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Disc brake alignment - how long should back wheel spin for?

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Disc brake alignment - how long should back wheel spin for?

Old 03-14-17, 10:42 AM
  #26  
cpach
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Originally Posted by 1Coopgt View Post
Maybe I should have put a disclaimer in there .... Your results may very . With that said it worked fine on my Goose.
I do this and pray--then check, and manually adjust if necessary.
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Old 03-14-17, 09:24 PM
  #27  
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Originally Posted by dabac View Post
I've never had much luck with that approach. Tightening the bolts, even in stages, tend to shift the caliper out of alignment again.

I prefer to loosen the bolts just enough so that firm pressure or tapping with a screwdriver handle (or comparable) is enough to push the caliper into position, and then to tighten in stages while alternating between the two.
Stuff a business card on both sides. Grab the brakes firmly and tighten both screws down. It'll come out just fine. Business cards are almost the perfect thickness for shimming the pad/rotor gap and they're widely available.
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Old 03-15-17, 05:52 PM
  #28  
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Originally Posted by 1Coopgt View Post
Your Brakes bedded in while you were riding it . You would need to lightly sand the disc's to remove the brake pad material in order to start over. I wouldn't worry about it now. Depending on what the pad material is they could be very noisy. My Motorcycle has sintered metallic pads and they can be very noisy ( the compound is very hard). Same thing can happen with your cars brakes depending on the type of pads you buy.
I tried (successfully, I think) to re-centre the rear caliper as described above and can now discern a very thin gap between pads and rotor on both sides. The rubbing/squeak does seem to have disappeared.

The brakes were still a bit noisy, so I went through a brief bed-in process (gentle brake pressure for 5 seconds, followed by almost 100% braking until wheels locked up), done about 3-4 time. I then went for a gentle ride over wet grass, and the noise has substantially reduced. Probably all is now normal, but I'll ask the LBS to check everything when I go for my post-sales check-up.

Thanks for the advice!

John
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Old 03-15-17, 05:57 PM
  #29  
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Originally Posted by johngwheeler View Post
I tried (successfully, I think) to re-centre the rear caliper as described above and can now discern a very thin gap between pads and rotor on both sides. The rubbing/squeak does seem to have disappeared.

The brakes were still a bit noisy, so I went through a brief bed-in process (gentle brake pressure for 5 seconds, followed by almost 100% braking until wheels locked up), done about 3-4 time. I then went for a gentle ride over wet grass, and the noise has substantially reduced. Probably all is now normal, but I'll ask the LBS to check everything when I go for my post-sales check-up.

Thanks for the advice!

John
Glad it worked out for you .
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Old 03-16-17, 02:53 PM
  #30  
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Originally Posted by gsa103 View Post
Stuff a business card on both sides. Grab the brakes firmly and tighten both screws down. It'll come out just fine. Business cards are almost the perfect thickness for shimming the pad/rotor gap and they're widely available.
This is an easy and reliable technique. Personally, I use a couple thin shims taken from a feeler gauge.

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Old 03-16-17, 03:35 PM
  #31  
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Originally Posted by 1Coopgt View Post
Loosen the 2 allen head bolts that hold the caliper to the frame. Apply and hold the rear brake on ,with the brake on tighten the to bolts that you loosened . The disc should be centered at that point .
get someone to help makes it easier than monkeying around with the brake in your hand, body over the rear and tools in the other trying to keep balance
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Old 05-23-19, 10:03 AM
  #32  
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Originally Posted by cpach View Post
It would be helpful if you mentioned the exact make and model of the brake. You mentioned that the clearance to the pad that was not rubbing seemed very close. This may or may not be wrong--pads on disc brakes are spaced very close because the system can operate with higher mechanical advantage with the pads closer, particularly if the pads travel at a linear rate as the lever is pulled, which varies by brand/model.

However, not infrequently on new bikes, particularly on brakes that are actuated by DOT fluid there will be too much fluid in the system which will space the pads too close to the rotor.

