Front Disc Brake not grabbing after cleaning, 1000 miles

[hoboin]

hello all i did major cleaning of my chain and than cleaned my brake rotors with rubbing alcohol. I took the bike out for a spin and didn't notice it until i was pretty long into the ride, but the front brakes were not grabbing at all, just cutting off the motor. I made it home using the rear brakes but i can't seem to find out whats wrong. I can squeeze it and not have the brake handle hit the handlebar, and i tried readjusting the cable at the brake end but that didn't help, it is stopping at about 5% of the total stopping power, almost no stopping. I tried doing the steps to center the brake pads but that did not help. I couldn't really find any solutions easily online, im thinking maybe the brake pad has gone dirty? Could i have worn out the pads already at 1000 miles? I think i tend to use the front brakes more than the rear just because i am left handed and prefer braking with that hand.

edit: i watched the video at reply #6 in this thread and was able to push out the inner pad towards the rotor using the adjuster and was able to fix it. Thanks for the replies. I had a brain fart and couldn't figure out what was going on. I am new to disk brakes and have only had experience with v-brakes.

 

[rich c]

sounds to me like it dramatically changed after the cleaning. I get 5.000 miles on pads for my Trekking ebike so I wouldn't jump to that conclusion. Rubbing alcohol is usually 30% water. Did the pads get soaked?

 

[hoboin]

i wouldn't say they got soaked, they may have had some alcohol when i was moving the rotors to clean them, but really not much as i was using a spray bottle to apply the alcohol. Yeah seems weird that it happened after the cleaning. I did take the wheel off and put it back on, maybe i bumped or pushed something out of alignment?

 

[harryS]

My SRAM Avid BB7 mechanical disk brakes also quit working last year on my fat tire 26", Since I don't ride that bike much, I let it go all winter til Spring, and I installed a Shimano Hydaulic caliper that I had sitting around since 2019.

Aha, I don't remember the exact reason why, but when I actually looked at the brakes, for some reason the caliper was cocked on the BB7's, and one side was hitting the rotor before the pads. I installed the Shimano hydraulics anyway.

 

[hoboin]

looks like the pad is not past the frame to make contact with the rotor. I have to see how i can move the pad closer to the middle.

 

[hoboin]

I am going to follow this video to push the pad closer, i think that is what i need to do.

 

[hoboin]

I am wondering if i need to replace the pads. I am going to look into measuring them and making sure i have enough stopping power. I am at 1200 miles and im having issues with the rear brakes not having enough stopping power.

 

[indianajo]

I have cable pull disks. I have to adjust the pad in on the wheel I use most every 6 months, or about 1000 miles. Mostly the front. I use organic pads which wear faster than metallic pads, but require less hand force. I'm age 71, too much force can cause joint arthritis.
DIfferent power wheels have the disk at different offsets. I have had to put washers under the caliper screws, or file down the caliper block, as I change from one hub motor to another. One side of the caliper does not move. It can have too big a gap, or too small a gap.

 

[hoboin]

I followed the above video to try to figure out whats going on with my rear mechanical disk brakes. The brakes just aren't gripping good enough even after alignment, single arm brake and single inner adjustment. I followed instructions and when adjusting the inner adjuster like they said and doing final turning does NOT give me braking. I have to move the lever arm closer to the bike mount.

I have adjusted my brakes by moving the caliper arm closer inwards, i now know that is wrong. But that is the only way i could get stopping power. Maybe i wore out my brake pads by adjusting incorrectly?

Also when i apply front brakes and try to move the wheel it always stays put, but whenever i have tried that with the rear wheel for the last few weeks it doesn't grip and goes forward a bit. If i apply brake and go backwards it holds tight. Is that a problem with my tire or the brakes? The rear tire is in the correct rotation position right now, but i was riding with the tread going the wrong with for a few hundred miles so maybe tread got worn down quickly? Tire is slightly worn directly in the middle.

 

[Scooteretti]

Just a few tips that may help:

• Remove your brake pads and ensure that you have the recommended minimum pad thickness remaining
• Inspect the pads. If they look glazed, feel or look oily (contaminated) or they are worn unevenly then this would certainly be the cause of poor braking
• If the pads have been exposed to any oils/degreasers etc.... it's usually best to just replace. We do not recommend some old tricks of taking a blow torch to the pads to burn the contaminants off.
• Clean the pads with rubbing alcohol. Typically when pads are glazed you would change them but one could also use a file and roughen up the surface of the pad. You want to try and file/roughen up the surface as evenly as possible to remove any glazing/surface contamination.
• With a clean paper towel clean your rotors with rubbing alcohol to remove any surface contaminants.
• Do not touch the cleaned pad and rotor surfaces with your fingers, dirty rags etc.....
• Clean the calipers before reinstalling the pads
• Reinstall and ensure that you get your pads set as close to the rotor without getting any brake rub
• Once installed go for a ride and bed in the brake pads. When riding squeeze the one brake and slow down but don't come to a full stop. Repeat this process 30 times or so to bed the brake. Then repeat with the next brake if required.

hope this helps,


Will

 

[m@Robertson]

The pic of the pads and rotor looks just great. Nice thick pad, not too far away from it. Looks like good pad alignment. For sure your pads are not worn down.

Are these cabled brakes? Have you adjusted your cable so there is zero play? Did it perhaps slip a tad when you were doing this work on the brakes?

What @Scooteretti is telling you is all spot on.

 

[PedalUma]

I get that I am late to the party on this thread and it is favorably resolved.
Something I like about Avid mechanical calipers are the red knobs. One on the inside one on the outside. You can adjust them in seconds without any tools. Tighten until it rubs, then back off slightly for each side. Then it will be tight and dialed in.