Braking on hills: scrub off speed vs riding the brakes?

[Avg_Joe]

Pardon the ignorance, but my wife and I were discussing this after a recent ride. There's a 3/4 mile steep downhill section on part of my route and I have gotten up to 32mph just coasting down it. Wife is not a fan of speed, so I suggested she scrub off speed as we descended: coast, squeeze the brakes to slow down to ~10-12mph, coast, rinse, repeat. She said "I'll just use the brakes all the way down."

Admittedly I don't know a great deal about bicycle disk brakes, but I'm quite familiar with vehicle brakes. And in a car, it's not recommended to ride the brakes: rotors can get warped, brake fluid can heat up/boil. Use the transmission and engine braking to control speed on long descents. That's not an option on an ebike.

My question is: Does it even matter on an ebike?

Does riding the brakes pose a risk of warping the rotor? and on bikes with hydraulic disks, is there a risk of boiling the fluid? Any impact on pads?

(I searched here and came up with nothing, pardon me if my search-fu is weak.)

 

[fauconnier]

Can Disc Brakes On Your Bike Overheat | Decline Bikes

Can Disk Brakes Overheat? What causes the overheating? Is it possible to control the brakes overheating before damage? Here are some insights for you.

www.declinebikes.com

 

[AHicks]

I agree with you. I think she'll have the answer soon enough if she were to "just use the brakes all the way down" on a long enough hill. Hopefully she won't blow through a stop sign learning that lesson.

My own experience, tempered with the fact I'm a little over 300lbs, would indicate it doesn't take a REAL big hill to get you interested in doing things correctly.... Just like if you were driving a car in the mountains.

 

[fauconnier]

IMO don't stress you wife with that, I know my wife do it all the time, in 3 years only 50% brake pads wear. I do a lot worst with my MTB, I never had a problem and I am not alone...

 

[fooferdoggie]

you can overheat brakes we have to watch it on our tandem. but only 3/4 a mile is usually not enough. but usually the best way is to apply brakes hard then let up and keep doing that so your not using them constantly.

 

[AHicks]

IMO don't stress you wife with that, I know my wife do it all the time, in 3 years only 50% brake pads wear. I do a lot worst with my MTB, I never had a problem and I am not alone...

I don't usually stress my wife with calls like this either (anything to do with shifting would be another example). I answer her questions, then let her do her thing. The issue with brakes is, if you are riding in an area with big enough hills, somebody could get hurt learning this lesson. Be careful!

 

[Jason Knight]

I live in New Hampshire, I know hills.
On a nearby hill I normally don't come down I smoked my front pads riding the brakes too much. New to disc brakes myself and having just replaced the rotor I wanted to give a burn-in.

It literally started blowing smoke halfway down. They started to feel like they had less braking power than they did at the start... and, well...

I stopped and let them cool for a bit, and there's the first lesson. If you feel it starting to lose grip, come to a complete stop and wait. There's no shame in that, take your time and do it right.

Next thing I did when I resumed the downhill was to zig-zag my course across the lane. It's called "tacking" just like in sailing. You can't do it in busy areas, people will look at you funny thinking you're showing off or something, but "tacking" a hill increases the distance thereby decreasing the grade, changing direction burns off momentum, and the end result is less wear on the brakes and a slower descent.

Considering I smoked them it means I got them as hot as hot gets, and the rotor itself is still fine. This is actually AFTER that ride and they're fine.

I did end up replacing the pads recently, but that was due to a mineral oil accident. They are glassed smooth, but until I dripped oil on them accidentally they were still working fine. Even after he oil accident they were still working, just extra squeaky!

Honestly I don't know what normal wear on pads for bikes looks like, so I can't say if they were abnormal or no.

... and the rear with the stock rotor still seems to be fine. I might leave that be even though I have a replacement I keep forgetting to install.

Bottom line, if it starts to smell, loses grip, or starts smoking, STOP. Let them cool, then apply other techniques to see if you can find a way to slow it down. "tacking a line" being one of the best ways to deal with it. You might even want to keep some water handy just to give a light splash for evaporative cooling while stopped.

Evaporative cooling is fun stuff, a little water on a hot surface can actually through evaporation suck so much heat away, it cools below ambient.

