Replace Q7 front rotors and pads - Page 2 - AudiForums.com


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  #11  
Old 07-21-2012, 08:10 AM
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Have not done rears. Can't figure they would be any harder. Will let you know when I get there. The sensor came in the pads. Just had to connect wire.
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  #12  
Old 07-22-2012, 09:44 PM
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I heard rear piston retraction needs special tool as it is screwed back in, as oppose to front that is just pushed via c clamp like any other car.

My repair manual is on the way and looks like it will be another week. Can you take pics of brake replacement manual references and post or specify what bolts need to be set at what torques.
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  #13  
Old 08-06-2012, 10:52 PM
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Quote:
Originally Posted by mj-tj-aj View Post
I heard rear piston retraction needs special tool as it is screwed back in, as oppose to front that is just pushed via c clamp like any other car.

My repair manual is on the way and looks like it will be another week. Can you take pics of brake replacement manual references and post or specify what bolts need to be set at what torques.
You can retract piston with no special tool. I personally found back brakes a bit easier than front
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  #14  
Old 08-06-2012, 10:53 PM
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Originally Posted by Q72010 View Post
You can retract piston with no special tool. I personally found back brakes a bit easier than front
Also, where did you order your repair manual?
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  #15  
Old 07-24-2013, 10:07 AM
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Nice DIY article, it was very easy to follow. I would take one of your recommendations a step further and also remove the bolt for the upper brake line bracket in addition to the lower one. It's a T30. A little difficult to access (absolutely must have the wheel turned all the way to the right), but it made it completely effortless to move the brake caliper around.

Just one question - can you confirm the caliper bolt torque? 200 ft-lbs seems incredibly high, and usually these specs are provided in a 'round number' in Newton-Meters and then converted to ft-lbs, and after the conversion it never works out to a nice round number in ft-lbs units. If the spec was 200 N-M, it would convert to 147 ft-lbs, which is a big difference. In my experience, 147 ft-lbs would be much more reasonable for caliper bolts, especially considering my Porsche caliper bolts are under 100 ft-lbs, less than 2/3's of this spec. Also, it really didn't take 200 ft-lbs of force to remove the old ones, although they have already been replaced once by a dealer. I have searched the Internet extensively and cannot find any other references to the Q7 brake caliper bolt torque.
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  #16  
Old 07-25-2013, 06:25 PM
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Quote:
Originally Posted by jmjq730tdi View Post
Nice DIY article, it was very easy to follow. I would take one of your recommendations a step further and also remove the bolt for the upper brake line bracket in addition to the lower one. It's a T30. A little difficult to access (absolutely must have the wheel turned all the way to the right), but it made it completely effortless to move the brake caliper around.

Just one question - can you confirm the caliper bolt torque? 200 ft-lbs seems incredibly high, and usually these specs are provided in a 'round number' in Newton-Meters and then converted to ft-lbs, and after the conversion it never works out to a nice round number in ft-lbs units. If the spec was 200 N-M, it would convert to 147 ft-lbs, which is a big difference. In my experience, 147 ft-lbs would be much more reasonable for caliper bolts, especially considering my Porsche caliper bolts are under 100 ft-lbs, less than 2/3's of this spec. Also, it really didn't take 200 ft-lbs of force to remove the old ones, although they have already been replaced once by a dealer. I have searched the Internet extensively and cannot find any other references to the Q7 brake caliper bolt torque.
I will check either tonight or tomorrow. It's from the Audi shop manual on my laptop
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  #17  
Old 07-26-2013, 04:34 PM
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I just checked my Audi manual.

It says 270 Nm

So 200 ft/lbs would be correct

I don't have a 200 ft/ld torque wrench so I just made them really frigging tight (and equal)
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  #18  
Old 07-30-2013, 09:13 AM
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Quote:
Originally Posted by dgjks6 View Post
I just checked my Audi manual.

It says 270 Nm

So 200 ft/lbs would be correct

I don't have a 200 ft/ld torque wrench so I just made them really frigging tight (and equal)
Thank you very much for confirming. That's frustrating, because most standard torque wrenches like mine only go up to 150 ft-lbs. I don't even know anyone that has a stronger torque wrench, but I'll definitely have to find one now.

Based on how the bolts came out, I can almost guarantee the dealer that changed my front rotors last time did not torque those bolts down to 200ft-lbs (I don't know why they wouldn't, but they definitely weren't that difficult to remove), and I never had a problem with the calipers - while using those rotors through two sets of pads.

