Announcement

Collapse
No announcement yet.

Avid BB7 cable disc brakes for E bikes.

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Avid BB7 cable disc brakes for E bikes.

    Avid BB7 Cable Disc Brakes for E bikes.

    This is based on my experience with these brakes for 3 years on a 1500W BBSHD bike that can go 35mph, and has a 24Ah battery. Like any DIY
    project it's up to you to be sure you have the skill, tools, and experience to do this work correctly. If not pay somebody who does to do it
    for you. I actually had these brakes on this bike for 20 years, but the E bike conversion required some upgrades.

    1- Get big rotors 200mm F and 180mm R works well. This give you leverage for stopping from high speeds. Some older rotor sizes are 203mm, and
    185mm. The brackets are a little different. There are 220mm rotors out there. Skip 160mm for E bikes. The older brackets list rotor size and
    position, 203f,185r the newer ones have an offset number like +20mm,+40mm, base size is considered 160mm f/140mm R, so a pair of +40mm brackets
    will work. Unfortunately nobody sells a BB7 kit for Ebikes with everything in one place (hint, hint). They all seem to come with organic pads.
    My advice- don't bother with them on an Ebike (seei.tem 3).

    2- There are original Avid BB7s, and newer SRAM BB7s (from 2008) They look different but work the same. The older ones had an anodized finish
    the newer ones are painted unless you get the MTB S model. E bikes can blister the paint on the newer ones. The new painted ones have a window so
    you can see the pads easier. The newer ones have a larger inner adjusting knob. There are some knockoffs out there. Real BB7s do not have a
    threaded cable adjuster on them. The older ones are good if a bike came with those, the newer BB7 MTB S version is good too. The painted ones
    work just fine, but the paint may not hold up 100%.

    3- Use metallic brake pads for an Ebike. The 28mph legal limit is fast enough to glaze the organic pads these come with. SRAM makes some, EBC
    and Jagwire do too. The same pads fit Avid juicy hydraulic brakes. They can boil the fluid on those. The BB7 can handle the extra heat. The
    metallic pads last about 5X as long as organics. This means they are actually less expensive to use. You will also not have to spend all your
    time adjusting them. Every couple days will do.
    a- These are hard pads and will need to be bedded in to the rotors. They won't feel that good until you do this.
    b- They must be installed on clean rotors. Especially if they've had organic pads on them. A light scufff with sandpaper works.
    c- They can get noisy if they aren't kept adjusted. If just the outer pad is hitting the rotor under light braking it can "ring". Tighten the inner pad adjuster
    and it should go away. They will produce a soft hissing sound that organic pads do not.

    4- Avids aren't fussy about cables and levers. MTB levers will work, and normal cables work also. They will stop your bike just fine. But
    there is a lot to be gained fine tuning and upgrading these items. Response and sensitivity can rival some hydraulics if you do it right.
    a-High performance brake cables like Jagwire. They're stainles steel, not galvanized. They're pre stretched so will hold adjustment better.
    They're pulled through a die to make them round and smooth on the outside. The housings are Teflon lined, and don't compress. At least get
    decent cables.
    b- On an Ebike you will probably use the levers that came with brake switches. An upgrade would be Avid Speed Dial FR7 adjustable ratio
    levers. You can fine tune the leverage and front to rear balance with these. You would need to add switches if you use them. Some riders don't
    use switches (I do).
    c-Consider upgrading the cable housings at this point for compressionless Teflon lined ones.
    d- You can eliminate as much cable housing slack as you can with hard metal lines in some places. This is kind of an advanced mod but helps
    some. Avid called theirs Full Metal Jacket. (see items 6-7) Some fabrication skills required.

