Mechanical disk brakes for dummies
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Mechanical disk brakes for dummies
Just learned that road brakes pullers have different brakes pull ratio from mtb pullers. Ok, makes sense, but I am confused now.
- Does it mean that mechanical road calipers are different from mtb calipers (besides the flat vs post mount)
- Do you get better control/modulation with road pullers and mtb calipers?
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1.
Yes, calipers are different. Drop bar levers pull less cable, so the leverage arm that is pulled by the cable is shorter on disc brake callipers, to avoid having too much mechanical advantage, and too little pad movement.
See the mechanical brake working principle for details
2.
Already answered, but to stress it: you'll get too much mechanical advantage, and too little brake pad movement. Modulation and control will be worse in practice. And, unless you manage to get the brake pads super-close to the disc to begin with, you could end up with your brake levers hitting the bars, without the brake pads properly engaging (even if they reach the disc closely enough to start "rubbing" it, there won't be much braking force).
Yes, calipers are different. Drop bar levers pull less cable, so the leverage arm that is pulled by the cable is shorter on disc brake callipers, to avoid having too much mechanical advantage, and too little pad movement.
See the mechanical brake working principle for details
2.
Already answered, but to stress it: you'll get too much mechanical advantage, and too little brake pad movement. Modulation and control will be worse in practice. And, unless you manage to get the brake pads super-close to the disc to begin with, you could end up with your brake levers hitting the bars, without the brake pads properly engaging (even if they reach the disc closely enough to start "rubbing" it, there won't be much braking force).
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1.
Yes, calipers are different. Drop bar levers pull less cable, so the leverage arm that is pulled by the cable is shorter on disc brake callipers, to avoid having too much mechanical advantage, and too little pad movement.
See the mechanical brake working principle for details
2.
Already answered, but to stress it: you'll get too much mechanical advantage, and too little brake pad movement. Modulation and control will be worse in practice. And, unless you manage to get the brake pads super-close to the disc to begin with, you could end up with your brake levers hitting the bars, without the brake pads properly engaging (even if they reach the disc closely enough to start "rubbing" it, there won't be much braking force).
Yes, calipers are different. Drop bar levers pull less cable, so the leverage arm that is pulled by the cable is shorter on disc brake callipers, to avoid having too much mechanical advantage, and too little pad movement.
See the mechanical brake working principle for details
2.
Already answered, but to stress it: you'll get too much mechanical advantage, and too little brake pad movement. Modulation and control will be worse in practice. And, unless you manage to get the brake pads super-close to the disc to begin with, you could end up with your brake levers hitting the bars, without the brake pads properly engaging (even if they reach the disc closely enough to start "rubbing" it, there won't be much braking force).
Thank you. No intentions to argue with you, I am still new to all this stuff, would be silly of me to prove anything to "Bike Gremlin". 😁
But... I still can't get my mind around it. Can you maybe explain to me where I am wrong?
I somehow ended up with a Frankenbike i. e. an mtb converted to gravel with drop bars, ST-2200 shifters and MTB V-brakes. It took me quite a surprising lot of efforts to ensure the levers can properly lock wheels. I had to true the wheels and to set the pads as close to rims as it gets.
It works great, plenty of control and modulaltion before the wheels are locked. That's when I started to suspect different pull ratios between mtb and road bikes.
So... This is where I imagined replacing mtb mechanical brakes with V-brakes. As long as the pads and the disk are properly aligned, I imagine being able to set the pads close to rims and have the same level of progression before locking the wheel. After all I did it with V-breaks.
So... Did I get it wrong? What do I miss?
Last edited by alexk_il; 08-06-22 at 09:05 AM.
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Thank you. No intentions to argue with you, I am still new to all this stuff, would be silly of me to prove anything to "Bike Gremlin". 😁
But... I still can't get my mind around it. Can you maybe explain to me where I am wrong?
I somehow ended up with a Frankenbike i. e. an mtb converted to gravel with drop bars, ST-2200 shifters and MTB V-brakes. It took me quite a surprising lot of efforts to ensure the levers can properly lock wheels. I had to true the wheels and to set the pads as close to rims as it gets.
It works great, plenty of control and modulaltion before the wheels are locked. That's when I started to suspect different pull ratios between mtb and road bikes.
So... This is where I imagined replacing mtb mechanical brakes with V-brakes. As long as the pads and the disk are properly aligned, I imagine being able to set the pads close to rims and have the same level of progression before locking the wheel. After all I did it with V-breaks.
So... Did I get it wrong? What do I miss?
But... I still can't get my mind around it. Can you maybe explain to me where I am wrong?
I somehow ended up with a Frankenbike i. e. an mtb converted to gravel with drop bars, ST-2200 shifters and MTB V-brakes. It took me quite a surprising lot of efforts to ensure the levers can properly lock wheels. I had to true the wheels and to set the pads as close to rims as it gets.
It works great, plenty of control and modulaltion before the wheels are locked. That's when I started to suspect different pull ratios between mtb and road bikes.