Lessons learned on using the front rotors for two sets of pads (all OEM parts):
1) I had no significant problems, not even a single instance of brake squeal. The rotors wore so evenly that I had to run my finger across its face to detect the grooving.
2) I did have some extra vibration that increased over time due to heavily used rotors, but it was hardly even noticeable in the steering wheel. I only noticed it because I have headrest mounted DVD players (stanchion mount) and the one on the passenger seat would vibrate when nobody was using the seat (when someone was in the seat, it would help control the vibration). That vibration is now almost completely gone since I've replaced the rotors, so it appears that some of the vibration is due to worn tires needing to be rebalanced.
3) When the rotors are re-used, the lip on the outer edge of the rotor is much more pronounced towards the end of the life of the second set of pads, as you would expect with greater wear on the rotor. This is significant because this lip will prematurely trigger the brake pad wear sensor, as it's cutting into the sensor at a deeper level than the pads are actually worn. The lip in the rotor had definitely cut a pronounced groove into the top of the brake pad wear sensor. My brake warning light had already been on for three weeks and I STILL probably could have gotten at least 2,000 more miles out of that second set of pads (the wear warning groove on the pad was still visible), but since I was already pulling it all apart, I just replaced it all (I was about to take the Q7 on vacation and I was tired of the really annoying brake wear indicator on the dash). If you can get rotors turned for free or cheap, I would definitely recommend having that outer lip removed after the first set of pads.

Measurements for Wear:
My rotors are now just barely under 30mm thick. The minimum thickness is supposed to be 32mm. These rotors start out at 34mm, so I averaged 2mm total wear (1mm per side) for each set of pads. It seems that Audi designed the rotors to be just thick enough to last one set of pads before going below the minimum thickness, so I can completely understand why dealers would have to change the rotors any time they change the pads.

Without a doubt, anyone who reuses their OEM front rotors with a second set of OEM pads will wear those rotors below the minimum thickness. Obviously, do so at your own risk. I would not reuse front rotors on a vehicle that tows anything heavy, or is driven in a location or manner that requires heavy braking, because it would be more prone to warping the rotors. You want to make sure that whoever drives this vehicle on the second set of rotors can sense/feel potential problems developing in the braking.

For those who want to reuse their rotors, make sure you replace the pads with exactly the same type of pad that was previously used on that rotor. Using two different brake pad compounds on the same rotors can have adverse results - which I have personally experienced with my track car when swapping street pads and high-temp race pads. The only way you can reuse a rotor with a different compound of brake pad is to turn/resurface the rotor, but the Q7 front rotors do not leave you with enough material after the first set of pads to do this safely.

Other thoughts:
I will definitely look at alternatives for my next set of rotors and pads. Stop Tech is a very reputable brand in north American racing and they produce slotted rotors for this vehicle at only $100 each, with a coating on the centers and edges! I'm sure there are many others worth checking out, such as Frozen Rotors (which I run on my Porsche's to maximize longevity), but I'm not going to do that search now. Having just changed my rotors, it will probably be another 35-40,000 miles before I use up another two sets of front pads. Regardless, I don't like the idea of running the rotors below their minimum thickness. If OEM rotors weren't so expensive, I wouldn't feel like I needed to reuse them. But, given how well the first experiment worked out, and given what I paid for new OEM rotors ($237 ea from ECS Tuning) I feel obligated to get at least 35,000 miles out of them!! In the future, I will use a quality aftermarket rotor that costs around $100 and I will change the rotors every time I change the pads. CAUTION: I will change all four rotors and pads at the same time with the same brand of parts, because a different combination of rotors/pads on the front versus the back will have different braking characteristics. Running a different set on the front versus the back could alter the braking characteristics when braking on the edge at high speeds (i.e. for accident avoidance). With ABS, maybe it's not a problem, but I wouldn't want to test the ABS's ability to compensate.

My rear rotors are also on their second set of pads now and that brake job is coming up soon, so I'll update this thread again after I have info and measurements from that experience.
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  #19  
Old 08-28-2013, 11:54 PM
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very clear write up, would be helpful for me when a brake job needed.
thanks
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  #20  
Old 07-08-2014, 02:53 PM
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Default where did you get the repair manual

where did you get the repair manual CD? Would like to get one as well.
Thanks!
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