Sudden loss of braking performance on rear brake - Vado SL 4.0

[Cycologist]

The other day, I washed the bike since it gets very dusty. I primarily ride on crushed limestone trails which get dry and dusty this time of year. I also cleaned and lubed the chain.

On my next ride, I had almost no friction in the rear brake and it was almost useless, even while squeezing the brake lever pretty hard.
Normally, if I'd squeeze that hard, the wheel would lock up. Not anymore. Even while squeezing the brake lever, I can turn the wheel by hand, if I push hard enough. That shouldn't be possible, and I can't do it to the front wheel, which brakes still work correctly.

I only clean the bike with water (no soap), but I did clean the chain with Parktool chain cleaner, which is a bit oily. I figured I might have gotten some on the brake disc somehow, even though it's on the other side of the wheel. I cleaned the brake disc with some polymer safe solvent and then lightly sanded them. I also cleaned the brake pads.

I still have no braking power back there. My only thought is that the brake pads got contaminated somehow, so I ordered replacements, which should be here in a couple days. The bike has over 2K miles on it and the rear pads are almost gone anyway.

I hope it's just bad pads, but any thoughts on what else the issue could be?

 

[Ben J]

Contamination of the pads/discs will cause this. You can get brake specific cleaner to try to decontaminate. You may need to remove the pads to do a thorough job.

 

[mschwett]

Once the pads (and rotors) are contaminated with chain lube or cleaner, it’s VERY hard to get them back to 100%. I put a ziploc bag around my rotors whenever i use drivetrain cleaner because it really doesn’t take much and we’re talking about rotating parts.

If you really want to try, take the pads out, take the rotors off. Soak the pads in 90% + isopropyl alcohol, and scrub them. Then sand them down a bit with regular sandpaper, and repeat the alcohol and scrubbing. Clean the rotors thoroughly, both sides, and lightly sand. Clean again. Reassemble everything and bed the brakes again. (need to do this since you’ve removed the film of pad material on the rotors.)

I’ve had success with this, but also failure. And it’s a PITA.

 

[fooferdoggie]

yep or just buy new pads and sand the rotor. chain cleaner or such will strip the rotor clean but don't use it on the caliper.

 

[Stefan Mikes]

The bike has over 2K miles on it and the rear pads are almost gone anyway.

If you brake a lot (hills?) then the brake pads may actually be worn. How do they actually look like? A lot of material left on the metal supports?
I'm slightly surprised it is the rear that is worn; usually the front brake pads are gone first.

You would be really unlucky if you contaminated the pads. I usually wash my e-bikes with a low-pressure rim cleaner and then rinse them with low-pressure water from a long distance at a good car wash. I clean and oil the chain with the e-bike upside down. It has never happened to me to contaminate the brake pads...

If you want to be on the safe side, just clean the rotor with an automotive brake cleaner (do not sand it!)

 

[Cycologist]

The only problem with covering the rotor and caliper is that to clean the chain, you must turn the crank in the direction which spins the wheel, so they must be free of obstructions.

I heard it's a bad idea to force the crank to go in reverse on these bikes.

 

[spokewrench]

That happened to me this summer. I hadn't done anything to the bike but leave it in the garage. The mechanical brakes had been well adjusted with plenty of friction against the disc. When I rode it after a few weeks in the garage, the brakes were dangerously weak. Repeated braking with one brake at a time improved them greatly. Then I noticed that both brake levers could be pulled until they touched the handlebars. In a few stops, I'd worn so much off the pads that I ordered replacements.

I'd kept the garage door open so the bike wouldn't get so hot during the day and would cool down at night. This meant that from late night until late morning, it had sat in nearly 100% relative humidity. Brake pads can absorb moisture from the air, and moisture can soften them.

Your problem sounds so much like mine that I think wash water softened your pads. In conditions where pads may have absorbed moisture from humid air, a couple of minutes with a heat gun seems to improve performance.

 

[spokewrench]

The only problem with covering the rotor and caliper is that to clean the chain, you must turn the crank in the direction which spins the wheel, so they must be free of obstructions.

For lubing chains, I bought a set of squeeze bottles of an ounce or so and hypodermic needles. I use a 25 gauge needle to add a drop of Finish Line Dry to each side of each roller, then inject the rest back into the storage bottle. That way I know I lubed every "hinge," and there's no excess to drip. With this kind of lube, the chain stays so clean that I can just wipe it with a paper towel.

 

[Cycologist]

I cleaned and sanded the rotors and pads again.
I went out for a ride and still had not much friction until about a mile when it started to come back.
After two miles it was much better and after my 30-mile ride, it seemed like it was almost at 100%.

I got the new pads, but now I'll probably wait until the end of the biking season to swap them out.

 

[spokewrench]

That's what happened to me. Because I had mechanical brakes, I realized that by the time they were almost 100%, the pads had worn down a lot. I checked, and they were so thin that I replaced them immediately. I concluded that moisture had softened them to the point that braking was very poor. As I used them, they warmed and gradually got drier and harder. A heat gun can dry them without all that wear.

