeder valve is closed, you risk messing up your ABS pump or master cylinder)





Skip to step 27

Route B: Use the RS4 caliper:

B23 Install the RS4 Brake line on the RS4 caliper.

This is why the OEM S4 line don’t work, it bolts up to the body and the caliper but the mounting bracket is different, it technically ‘fits’…but this is not safe to have it at a weird angle.





you will need either aftermarket SS lines or oem but these are very expensive, currently there are only two manufactures for rear RS4 lines: StopTech and ECS, I went with StopTech.

working as quickly as possible, using an 11mm open ended wrench disconnect the old brake line from the hard line at the body and attach the new brake line.

B24
a.Once the S4 caliper is loose and on the ground, with a flat head screw driver remove the metal clip that holds the e-brake cable.



(under no circumstance should anyone pull the hand brake inside the car while the lines are disconnected, there is a self tightening mechanism that will wind up and you are SOL, you’ll have to remove the center console and with a special tool release the mechanism)
b. Squeeze both sides of the mechanism (removing the tension spring will make it easier) while squeezing push the cable 90 degrees down to release the ball joint, this is a bit tricky if doing it for the first time.



B25 Reinstall the brake cable to the RS4 caliper with the metal clip.



B26. a. Install the caliper over the pads, just like in route A if the piston expanded and won’t fit, in order to push it in, open the bleeder valve and with a special rear piston tool push in and turn clockwise. (under no circumstance should you rewind the piston while it is connected to the hard line and the bleeder valve is closed, you risk messing up your ABS pump or master cylinder)

b. Bleed the caliper.

27. Both for A&B:
a. put the fender liner back in,
b. put the wheel back on,
note about centering the rotor: in order for the rotor to be centered, the parking brake needs to be off, then tighten the lug nuts in a star pattern but with many more passes than normal, so hand tighten all five and keep going around hand tightening until you can no longer tighten them by hand, then with a small wrench do 1/8-1/4 turn going around and around in a start pattern then switch to your bigger torque wrench and repeat, so far my rotors are spot on centered.
c. lower the car and tighten the axel bolt to 145 ft/lb.

28. Drive around to make sure you have no rubbing and your rotor is not wobbling.

On my car on the passenger side, the outer edge of the rotor was rubbing against the carrier, to solve this issue I drove on the freeway for 10 miles with the hand brake until I had brake fade and the hand brake would no longer decelerate the car, then drove another 20 miles to cool the brakes, I have no more rubbing. If you are doing this method don’t pull the hand brake all the way up, just 2-3 notches is fine

29. Repeat other side. See step 1.





If you are doing a full system flush the order is as follows: passenger rear, driver rear, driver front, passenger front.

High performance brake fluid is obviously recommended, this time around I used Wilwood EXP 600 Plus it has some very impressive specs at 594F dry, 399F wet boiling points, although at 20 bucks a bottle it is pricey, and you need 2…



If installing new pads follow the instruction for proper bed in.

[CHECKERED]

To answer the old age question of: Are the RS4 OEM lines stainless steel braided?…as you can see they are not braided on the outside



and when I cut one in half



it is not a stainless steel braided on the inside just your common dense fibers, they do feel stiffer then the OEM S4 lines, but they are not SS braided.





Comparison:





DONE DONE DONE:











Impressions:

Car decelerate faster from high speed, not as significant as going to Front RS4 but noticeable, after a few canyon runs the brakes are as cool as a cucumber, while the OEM would get so hot you can’t even touch the wheel.
The car no longer inches forward when brake boosting
Overall, very happy.

Special thanks:

Thank you Matt Devo who was so patient waiting for me to do this swap (he bought my S4 rear setup in Jan)

Thank you to Dave (KryptoniK) who sent me his oem rs4 rotors refusing any payment even after I insisted

NO thanks to JHM who wanted to charge me $200 for one used rotor

Thanks to Greg and David @ eurocode who hooked me up with some bolts and machine work.

[Mr.Wrong]

Awesome DIY
Can't wait to do the same once I source out a set.

