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Stopping with mechanical disc brakes

Old 10-30-17, 12:51 PM
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Stopping with mechanical disc brakes

I have a 2012 Kona Sutra that came with mechanical disc brakes (Avid BB7 and Tektro 340 levers). In the 4 years that I have owned it (I bought it new in the fall of 2013), the brakes have never really been that great. The levers aren't bottoming out (but I could try to tighten them up a bit more), I've cleaned the rotors with isopropyl alcohol, I've cleaned the pads and I've replaced the pads too. My LBS seemed to think that I've done all I can with them and that mechanical discs are never as good as hydraulic (I have hydraulic on my mountain bike and they are much better, even though the two bikes are of similar quality so it is not like I'm comparing highend vs lowend bikes). Also, my LBS said that, at the time being, road-style hydraulic discs are very expensive.

Are the LBS opinions correct? Are there better quality road style mechanical disc brakes that I could consider? Are there "cleaning" options that I could try? Are there less expensive road style hydraulic disc brakes that I could consider?

Thanks
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Old 10-30-17, 01:15 PM
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Check the housing - until only recently OEM were not that great about using the proper compressionless housing for mechanical discs.

Also, try using 120-200 grit sandpaper on your rotors. A lot of times alcohol won't remove the glaze/contaminant that can be present.
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Old 10-30-17, 01:42 PM
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My BB7 (Mtn) worked better with aftermarket pads, than with the original ones.

Mine work just fine .. you seeking the ultimate brake? willing to pay Big Bucks?
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Old 10-30-17, 01:50 PM
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Originally Posted by fietsbob View Post
My BB7 (Mtn) worked better with aftermarket pads, than with the original ones.

Mine work just fine .. you seeking the ultimate brake? willing to pay Big Bucks?
I have replaced the OEM pads with OEM pads so no, I haven't tried another brand.

Not seeking the ultimate brake, just better: my calipers on my 1988 Bianchi Strava work better than my mechanical discs. In an emergency, it is unlikely I'll stop in time.
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Old 10-30-17, 01:53 PM
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Originally Posted by Spoonrobot View Post
Check the housing - until only recently OEM were not that great about using the proper compressionless housing for mechanical discs.

Also, try using 120-200 grit sandpaper on your rotors. A lot of times alcohol won't remove the glaze/contaminant that can be present.
Ok, I'm not quite sure what you're talking about with regard to housing. However, I can certainly try the sandpaper idea.

Just happened to watch a YouTube video of a fellow who used a car disc brake (rotor) deglazer on his mountain bike rotors: spray on both sides of both rotors, ride up and down the road for a few minutes with the brakes on lightly, gradually pressing harder over the minutes. Rotors will be hot to touch and any squeaking (mine don't sqeak too much, nothing that really bothers me) will be eliminated. However, I'll try the sandpaper first.
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Old 10-30-17, 02:04 PM
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Now there is Low compression Housing, its like Indexed Shift Housing, just adding a Kevlar braided overwrap on the outside sheath,
to keep the spikes of braking force from bursting the housing..

(Shift cable housing has a more constant end force applied)



I got pads from Kool Stop , organic compound.. I'm not trying to go fast, Its a Rain braking benefit,
[160 disc, 20" 406 wheels, Bike Friday.]





....

Last edited by fietsbob; 10-30-17 at 02:08 PM.
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Old 10-30-17, 08:35 PM
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I recently went through this with Avid BB5's. BB5's are tuned similarly to BB7s, except that the small knob is missing. Is the brake arm fully relaxed when your brake lever is not pulled? I find that my BB5s exhibit bad modulation, if the brake arm is too far in (in the not-breaking state).
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Old 10-30-17, 09:31 PM
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You've adjusted/aligned the brakes using park tool or avid recommended technique?
I find this very helpful: https://www.parktool.com/blog/repair...isc-adjustment
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Old 10-31-17, 07:03 AM
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Originally Posted by JanMM View Post
You've adjusted/aligned the brakes using park tool or avid recommended technique?
I find this very helpful: https://www.parktool.com/blog/repair...isc-adjustment
I don't have the tool (I haven't even looked at the video to know that I don't have the tool, LOL) but I'll have a look at the video tonight and see what that does.