So... This is where I imagined replacing mtb mechanical brakes with V-brakes. As long as the pads and the disk are properly aligned, I imagine being able to set the pads close to rims and have the same level of progression before locking the wheel. After all I did it with V-breaks.
So... Did I get it wrong? What do I miss?
With disc calipers, the pads already have to be very, very close to the rotor for the brakes to work properly, even with the proper levers. You may not be able to adjust the pads close enough to the rotor if you are using a short pull lever with a long pull brake. You run out of lever movement (and cable movement) before the pads hit the rotor with the proper amount force.
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You can do what you have done with long pull linear pull brakes and short pull road levers but it far from ideal as you can probably see. The pads have to be very, very close to the wheel for it to work. Any change in cable length due to stretch of the cable will likely knock off the adjustment.
With disc calipers, the pads already have to be very, very close to the rotor for the brakes to work properly, even with the proper levers. You may not be able to adjust the pads close enough to the rotor if you are using a short pull lever with a long pull brake. You run out of lever movement (and cable movement) before the pads hit the rotor with the proper amount force.
With disc calipers, the pads already have to be very, very close to the rotor for the brakes to work properly, even with the proper levers. You may not be able to adjust the pads close enough to the rotor if you are using a short pull lever with a long pull brake. You run out of lever movement (and cable movement) before the pads hit the rotor with the proper amount force.
Even minor pad wear needs to be compensated by barrel adjusting the brake cable tension, otherwise you get low braking power when the road brake levers hit the bars.
Huge mechanical advantage though, but hardly useful in practice for that reason.
The rest is answered and nicely explained by cyccommute
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im also trying to convert rim break to disc breaks, already brought hub and clip. waiting to break and rotter. im not sure it will fit in to my 20 inch rim,
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Same with TRP Spyre ("road") and Spyke ("mountain").
To add to what Bike Gremlin and cyccomute said, there can be minor differences in the amount of cable pull between different short pull ("road") levers - an example is new Shimano vs Campagnolo. People even do modifications to TRP HY/RD (short pull) to make the cable pull even shorter:
Regarding V-brakes: they differ as well. This table lists arm lengths for different V-brake models, and it can vary from 75mm to 120mm. V-brakes with shorter arms ("mini-V brakes") can be run with short pull levers. Here we have a gray zone as well.
I have heard that some bikes run Tektro RL520 (long pull drop bar levers) with TRP Spyres (short pull version) - however, TRP brakes are on the longer side of the short pull (compared to, for example, Juin Tech/Yokozuna).
Sometimes you can go beyond the compatibility charts to some extent, but as the others said your case is not the best for this.
Last edited by csport; 08-07-22 at 11:42 PM.
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Thank you all, for your help.
Just to confirm, I took my bike with MTB V-brakes with road shifters for their first long ride on a flat track. The brakes stop relatively well however they definitely lack the sharpness of hydraulic brakes on my other bike, not sure if I can trust them for emergency braking.
I will try TRP Spyre/Tektro C550, they might not be as good as hydraulics but I hope to see the improvement from the shorter pull.
Just to confirm, I took my bike with MTB V-brakes with road shifters for their first long ride on a flat track. The brakes stop relatively well however they definitely lack the sharpness of hydraulic brakes on my other bike, not sure if I can trust them for emergency braking.
I will try TRP Spyre/Tektro C550, they might not be as good as hydraulics but I hope to see the improvement from the shorter pull.
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Compressionless housing (Jagwire Pro, Yokozuna Reaction) also helps.
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Also read somewhere in the forums that lower quality housing provides a better modulation.
Anyway, if I don't like them I can always sell them and upgrade to Juins, Zooms or
Last edited by alexk_il; 08-09-22 at 11:04 AM.
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Read a few reviews about Juin's seals eventually leaking, decided to go with full mechanical calipers. If V-brakes are good enough pro racers, then mechanical calipers are more than enough for my needs.
Also read somewhere in the forums that lower quality housing provides a better modulation.
Anyway, if I don't like them I can always sell them and upgrade to Juins, Zooms or Nutts.
Also read somewhere in the forums that lower quality housing provides a better modulation.
Anyway, if I don't like them I can always sell them and upgrade to Juins, Zooms or Nutts.
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"However you either noticed or were made aware by someone that cares more than they should that Pogačar and his UAE Team Emirates squad actually switched between disc and rim and funnily enough every one of the team's stage wins came on rim brakes. Funny that."
https://www.cyclist.co.uk/in-depth/1...-tours-in-2021
https://www.cyclist.co.uk/in-depth/1...-tours-in-2021
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So, the Tektro C550 (almost identical to Trp Spyre) is out, they come with flat mount, not compatible with my post mount. TRP Spyres is the next candidate. Looks like it's serviceable, should last as long as I have desire to maintain it. Will try to go with oversized (180mm, 203mm?)front rotor to improve the braking power.
Thanks everyone.
