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BB7 Question

Old 04-30-21, 06:24 AM
  #1  
Tandem Tom
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BB7 Question

Has a adapted a cable adjuster to a BB7 Disc Brake Caliper?
Would appreciate hearing about it.
Thanks!!
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Old 04-30-21, 07:05 AM
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Originally Posted by Tandem Tom View Post
Has a adapted a cable adjuster to a BB7 Disc Brake Caliper?
Would appreciate hearing about it.
Thanks!!
Morning Isle of Man TT , it's unclear what you are asking, if you are wondering if you can use a cable adjuster to take up slack from pad wear, I've always read never to do this, but to use only the two dials with torx holes, to bring the pads in a bit to compensate for wear.
Seems to me from memory is that it is to avoid shortening the pull, which could be tricky. Others will explain better, but I just heeded the avid warning not to use a cable adjuster, like the ones right at the lever.

I hardly ever have to move pads, so the inconvenience isn't a hassle at all.

PS Tandem Tom, if you were wondering what on earth I was meaning, your name always makes me think TT, which is a motorcycle racing event that has been around since just after ww2 on the isle of Man , and that I've watched sometimes for decades.....

Last edited by djb; 04-30-21 at 07:49 AM.
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Old 04-30-21, 08:55 AM
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Never use a barrel adjuster for cable disc brakes. As posted by djb ONLY use the pad adjusters to move the pads in as they wear. If you tighten the cable you will pull the actuating arm forward and kill the leverage needed to make the brake work.
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Old 05-02-21, 06:47 AM
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Your question makes no sense.
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Old 05-02-21, 08:28 AM
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I believe cable adjusters are OK to use on cable controlled disk brakes. Seems that most all the bike industry (and so far the legal community given the lack of law suits) as nearly every flat bar bike that used cable disks also have lever barrel adjusters.

But the devil is in the details, or in this case how you use the barrel adjuster. I agree completely with the danger of reducing the caliper's actuating arm's travel as that could cause the arm to bottom out before the pads get full bite on the rotor. But using the barrel adjuster to establish the fine tuning of the cable anchor WRT the arm's initial start of it's travel is, IMO, acceptable. To only rely on the cable anchor bolt and where along the cable is clamped is like using a base ball bat to swat a fly. Sure can be done but it's easy to damage stuff if you don't get it just right the first time. Andy (who is failing to come up with a better analogy that is also funny).
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Old 05-02-21, 08:57 AM
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Originally Posted by Andrew R Stewart View Post
I believe cable adjusters are OK to use on cable controlled disk brakes. Seems that most all the bike industry (and so far the legal community given the lack of law suits) as nearly every flat bar bike that used cable disks also have lever barrel adjusters.

But the devil is in the details, or in this case how you use the barrel adjuster. I agree completely with the danger of reducing the caliper's actuating arm's travel as that could cause the arm to bottom out before the pads get full bite on the rotor. But using the barrel adjuster to establish the fine tuning of the cable anchor WRT the arm's initial start of it's travel is, IMO, acceptable. To only rely on the cable anchor bolt and where along the cable is clamped is like using a base ball bat to swat a fly. Sure can be done but it's easy to damage stuff if you don't get it just right the first time. Andy (who is failing to come up with a better analogy that is also funny).
when I set up my troll with dropbars and Gevenalles, as there are no barrel adjusters, I recall having to read the setup stuff twice to hopefully get the arm travel right, and trying to figure out what would be the right position. Think I did have to loosen the bolt a few times to get it right, but purposely didn't snug it down so I wouldn't sqwersh the cable.
don't recall the exact details but just thought of watching the arm movement pre cable.

