Strong mechanical disk brake?
 

Hello,

To replace a front Shimano Roller Brake to stop a cargo bike (total weight ~150kg/330lbs) in steep descents (~10%), I'm thinking of having the fork replaced so as to install a cable-actuated disk brake. I prefer 100% mechanical brakes to keep things simple and affordable.

What model would you recommend? I read that most are single piston, but models with dual pistons are also available.

Thank you.

https://cimg6.ibsrv.net/gimg/bikefor...b9e92ac6d7.png

Good mechanical disc brakes are not exactly cheap. Here is a review of Paul Klampers and Growtac Equal. He also reviews Yokozuna, which is a rebranded Juin Tech hybrid hydraulic brake.

I upgraded from TRP Spyres to Juin Tech R1 and never looked back.

Otherwise the common recommendations are Avid BB7 and TRP Spyre/Spyke.

Also pay attention to whether the levers are short pull or long pull.

If you run flat bars it may be better to just go with some full hydraulic MTB brakes.

Edit: I am a heavy rider myself, probably around 150 kg if with the bike and the gear. TRP Spyres were not good enough for me on steep descents, Juin Tech are good with any pads (stock ones, Shimano organic, metallic).

We touring on a loaded tandem (210kg/460lbs) often on greater than 10% slopes in remote areas. 2 cantilevers and a rear disk. Heat dissipation is the concern. We switched from TRP Spyres to Klampers. The Klampers have no plastic parts and are noticeably stronger when braking. I like the dual pad movement of the Spyres, but that design for mechanical brakes compromises strength. I have disassembled both for cleaning, the Klampers are much easier in that regard.

I tend toward full mechanical brakes because they're a no-brainer to install and maintain. Otherwise, I might as well go full hydraulic intead of hybrid, provided there's an offer that's solid (no bleeding every so often) while reasonably priced.

My tour bike is 290 lbs. Front hub is a SA XL-FDD dyno DRUM brake. Set and forget for 30,000 miles in any weather.
Nothing is better or safer. Overheating is a laughable concept. The first tour I had a useless caliper on the back doing 3% at best. LOL.
My Rohloff14 has a cable TRP Spyre with SA levers set to long pull. Stops dead instantly, can't beat that. Resin pads only lasted 5,300 miles, but never squeaked. The gap is of little concern. My dropout is horizontal.

BB7 are dinosaur tech with one piston and 15 mm clunkier. LOL.

TRP Spykes on my cargo bike and they stop remarkably well. I run 203mm front and 180mm rear rotors. Haven’t had any issues which would decrease my confidence in the brakes so far.

I have used Avid BBDB, Avid BB7, TRP Spyke, and Paul Klamper. None of them work better than the others. Paul Klampers are works of art but, honestly…and this is coming from someone who own 3 bikes equipped with them…, they aren’t significantly better at stopping than the others. They have other bells and whistles that make them a bit better like arms that allow you to change the lever you can use and they can be rebuilt as well as th pad adjusters are easier to use than the other brakes, but they are also about 2 to 3 times the cost.

I’m not much of a fan of the Spykes. Not because they don’t work well but the pad adjustment mechanism is very weak and easily damaged. It takes a 3mm allen wrench to adjust it but the adjuster is aluminum and fits too tightly into the caliper body. The socket strips out far too easily. They work well but maintain poorly.

In all honesty, the BB7 is probably the best bag for the buck. Relatively inexpensive…can be found for less than $50 per wheel…, works well, is easy to adjust, and stops just as well as the others.

Yokozuna/Juin Tech are a closed system and require no bleeding. Adjustment for the pad wear is done manually by turning an adjuster screw.

Also, hybrid or full hydraulic setup is better for the QR fork in the photo: when the wheel is inserted slightly differently (as it happens with the QR setup), the pads will just extend by a different amount according to the position of the rotor. This is not the case with pure mechanical brakes like TRP Spyres or Avid BB7.

Why is that? Because on mechanical brakes, the pad doesn't move to adjust for wear?

If you move the rotor from side to side (say to the right), the right piston will extend by a smaller amount and the left piston will extend further because they are both pushed by the same fluid in the same reservoir.
The pads of the mechanical brakes are centered on a fixed position w.r.t. the caliper, and it would need to be changed manually (as cyccommute said, it is a pain with TRP Spyres, I managed to strip an adjuster myself).
The smaller the gap between the pads, the more prominent this problem becomes.

Otherwirse the closed hydraulic system does not adjust for wear either, you need to manually adjust by turning a screw (pushing pistons further). This adjustment changes the gap between the pads to compensate for wear.

I would not want cable actuated brakes for a cargo bike. I would go Magura MT5s or the TRP equivalent (c 1.2 or something). Longer cable runs lead to less braking performance.

If I absolutely was stuck on cable brakes I would go TRP Spyres or Spykes or Paul Klampers with Jagwire Elite Link Housing kit and the biggest rotors I can fit on the bike ideally a Magura MDR-P (which I would use on the hydro brakes as well) and would still want the hydraulics.