I did a thorough cleaning with isopropyl alcohol last night and a thorough sanding/deglazing but to no effect. However, perhaps there is more movement of my brake lever than there should be (it is not bottoming out on the bar but a little less movement might be beneficial).
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Old 10-31-17, 11:10 AM
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Only tool needed is a hex wrench. Needle nose pliers can be helpful, too. Park Tool makes bicycle tools. And offers useful repair/maintenance advice on their website.
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Old 10-31-17, 05:34 PM
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my bb7's on a heavily loaded touring bike in steep mountains have performed flawlessy, with very good stopping power, and require so little finger pressure to get hard full stops from 50, 60kph compared to all my years touring with cantis in similar mountainous roads.

of course I cant comment on how your brakes are working, but I've been suitably impressed with BB7's being used in rather tough riding conditions (steep hills) and how they routinely hauled my touring bike down to a stop when I would spot a photo opportunity I didnt want to miss.
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Old 11-01-17, 05:20 AM
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Properly adjusted BB7 work very well. I have road and MTB set-ups and both work just fine. There's no need for compressionless housing, that takes all the feel/progressiveness away. In the last 7 years I've never had to clean my rotors, just run 'em and enjoy the consistency and sureness. Once the pads get thin, slap in a new set.

Here's a great video that explains it very well. The most important point is getting the inner pad as close to the disc without rubbing, then set the outer pad to preference. Once BB7 are set up correctly all it takes is occasional adjustments of the pads for wear just like rim brakes. When I ride lift assist in Vail I adjust them at lunch. On my road bike after 2000 miles they're still untouched.


When I worked at an LBS none of the other mechanics knew how to adjust BB7s. Most new bikes all come with hydros, bleeding brakes is much more common than setting up BB7s.
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Old 11-01-17, 07:30 AM
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Originally Posted by Mr IGH View Post
Properly adjusted BB7 work very well. I have road and MTB set-ups and both work just fine. There's no need for compressionless housing, that takes all the feel/progressiveness away. In the last 7 years I've never had to clean my rotors, just run 'em and enjoy the consistency and sureness. Once the pads get thin, slap in a new set.

Here's a great video that explains it very well. The most important point is getting the inner pad as close to the disc without rubbing, then set the outer pad to preference. Once BB7 are set up correctly all it takes is occasional adjustments of the pads for wear just like rim brakes. When I ride lift assist in Vail I adjust them at lunch. On my road bike after 2000 miles they're still untouched.

https://www.youtube.com/watch?v=NasGJFtgq0A

When I worked at an LBS none of the other mechanics knew how to adjust BB7s. Most new bikes all come with hydros, bleeding brakes is much more common than setting up BB7s.
This is good to hear. My BB7s are on my Kona Sutra touring bike and I use it for daily commuting (so the rear panniers have at least a little bit in them all the time including rain gear). I'll get back to working on them this weekend.
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Old 11-01-17, 07:40 AM
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jrick, I will bring this up just out of thoroughness, if you are aware, ignore. Don't forget that for a good hard stop, one should be using the front/rear brake force ratio at something like 70% front 30% rear. In a hard stop, its the front that does nearly all the stopping. When we stomp on the brake pedal in our cars, they are set up automatically with this range of brake balance.

when we brake in a car, or a motorcycle, or a bicycle, the weight transfers forward during the slowing down, with the majority of weight on the front, and so we need to haul more on the front brake. If you are not doing this, you will not get the proper braking that your brakes can do, and you will be overtaxing the rear brake and you wont be slowing down enough compared to predominantly using the front brake.
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Old 11-01-17, 09:05 AM
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Originally Posted by jrickards View Post
The levers aren't bottoming out (but I could try to tighten them up a bit more),
There's your problem. Mechanical discs simply don't work that well if you set them up like many people set up rim brakes. In other words, you can't set them up so that the brake engages at half lever travel. If you do, the brake feels mushy and ineffective. Simply shortening the cable won't help either. You need to set the pads up so that they are a minimal distance from the rotor when the brake is open.

The Avid BB7 is a bit touchy about setup as well. This article describes the setup nicely. I've used this technique on the BB7 as well as other, cheaper brakes and it have improved them greatly.