[audivoodoo]

Holy Photobucket Batman (well, make that cardomain)!! Very nice job. Thank you for all the time that you put into this for people like me whom you don't even know. You are one hell of an asset to this community.
Dave

[B6JoeS4]

NO thanks to JHM who wanted to charge me $200 for one used rotor

You have their supercharger and yet you're slamming them for not giving you freebie rotors?

For everyone else, JHM has a rear big brake kit that uses the OEM caliper and a 335mm light weight rotor. All for a few hundred more than what Check spent to get the RS4 kit on his car. No safety comprimises either.

[beemercer]

^Joe, slight nitpick, the JHM setup is a 335mm rear rotor.

[Axel-]

For everyone else, JHM has a rear big brake kit that uses the OEM caliper and a 355mm light weight rotor. All for a few hundred more than what Check spent to get the RS4 kit on his car. No safety comprimises either.

I don't see it on their website. Is this one of those "gotta call/email them and ask about it" products?

[RelakS4]

for the front plate

[kagangen]

first off, great write up. i think people should really be commended for taking the time to explain in words and pics how to do things to our cars. its incredibly helpful, particularly to a guy like me who thinks he is a grease monkey but is really a neophyte with a fancy socket wrench. btw, i love your car's stance and, although i never really loved the avus wheels, i think they look good on your car with its stance and the agressive look without the center caps.

[CHECKERED]

In response to Joe, I didn’t even see your post because of this:



But because ‘Axel’ quoted you and realized it's more of your BS, I had to respond:

You really need to stop assuming things, jumping to conclusions, putting words in my month, it is REALLY getting fucking annoying…hence the ignore list
Nowhere did I say I was expecting free rotors, but $200 + tax + shipping on one used rotor with 50K miles, when I can get a new one for $300 shipped, that’s BS. It’s not like they had to order one from somewhere or pull it off a car, it was lying around the shop collecting dust.

As far as having their supercharger, so what? I know it’s hard concept for you to grasp, I am not a JHM fan boy, some of their parts are awesome; tune, supercharger, short shifters. But other parts are garbage; all their “big” brake kits and all their NASCAR rotors…what a joke…why would I have rotors that are manufactured for NASCAR teams, stock cars hardly use their brakes.

If you are a hardcore ¼ time of guy, then yes, lightweight rotors is the way to go, if you actually drive your car you need the heaviest rotor you can muster, bigger rotor = bigger heat sink. More metal = bigger heat sink.

And I’m sure someone will jump in and say…”well they have a bigger air gap for better cooling”

They know NOTHING….about NOTHING…anyone I talked to about JHM lightweight rotors, one thing always comes up = warp, do you know why? Because the thin metal is prone to hot spots creating uneven pad material distribution. I personally know one guy who went thru 3 sets of rotors until finally gave up going back and forth with JHM and just sold them.

Air is not a good heat conductor, so you need to increase the surface area as much as you can, thinning out the metal doesn’t do that…big rotors on the other hand…
Lastly, I probably know more about brakes then anyone here on the forum, and certainly more than JHM, my knowledge and firsthand experience comes from a local ALMS (American Le Mans Series) team, on top of all the routine duties I was their brake guy, I was the only one who was allowed to work on the cars’ brakes.

/RANT

[S4fun]

Wow Checkered, you weren't kidding when you said there is a lot more involved. I want to upgrade my rear brakes as well, mostly to keep things balanced, but this is probably a bit more involved then I'm prepared to go at the moment. It seems like it was worth it all to you though, which is good to hear. How many pistons are the rear calipers? Are they dual piston, all on one side, or on both?

[CHECKERED]

Wow Checkered, you weren't kidding when you said there is a lot more involved. I want to upgrade my rear brakes as well, mostly to keep things balanced, but this is probably a bit more involved then I'm prepared to go at the moment. It seems like it was worth it all to you though, which is good to hear. How many pistons are the rear calipers? Are they dual piston, all on one side, or on both?

haha...told ya...
The rear RS4 caliper is the same as the S4, just beefier: single piston, obviously one side, and the piston size is identical.

