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Absolutely not.Best practice requires that you ensure that the threads are clean, brake cleaner will usually do that, and the use a good product like Loctite to ensure that everything stays in its place.Also make sure that everything is properly torqued.
Audi spec is to replace them. Below is an excerpt from the quick specs Q5 booklet where you can see the reference. Notice on the rear ones it also uses a fixed torque, and then a further 90 degree rotation. That is a sign of a stretch type bolt, which is single use to torque properly as best practice. Honestly I am not convinced they are true stretch bolts (from having worked with them), but it is the spec. and their manual procedure.
Nonetheless, most indy mechanics and DIY'ers probably don't replace them. These days I do since it's a small part of the job price and I just throw it into some other online dealer parts order ahead of time. As noted in the preceding reply, if you don't replace, clean the threads and Locktite them. By the way, in back there are also carrier to caliper bolts. I usually replace those regardless at least once every couple of pad changes, since the hex head tends to get burred up. Also, if you live anywhere with snow or ice, replace the little Torx screws that hold on each rotor to the hub. They are less than $1 discounted, and they have a nasty habit of freezing in the threads when they get old. Unlike other parts, because those are trapped by the wheel when it bolts to hub, not only do I not not Locktite those, but I actually apply some anti seize paste.
MP4.2+6.0 Thanks for the info.So stretch bolts on the caliper retaining bracket ? I'm trying to wrap my mind around what advantage the German engineers sought by making this change .They didn't do it for fun.
MP4.2+6.0 Thanks for the info.So stretch bolts on the caliper retaining bracket ? I'm trying to wrap my mind around what advantage the German engineers sought by making this change .They didn't do it for fun.
Google something like "audi stretch bolt use" for more context. Lots of posts--and questions--about it. Audi hasn't really explained the why's AFAIK. Other big players use them more and more these days too.
FWIW, my own sense/speculation is a combination of minimizing on the road issues (until the part is touched) and probably more reliable factory build/torquing. The part gets well cinched down, but presumably repeatedly tested to be sure it won't strip, particularly for the hardened bolts in or through aluminum stuff that comes up in various places. Like me, you may have also had the experience of torquing something where the bolt sort of hangs up as you firm it up, but then yields in a non-linear way. On internal engine I would lightly oil the contact surfaces, but obviously on brake and suspension type stuff anything but LockTite (the other direction) isn't the way to go. By starting from a lower torque, that hanging up near the torque limit is probably less likely to happen, and instead the 90 degree (or 180 on some) gets the bolt/fastener more reliably to final spec. Perhaps easier to program the robots that do most of the factory build wrenching now too. Still, I scratch my head some on the fasteners themselves--they look like regular bolts. I have worked with classic stretch bolts on Audis and VW's that are more obvious--head bolts are where I first found them, plus the CV joint center axle bolt for a long time now. Those may have a slightly tapered shaft and not threaded in that area--where the stretch presumably happens more.
Having recently acquired a used last gen Golf R BTW--pretty contemporary to gen 1 Q5, but the transverse platform--the number of bolts following this type of spec has increased more and more. Just did a brake job and some light suspension modding on it last month. Much of the suspension and the larger brake bolts have stretch/torque to yield specs. Again, most look like regular bolts, though a few important long ones that bolt the engine subframe to the body are the tapered shaft classic stretch ones. Gets you into a quandary like on alignments where things are inevitably loosened to be moved around, subframe included at times. Fortunately the R is pretty much the A3/S3 underneath and shares part numbering, so I just throw any critical bolts in with my Audi online orders.
As an aside, there are also the lowly self locking nuts. Having owned the fun and ridiculously unreliable original C1 where I learned my Audi mechanical wrenching, it broke and spun loose exhaust nuts and studs like clockwork. If it happened on lower side, often you had to pull the head. Or, they corroded and froze in place, leading to broken hardened studs on attempted removal. Got me used to replacing those preemptively for the predictable head gasket problems. That reduced the fastener failure rate considerably--four different ones that racked up over half a million miles of wrenching and rebuilding. Actually, on subject that is also the only car I ever had a key caliper bolt come undone--fortunatey in the immediate neighborhood and only one of them. It was probably operator error forgetting to torque it, but ever since I am very mindful of all critical safety or reliability fasteners.
I'm in the process of replacing front rotors on my '14 Q5 TDI. The process is straight forward but I need clarification. I did the pads a few weeks ago. To replace the rotors I need to remove the calipers. Is this done by removing the brake caliper-to-brake-carrier bolts OR do I have to remove the brake carrier from the wheel bearing housing for clearance? I have replacement carrier bolts on hand. I appreciate any feed back. It's been while since I prepped my b8S4 for HPDE's back in the day.
I'm in the process of replacing front rotors on my '14 Q5 TDI. The process is straight forward but I need clarification. I did the pads a few weeks ago. To replace the rotors I need to remove the calipers. Is this done by removing the brake caliper-to-brake-carrier bolts OR do I have to remove the brake carrier from the wheel bearing housing for clearance? I have replacement carrier bolts on hand. I appreciate any feed back. It's been while since I prepped my b8S4 for HPDE's back in the day.
I'm in the process of replacing front rotors on my '14 Q5 TDI. The process is straight forward but I need clarification. I did the pads a few weeks ago. To replace the rotors I need to remove the calipers. Is this done by removing the brake caliper-to-brake-carrier bolts OR do I have to remove the brake carrier from the wheel bearing housing for clearance? I have replacement carrier bolts on hand. I appreciate any feed back. It's been while since I prepped my b8S4 for HPDE's back in the day.
I am in the middle of this procedure now and for some reason, after replacing the pads and rotor, then re-attaching the carrier, I could not get the caliper slide bolts to realign with the carrier holes! So frustrated! and can not figure out why? Everything seems the same. Any advice? 2015 A6 supercharged.
09-06-2018, 03:50 PM