My Hydraulics don't require much maintenance really just the normal replacing pads and rotors when needed which you do on cable stuff and maybe once in a blue moon I might bleed them but in 4k miles I haven't had to do it and probably won't for another 4k miles and maybe another 4k after that too. I think people assume hydraulic brakes are harder to work with because...uhhhh...maybe the very occasional bleeding which a shop can handle quite easily if you don't want to do it and every few years or more is really not much I would likely be wanting to replace cable and housing every year or two years and may have to adjust things in between that.

Thanks much for the infos.

If I go full hydraulic, what would be the best compromise in terms of 1) cost, 2) reliability 3) for use with that heavy bike in a hilly area (with the brake only installed in the front, since the rear can only take a Roller Brake)?

Shimano deore 4 piston are not too expensive and they stop our tandem with a single finger on 20% grade and at about 400 pounds. I do have 203 rotors on it though.

Too much is made of the supposed weakness of certain brakes or the supposed strength of hydraulics. If…and that’s a big “if”…there is a difference, it is relatively small difference. Cargo bikes predate discs by many years (decades?) and I’ve never heard anyone complain that they couldn’t stop their cargo bikes with the (assumed) super weak rim brakes. I have tandems which only have cantilever brakes…the Horror!…that stop just fine and that bike is carrying far more load than any cargo bike will. I even took the drag brake off the tandem because it was unnecessary. My current tandem has mechanical discs front and rear and I have no issue with controlling speed.

We assume that hydraulics are harder to work on because they are harder to work on. A brake bleed isn’t “simple” or “easy” or “trivial”…all things I’ve had people tell me. I also had people try to convince me that changing a cable on a mechanical brake is more difficult than a brake bleed. I don’t know if those people have never done a brake bleed or are just stupid. I’ve also heard the thing about replacing cable and housing every year or two which is also very silly. Cables can last decades without the need for replacement.

Replacement of cable and housing brings up another issue related to hydraulic systems…replacement of housing or adjustment of housing length. If you have cables or housing that is too long or too short, it’s simple to cut new housing to the proper length. If you have hydraulic housing that needs length adjustment, you need something to cut the hose, barbs and olives, something to help install the new barbs, and you have to do a brake bleed. It’s far more complicated and, thus, more difficult. I can, and do, change housing and cable on mechanical brakes all the time. If it takes me 10 minutes to do a whole bike, it’s probably because I’m shooting the breeze with someone in the shop and not paying attention to what I’m doing. It would take me 10 minutes just to set up for a hydraulic housing swap and another hour or two to do the job.

It doesn’t matter if you use and like hydraulics, just don’t try to convince me or others that they are simple to maintain, especially when compared to cable brakes.

I have Spyres (road pull versions of the Spykes) on one bike and they do work well. You are correct that the pad adjusters can be a bit fragile if you are careless. You have to use a good allen wrench and align it properly but, with decent care, they are fine.

I found them to be too delicate even with a good wrench. I had an early pair that I couldn’t adjust from the factory because the adjuster was installed too tightly. I contacted TRP and was informed that it was a know issue and they were working on a fix. They are good enough to send me a number of adjusters to fix the problem. I did have a similar problem on a later set that had been on the bike for a while and had seen some winter use. I ended up swapping them for a set of Avid BB7 because of the issue. They are good brakes but the adjuster needs to be steel.

You might want to look for a fork with a thru axle, there is a reason the standard for disc brakes has moved to thru axle.

It doesn't look like such fork exists for a Bakfiets, which is not very surprising considering the bike.

https://cimg2.ibsrv.net/gimg/bikefor...2fc1609723.png

those are very cool, but my concern would be making it up the 10% ascents.

has the roller brake not worked well on 10% down hills?

At the cost of stating the obvious:

Make sure the fork is strong enough to take a large disc (some forks are weak and will bend noticeably even with a 180 mm large disc).
A larger disc diameter gives you more leverage and greater stopping power with all else being equal.

And I second the Avid BB7 recommendation for the calipers.

The 250W BBS01 is good enough, and the C6000 brakes that replaced the useless, original IM45 work but I'm interested in replacing the front brake for a bit more stopping power.

Thanks for the tip.

Larger rotors and TRP spyres
 

The breaking power can be improved by larger rotors and better pads

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I have TRP Spyres +185mm rotors + Discobreaks Copper pads on my MTB. Took a bit of efforts to install the breaks correctly, making sure they are absolutely in parallel to the rotors was the key for the best performance.
​​​​​​I can easily lock my wheels and skid, not sure if better breaks will stop the bike quicker though.

No issues with the breaks adjusters, all is fine.

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LOL my mind still has not wrapped around pedal assist being more common

Otherwise, it wouldn't be possible to pull a ~150kg/300lbs cargo bike up a 10% grade road.