Most factory cable-operated rim brakes are actually pretty decent. Even so, their performance can be improved by simply swapping to better pads. However…I am getting a lot of questions about upgrading with hydraulics, and swapping to disc brakes, so…here are my latest thoughts on this.
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I like disc brakes
V-brakes that press pads against the flat machined aluminum-rim sidewalls are very light, and very affordable. If your front and rear brakes are both functioning, and both are properly adjusted?…it’s likely that you can lock up both wheels if you want. So…if you can lock up the wheels, why would you “upgrade” to stronger brakes?
“Quick Disconnect” (QD) axle nuts, with a common cable-operated disc brake. I added a 1/2-inch stainless steel split washer between the outer and inner parts of the QD assembly. You can’t see the other side from here, but it is an identical set-up.
I have the silliest reason you will likely ever hear to prefer disc brakes. It makes it easier for me to take the front wheel off-and-on frequently (for loading my stretch cruiser onto the bike rack of my car). If you have quick-disconnect axle-nuts, and a disc brake?…it is VERY fast and easy to take the front wheel off, and without needing any tools. However, even if I had to use a small wrench to get normal axle-nuts off, I’d still like disc brakes for this. Rim brakes coupled with normal axle-nuts aren’t horrible for removing the front wheel, but…this is worth it for me…
Now that my personal preferences are out of the way…lets move on to some info I gathered.
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Rim Brakes
If your stock brakes are the common and popular V-brakes, they can actually work pretty good.
Common V-brakes
However…the next time the pads are worn, you might consider swapping to Kool Stop Dual-Compound pads. The salmon-colored compound works very well in wet conditions, but…it is soft enough that high-mileage riders say they wear out faster, and have to be replaced often. Of course, that would probably NOT be a problem if you only ride once a week.
The dark Kool Stop compound is a little harder so it lasts longer, but…even though it works OK in wet conditions, it doesn’t grip quite as well as the salmon compound. Kool Stop has a dual-compound pad that is half salmon, and half black. It has the best of both worlds. Try these first, before you spend a lot of money and time swapping to a disc brake system that you might not need…
Kool Stop Dual-Compound rim pads
FLIR is a Forward Looking Infra Red camera. It converts energy in the infrared spectrum to an image that uses colors to show where the subject is hot or cold, and by how much. If you compare the FLIR image of the disc brake on the header pic, and compare it to this front rim brake below, you can see that they both captured about the same amount of heat in the process of slowing down (both were using the same rider at the same speed, on the same downhill road).
A FLIR image of the heat coming off of a front rim brake, immediately after a hard stop. The top-tube is yellow because the rider lifted the bike out of a van with his warm bare hand holding it there. During this testing series, the rider did not use the rear brake at all (see how it is still completely blue)
These rim brake pads are rubbing against aluminum, which absorbs and sheds heat better than a steel disc, and the aluminum rim also has more mass than the disc. These FLIR images of the front wheel are very relevant because they show that when any vehicle is stopping, most of the weight is shifted forward. This means that the rear wheel is more likely to skid than the front wheel, and also that it is the fronts that absorb most of the heat of braking.
Even if both of your brakes are properly adjusted, if you test your bike by making some hard stops?…you will likely be able to feel a very big difference in the heat levels between the front braking surface compared to the rear. Of course, be aware that braking surfaces are often much hotter than riders realize, so exercise caution if you touch them with your hand. I use a non-contact IR thermometer. I point it at something and it gives me a digital readout of the temp. If you burn your finger, it’s on you (The Navy taught me to use the back of my left hand to test for heat, when trying to escape a fire).
If, for some reason…you decide you want to keep rim brakes, but you want to upgrade to hydraulic calipers (instead of the common cable-operated), Magura makes the HS33 hydraulic rim brakes.
One last word on “rim vs disc”…you may not be a downhill racer (DH), but one of the reasons discs have taken over this extreme application is that…a minor ding in the rim will not affect the function of a disc brake, allowing the rider to finish the race (or to limp back home, for a street commuter). But…any rim damage (however small) might stop rim brakes from working at all…
[edit: Scott Tuttle reminded me that when riding through wet conditions, rim brakes often work poorly. Thanks, Scott]
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Disc brakes…cable or hydraulic?