If your bike was in my stand, I'd first center the caliper so that the disc was centered between the pads Loosening the brake mounting bolts, squeezing the lever, and tightening them down SHOULD center the caliper correctly, but often due to some kind of friction this doesn't work, and I always double check and frequently have to slightly loosen the bolts to align them by hand. Be careful to never do this with the wheel moving--I ended up in the ER with a bisected fingernail trying to adjust a caliper with the wheel moving this year.

Then, if I determined that the pads were too close to the rotor, I'd remove the pads and open up the lever bleed port, cover it with a rag, and them press the pistons out to force out any excessive fluid, then close the bleed port, clean up the lever, and reinstall the pads, and recheck. I've built a handful of new bikes that needed this with SRAM brakes.

Also, the cases of pads wearing out involve racing in extremely muddy conditions, and were mostly problematic with cable-actuated disc brakes (because they don't automatically advance the pads as they wear). It would be extraordinary if you did excessive wear with the riding you've described. My advice for your cross bike is to ride it wherever you feel you want to. My experience is that the relative lack of traction and the brutalness of riding a rigid bike with not-particularly-wide tires results in a pretty cautious approach to riding semi-technical singletrack, and I've felt pretty safe about the bike, even when not feeling safe about myself.
I am having this very issue with SRAM hydralics on the rear wheel. Where is the bleed port for these calipers located? thx
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Old 05-23-19, 10:29 AM
  #33  
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Originally Posted by coltcraft View Post
I am having this very issue with SRAM hydralics on the rear wheel. Where is the bleed port for these calipers located? thx
I would recommend only opening the bleed port on the lever if I was checking for excessive fluid in the line. This also has the advantage of releasing air in the reservoir. It's a T8 bolt on the inside of the lever.

While this can resolve some problemsit does not preclude the need to bleed the brakes for real approximately annually. If you have older elixirs of juicys and they're not functioning after a bleed they belong in the trash as the time and money to service then further is better put towards new brakes.
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Old 05-23-19, 12:50 PM
  #34  
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I have a bike with the same brakes as the OP, and they were noisy from the get-go. They emitted a grating sound when they were applied, and the rear also had a howling sound. I centered the brakes, cleaned all surfaces, had the shop work on them, and the noise was still there. But the brakes worked great! Finally, this winter I replaced the pads with a different brand, and the noise stopped - but the pads were too thick and that caused the rotirs to rub. I eventually removed the pads and sanded them down a tiny bit. The brakes are oerfect, now. I never had those problems with Shimano brakes on my mountain bike, but maybe they were a different animal.
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Old 05-24-19, 12:01 PM
  #35  
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Ref disc brake squeal: If you didn't break in the pads/rotors before your ride, they can load up with "contaminants" and then begin to squeal. Ask me how I know…lol. I ended up sanding the rotor surfaces with 1000grit sandpaper and washing the pads with dishwashing liquid to remove all "contaminants". That got rid of most of the noise. I then used CRC Disc brake quiet to eliminate the rest. Good Luck.
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Old 05-24-19, 12:30 PM
  #36  
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a few SRAM manual PDF https://www.sram.com/service/sram/3,43

Sure the wheel QR isn't causing the over tightness if the hub axle bearings ,

and that's where the drag is, but you think it's the brakes ..







...

Last edited by fietsbob; 05-24-19 at 12:37 PM.
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Old 05-24-19, 02:28 PM
  #37  
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If it is QR, there is some more flex. TA seems better. Some occasional contact also happens with dirt, or different temps.

But one thing to check with all discs is to get the wheel on an actual truing stand with rotor adapter. I once had some flex noise and tried all the above suggestions to no avail. Truing on the bike isn't so great. I finally gave in and bought the $40 Park rotor thingy for my truing stand. Solved all my problems.

My fork still flexes, it still is QR, but I'm now in good enough tolerence to not have issues.

You problem may be different, but starting out with a true rotor makes all other attempts more likely to succeed. Keep in mind rotors get dinged up in racks, or in cars etc.
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