    Installation.
    The attaching bolts on these have spherical washers, and slotted holes. They can basically align themselves.
    Note: BB7s are a little strange in that Avid says to set them up off center on the rotor. 2/3 towards the inside.
    1- Install the pads, and install the bolts loosely.
    2- Adjust the pads so they hold the caliper 2/3 in from center. Hold in the caliper lever so it grips the rotor and tighten the mounting
    bolts.
    The pads and rotor should be aligned to each other now.
    3- Looking at the rotor from the edge adjust the inner pad first so the rotor doesn't bend when you apply the brake, but the wheel still turns
    freely. Any tight spot means the rotor isn't straight.
    4- Before adjusting the outer pad you should get the cable adjusted at the lever as much as you can. Turn the cable adjuster at the brake
    lever all the way in. Now install the cable to the caliper. Pull the cable tight, and push any slack out at the caliper lever, before
    tightening the lock bolt. Now check at the lever for any free play. You want the lever on the brake to move when the lever on the handlebars
    moves with no delay. Use the adjusting barrel. But if it comes very far out you need to move the cable at the caliper clamp, and try again.
    Apply the brakes pretty hard a few times to set the cable. It should feel firm and hold it's adjustment. It shouldn't move very much. Brakes
    work on pressure not movement.
    5- You should be able to adjust the outer pad so the wheel spins free. Ride the bike and break in the pads and readjust them. This would be a
    typical installation.

    6- Fine tuning the brakes. With the bike sitting still apply the brake cable pretty hard while looking for any movement of the cable housings.
    This is wasted motion. The housings are too long or curving around for no reason or are just compressing. Sometimes hooking the 2 cables
    together where they cross can help. Square off the cut housing ends can help. This is where you decide whether to go for high end cables,
    housing and maybe hardlines or not. Slicker cables, and stiffer housings are where you will get that solid responsive feel hydraulics have. The
    plastic hoses on hydraulics flex too BTW.
    7- There is another adjustment on the BB7. The return spring tension is adjustable. There is a tiny Allen screw near the shaft of the caliper
    lever. If you have smooth slick cables, and have gotten all the slack and mush out, this can be loosened up so instead of feeling the return
    spring when you pull the lever you will feel what the brake pad is doing. If you left the friction and mush in the system then you will feel
    that instead. The one nice thing about doing all these fussy little things is they are pretty much permanent. Once setup the only adjustment
    should be the inner pad first, then the outer pad. Because any play in the lever will be from pad wear. The barrel adjuster is to adjust slack
    out of the cable. Check the levers for play before you ride, and adjust it if needed while the brakes are still cold. OK it ain't hydraulics. It
    won't leak, boil the fluid, get air in the system, or spit a piston when you take a wheel off. Not likely to cut a hose either. Judging by the
    blistered paint on my rear one you could probably set them on fire and not notice. The paint problem happens on the side of the caliper towards
    the bracket, so you can only see it with the bike upside down.
    8- If you have more than one wheelset you can get rotor shims for 6 hole rotors to shim one rotor out to match the other.​
    Last edited by Retrorockit; 01-12-2023, 07:18 AM.

    #2
    My bike had rim brakes when it was new. In 2004. Disc brakes were still controversial for bikes back then. Since it's a hardtail it ended up with about 2' of flexible brake housing at the rear it didn't really need.
    I replaced that with 1/8" T.D. (3/16" O.D). hydraulic brake steel tubing. The Jjagwire Teflon lining fits inside, and the metal ferrules from the old flex lines go over the ends so they fit in the frame lugs.
    I did have to drill the brass end pieces to 1/8" for this. I stuck one end in the caliper and bent it to run to the frame lug, and cut it to length. To install it I took out 1 of the cliper bracket cross bolts and loosened the other. The caliper swung up, and the hard line could be installed w/o changing the caliper alignment. It's kind of funny that my cable brakes have actual hydraulic lines going to them. The Avid rubber boot fits over them just fine also.

    The Jagwire Elite link kit is what I used for this.
    https://jagwire.com/products/diy-cab...link-brake-kit
    Other options.
    Last edited by Retrorockit; 01-12-2023, 09:13 PM.