Many of our readers are fairly new to bicycles, but they really love their new ebike. As far as the stock brakes, many bike models are made to spend most of their time below 20-MPH (32 km/h), and their stock brakes are…adequate? But what if an owner has some money to spend, and wants to improve the stopping power of their street commuter ebike, now that they spend a lot of time at the national PAS speed limit of 28-MPH (45-km/h)? And of course…off-roaders frequently go faster than that, while using even more power than a street commuter.
I have seen owners buy an entirely new fork, just so it would have the caliper mounts, allowing them to swap-in disc brakes.
These are Surly Ogre forks. Many Ogre owners upgrade to a suspension fork, and then they sell their Surly disc brake Cromo solid-fork for $100 on Ebay. The additional threaded mounts shown are for various cargo bags, and the steerer tube fits a 1-1/8th inch head-tube format, and it is designed for a 29 X 2.1 tire. If you have a 1-1/8th head tube with rim brakes, you can swap-in this fork to add disc calipers. The Surly Troll is almost identical, but made for a 26-inch tire.
So, what about hydraulic brakes?
Replacing a cable-operated disc brake system with hydraulic calipers will have two major effects, and whether or not they are a benefit, is up to your individual preferences. One advantage is that instead of needing to adjust the pads regularly as they wear away, the hydraulic calipers automatically adjust for pad wear, so…the engagement point of the pads when you pull the brake handle will be more consistent. (Of course, you’d still need to replace the pads when they are worn down to their low mark).
The second effect is that it eliminates the sponginess of a cable system. Cables will stretch a little (even though they are made from steel wire strands). That tiny amount of stretchiness is not actually a horrible thing, because it makes the brakes more progressive. A light touch can apply light braking, and you have to take up some stretch in the cable before the handle really starts grabbing the brakes hard. They are less “grabby”.
However, some riders don’t like that, they only want their hand to have any effect on the amount of braking. This is referred to as a the “feel” of the brakes. Some high-performance riders have tried hydraulics, and they like them enough that they will never go back to cables.
Some off-road riders hate cables because the openings in the sleeves allow wet mud to get up inside the cable-sleeves, leading to a variable friction and a build-up that is difficult to clean out. This is why “gravel bikes” and Cyclocross bikes sometimes have full-length cable-sleeves, since saving a few grams of weight by having several shorter sheaths (with lots of exposed cable) is just not worth the aggravation.
Just for fun, here’s an insanely large-diameter 1190RX disc brake from Erik Buell Racing (EBR), for those times when too big is still not enough. He preferred one huge disc, compared to two smaller discs.
Are there any downsides to hydraulics? (other than the higher price, of course)
Hydraulics may occasionally have small leaks, and…that means more than just oil spots on the garage floor. It also means that any air which gets into the system needs to be bled out, or they become spongy and unresponsive.
Also, very few currently-available hydraulic brakes have any type of power cut-off (E-brakes) so the motor is prevented from being powered at the same time that you are braking. It’s possible to hook up a reed switch to the stationary part of a hydraulic brake handle, with a magnet epoxied onto the handle of the system. This way, when you pull the brake handle?…the magnet is also moved in relation to the Reed switch, and that will actuate a power cut-off. Some popular mid drives have a delay in the power cutoff of the pedal-assist-sensor system (PAS). A sudden stop can have the brakes “on” at the same time as the motor (at least for a few moments), so…an E-brake power cutoff is a very important safety feature.
One easy way to deal with this is to have a cable-operated E-brake on the rear brakes (either a disc brake, or the common rim brake), and put the hydraulic disc you may want on the front wheel, to handle the heavy work. Since this is a safety issue, only you can decide if this provides an acceptable level of safety (as opposed to have TWO operational E-brakes to cut power during braking)
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Bigger Disc Rotors?
I have noticed that many stock disc brake systems have a 160mm diameter rotor on both fronts and rear (and sometimes a smaller 140mm on the rear). If a certain model has one of the discs larger for additional braking leverage, it is usually the front rotor that is one size larger. The popular sizes are 160mm, 180mm, and 200mm diameter.
left to right, the official electricbike.com “banana for scale” calibrated in 4 inches and 10 centimeters, an Avid 160mm disc, Promax 180mm, and the Hayes 203mm. All of them are 1.8mm thick steel. I’m waiting for a Kung Fu movie where a young Chinese bike mechanic uses these to avenge the death of his father.