Thanks everyone.
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"However you either noticed or were made aware by someone that cares more than they should that Pogačar and his UAE Team Emirates squad actually switched between disc and rim and funnily enough every one of the team's stage wins came on rim brakes. Funny that."
https://www.cyclist.co.uk/in-depth/1...-tours-in-2021
https://www.cyclist.co.uk/in-depth/1...-tours-in-2021
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Every picture I am seeing is disc brakes, Shimano's to be exact. Also haven't really seen any road bikes with linear pulls. I guess some of the Tri/TT bikes had some odd kind of linear pull brakes sometimes but you really aren't seeing that anymore.
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Sorry if anyone took it seriously. I intentionally added the reference to TravelAgents to make it even less realistic.
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OK but what team is using linear pull brakes? Road caliper brakes are different from linear pull brakes? All of the MTB pros have been long gone from linear pull and cantilever brakes and I don't think there are any pro cyclocrossers using cantilever brakes or "mini-Vs" anymore either.
Having said so, I might be missing something bigtime here, you are more than welcome to drive me to better understand of my options for my Frankenbike. In my particular case, I am looking to use existing R7000 levers with whatever brakes are available for disk wheels with 27.5 2.2" tires. I somehow concluded that TRP Spyres with larger rotors should be good enough for non-competitive fun on rural roads with mild uphill and downhill sections. I ruled out Hy-Rd's because of the alarming number of reports of oil seals broken with Juin's.
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Not sure if I am motivated to follow a general discussion of the modern trends in the velo industry. Perhaps my original point that triggered your concerns was not expressed in the most concise way. I was just saying that if pros (see my link in the other post) use rim brakes, I should be more than happy to use mechanical disk brakes without going all the way up to hydraulics.
Having said so, I might be missing something bigtime here, you are more than welcome to drive me to better understand of my options for my Frankenbike. In my particular case, I am looking to use existing R7000 levers with whatever brakes are available for disk wheels with 27.5 2.2" tires. I somehow concluded that TRP Spyres with larger rotors should be good enough for non-competitive fun on rural roads with mild uphill and downhill sections. I ruled out Hy-Rd's because of the alarming number of reports of oil seals broken with Juin's.
Having said so, I might be missing something bigtime here, you are more than welcome to drive me to better understand of my options for my Frankenbike. In my particular case, I am looking to use existing R7000 levers with whatever brakes are available for disk wheels with 27.5 2.2" tires. I somehow concluded that TRP Spyres with larger rotors should be good enough for non-competitive fun on rural roads with mild uphill and downhill sections. I ruled out Hy-Rd's because of the alarming number of reports of oil seals broken with Juin's.
Juin Tech and TRP are two different companies so ruling out a brake from a completely different manufacturer with a different design is absolutely silly unless we knew the overall idea was bad but disc brakes are not bad at all and mechanical and hydraulic discs are not bad. TRP makes good quality stuff and has for a long time and of course they are Tektro Racing Products and while Tektro doesn't make high end they make decent quality brakes found on a lot of OEM bikes and at a lot of shops around the globe. Don't throw out the baby with the bathwater and especially don't put that baby in another baby's bathwater and then throw out that bathwater with that baby.
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Juin Tech and TRP are two different companies so ruling out a brake from a completely different manufacturer with a different design is absolutely silly unless we knew the overall idea was bad but disc brakes are not bad at all and mechanical and hydraulic discs are not bad.
But may be I'm wrong, please feel free to to provide more info on how to replace leaked seals on Juins or how to clean them when one of the pistons is stuck.
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I'm not aware of Tektro dual piston mechanical disk brakes that can fit my post-mount frame. Please feel free to recommend me a product, will gladly consider.
Not sure why you generalize by saying "we", I have a pretty good idea of what to expect with Juin and Spires, the internet is full of posts describing potential issues with Spyres and Juins. Main difference is that TRP Spyres are more reliable and fully serviceable with parts available on ebay. Juins brake better as long as the seals are not leaking, which makes them an expensive and unserviceable toy in my personal book. YMMV.
But may be I'm wrong, please feel free to to provide more info on how to replace leaked seals on Juins or how to clean them when one of the pistons is stuck.
Not sure why you generalize by saying "we", I have a pretty good idea of what to expect with Juin and Spires, the internet is full of posts describing potential issues with Spyres and Juins. Main difference is that TRP Spyres are more reliable and fully serviceable with parts available on ebay. Juins brake better as long as the seals are not leaking, which makes them an expensive and unserviceable toy in my personal book. YMMV.
But may be I'm wrong, please feel free to to provide more info on how to replace leaked seals on Juins or how to clean them when one of the pistons is stuck.
We as in people in the industry and other professionals and riders not necessarily adding you in that. But yes people have decided disc brakes are good and work well. That is why we keep using them and they are becoming more and more ubiquitous on more bikes and why you rarely see linear pull brakes on anything new but really low end hybrids and cheap e-bikes and maybe some oddities here and there.