    Comment


    • Retrorockit
      Retrorockit commented
      Editing a comment
      BB7 tip.
      On the newer large knob calipers do not grab the knob with pliers if it gets tight. The knob snaps over a stationary ring on the caliper. It will just be harder to turn. Get a Torx wrench and turn it in the center.from the other side.
      A word on the similar BB5 calipers. They are not suited for E bike use. Metallic pads are listed, but I've never actually seen any. Those do have a barrel adjuster for the outer pad. This means pad adjustment and cable adjustment are not separate. As the pads wear the lever will be in a different position, changing leverage and travel. Aside form having ball bearing actuation they aren't much better than low end stuff.

    • Retrorockit
      Retrorockit commented
      Editing a comment
      I've suggested older BB7 equipped MTBs for donor bikes. They were upper mid level bikes when new and would also have decent forks, and strong wheelsets. 26" bikes are no longer popular for offroad use. Replacing the triple chain rings with 1x8-9 speeds works well for an Ebike. The low price of chains and cassettes makes them service parts.
      Unless you find a DH bike with metallic pads and big rotors the brakes will need a couple upgrades for E bike use. The parts for this are readily available and DIY simple.

    #3
    Most of my life I was in that situation. Right now i can afford the luxury of trying several things to see what works, and share what I find out. But I still do cheap thrills too. Like the zip tie mod. But to get it working 100% I bought just about every chain idler I could find. Worked my way up from cheapest to what really worked. It turns out the $65 part is what was needed. Cost me about $200 to figure that out LOL. So when I say "The only thing that costs more than doing it right the first time, is doing it right the second time" there is a little bit of "Do as I say, not as I do" going on there.
    I no longer have a warehouse full of tools to work in. But my back ground in factory maintenance lets me relate to having the skill to fix it right the first try. It's just that parts are cheaper than storage/work space here. If you're working with BB7s you can just stick them on the bike with any old cables, and they will stop your bike first time every time. I got into the fancy cable thing because I was testing some TRP Spyke calipers, and TRP said they needed them. I bought some TRP Spyres by mistake too. The BB7s are still on my E bike. But now with fancy cables. They do make a difference. But if you need time to save up for the good stuff it shouldn't be a problem. I spent about $400 on TRP R&D to figure out the BB7s I already had are still the way to go. So I'm not just being a retro-grouch when I recommend using them. I learned most of what I know doing exactly what you're doing. I'm still doing it in a different way.
    One nice thing about the BB7 separate cable adjustment form the pads is you can set them up with a slight tension on the cable with the brakes released, and your brake levers don't rattle over bumps any more.
    Last edited by Retrorockit; 01-21-2023, 06:13 AM.

    Comment


    • Retrorockit
      Retrorockit commented
      Editing a comment
      It's official Avid BB7s properly set up will do a stoppie. I had to do one in traffic at night. Some dork absolutely had to come speeding up to the already red light and slam on his brakes to stop in the crosswalk. There is no cross lane to take there for those who like to pretend they're in a car. Crosswalk only from the greenway.

    • Retrorockit
      Retrorockit commented
      Editing a comment
      Part of the problem was I had left my Blackburn yellow side strobes on the charger and didn't have them on like I usually would. They really make a difference.

    #4
    This is helpful info. I'm converting a bike that came with BB7's. I was thinking originally I'd swap them for hydraulics, but I'll probably just keep them and see how well they work with metal pads. The Jagwire Elite Link cables look awesome too. Do you need to get the mountain version for BB7s, or does the road version work?

    Comment


    #5
    Manufacturers claim that multi-layer rotors (like Shimano IceTech) are less prone to warping. Has anyone found that to be true in practice? It could be another way to upgrade mechanical brakes to get them to stay quiet more consistently. I have mostly only ridden with fairly basic rotors.