It is worth it in the end (to me), as I mentioned the problem I was having was when I stage at the drag strip the car would start to inch forward starting the clock, so I wouldn’t get good times ~ 1.9XX 60’
I would have to shallow stage praying the wheels don’t cross the second beam while I’m torque breaking…eh…September 3rd in Fontana is when the true test will be.

[S4fun]

haha...told ya...
The rear RS4 caliper is the same as the S4, just beefier: single piston, obviously one side, and the piston size is identical.

It is worth it in the end (to me), as I mentioned the problem I was having was when I stage at the drag strip the car would start to inch forward starting the clock, so I wouldn’t get good times ~ 1.9XX 60’
I would have to shallow stage praying the wheels don’t cross the second beam while I’m torque breaking…eh…September 3rd in Fontana is when the true test will be.

Thanks for the info. I had the same problem on a Subaru a used to have once I put a turbo on it (before the WRX came over to the US). Once I got that taken care of I snapped a front axle at the line, so don't torque break too high. Even AWD won't get you home with a snapped axle.

Definitely post up your times once you go. I'd love to see them!

[B6JoeS4]

In response to Joe, I didn’t even see your post because of this:

But because ‘Axel’ quoted you and realized it's more of your BS, I had to respond:

You really need to stop assuming things, jumping to conclusions, putting words in my month, it is REALLY getting fucking annoying…hence the ignore list
Nowhere did I say I was expecting free rotors, but $200 + tax + shipping on one used rotor with 50K miles, when I can get a new one for $300 shipped, that’s BS. It’s not like they had to order one from somewhere or pull it off a car, it was lying around the shop collecting dust.

As far as having their supercharger, so what? I know it’s hard concept for you to grasp, I am not a JHM fan boy, some of their parts are awesome; tune, supercharger, short shifters. But other parts are garbage; all their “big” brake kits and all their NASCAR rotors…what a joke…why would I have rotors that are manufactured for NASCAR teams, stock cars hardly use their brakes.

If you are a hardcore ¼ time of guy, then yes, lightweight rotors is the way to go, if you actually drive your car you need the heaviest rotor you can muster, bigger rotor = bigger heat sink. More metal = bigger heat sink.

And I’m sure someone will jump in and say…”well they have a bigger air gap for better cooling”

They know NOTHING….about NOTHING…anyone I talked to about JHM lightweight rotors, one thing always comes up = warp, do you know why? Because the thin metal is prone to hot spots creating uneven pad material distribution. I personally know one guy who went thru 3 sets of rotors until finally gave up going back and forth with JHM and just sold them.

Air is not a good heat conductor, so you need to increase the surface area as much as you can, thinning out the metal doesn’t do that…big rotors on the other hand…
Lastly, I probably know more about brakes then anyone here on the forum, and certainly more than JHM, my knowledge and firsthand experience comes from a local ALMS (American Le Mans Series) team, on top of all the routine duties I was their brake guy, I was the only one who was allowed to work on the cars’ brakes.

/RANT

I cannot believe how much of a dousche you are. Why do you buy their products?

[koolade9]

<devil's advocate>
What about just swapping in RS4 rear knuckles vs. machining/spacer cost & additional work?
</devil's advocate>

Either way, solid write-up! I know this has been asked many-a-times in the A4 sections...

[CHECKERED]

<devil's advocate>
What about just swapping in RS4 rear knuckles vs. machining/spacer cost & additional work?
</devil's advocate>

I did think about that, first new they are $620 for both, canceling out the added machine work, and no guarantee that they are “bolt on” the smallest of differences and it won’t work, this is not something I wanted to experiment with mostly because sourcing used parts from an RS4 is incredibly challenging due to low production numbers and what seems like even lower wrecking rates and sourcing suspension parts from a wrecked car has its own risks, my the driver side carrier and rotor were messed up, hence the new carrier and used rotors from Dave.