There is one warning I have about swapping-in a larger diameter rotor. I have seen pics of a fork that had some minor defect. It might have never surfaced with normal riding, but…the owner went to much more powerful disc brakes, and when he was riding at a very high speed, he applied the brakes firmly on a steep downhill, and…the fork bent back from the momentum of the heavy bike and rider. It was an electric longtail cargobike, about the heaviest you’d ever see.
That being said, why would anyone want a larger diameter disc, when the stock disc can “lock up the wheels” already? From my reading, enthusiasts have stated that they like the “feel” of being able to adjust the braking with just one or two fingers, rather than needing to pull hard with their entire hand to get enough grip (while on a fast downhill run).
The second reason is heat management. All common brake rotors are steel, so their ability to absorb and shed heat has limits. If you exceed those limits, the excessive heat build-up can warp discs, and fry pads, losing all braking ability at just the worst possible time (just when you need them most). My riding style might be different than yours, so…only you can decide if you “really need more”.
The holes and slots in the swept faces of discs are there to allow gasses that are produced from hot pads to vent away. Hot pads smell because they are producing gasses from being near combustion temperatures, and it is that off-gassing that could cause a hot pad to “float” instead of grip the disc. There are compounds that are resistant to off-gassing when hot, but…that type NEEDS to stay hot to have any grip.
This custom GIANT dual disc brake system is on the prototype of the Greyborg (notice it’s spelled with an “A” instead of “E”). The designer would ride the electric hubmotor to the top of a steep mountain road, and then…he’d roll downhill non-stop VERY fast. He kept enlarging the discs until they didn’t over heat any more.
A larger diameter rotor has more mass to absorb and shed heat (so it should run cooler than a smaller rotor), but be warned…if you are the type to crush the brake handle in a panic situation, a larger disc might cause you to stop very abruptly and fly over the handlebars. Wear a helmet and gloves…I do.
Be aware, when you move to a larger-diameter disc, the caliper has to also be moved farther away from the axle. There are adapters for this (I will try out the Origin-8 version, and post back here), so do your homework before buying.
One more caveat is…I had to buy a T25 Torx bit, because an Allen wrench will not work. (The tamper resistant Torx will also work. They have a hole in the center, and are useful for disassembling cordless tool batteries)
An Allen / Hex wrench on the left, and a Torx wrench on the right. Many disc brake rotors are held on by six Torx T25 bolts. I have also seen T20, though it is rare (Torx bits are cheap, so maybe get both?)
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Shimano Ice Tech
I doubt any of my readers will ever need disc brakes that are this high level, but…I couldn’t help but to be curious about what professional engineers are trying out, when a factory racer says the common style of hydraulic disk brakes still get too hot when he is beating on them like a rented mule? I thought the Shimano Ice Tech’s were very interesting, so here is what they are, and why they designed what they did.
Shimano Ice Tech rotors
The first thing I noticed is that the rotors have an aluminum spider. This isn’t to save cost when the worn part has to be replaced. Doing it like this makes the entire assembly heavier (by a few grams)…which most bicyclists resist. The aluminum spider is part of a system that absorbs the braking heat as fast as possible, and then tries to shed it as fast as possible to the surrounding air. That’s nice, but…it’s actually even more sophisticated than that.
If you look closer at the swept rim (the part that is replaced when it’s worn), it is a “sandwich” of two steel faces, with an aluminum core that is the part which is bolted to the spider tips. This is some serious heat management engineering! There is a less expensive version available if you don’t need the three-layer sandwich, found here.
Shimano Ice Tech pads, with aluminum backing plate and heat-shedding fins.
The engineering doesn’t stop at the rotor, either. Here is a pic of the pads, and they have an aluminum backing plate to immediately capture heat, and send it up to integral fins that are out in the airflow. I don’t think you will see many riders with this extreme braking system. You can use the Ice Tech rotors with the normal pads, but…these are the icing on the cake, if you want to go all the way…
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Some Antique Brakes
People who are new to ebikes might not have ever seen some of these antique varieties, so I enjoy any opportunity to add stuff like this. The front brake shown below is a “spoon” brake. The tire is solid rubber, mounted on a Penny Farthing (High-wheeler) from the 1800’s.