    Comment


    • Retrorockit
      Retrorockit commented
      Editing a comment
      I didn't understand what Multi layer was. I just ordered a set of ICE rotors. , Shimano says 100*C cooler and it looks like they can hold that temperature.
      I didn't have a warping problem so I missed this the first time.
      Last edited by Retrorockit; 06-09-2023, 06:20 AM.

    #6
    I think it depends on what your needs are. if long runs down the mountain are considered then probably 2 piece rotors, and anything else will help. It's flat where I live so one hard stop every now and then is all I need. Standard rotors haven't been a problem for me. When my rotors aren't straight I just figure I bumped against something. Maybe I'm wrong?.

    Comment


      #7
      Thanks to brothergc I became aware of Shimano ICE rotors. They come in 6 bolt and center lock. They feature an aluminum rotor with a stainless steel cladding on both sides.
      To Build Closer Relationships between People, Nature, and Bicycles. We believe in the power of cycling to create a better world as we move forward. We inspire all people to enjoy our products in their everyday lives and where they take them.

      They run 100*C cooler than solid rotors. from the curves I see on the graphs at Shimano it looks like they can dissipate the heat as fast as it's being put into the rotors. This would be a BFD for someone riding down a mountain road at high speeds. There is an even higher level Freeza version, but it looks kind of fat right at the inner edge of the brake face, so may not fit all calipers.
      I just ordered a set of these and will report back on how they fit and work.
      The RT86 rotor is the ICE version, the similar RT76 is just a 2 piece solid rotor.

      Click image for larger version

Name:	image.png
Views:	369
Size:	421.4 KB
ID:	162636Click image for larger version

Name:	image.png
Views:	386
Size:	421.4 KB
ID:	162637
      Last edited by Retrorockit; 06-09-2023, 06:26 AM.

      Comment


      • Retrorockit
        Retrorockit commented
        Editing a comment
        Aluminum has a higher thermal conductivity of 215 W/(m K) compared to stainless steel's 17 W/(m K),
        That's an order of magnitude, Dude..
        It is also a parallel path away from the caliper (a ++).All I really need to know is that it's better than what I have now.
        The more expensive Freeza versions ($100) increase the surface area exposed to air. Another parallel path.
        Last edited by Retrorockit; 06-09-2023, 11:03 AM.

      • AZguy
        AZguy commented
        Editing a comment
        For my brakes the aluminum backs only come with organic pads and I got terrible mileage on those, completely shagged in around 1200mi

        I've gone with the steel backs and metallic pads and get ~4+x the mileage

        I don't do a lot of downhill, just hard fast stops so don't really need the heat shedding... but it would be nice to be able to run actual numbers

        I really love my brakes and think they are super well suited for the kind of riding I do - very powerful but the hydraulics give awesome control


        Just Wednesday a car pulled right in front of me - I was doing about 15-17mph and did a stoppie with the rear wheel nearly two foot up! Came to a stop in just a few feet though LOL

      • Retrorockit
        Retrorockit commented
        Editing a comment
        I certainly wouldn't take good 4 piston hydraulics off of a bike that already has them. But if bike already has BB7s I see no reason not to use them unless your riding in some slippery offroad situations. Bur cheap 2 piston hydros on a fast Ebike scare the shit out of me. I look at all the mods Shimano and TRP do to make their DH brakes suitable for Ebikes.

        The G-Spec DH-R brake has been re-designed to the all-new DH-R EVO. A new caliper, new lever, new hose, new oil, new pads, new 223/2.3mm rotors and a new hydraulic leverage ratio,

      #8
      Ive got BB7s with metallic pads. Of course the classic drawback to metallic is they can make more noise. If you keep the discs clean the metallic pads grab better. On a severe downhill they hold up better with the heat.

      Comment


      • Retrorockit
        Retrorockit commented
        Editing a comment
        Clean rotors, and I find usually adjusting the inner pad so they both hit right away stops the noise for me. If just the outer pad hits they can ring like a bell. If they're noisy under light braking but shut up when you pull harder that's usually it.