If someone can source RS4 knuckles in good condition and see if they fit the S4, by all means…

[jfunkey]

As far as having their supercharger, so what? I know it’s hard concept for you to grasp, I am not a JHM fan boy, some of their parts are awesome; tune, supercharger, short shifters. But other parts are garbage; all their “big” brake kits and all their NASCAR rotors…what a joke…why would I have rotors that are manufactured for NASCAR teams, stock cars hardly use their brakes.

If you are a hardcore ¼ time of guy, then yes, lightweight rotors is the way to go, if you actually drive your car you need the heaviest rotor you can muster, bigger rotor = bigger heat sink. More metal = bigger heat sink.

And I’m sure someone will jump in and say…”well they have a bigger air gap for better cooling”

They know NOTHING….about NOTHING…anyone I talked to about JHM lightweight rotors, one thing always comes up = warp, do you know why? Because the thin metal is prone to hot spots creating uneven pad material distribution. I personally know one guy who went thru 3 sets of rotors until finally gave up going back and forth with JHM and just sold them.

Air is not a good heat conductor, so you need to increase the surface area as much as you can, thinning out the metal doesn’t do that…big rotors on the other hand…
Lastly, I probably know more about brakes then anyone here on the forum, and certainly more than JHM, my knowledge and firsthand experience comes from a local ALMS (American Le Mans Series) team, on top of all the routine duties I was their brake guy, I was the only one who was allowed to work on the cars’ brakes.

/RANT

Checkered not to be a Dick but what you posted makes no sence. Why because all race teams La mans NASCAR or otherwise use the same weight saving air gap rotor tech

Stoptech
Willwood
Brembo
Jhm

Use the same rotors and design when you look the weights are almost the same the designs are the same.

Here are the new Rotors from the CTSV street car they come with brembo two piece large air gap rotors with 20% weight reduction on the rotor rings. The compition CTSV as larger rotors that weigh less then the OEM ones. What is the most noticable difference.....the air gap is larger on the Compition CTSV rotors



And its one thing to work on brakes its another to know how they work

Notice how the Audi 24 hour at le mans uses the same brake rotors technology and so does gm performance our ALMS HAS THE SAME KIND OF ROTORS TECH that you see with the jhm rotors.

Just thought you should know

Regardless your a smart guy your going to think what you want to think. This post is about your rs4 upgrade and while I at first thought it was over kill remembering your trip home and how you were able to get the car upto 170mph so quick I would say its not over kill it was a smart investment of time
Looks clean great job

[boravr6]

(2)They know NOTHING….about NOTHING…anyone I talked to about JHM lightweight rotors, one thing always comes up = warp,(3)do you know why? Because the thin metal is prone to hot spots creating uneven pad material distribution. (4) I personally know one guy who went thru 3 sets of rotors until finally gave up going back and forth with JHM and just sold them.

Air is not a good heat conductor, so you need to increase the surface area as much as you can, thinning out the metal doesn’t do that…big rotors on the other hand…
Lastly, (1) I probably know more about brakes then anyone here on the forum, and certainly more than JHM, my knowledge and firsthand experience comes from a local ALMS (American Le Mans Series) team, on top of all the routine duties I was their brake guy, I was the only one who was allowed to work on the cars’ brakes.

1,. Its clear to me you know SOME about breaks... but your certainly not the expert you claim to be, and i doubt you were ever "in charge" of any race teams brakes. Any one in that position would know the "basic" information listed below...

2. Rotors don't warp. I wish you closet experts would eventually clue in since this has been covered so many times. They will CRACK before they warp PERIOD.

Reference material:

Break pad / rotor break-in

http://audirevolution.net/forum/index.php?topic=169.0

But if you don't trust what another well respected user in the Audi scene has to say about it... lets so what StopTech has to say on the matter...

http://www.stoptech.com/tech_info/wp...rakedisk.shtml

3. Finally you get something right. Hot Spots. These are the culprits for causing brakes to vibrate. If you HOLD on the brakes in one spot when the brakes are hot the brake pad material will literally bake on to the disc.