 

[AHicks]

To add a level of discussion I just thought of, there's also the potential for said wife to be using rear brake only.....

 

[fooferdoggie]

I live in New Hampshire, I know hills.
On a nearby hill I normally don't come down I smoked my front pads riding the brakes too much. New to disc brakes myself and having just replaced the rotor I wanted to give a burn-in.

It literally started blowing smoke halfway down. They started to feel like they had less braking power than they did at the start... and, well...

I stopped and let them cool for a bit, and there's the first lesson. If you feel it starting to lose grip, come to a complete stop and wait. There's no shame in that, take your time and do it right.

Next thing I did when I resumed the downhill was to zig-zag my course across the lane. It's called "tacking" just like in sailing. You can't do it in busy areas, people will look at you funny thinking you're showing off or something, but "tacking" a hill increases the distance thereby decreasing the grade, changing direction burns off momentum, and the end result is less wear on the brakes and a slower descent.

Considering I smoked them it means I got them as hot as hot gets, and the rotor itself is still fine. This is actually AFTER that ride and they're fine.

Bottom line, if it starts to smell, loses grip, or starts smoking, STOP. Let them cool, then apply other techniques to see if you can find a way to slow it down. "tacking a line" being one of the best ways to deal with it. You might even want to keep some water handy just to give a light splash for evaporative cooling while stopped.

Evaporative cooling is fun stuff, a little water on a hot surface can actually through evaporation suck so much heat away, it cools below ambient.

that may cause the disc to warp with that sudden cooling better to learn to modulate your braking. on a regular bike you can use the back brake for a bit then switch to front while the back cools off. thats how I do it on the tandem on really long descents.

 

[Rexlion]

I live in New Hampshire, I know hills.
On a nearby hill I normally don't come down I smoked my front pads riding the brakes too much. New to disc brakes myself and having just replaced the rotor I wanted to give a burn-in.

It literally started blowing smoke halfway down. They started to feel like they had less braking power than they did at the start... and, well...

I stopped and let them cool for a bit, and there's the first lesson. If you feel it starting to lose grip, come to a complete stop and wait. There's no shame in that, take your time and do it right.

Next thing I did when I resumed the downhill was to zig-zag my course across the lane. It's called "tacking" just like in sailing. You can't do it in busy areas, people will look at you funny thinking you're showing off or something, but "tacking" a hill increases the distance thereby decreasing the grade, changing direction burns off momentum, and the end result is less wear on the brakes and a slower descent.

Considering I smoked them it means I got them as hot as hot gets, and the rotor itself is still fine. This is actually AFTER that ride and they're fine.

That gives new meaning to the phrase, "What have you been smoking?"

 

[Avg_Joe]

Hey I didn't stress my wife about it, she brought it up! As we approached the hill, I suggested she use the brakes to keep a speed she is comfortable with. I think she just applied gentle pressure on both brakes to keep at a pace she was comfortable with. It was after the ride that this discussion occurred.

Anyway, seems this little hill ain't much, and the likelihood of us causing brake problems is almost nil. But this has been informative and useful, thank you all. O and @Jason Knight that "tacking" suggestion is great; splashing water on hot rotors to cool them off not so great.

 

[JES2020]

Next thing I did when I resumed the downhill was to zig-zag my course across the lane. It's called "tacking" just like in sailing.

It's used in skiing also and for slowing down on a grade.

 

[Catalyzt]

IMO don't stress you wife with that, I know my wife do it all the time, in 3 years only 50% brake pads wear. I do a lot worst with my MTB, I never had a problem and I am not alone...

Mmm, I think it's worth stressing about just a little bit. I just replaced the front brake pad for the second time and replaced the original rear brake pad at 20 months of ownership and with about 1,000 miles on the odometer.

The terrain here is unusually steep, and also sometimes involves stop signs and light traffic on the way to the trail. I do go pretty fast downhill, but nothing crazy -- high 30s, fastest ever was 41 MPH. I'm still pretty new to all this, but it seems to me that the biggest risk is burning through the pads more quickly than you'd expect-- and not getting them serviced in time-- rather than the hydraulic fluid or the rotors, though I'm sure there are some potential concerns there as well.

I was with the mechanic as he replaced the pads yesterday, and had a great conversation with him. He said, "You're not doing anything wrong, the hills are what they are, you ride the way you ride." In other words, he did not suggest using a different technique, and did not think that would make a big difference.