Last edited by djb; 05-02-21 at 09:06 AM.
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Old 05-07-21, 11:44 AM
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Originally Posted by cxwrench View Post
Never use a barrel adjuster for cable disc brakes. As posted by djb ONLY use the pad adjusters to move the pads in as they wear. If you tighten the cable you will pull the actuating arm forward and kill the leverage needed to make the brake work.
Many disc brakes have an integral cable adjuster.
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Old 05-07-21, 01:58 PM
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Originally Posted by Tandem Tom View Post
Has a adapted a cable adjuster to a BB7 Disc Brake Caliper?
Would appreciate hearing about it.
Thanks!!
On my BB7s, I use the barrel adjuster to take up cable slack, but this adjustment was too crude to adjust brake pad clearance and centralizing - I used the two red/orange adjustment dials on each side of the caliper for that. When I refitted the front wheel (QR rather than thru-axle) I would occasionally need to tweak the red dials ti set the brake engagement as I liked it - the downside of QR in this application, I guess.
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Old 05-07-21, 02:26 PM
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Originally Posted by oldbobcat View Post
Many disc brakes have an integral cable adjuster.
Let me repeat...you should not use the barrel adjuster to take up pad wear. Cable slack when installing a brake/cable is one thing. Do NOT adjust for pad wear w/ the barrel adjuster, that is the exact reason why there are pad position knobs.
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Old 05-07-21, 04:38 PM
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Originally Posted by cxwrench View Post
Let me repeat...you should not use the barrel adjuster to take up pad wear. Cable slack when installing a brake/cable is one thing. Do NOT adjust for pad wear w/ the barrel adjuster, that is the exact reason why there are pad position knobs.
Just to be clear, this is true for BB7s, but some mech disc calipers do not have a pad adjuster for the outer pad.
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Old 05-07-21, 06:15 PM
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Originally Posted by Kapusta View Post
Just to be clear, this is true for BB7s, but some mech disc calipers do not have a pad adjuster for the outer pad.
It's always the correct way to adjust. If there is only one adjustable piston you move the caliper and then adjust the inner piston. I don't think I need to repeat my earlier advice again.
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Old 05-07-21, 06:50 PM
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Originally Posted by cxwrench View Post
It's always the correct way to adjust. If there is only one adjustable piston you move the caliper and then adjust the inner piston. I don't think I need to repeat my earlier advice again.
Re-aligning the caliper every time you need to compensate for pad wear would be a huge waste of time. On my MTB I would be doing that every other ride.

Avid seems to agree with me, as they specify using the barrel adjuster for the BB5: https://www.servicearchive.sram.com/...d7_English.pdf

But this is really just a sidebar, as the OP has BB7s.

Last edited by Kapusta; 05-07-21 at 09:56 PM.
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Old 05-07-21, 10:04 PM
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This is step 4:
INSTALL THE CABLEPass the brake wire through the anchor bolt on the actuating arm. Cable slack may be removed with a fourth hand tool. Be careful not to advance the torque arm as you pull the cable. Tighten cable anchor bolt to the specified torque. Use the barreladjuster at the brake lever to remove any remaining cable slack (if there is any)
SRAM is giving conflicting instructions...above they say to 'not advance the torque arm' but below they say to do that.

They do say to use one of the barrel adjusters to make up for pad wear but I will stand by my advice. The further you move the torque arm forward and approach a 90* angle between it and housing stop arm you will lose power. Once you reach a 90* angle and pass it the brake will have virtually zero power. I have adjusted dozens if not hundreds of mechanical disc brakes over the years and I would never shorten the cable to take up pad wear. It's not at all hard to dial in a piston and move the caliper a bit, it's very easy. If this is a problem for the user they need to learn how to adjust the brake properly.
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Old 05-09-21, 09:07 PM
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Originally Posted by cxwrench View Post
This is step 4:
INSTALL THE CABLEPass the brake wire through the anchor bolt on the actuating arm. Cable slack may be removed with a fourth hand tool. Be careful not to advance the torque arm as you pull the cable. Tighten cable anchor bolt to the specified torque. Use the barreladjuster at the brake lever to remove any remaining cable slack (if there is any)
SRAM is giving conflicting instructions...above they say to 'not advance the torque arm' but below they say to do that.