 

[fooferdoggie]

I cleaned and sanded the rotors and pads again.
I went out for a ride and still had not much friction until about a mile when it started to come back.
After two miles it was much better and after my 30-mile ride, it seemed like it was almost at 100%.

I got the new pads, but now I'll probably wait until the end of the biking season to swap them out.

did you use the bedding method of getting going and then using your brake lightly and coming close to a stop about 10 to 15 times? that's critical when starting fresh and its critical not to come to a stop while braking till you have done so. this will put the brake pad material on the rotor and make it grab. if you did not do this yo may want to sand the rotor again and do it right.

 

[Cycologist]

did you use the bedding method of getting going and then using your brake lightly and coming close to a stop about 10 to 15 times? that's critical when starting fresh and its critical not to come to a stop while braking till you have done so. this will put the brake pad material on the rotor and make it grab. if you did not do this yo may want to sand the rotor again and do it right.

Yes. I used to race cars years ago, so I used the same method I used to bed-in new car brake pads and burnish rotors. It seemed to work.

I'm contemplating replacing the rotor when I finally replace the pads though.

 

[Abridged]

I had trouble with my SL. 5.0 brakes. I went to Halfords who were no help at all. Found another mechanic who showed me the brake pads worn down to the metal! It caused much merriment in the shop. I admit I'm pretty useless at mechanics of any sort!

 

[fooferdoggie]

I had trouble with my SL. 5.0 brakes. I went to Halfords who were no help at all. Found another mechanic who showed me the brake pads worn down to the metal! It caused much merriment in the shop. I admit I'm pretty useless at mechanics of any sort!

you can usually hear the difference when the pads are that worn. they make a grinding sound

 

[MacCrackin]

Once the pads (and rotors) are contaminated with chain lube or cleaner, it’s VERY hard to get them back to 100%. I put a ziploc bag around my rotors whenever i use drivetrain cleaner because it really doesn’t take much and we’re talking about rotating parts.

If you really want to try, take the pads out, take the rotors off. Soak the pads in 90% + isopropyl alcohol, and scrub them. Then sand them down a bit with regular sandpaper, and repeat the alcohol and scrubbing. Clean the rotors thoroughly, both sides, and lightly sand. Clean again. Reassemble everything and bed the brakes again. (need to do this since you’ve removed the film of pad material on the rotors.)

I’ve had success with this, but also failure. And it’s a PITA.

The only true way to remove contamination from pads is simply automotive spray on brake cleaner.
Alcohol is not going to remove oils embedded in pads or rotors.
Removing pads and a good soaking brake cleaner application. Lay pads flat on 180 grit wet or dry 3M sandpaper, on solid flat surface, and remove glaze on pad face
still wetted, simply scrubbing pad back and forth on sandpaper. Till sand scratch is edge to edge.
This solvent flashes off quickly, and if hit again wipped off with paper towel a second time wetted will guarantee any oil type contamination has been removed.
Keep fingers off face of pads.

Presoak a clean micro fiber 4x4 section cut from towel, and scrub clean both sides of rotors. Contaminate can hide in milled holes of rotors, scrub them clean as well, or what's hiding in them can leach out onto pads.

Car washing soap could easily contaminate pads with a silicone/wax additive. Keep this washing container and scrubbing tools used only for the bike.
Small butane torch, heating them up to about 400f° maybe the only option where this isn't possible appling brakes to heat them up on a bicycle.
This happens often on motorcycles, and one simply applies brakes after wash down off & on for a couple miles to heat the pads up, and they'll work fine again after a few hard stops. But it is spooky the first time, on 1000lb cruiser, and zero brakes.
One can also dress both sides of rotors with same 180-220 sandpaper. Pads will break in a lot nicer.
Cheers

 

[spokewrench]

The only true way to remove contamination from pads is simply automotive spray on brake cleaner.
Alcohol is not going to remove oils embedded in pads or rotors.

Car washing soap could easily contaminate pads with a silicone/wax additive. Keep this washing container and scrubbing tools used only for the bike.
Small butane torch, heating them up to about 400f° maybe the only option where this isn't possible appling brakes to heat them up on a bicycle.
This happens often on motorcycles, and one simply applies brakes after wash down off & on for a couple miles to heat the pads up, and they'll work fine again after a few hard stops. But it is spooky the first time, on 1000lb cruiser, and zero brakes.

@Cycologist washed with plain water. Unless he applied chain lube with a squirt gun near the cassette on the right, I don't see how he could have lubed the brake, 4 to 6 inches away on the left.

I'd ridden daily for 3 years the first time I lost brakes. I was trying to get rid of that bike because I couldn't ride them all. It had been parked in humid conditions for weeks when a neighbor asked to try it. The garage door was open and it was foggy, which can mean the dew point is higher than surface temperatures. Condensation had made the bike wetter than I'd ever seen it, and neither brake worked.

I got the brakes back by riding them to warm and dry them. I thought that would warm the discs enough to prevent condensation, but a few minutes later I lost the brakes again.