How do you get deposits on your brakes?

a. Use and abuse ANY brake until it gets hot. i mean HOT! Spending an afternoon on a road course will do it.
b. Once your brakes are hot, bring the car to a complete stop and keep your foot on the brake, causing the brake pad material to properly bake on to your rotor.

How can you avoid getting brake pad material baked on to your rotors you ask?

a. When you KNOW your brakes are hot.... (like being on the track) don't keep your foot on the brake when your at a standstill.

4. Too bad this guy you personally know doesn't have anyone in his entourage who know anything about brakes... could have saved him a fortune if he was properly educated by someone who knows... and not someone who THINKS he knows!

[CHECKERED]

Checkered not to be a Dick but what you posted makes no sence. Why because all race teams La mans NASCAR or otherwise use the same weight saving air gap rotor tech
Stoptech
Willwood
Brembo
Jhm
Use the same rotors and design when you look the weights are almost the same the designs are the same

haha, I agree most of that was banter.

As far as brembo, I can’t comment on other brands, I know that they look similar, and I was in the same boat thinking how different can they possibly be, then I started working on racing calipers and rotors, you won’t believe the difference in the specs and tolerances vs the street stuff, I know they claim “racing performance” but the design, cooling fins, alloy used, hats, down to casting machine that the use for racing rotors is different than the street application.

I’ll give you the best example I have: a very common size that comes in 15 different offsets Brembo rotor: 328mm diameter (12.913”) the lowest weight is 10lb (not including aluminum hat or hardware) 12 lb with…the smallest thickness they sell (for motorsport teams) 27mm with a 16.5mm air gap = 5.25mm of friction surface thickness on each side, by the way if you car weight more than 2160lb you can’t use those, if you have a 4000lb car you’ll need 32mm thickness with same air gap =7.75mm

And guess what thickness is on a Flying Lizard 996 RSR? 32mm
guess what the air gap is?17mm so there is 7.5mm of friction surface thickness on both sides, by the way that car weights 2425lb (dry FIA spec)

Volvo S60R race car Brembo brakes



Volvo S60R street car Brebmo brakes

2. Rotors don't warp. I wish you closet experts would eventually clue in since this has been covered so many times. They will CRACK before they warp PERIOD. !

Your reading comprehension is very poor, I didn’t say rotors warp…I said the term ‘warp’ comes up when talking about lightweight rotors specifically JHM, then IN THE SAME SENTENCE I talk about uneven pad material distribution = what people refer to as ’warp’….please read don’t skim thru…

1…Any one in that position would know the "basic" information listed below...

3. Finally you get something right. Hot Spots. These are the culprits for causing brakes to vibrate. If you HOLD on the brakes in one spot when the brakes are hot the brake pad material will literally bake on to the disc.

do you see the conflict in what you wrote. so do i know any basic info or not?
Ok dear sir, what causes hot spots?

4. Too bad this guy you personally know doesn't have anyone in his entourage who know anything about brakes... could have saved him a fortune if he was properly educated by someone who knows... and not someone who THINKS he knows

I met him after the ordeal with the JHM rotors, but you assumed otherwise. Fine, I wasn’t clear

[CHECKERED]

Alcon

Mustang street car:



Mustang race car:




Corvette race car:



StopTech

Porsche street car:






Porsche race car:




Do you see the difference in the fin design? The hardware used to secure the friction ring to the hat…the calipers the pads…everything is completely different between the street and race aplications

[crabpot]

Wow, that is an insane amount of work ... looks great though and I bet they feel amazing.

[Justincredible]

Good stuff checkered Ill get this over into the DYI section.

As for the JHM brakes. Im not an expert but from what Ive seen they are as jfunkey said directly comparable to The Stoptechs Ive seen and replaced even down to the willwood brakes on the mustangs. So it seems you might be a bit confused. The air gap has nothing to do with the weight of the car. Ive seen diesel race trucks that have a bigger air gap then we do and they weight closer to 6000lbs Ive known several people to road race with the JHM rotors just fine.

Hope this clears things up.

[CHECKERED]

Good stuff checkered Ill get this over into the DYI section.