When bicycles were a new thing, much of their mechanical design were taken from the common solutions found on horse carts. The spoon brake simply rubs against the tire tread, and it works as well as you might guess. Slowing down on one of these is much like docking a power boat. You have to plan ahead, and really take your time slowing down.
A spoon brake on a high-wheeler from the 1800’s
When the “safety” bicycle became popular (made famous by John Starley), it was a milestone. After adding a freewheel (so the pedals didn’t have to move when the bike was rolling) and also adding pneumatic tires, there was an explosion of customers buying millions of these new “velocipedes”.
The hollow pneumatic tire meant that pressing a metal plate against the tread would no longer be desirable as a brake, so…a way had to be devised to make a more long-lasting brake system using the solid-rod linkages that were common. There was a short era when the replaceable brake pads were lifted by a solid-rod linkage to rub against the radial face of the wheel rim.
A radial rod-actuated rim brake
Somewhere along the line just a short time after this, some clever inventor realized that if the pads rubbed against the sides of the rim, the braking system could use pivoting levers to achieve very high clamping forces with a low hand effort. As a result, rims were then made with taller sides that were flat, for the pads to rub against in an axial direction. Axially-clamping pads that were operated by rods performed better, and once the rods were replaced by cables inside sleeves, that style of modern bicycle brake system ruled brake design for many decades.
{Theron reminded me that drum brakes are still available and work quite well. they are well-regarded in the heavy pedicab industry, so…don’t laugh at them. They can handle high heat, and they are fully enclosed away from rain and mud}
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My personal brake upgrades
The victims of my abuse this month will be my Electra Lux Fat 7D cruiser, and my “Junkyard Dog” Specialized GT Chucker DH.
The Electra has dual 180mm cable-operated discs from the factory, and they work “OK”. The rear will have the caliper swapped for an Avid BB7 caliper, which has a knob for adjusting the pad wear with no tools needed (using an E-brake handle). Not a huge upgrade, but…I have the parts laying here, so why not? The front will have a Shimano hydraulic system swapped-in, to see how much of a difference that makes, while keeping the stock 180mm disc.
Yup…I put the disc on backwards, who reads instructions right? (if you look close, there’s an arrow on the disc) So, I figured, why not take a pic? If you are new to bikes, the direction of the twisted-pattern rotor supports (spokes?) is actually important.
The Chucker will get a big upgrade from the stock 160mm disc to a 203mm. I suppose I could have just made it a small bump to the 180mm disc, but…This rear-hub ebike can do 40-MPH when a car is trying to kill me, so…203’s exist, and I’m putting one on. If the fork breaks at 40-MPH and I die, it’s been nice writing for you guys. I’ll try it first with a cable-operated caliper, and then I’ll swap-in a hydraulic caliper.
If those mods interest you, come back in a month, and this last section will have my impressions of those particular upgrades. Front cable to front hydraulic, small disc to large disc, small disc cable to large disc hydraulic. See you then…
The Origin-8 caliper mount adapter. It moves the caliper farther away from the axle, and you need one if you are swapping-in a larger diameter disc.
I’m back. The $12 “Origin-8 Torqlite” adapter moves the caliper farther out, which you need to do if you swap-in a larger diameter disc (*duh!…slaps forehead). Part number 12471 moves it out 20mm so you can go from a 160mm disc to a 203mm. If you are going from a 180mm disc to a 203mm, or 160mm to 180mm, use part number 12470…
UPDATE!
I recently test-rode an ebike a friend brought, and I assumed that the brakes were hydraulic. They felt awesome. I could brake light or hard, and the stopping power was impressive. I asked what kind of hydros they were and he said they were cable actuated with BB7 calipers, with a 203mm disc on front and a 160mm on the back. I asked why no 180mm on the back and he said the bike was so short that a bigger disc skids too easily when the weight of the bike is shifted forward on braking. However, if you have a longtail cargobike, a 180mm disc on the rear might work well (more mass for better heat absorption and dissipation?).
I weigh 200-lb, and the bike in question was an average full-suspension aluminum frame with a BBSHD and a 20-Ah 18650 pack, hard stops from approximately 30-MPH (48 km/h). Braking opinions without speed and weight criteria are not as useful as an assessment with that info included, amirite?
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FLIR
The awesome FLIR images in this article are from “the bike comes first” website.
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Written by Ron/spinningmagnets, March 2017
