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Type of brake(s)?

Old 03-03-21, 07:49 PM
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cajunpedaler
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Type of brake(s)?

Specialized Apex Frame. Has rear brakes that are mounted under the chain stay.
what kind of brake would it be?





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Old 03-03-21, 08:00 PM
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shelbyfv
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Originally Posted by cajunpedaler View Post
Specialized Apex Frame. Has rear brakes that are mounted under the chain stay.
what kind of brake would it be?





U brakes? https://www.sheldonbrown.com/canti-u.html Also, that appears to be a Diamondback, not a Specialized, FWIW.Value of 80s DiamondBack Apex? edit- some in the other thread say it's a "roller-cam."

Last edited by shelbyfv; 03-04-21 at 07:43 AM. Reason: link
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Old 03-03-21, 08:00 PM
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https://bikeindex.org/bikes/709212

I think I got the year wrong, but it's close

Last edited by daverup; 03-03-21 at 08:06 PM.
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Old 03-04-21, 03:10 AM
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Yes it will use a U brake, was trendy in the late 80's early 90's
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Old 03-04-21, 06:25 AM
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U-brakes have the mounting bosses "above" the braking surface while cantilever or linear pull brakes (called V-brakes by Shimano) have the mounting bosses "below" the braking surface. Be watchful for this, as your rear brake mounts are almost certainly designed for a U-brake while your front brake mounts are almost certainly designed for cantilevers. So if you're ordering parts, you probably cannot buy two sets of U-brakes...you'd need a U-brake for the back and a cantilever for the front. Alternatively, you could possibly use a Mini-V linear pull brake from Tektro on the front, to work with short-pull brake levers, as long as you're tires aren't too large.
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Old 03-04-21, 09:51 AM
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U brakes. Yuck. Placed in the worst possible place for getting mucked up, and are practically impossible to adjust. THis was the style for one or two years, then the industry smartened up and put the brakes back up on the seatstays.

U brakes can stop the bike OK if set up properly and with good pads and cables. But if the bike is for use off road then find something else as this mounting position makes the bike basically unridable in any amount of mud. It can still work for a commuter or city bike, though.
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Old 03-04-21, 09:57 AM
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BMX (freestyle) bikes use u-brakes and some of them work very well. I never had a problem with Fly, Diatech Hombre, or Odyssey Evolver calipers. I could consistently modulate or instantly lock up my rear wheel with one finger on the lever. might be a problem for muddy conditions, so it depends on where you are riding this bike. pick up some brakes designed for a BMX bike (Empire BMX is a good shop for this), set them up with minimal spring tension, and use the appropriate brake pad compound for your rim surface (usually black/hard for chrome sidewalls, red/salmon for machined/ bare aluminum, and super-soft clear pads for chrome plated) and they should work well.
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Old 03-04-21, 11:23 AM
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I don't think it's a roller cam brake at all but likely a Shimano Deore XT U brake along the lines of a BR-M731 or similar model. You can't really use a V brake as it might hit the crank arm. They started putting U brakes on chain stays because chain stays have less flex then the posts on seat stays and the cable routing is simpler. But like everyone says on a MTB with mud etc getting stuck in it, and getting hung up on things was more trouble then the system was worth.
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Old 03-04-21, 11:34 AM
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Most common from 1987-1989. Some carry over to 1990.
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Old 03-04-21, 12:29 PM
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ClydeClydeson
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Originally Posted by cbrstar View Post
I don't think it's a roller cam brake at all but likely a Shimano Deore XT U brake along the lines of a BR-M731 or similar model. You can't really use a V brake as it might hit the crank arm. They started putting U brakes on chain stays because chain stays have less flex then the posts on seat stays and the cable routing is simpler. But like everyone says on a MTB with mud etc getting stuck in it, and getting hung up on things was more trouble then the system was worth.
V brake and cantis won't work at all because the pivots (a) are in completely the wrong place (pads might contact the top of the tire but will be nowhere near the rim) and (b) the pivots are fatter and Cantis and Vs won't fit(IIRC).

Roller cams and U brakes use the same mounting posts and location relative the rim, but I think the whole RC assembly (including the 'actuation triangle') might not fit behind the BB shell.

The cable routing issue got figured out for the next generation of bikes ca. 1992 - run all the cables along the top tube.
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Old 03-04-21, 12:59 PM
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Originally Posted by ClydeClydeson View Post
V brake and cantis won't work at all because the pivots (a) are in completely the wrong place (pads might contact the top of the tire but will be nowhere near the rim) and (b) the pivots are fatter and Cantis and Vs won't fit(IIRC).

Roller cams and U brakes use the same mounting posts and location relative the rim, but I think the whole RC assembly (including the 'actuation triangle') might not fit behind the BB shell.

The cable routing issue got figured out for the next generation of bikes ca. 1992 - run all the cables along the top tube.
Sorry maybe my brain is still in OS bmx mode. I've seen people try to use a post extender similar to this.


but as you can imagine it doesn't work.
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Old 03-04-21, 01:11 PM
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cbrstar I think even with those, you cannot put V or canti brakes on U brake posts. Those adaptors, I believe, are to allow use of a different wheel size with canti posts. The difference in location between U and V posts is a lot bigger than those adaptors.
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Old 03-04-21, 04:39 PM
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Originally Posted by ClydeClydeson View Post
cbrstar I think even with those, you cannot put V or canti brakes on U brake posts. Those adaptors, I believe, are to allow use of a different wheel size with canti posts. The difference in location between U and V posts is a lot bigger than those adaptors.
Don't get me wrong I am not saying it's a good idea at all. I've just seen a rash of people in my local area that for what ever reason think it's a good idea to try it. They cut the posts off and re-drill and tap the holes and then are surprised when there isn't enough clearance.
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