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Why do my bike brakes loosen quickly? I have to adjust them weekly. (lemmy.nz)

submitted 1 year ago* (last edited 1 year ago) by sylverstream@lemmy.nz to c/diy@beehaw.org

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I've recently installed new brake pads on my bike, all good. They are disc brakes. After a week they were too loose, thought it was because they were new, so readjusted them. A week later and I have to readjust them again. I only cycle about 70km per week. Before the pad replacement I didn't have to do it so often.

Is it still because they're new or am I forgetting something? Thanks.

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[–] sylverstream@lemmy.nz 2 points 1 year ago* (last edited 1 year ago) (2 children)

Assuming these are cable actuated disc brakes: check the cable tension. You did be able to adjust tension by using a Barrell adjuster on your brake lever. This looks like a knob between the lever body and the cable housing. Rotating it should increase (or decrease) tension.

Thanks, will give that a try.

Can you describe ‘loose’ more precisely? Do you mean you can pull the lever too close to the bar. Or something else?

Yes, it comes too close to the bar, so I can't brake properly.

What did you do to adjust it that fixed it?

I re-adjusted the brake calipers, so they would be closer to the disc again.

[–] indun@feddit.uk 3 points 1 year ago

Be careful with the cable tension barrel adjuster. As you turn it, watch the brake caliper: is there is any movement, stop turning the caliper and back off.

It would only be used to remove slack in the cable on installation - it shouldn't be used to adjust the brakes.

This is because a disc brake caliper only has a few mm of travel. So if use of the barrel adjuster "removes" 1mm of that travel, you end up with far less modulation available.

[–] Dave_r@reddthat.com 3 points 1 year ago (1 children)

Sorry - not trying to be pedantic, but say more about how you adjusted the caliper! Did you turn a knob on the brake caliper body (big red dial on the spoke side - at least on my old mechanicals)? Or did you tighten the cable tension at the brake itself? Or did you tighten the bolts that attach the caliper to the bike?

[–] sylverstream@lemmy.nz 2 points 1 year ago (1 children)

No worries at all! I'm so happy people are responding nicely here.

I have adjusted with that knob you mention, and with the bolts on the caliper.

Haven't touched cable at all, so guess I should check that first.

[–] Dave_r@reddthat.com 1 points 1 year ago (1 children)

The likely cause is that the cable is slipping, probably where it connects to the caliper. This is more likely if you loosened then re-tightened that bolt, less likely if you did not.

Loosen the cable fixing bolt on the caliper. Make sure the brake lever is free (not depressed). Carefully follow the cable housing from the lever all the way to the caliper - is it seating correctly in any cable stops? If so:

Pull the cable so that it is tight
Tighten the cable fixing bolt tightly (you may need a friend to help maintain cable tension while you tighten the bolt).
Wrap some tape around the cable just below the fixing bolt, as a marker.

How does it feel after that? Carefully try it out on a ride. Check the tape - is it squished/has it moved? (Probably not).

Ride for a few more days (carefully! Brakes are the most important thing on a bike!). How do the brakes feel?

If they are getting looser, but the tape has not moved that means the cable itself is not slipping, something else is changing.

I would avoid loosening the bolts that connect the caliper to the fork - if you do, make damn sure they get tightened again

Other things to check are:

How much wear do the pads have? Take them out and measure them. (If you have been dragging the rotors with the pads, you could be wearing them down. Seems unlikely). To measure, stack them on a flat surface and measure the height.
Are the adjuster knobs on the caliper moving? Mark then with a sharpie then take a picture, check if they are in the same place when things feel loose again (this is possible, but rare).
Are the calipers themselves in reasonable shape? (A cracker caliper could do this. I've never heard of that, but I'm not a bike mechanic, so... Maybe?)

Last time: brakes are the most important thing - if they don't work, go get them fixed by a pro before you ride.

Look up mechanical brake adjustment on Park Tools YouTube for videos.

Good luck, keep the rubber side down.

[–] sylverstream@lemmy.nz 2 points 1 year ago

Thanks for the detailed post! Much appreciated.

I watched Park Tools before, very good. I now remember that I wasn't able to use the inner adjuster knob when the caliper is mounted, because then it sits 1cm next to the electrical motor. I had to remove the caliper, adjust that bolt, then put it back in. It works, but not ideal.

I think I'll take it to a mechanic. I use the bike on a long hill, so definitely need my brakes to work.

Thanks again heaps.