What he did tell me was that the front pads were 20% and the rear pads were almost entirely gone-- had I ridden longer, I would have damaged the rotors or even the rest of the braking system. What I can add to that is: I didn't feel like I'd postponed this maintenance much, and wear on the rear brake was harder to hear than wear on the front brake, which makes sense because the brake is behind you. Your ears hear what's in front of you more easily. I would say that I rode only about 25 miles after I was certain that I was hearing something and it wasn't my imagination-- and by the time the bike was in the shop, the pads were basically at 0%.

Before my last big ride, I had thought that maybe I noticed some intermittent scraping sound, but at other times, it was absent. So I figured I was good for the long ride (which was only 26 miles.) Of course, at the point when I was furthest from home, after dark on the trail, and had climbed 1,500 feet or so and began my descent? That was the first time I knew for sure, "Okay, there is definitely a scraping sound, and it's definitely worse when I squeeze the rear brake lever harder." It's noteworthy that I only realized this on a trail that was nearly silent with no background noise, just crickets chirping. So I started avoiding the rear brake on the way home, which only had one steep section. And after that I did take one eight-mile ride with few hills, and a second four mile ride with many short hills before taking the bike in, though I was able to use the front brake almost all the time because the hills were short and not steep.

What it sounded like to me: A rhythmic scraping sound with a tempo that increases as speed increases, almost as if a leaf were rubbing against the rotor, like shh-silent-shh-silent-shh-silent.

So as soon as you hear something like that, take the bike in immediately. Visual inspection is difficult-- I've tried, but so far, it's beyond my pay grade.

 

[retiredNH]

Pardon the ignorance, but my wife and I were discussing this after a recent ride. There's a 3/4 mile steep downhill section on part of my route and I have gotten up to 32mph just coasting down it. Wife is not a fan of speed, so I suggested she scrub off speed as we descended: coast, squeeze the brakes to slow down to ~10-12mph, coast, rinse, repeat. She said "I'll just use the brakes all the way down."

Admittedly I don't know a great deal about bicycle disk brakes, but I'm quite familiar with vehicle brakes. And in a car, it's not recommended to ride the brakes: rotors can get warped, brake fluid can heat up/boil. Use the transmission and engine braking to control speed on long descents. That's not an option on an ebike.

My question is: Does it even matter on an ebike?

Does riding the brakes pose a risk of warping the rotor? and on bikes with hydraulic disks, is there a risk of boiling the fluid? Any impact on pads?

(I searched here and came up with nothing, pardon me if my search-fu is weak.)

Am few things....first, in a car, "riding the brake" usually refers to folks who use their left foot for braking, and leave it on the brake pedal even when they don't mean to brake. This wears out brakes petty fast.
Second, it should not matter on a bike whether one steadily brakes on a long decline or brakes hard then releases for a time. The energy that the brakes must dissipate is the same in either case (ignoring very minor contributions by wind resistance etc, that are speed related). It might be helpful to enter into a steep decent at a lower speed, but the advantage is pretty minor.

Jason, I'm up the hill from you so to speak, on the ridge between Keene and Peterborough. Any ride we do from home will be downhill, so yea, you're right about our local hills in SW NH. But the scenery is great, and the car traffic minimal as long as we stay off the numbered roads...

 

[JES2020]

Mmm, I think it's worth stressing about just a little bit. I just replaced the front brake pad for the second time and replaced the original rear brake pad at 20 months of ownership and with about 1,000 miles on the odometer.

The terrain here is unusually steep, and also sometimes involves stop signs and light traffic on the way to the trail. I do go pretty fast downhill, but nothing crazy -- high 30s, fastest ever was 41 MPH. I'm still pretty new to all this, but it seems to me that the biggest risk is burning through the pads more quickly than you'd expect-- and not getting them serviced in time-- rather than the hydraulic fluid or the rotors, though I'm sure there are some potential concerns there as well.

I was with the mechanic as he replaced the pads yesterday, and had a great conversation with him. He said, "You're not doing anything wrong, the hills are what they are, you ride the way you ride." In other words, he did not suggest using a different technique, and did not think that would make a big difference.