      • Retrorockit
        Retrorockit commented
        Editing a comment
        I've also found that some pads are noisier than others. I had some cheap Chinese pads that hissed all the time. EBC are pretty much silent. I have some Avid metallics to try and I expect those to be good too.

      #9
      So here is the theory on BB7s. They have no disastrous failure mode due to heat. No fluid to boil. no hoses and fittings to melt. They will cook organic pads, and on an Ebike they wear out about once a month, and require daily adjustment. 3 reasons to run metallic pads. The ball bearing actuation, and compressionless cable kit can provide modulation that's good enough for most situations. Some people say they're as good as mid level hydro brakes IDK, never had a reason to use hydros. In fact several reasons not to.
      Now here is where the Shimano ICE rotors come in. Trying to fix the heat problems with hydraulic brakes they came up with a rotor that reduces the heat before it goes into the caliper by 100*C.
      They also needed finned heatsinks on the pads, and special hoses and fittings. This is on a pedal bike system with no mention of Motors, or speeds over 25mph.............................
      Back to the ICE rotors. BB7s with metallic pads run hot because they can. But this can make them less consistent.
      Stainless steel rotors have a low ability to transfer heat. Aluminum is over 10x bettter. Bigger rotors help some (takes longer to heat them up, and provide more leverage for high speeds. But if heat is being produced faster than the rotor can dissipate it to the air it has to either go somewhere (the pads are the only thing touching the rotor), or the temperature must go higher, and higher. Since the pads are wha'ts producing the heat guess what happens.
      High end hydraulic brakes will run cooler because they have to. Expect to pay almost $200 a wheel for Ebike rated brakes.
      If the ICE rotors can dissipate the heat as fast as it's being produced the temperature will stabilize at some level, and the braking will be more consistent.
      I'm saying this is theory for 2 reasons. I don't have these rotors yet, and where I am it's very flat so my testing will be limited to fast flat running. I've had no problems with BB7/ metal pads/big rotors. But a simple bolt on upgrade like this is hard to ignore.
      Last edited by Retrorockit; 06-10-2023, 07:15 AM.

      Comment


        #10
        Do all hydros have piston(s) on both sides? If so I could see an advantage with not needing adjustment for longer especially for someone that isn't pushing that hard.

        I am a little lazy when it comes to adjusting and what has been killing pads for me is I let them get out of adjustment and they wear crooked so when I finally notice a problem there is no adjusting they have to be replaced. I don't know why I don't remember to adjust them. Its not hard to do and doesn't require tools unless they are kinda mucked up and you have not adjusted them in a while. When I'm riding semi daily I have my bike in the stand at least once per week so it would only take me another minute total to give em a few clicks. But then I would have to stand to reach the brake levers and like I said I'm lazy.


        The other cable brakes I have messed with were not tool less, some requiring 3 or 4 different tools and even with the tools were kinda a hassle and that was before the screw heads started to round out. I think it was the cheapo no name ones that came on my wallyworld schwinn that had tiny locking screws that directly locked into and damaged the threads on the non moving side of the caliper. They didn't turn smoothly the first time and after a few the threads really got chewed up. I think I just quit trying to use the locking part because the threads were sort of self locking at that point. Nothing wrong with pressing on threads but most of the time when that is done they use some sort of a soft material between the end of the screw and threads.

        Comment


        • Retrorockit
          Retrorockit commented
          Editing a comment
          I've looked at a couple other cable brakes. Couldn't get any actual metallic pads for BB5. They're listed but don't exist. I tried the TRP Spyre/Spyke twins.
          Both pistons move, metallic pads available. But notchy action, and not as good cable leverage management has kept the BB7s on the Ebike. The Spykes are still on my XC bike w/slicks, and I have been riding it lately. One thing about the BB7s is you set your cables up, and don't have to touch them again.
          In fact buying metallic pads for the BB7s I saw a warning not to use them on the Avid Juicy 7s. This is what got me looking at the heat issues of hydraulic brakes. If it's an issue on pedal bikes, it will be much worse on an Ebike. That's why I tell people to think about the brakes when converting a bike with hydros.