As for the JHM brakes. Im not an expert but from what Ive seen they are as jfunkey said directly comparable to The Stoptechs Ive seen and replaced even down to the willwood brakes on the mustangs. So it seems you might be a bit confused. The air gap has nothing to do with the weight of the car. Ive seen diesel race trucks that have a bigger air gap then we do and they weight closer to 6000lbs Ive known several people to road race with the JHM rotors just fine.

Hope this clears things up.

Thank you.

I apologize for not making myself very clear, I am referring to the friction surface thickness = the overall thickness of the rotor – air gap /2= friction surface thickness on one side.

The oem friction surface thickness on an S4 is: 10.25mm

Which is your typical OEM style rotor plenty of material which is enough to go thru 2-3 sets of OEM pads.

JHM offers a thickness of: 5.75mm which is the absolute minimum, and not suitable for race applications on a 4000lb car, but the S4 is not a race car, so never mind that.

Surprisingly JHM 380mm and 365mm RS4 friction rings are at 7.75mm which is a satisfactory thickness, I might even buy the 380mm rings when I get 19” wheels.

NASCAR stock cars (couldn’t find any official specs) from pictures they look to be about 5-6mm of friction surface thickness , these are prone to overheating, cracking and hot spots, to solve this problem, they provided each rotors with an enormous amount of cooling, much more than any type of road course car.

Here is a few examples of the type of cooling NASCAR provides their brakes




What happened when the team didn’t provide sufficient cooling to the rotors





Here is a road course car: notice the top right corner, a single air duct.





If a few S4 owners run light weight rotors at the track without problems, great, I however won’t recommend them.

[jfunkey]

Thank you.

I apologize for not making myself very clear, I am referring to the friction surface thickness = the overall thickness of the rotor – air gap /2= friction surface thickness on one side.

The oem friction surface thickness on an S4 is: 10.25mm

Which is your typical OEM style rotor plenty of material which is enough to go thru 2-3 sets of OEM pads.

JHM offers a thickness of: 5.75mm which is the absolute minimum, and not suitable for race applications on a 4000lb car, but the S4 is not a race car, so never mind that.

Surprisingly JHM 380mm and 365mm RS4 friction rings are at 7.75mm which is a satisfactory thickness, I might even buy the 380mm rings when I get 19” wheels.

NASCAR stock cars (couldn’t find any official specs) from pictures they look to be about 5-6mm of friction surface thickness , these are prone to overheating, cracking and hot spots, to solve this problem, they provided each rotors with an enormous amount of cooling, much more than any type of road course car.

Here is a few examples of the type of cooling NASCAR provides their brakes




What happened when the team didn’t provide sufficient cooling to the rotors





Here is a road course car: notice the top right corner, a single air duct.





If a few S4 owners run light weight rotors at the track without problems, great, I however won’t recommend them.

bro I love ya but you seem to not know what your talking about. The point your missing is brembo stoptech willwood and others still have a ~6. NASCAR brakes and JHM brakes alike are not prone to over heat. They don't crack or hotspot more then thicker wall rotors. Thicker wall rotors actually are prone to have more hot spots then thin wall AIR gap rotors. Actually I posted this in my JHM roitor thread. My JHM rotors cooled quicker then my stock rotors.

The AIR gap tech allows you to run thinner serface. for a more efficent rotor.

While you might not recomend the kind of rotors JHM uses. Companys like brembo/stasis/stoptech/willwood/ and the new race brakes on the CTSV all use the same make up.

Just something to chew on. The CTSV weighs more then the S4 makes more power then the S4 and it comes with the same style rotors JHM sells.

Like I said you think what your think and I respect that. I see no need to take your great post about your RS4 upgrade and fill pages with this. If your feel that you need certian specs on your rotors then all the better for you. You and me have shown botrh sides to thisnk about lets get back on topic to your great rear upgrade.

Where are your dam videos get them up here

[CHECKERED]

lets get back on topic to your great rear upgrade.

Where are your dam videos get them up here

Agreed…
hey! I’ve been busy doing this…patience