The second time I had no brakes, it was another bike I hadn't ridden in weeks. The bike hadn't been wet, but it had been parked where nighttime humidity was nearly 100%. Repeated applications of each brake gradually improved them. Because they were mechanical, the levers told me that I'd lost more pad material in 10 brake applications than in the previous thousand miles.

Online I learned that car pads should be stored between 40 and 60% relative humidity. It affects the moisture content of the pad material. If it's too low, they get brittle. If it's too high, they get soft. It seems that humidity had softened my pads to the point that they were letting the discs slide pretty easily.

@Cycologist said he washed with plain water. I say moisture, not chain lube or soap, is the obvious problem. If the back brake sat wet until his next ride, I think the pads could have absorbed enough moisture to lose their grip. Riding and braking would have warmed and gradually dried them.

 

[Cycologist]

It might have been just water on the pads that caused this. It's strange that they didn't come back after two rides though if that were the case. I had to clean and sand the pads and rotor before they started to work again. I didn't have any brake cleaner handy, so I used polymer safe gun cleaner, which is probably similar and will dissolve oil and grease. The front brake also got wet when I washed the bike and it was fine.

I'm guessing bike brake pads are a little different than car brake pads. On my car, when the brakes get wet or there is high humidity, the brakes grab noticeably harder when I first start driving. They go back to normal when enough heat evaporates the moisture.

There is probably no way any chain lube got on the pads / rotor. I use Smoove chain wax which is in a small bottle with a tiny applicator tip.
I went on a ride yesterday and the brakes are definitely back to 100%.

 

[spokewrench]

A caliper will deflect a spray from most directions, so maybe spray didn't get into the front. My calipers are at different angles, so if water got into your front, maybe it drained better.

During a humid period, a third bike would start clanking each morning as soon as I touched the brakes over 20 mph. It could continue with the brakes off. Before long it would go away. The problem recurred on several days. I couldn't tell which wheel the noise was coming from. The next morning, I used the brakes one at a time on the hill. It was the front brake. I noticed another symptom: rough braking.

It went away after I removed the wheel and washed the disc. Braking was smooth, but the problem came back. The second washing, too, was a temporary fix. The third time, I washed it with wet sandpaper. It still returned.

I decided that humidity had softened the pads, but not so much that squeezing a little harder didn't compensate for a reduced COF. However, the first time of the day that I touched the brake going fast enough to heat the pad surface more than usual, material would be deposited unevenly on the disc. The heat would dry and harden the pad surface, and normal braking would smooth the disc.

If braking had dried only the surface of the pads and the humidity was too high for the pads to dry thoroughly while parked, the surface could again be damp the next morning. So I tested on my first ride, braking with one brake at a time, gently and at slow speed. They didn't feel quite right. After I spent a couple of minutes with a heat gun on each caliper, the pads performed better. I quit the test-and-warm ritual after a week because the pads no longer seemed to need it. I guess it took that many minutes with a heat gun to thoroughly dry the pads. Maybe it could be done in one session.

 

[BEC111]

A caliper will deflect a spray from most directions, so maybe spray didn't get into the front. My calipers are at different angles, so if water got into your front, maybe it drained better.

During a humid period, a third bike would start clanking each morning as soon as I touched the brakes over 20 mph. It could continue with the brakes off. Before long it would go away. The problem recurred on several days. I couldn't tell which wheel the noise was coming from. The next morning, I used the brakes one at a time on the hill. It was the front brake. I noticed another symptom: rough braking.

It went away after I removed the wheel and washed the disc. Braking was smooth, but the problem came back. The second washing, too, was a temporary fix. The third time, I washed it with wet sandpaper. It still returned.

I decided that humidity had softened the pads, but not so much that squeezing a little harder didn't compensate for a reduced COF. However, the first time of the day that I touched the brake going fast enough to heat the pad surface more than usual, material would be deposited unevenly on the disc. The heat would dry and harden the pad surface, and normal braking would smooth the disc.

However, If braking had dried only the surface of the pads and the humidity was too high for the pads to dry thoroughly while parked, the surface could again be damp the next morning. So I tested on my first ride, braking with one brake at a time, gently and at slow speed. They didn't feel quite right. After I spent a couple of minutes with a heat gun on each caliper, the pads performed better. I quit the test-and-warm ritual after a week because the pads no longer seemed to need it. I guess it took that many minutes with a heat gun to thoroughly dry the pads. Maybe it could be done in one session.

Very interesting analysis. Last month I was experiencing poor performance of the front brakes on my Vado SL 4. They worked but not strongly. I couldn’t lock the front wheel when I tried as a test. It’s been a hot and humid summer here in Northern Virginia, staying so until late in the season. It’s cooled off with lower humidity lately and brake performance is much improved. I suspect the pads could use a touch up - they’re new as of this spring and only about 850 miles - but the humidity issue could explain a lot.

 

[PCeBiker]

,.. One can also dress both sides of rotors with same 180-220 sandpaper.

Yeah,. that's what I used on my drill.