You don't say if you use them but I've also found that interrupter levers can degrade the performance of road bike levers with regard to disc brakes as well. The interrupters work very well but they build in some flexibility to the system that degrades the performance of the other levers.
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Old 11-01-17, 09:09 AM
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Originally Posted by cyccommute View Post
There's your problem. Mechanical discs simply don't work that well if you set them up like many people set up rim brakes. In other words, you can't set them up so that the brake engages at half lever travel. If you do, the brake feels mushy and ineffective. Simply shortening the cable won't help either. You need to set the pads up so that they are a minimal distance from the rotor when the brake is open.

The Avid BB7 is a bit touchy about setup as well. This article describes the setup nicely. I've used this technique on the BB7 as well as other, cheaper brakes and it have improved them greatly.

You don't say if you use them but I've also found that interrupter levers can degrade the performance of road bike levers with regard to disc brakes as well. The interrupters work very well but they build in some flexibility to the system that degrades the performance of the other levers.
I will look at this article and work on the brakes this weekend. No, I don't use interrupters so that isn't an issue (or part of the problem).

Thanks
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Old 11-01-17, 09:12 AM
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Originally Posted by djb View Post
jrick, I will bring this up just out of thoroughness, if you are aware, ignore. Don't forget that for a good hard stop, one should be using the front/rear brake force ratio at something like 70% front 30% rear. In a hard stop, its the front that does nearly all the stopping. When we stomp on the brake pedal in our cars, they are set up automatically with this range of brake balance.

when we brake in a car, or a motorcycle, or a bicycle, the weight transfers forward during the slowing down, with the majority of weight on the front, and so we need to haul more on the front brake. If you are not doing this, you will not get the proper braking that your brakes can do, and you will be overtaxing the rear brake and you wont be slowing down enough compared to predominantly using the front brake.
Yes, I'm aware that the front brakes should be the primary brakes and that is what I use most of the time. For that reason, it is my front brake that is less responsive than the rear and needs the most work. This weekend, my brake work will primarily be done on the front brake and if I can get that working better, great! Then I may work on the rear to see if that can be improved, even though I'm less concerned about it.

Thanks for raising this though.
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Old 11-01-17, 09:59 AM
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Mechanical disk brakes need to be adjusted at the pad. Cable adjusters are only used to remove slack in the cable. Anything else just reduces travel.
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Old 11-01-17, 04:41 PM
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As others have sufficiently covered, properly adjusted BB7's should work well for you. If you're interested in hydraulics, I would suggest checking out the TRP Hylex RS brakes. You can get a pair for under $250 and their performance is excellent.
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Old 11-01-17, 05:10 PM
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I would also mention that definitely I had to learn a whole new bunch of stuff playing around with my BB7s, my first bike with discs, and have made numerous mistakes along the way. Its like any new skillset we have to learn, it can be frustrating and I often think that I have a higher than usual ability to do stupid stuff along the way, but usually muddle my way along, and getting better with BB7's did work out in the end.

I would say the main thing to be aware of is how small small clearance differences, either with pad to rotor distance, or caliper alignment, make a real diff in things not working well.
I also always need to have reading glasses on, and it can be handy to have a flashlight with you, and or a white sheet or paper to place on the ground to help see rotor alignment, pad to rotor distances etc.
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Old 11-03-17, 11:20 AM
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Originally Posted by djb View Post
I would also mention that definitely I had to learn a whole new bunch of stuff playing around with my BB7s, my first bike with discs, and have made numerous mistakes along the way. Its like any new skillset we have to learn, it can be frustrating and I often think that I have a higher than usual ability to do stupid stuff along the way, but usually muddle my way along, and getting better with BB7's did work out in the end.

I would say the main thing to be aware of is how small small clearance differences, either with pad to rotor distance, or caliper alignment, make a real diff in things not working well.
I also always need to have reading glasses on, and it can be handy to have a flashlight with you, and or a white sheet or paper to place on the ground to help see rotor alignment, pad to rotor distances etc.
This is great advice, thanks
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Old 11-03-17, 05:19 PM
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Your welcome, follow the links suggested here by others and read others to become more familiar. Having a repair stand is a big help.
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Old 11-03-17, 07:20 PM
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Originally Posted by jrickards View Post
Are there better quality road style mechanical disc brakes that I could consider?
Definitely. Some have a U-shaped arm the cable attaches to that actuates both pads. The model I'm thinking of (can't remember the brand) also has adjustment of each pad via 3mm allen key. IMO these offer performance which is almost as good as hydraulic, without all the bother and unreliability - cables don't leak.
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