They do say to use one of the barrel adjusters to make up for pad wear but I will stand by my advice. The further you move the torque arm forward and approach a 90* angle between it and housing stop arm you will lose power. Once you reach a 90* angle and pass it the brake will have virtually zero power. I have adjusted dozens if not hundreds of mechanical disc brakes over the years and I would never shorten the cable to take up pad wear. It's not at all hard to dial in a piston and move the caliper a bit, it's very easy. If this is a problem for the user they need to learn how to adjust the brake properly.
I'm looking at the angle of the torque arm and seeing that there is minimal change in the force vectoring of the cable as that angle closes.

The number of different Youtube videos on this subject is scary. But the principle for solid braking force is this. Make sure there's some inner pad standing clear of the caliper. Make sure the inner pad is close as possible to the rotor without rubbing, And make sure the torque arm is in no danger of closing completely before full braking force is applied.

To adjust a brake that has been aligned properly but has pad wear is, first adjust the inner pad so it barely clears the rotor, using the inner pad adjustment dial. This gives the outer pad something solid to push against when it makes contact with the rotor. This is where most of the braking force comes from. Next, adjust the free play using the red outboard BB7 dial, cable tension, or a combination of both. In the case of the BB7, it makes more sense to use the outer pad adjustment knob, unless it's already maxed out for some reason. Also, other brake models don't have this feature.

For new brake installation or complete realignment, I first make sure the inner pad stands a couple millimeters clear of the caliper body. If it's a BB7, I want the outer pad dial somewhere in the middle of its range.Then I mount the caliper loose and attach the cable so the lever travel feels about right when I clamp down on the rotor. I release the lever, tighten the inner pad dial two or three clicks, clamp down again, and tighten the caliper mounting bolts. This aligns the caliper to the rotor. Then I release the lever and retract the inner pad dial, usually two or three clicks, so the pad just clears the rotor, the point where you no longer detect rub. Then I adjust the outer pad clearance for free play, usually where contact is made at a little less than half of full lever travel. It usually doesn't matter whether you use the knob or cable tension because at this point you're just fine-tuning. Now test. You should feel a solid thunk when you squeeze the lever. If it feels like a moosh, that's the outer pad deforming the rotor as it over-reaches for the inner pad. It means you need to bring the inner pad closer.

As long as the torque arm is in no danger of becoming completely closed under full braking force, the most important thing is to get the inner pad as close to the rotor without making contact until the lever is squeezed.

This whole exercise reminds me of what a dandy piece of equipment the BB7 is. It really is the class act of mechanical disc brakes. If only Juicy hydros worked as well.

Last edited by oldbobcat; 05-09-21 at 09:13 PM.
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Old 05-10-21, 04:53 AM
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I have road BB7s, and inline cable adjusters. And yes, I use them to make the brakes "sharper".

My set-up process is:

1. Loosen the cable clamp bolt on the caliper.
2. Pull the cable with a pair of pliers to take as much slack out as possible.
3. Clamp the cable again, while still pulling with pliers. There shouldn't be much slack left in the cable now.
4. Back both pads out.
5. Gradually wind the inner pad in, until it rubs. After EACH adjustment I apply the brakes, hard. To "seat" the pad properly. After I've got the pad so it JUST rubs, I back it off 1 or 2 clicks.
6. I do the same with the outer pad.
7. Then I take a little slack out of the cable, using the cable adjuster. I generally watch the caliper to see if it moves, and as soon as I see it move, I stop.

I don't think I'm really using the cable adjusters to take up pad wear. It's more that I'm taking the initial tension out of the cable. The brakes work very well, and the levers don't come anywhere near bottoming out on the bars.

By the way, the biggest improvement in braking I got was changing from modern Sora levers to 9 speed Ultegra levers, as the Ultegra levers have the correct pull for road BB7s.
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Old 05-10-21, 05:00 AM
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The Shimano BR-R317 (cable disc calipers) are adjusted using the cable adjuster, for the outside pad. See page 18 here:
Shimano disc brakes
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