Disc Brake Power loss

Hey everyone!

Today I cleaned my unicycle and did some TLC to it. I took off the wheel from the frame and took off the cranks then proceeded to check everything for any failures. I then took the wheel over to the solvent tank and brushed off all the grease on the hub with a tooth brush being very careful not to get any solvent on the disc. (the disc is attached to the hub). I then repacked the bearings once again being EXTREMELY careful not to get any grease on the disc. I then took some rubbing alcohol and cleaned off the disc just in case it got any grease on it. Put everything back together and went for a test ride.

I was going down a hill and went to press on the brake and it felt as if there was very little grabbing. I had to squeeze the lever much farther than normal to get the amount of braking power that I wanted.

I then googled my issue and came up with the option of having dirty pads. I then proceeded to wash the pads with rubbing alcohol and then took a small propane torch to them to heat them up and evaporate any fluids on them.

Put it all back together and it still felt the same with not so much braking power.

What did I do wrong??? Accidental contamination of pads??? Is there any solution to fix the issue, or just get new pads?

Could it be a hydraulic fluid pressure issue?

I would have guessed contaminated pads as well.

You could lightly sand the pads to get a fresh braking surface which may or may not help.

My most helpful advice would be to ask this question in the brake section of MTBR as there is way more brake expertise there.

Taking a torch to your pads is probably what caused them to become glazed…excessive heat and brakes cause failure.

Sand the pads, you don’t need to clean the pads with any kind of solution or heat, and the rotors need nothing unless they get “glazed” from excessive heat, then a light “swirling sand action” will tune it up nicely.

I carry a little piece of sand paper in my water bag, just in case the pads get to grabby on the trail, I pull em, sand, and put em back. Best thing about MT 2 is the pads come out the back for easy cleaning.

and why do you clean you muni? :stuck_out_tongue:

I then took some rubbing alcohol and cleaned off the disc just in case it got any grease on it. Put everything back together and went for a test ride. QUOTE]

When you put the alchohol on is when you coated the disc. Alchohol is only 3% usually when bought over the counter. Most of the time it’s mixed with water with a wetter additive so it stays mixed. These are left behind after evaporation. This is what caused your brake fade I would say.

Sanding the pads is your only real chance at reviving them at this point, I’ve used this method several times on my MTB and it’s worked. It’s defiantly a good idea to have a spare set of pads laying around just in case you get oil/grease contamination.

Sweet guys thanks so much for the responses :slight_smile:

I checked some mtb forums and I couldnt find any that said anything about sanding. I remember reading something about it on here but then i asked my dad and he sort of gave me a crazed look so i thought I would ask you guys!

Ill let you know if the sanding works.

Alcohol is usually 70-90%. I’ve seen it as low as 50%. Of course, that still means that there is at least one non-alcohol constituent.

You might have been thinking of Hydrogen Peroxide which does tend to be 3% as sold in drug stores.

just checking, did you use clean sand paper?

I’m not sure why it was said above, but scorching the pads to remove impurities is the first way to try to correct poor braking (if lever feel is proper, and not in need of bleed). So that was correctly done, sanding is actually not recommended unless there is a very visible glaze on the pad. That mostly happens to sintered pads rather than organic though. Also cleaning the rotor with rubbing alcohol is acceptable, but I would suggest a better cleaner like cleanstreak or brakeclean, these don’t leave residues that tend to cause noise

It seems like there is no right answer :thinking:

Yupp clean sandpaper! 320grit :wink:

After I sanded up the pads and the rotor it seemed to grab more, still not as much as before but that may all be in my head. I still need to go out and ride and then ill know for sure.

I am not sure if the brake needs to be bled. Just the other day it was fine and then after I cleaned the uni it was soft on braking power.

Also just to note, after I sanded I got the squeak back. I myself like the squeak, I know how hard the brakes are working then. As long as the squeak doesnt turn into vibrating I dont mind it :slight_smile:

The description in the mechanical disc brake serbice is more obvious, but they both say the same, no cleaner or torch needed, just a little sand paper. I’ve been preping my disc brakes this way for a long time (twenty years?), never had a problem. Great fix for pads that get messed up on a ride, just a little sanding on the pads will fix your squeaky brakes and no fade issues.

Not sure where the idea of using a torch comes from, why in the world would you want to overheat your pad?? Overheated pads is usually the reason they fade and or squeal. Sanding removes the glaze, good for rotors or pads.

It’s the same process with rim brake brake pads and rims, though for the rims I use a 3M pad since sandpaper is a little harsh on the rims.

Cleaning will not affect your bleed, but your brake may be out of alignment since you removed the wheel. Squeaking is often due to misalignment, esp if the brake didn’t squeak before, so try resetting the wheel. Try spraying a little water on the pads for teh first few uses, that’ll stop the squeaking until the pads break in.

You didn’t mention whether or not the braking was sufficient before you took your uni apart. In my experience a brake in working order doesn’t get glazed pads from just taking the wheel off the bike, and putting it back on.

One of the things that can cause poor braking in this situation is that you have a caliper with a static shoe, and that the caliper alignment is even just a hair off of what it was before you took the wheel off. If the static pad is too far, even by just a bit, the brake will have poor to absent performance.

It’s a shot in the dark since I don’t know what calipers you have, and I don’t have your uni in front of me.

Damn and I was on a roll too. Had it all figured out:o

If it is not working try new pads, cheap and nice to have a spare set on hand

Does it feel like you have air bubbles in your brakes?