        • mrpelican
          mrpelican commented
          Editing a comment
          I'm pretty sure hydraulic brakes always have a piston on both sides. And in my experience, this does eliminate the adjustment issue you're describing. Higher end hydraulics have 2 pistons on each side.

        • Retrorockit
          Retrorockit commented
          Editing a comment
          With organic pads adjusting is an issue. MTB guys have to stop and adjust their hot brakes part way down the mountain. With metallic pads once a week, or every 3 days or so puts it in line with chain lube scheduling. Some people who are too lazy to do this also run their hydro brake pads down to bare metal, and keep riding until the pistons pop out. To each their own.

        #11
        I found traditional bicycle rotors lacking after I got a crack in one from one of the cooling holes.Doing downhill single track. I found these, cheap and thick like a motorcycle rotor! Click image for larger version  Name:	20230610_104232.jpg Views:	0 Size:	1.36 MB ID:	162659

        Comment


        • Retrorockit
          Retrorockit commented
          Editing a comment
          Brake discs and drums on cars and trucks crack fairly often too. It looks like you're running the 160mm rotors, why not 180mm?
          The issue with thicker rotors on BB7 is that the rotor must flex to engage the inner pad. So how thick is it? and do they come in bigger sizes?
          Anyway thanx for the photo of the last century BB7 on a DH bike.

        #12
        Click image for larger version

Name:	image.png
Views:	345
Size:	80.7 KB
ID:	162665
        There were some Avid rotors that are almost solid back in the day. Roundagon they were called. You can probably still find some. Maybe Chinese knockoffs.

        Comment


          #13
          Centerline baby

          Click image for larger version

Name:	sram_mtbbremsscheibe1_1504180779.jpg
Views:	388
Size:	251.6 KB
ID:	162671

          Comment


          • Retrorockit
            Retrorockit commented
            Editing a comment
            I'm running the 203mm G2 Clean sweep version. So mines bigger than yours

          #14
            • Retrorockit commented
              8 hours ago
              The issue with thicker rotors on BB7 is that the rotor must flex to engage the inner pad. So how thick is it?
              • Flag
          ​Guess they are about 1/8th of an inch or so. They fit into the BB7 opening. Still flex but less than a regular bicycle one. Very stout! They look like a smaller version of my Kawi 650 brake rotors...

          Comment


          • Retrorockit
            Retrorockit commented
            Editing a comment
            I suppose it's actually the spokes that flex. TRP went to a thicker 2.3mm 220mm rotor for their E bike brake, but it won't fit their own cable brakes. The Avids have some extra room. I din't think of trying the big TRPs because of the flex issue. But since I keep my inner pad adjusted for noise control it would probably work. Could you link to those rotors so we can see what sizes are offered. For E bikes with sticky street tries bigger is better.

          #15
          Here's a little more on setting up the BB7s since there seems to be some interest. The return spring tension is adjustable. if you have old crummy cables it will need to be tight, and you will be feeling the spring and crummy cables when you try to modulate your brakes. With high end cables you can back off on the tension so the spring just balances the cable drag and the you will be able to feel what the brake is doing. That and the ball bearing action is why these have such a good rep. compared to other cable disc brakes. They can be almost as fluffy as the hydros.
          Another thing is the metallic pads cost twice as much as the organics. They last about 5x as long so you actually save money using them.
          Last edited by Retrorockit; 06-11-2023, 06:19 AM.

          Comment


          • AZguy
            AZguy commented
            Editing a comment
            2x for metallics? Wow! they don't cost any more on mine (~$20-$25 for a pair)... replaced the last set after >6500mi and they weren't shagged... you're right about the life - the organics lasted about 1/5 the miles and were completely gone...
        Working...
        X