What he did tell me was that the front pads were 20% and the rear pads were almost entirely gone-- had I ridden longer, I would have damaged the rotors or even the rest of the braking system. What I can add to that is: I didn't feel like I'd postponed this maintenance much, and wear on the rear brake was harder to hear than wear on the front brake, which makes sense because the brake is behind you. Your ears hear what's in front of you more easily. I would say that I rode only about 25 miles after I was certain that I was hearing something and it wasn't my imagination-- and by the time the bike was in the shop, the pads were basically at 0%.

Before my last big ride, I had thought that maybe I noticed some intermittent scraping sound, but at other times, it was absent. So I figured I was good for the long ride (which was only 26 miles.) Of course, at the point when I was furthest from home, after dark on the trail, and had climbed 1,500 feet or so and began my descent? That was the first time I knew for sure, "Okay, there is definitely a scraping sound, and it's definitely worse when I squeeze the rear brake lever harder." It's noteworthy that I only realized this on a trail that was nearly silent with no background noise, just crickets chirping. So I started avoiding the rear brake on the way home, which only had one steep section. And after that I did take one eight-mile ride with few hills, and a second four mile ride with many short hills before taking the bike in, though I was able to use the front brake almost all the time because the hills were short and not steep.

What it sounded like to me: A rhythmic scraping sound with a tempo that increases as speed increases, almost as if a leaf were rubbing against the rotor, like shh-silent-shh-silent-shh-silent.

So as soon as you hear something like that, take the bike in immediately. Visual inspection is difficult-- I've tried, but so far, it's beyond my pay grade.

Have you considered using a drag chute in a back pack?

 

[AHicks]

Have you considered using a drag chute in a back pack?

An anchor carried in your front basket?

 

[fooferdoggie]

An anchor carried in your front basket?

no that could hook your front wheel when deployed. the flintstone method could wear shoes out too quick.
I was getting black gunk on the rear rotor on our tandem. these are shimano ice-tech rotors too. I think from too much heat. not enough to cause failure but it made me have to bleed the back brake lines more often. got to use the front brake more.

 

[retiredNH]

no that could hook your front wheel when deployed. the flintstone method could wear shoes out too quick.
I was getting black gunk on the rear rotor on our tandem. these are shimano ice-tech rotors too. I think from too much heat. not enough to cause failure but it made me have to bleed the back brake lines more often. got to use the front brake more.

Ice-tech? Who knew? (not me obviously). Thanks for the idea!

 

[fooferdoggie]

Ice-tech? Who knew? (not me obviously). Thanks for the idea!

I also have finned pads though I doubt they do much to cool unless going really fast.

 

[m@Robertson]

I stopped and let them cool for a bit, and there's the first lesson. If you feel it starting to lose grip, come to a complete stop and wait. There's no shame in that, take your time and do it right.

Thats actually a bad thing to do. It will induce a rotor warp. The rotors will cool unevenly as the area the hot pads are sitting over will stay hot. The thing to do is to slowly, gently ride without touching the brakes and let the air cool the rotors. This is the same procedure you use when bedding in new rotors. Heat one axle up until it is smoking and then don't touch it - use the other axle for braking until the freshly bedded one is cool. If you can't let the bike roll to keep the pads off that one spot, then dismount and keep the bike moving, walking it or something. This is only if you've really overheated the thing.

In amateur auto racing we did the same thing. Coming off the track you see cars doing a 'paddock parade' where they do the track exit and then do a slowwww circuit or two around the paddock area, letting the brakes cool before parking at their spot in the paddock.

Bike disc brakes are subject to all of the caveats as auto disc brakes. So you have to bed them, watch out for glazing, take care not to warp them etc. etc. The only thing I have never seen transfer over is crazing (cracking), which is a good thing given how thin bike rotors are.

I have super-steep hills in the Monterey area, and the hill down from my house is so steep, I have to ride the brakes hard all the way down to the T intersection at the bottom. I can't allow myself to get up to any level of speed cuz if I do I'll be going too fast to stop no matter how hard I squeeze the levers (pressure has to be constant or else). To keep from glazing the pads I have to buy brake pads that can take that kind of added abuse, and I use thicker 'downhill' rotors. Tektro Type 17s. Cheap at $25 and maybe the heaviest duty rotors on the market. But they are so thick only a few brakesets on the market can fit them.