Direct Mount Brake Tight Clearance
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  1. #1
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    Direct Mount Brake Tight Clearance

    Greetings all,

    I have a 2018 Felt FR1 with an Ultegra direct mount rear brake, which mounts on the chain stays.

    My problem is that it doesn't seem to open all that wide. Even when I disconnect the brake cable and it is presumably all the way open, I can barely tug my tire out (700x25 GP4000 that measures out at about 700x28). In and of itself, that isn't really the problem.

    What is the problem is that I cannot get the adjuster to do anything, except make the brakes all but stick to the rims if I close it. This brake does not have the barrel adjuster or the open/close level on the brake itself. Instead, I have an inline SM-CB90.

    In short, the shoes/calipers just don't seem to open all that wide. They are not getting blocked by the stays at least. My Aforce Al-33 rims are said to be 26.2 mm outside width, but I can't find numbers on the maximum width the brakes will handle or open to when unrestrained by a cable.

    I've read through Shimano's manual several times and can find nothing. Are there maybe thinner brake pads I can use (just put in some Kwik Stops)? Am I overlooking something?

    Thanks,
    Bradley

  2. #2
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    You overlooked the fact you don't have disk brakes.

    Big tires are hard to get out, depending on the product and adj. I used to not put my wheels on before I inflated them when I had a flat. Just yank it out.
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  3. #3
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    That must be a little frustrating, all the reviews and info about this bike tout its being able to support 28mm tires... what about a different brake, like TRP or Bontrager, I think they have direct mount options. A Cane Creek option was also mentioned in a previous thread regarding this bike model... (https://forums.roadbikereview.com/co...em-364988.html)

    If braking performance is fine and you're just talking about trouble getting the wheel on and off, you might just have to deal with rubbing when you take off / put on wheel...

    Edit: Specs say that BR-R8010 brake should accommodate 28mm tires... wonder if something weird is going on. Can you supply a picture?
    Last edited by jetdog9; 03-16-2020 at 03:45 PM.

  4. #4
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    IMG-1087.jpg

    Hopefully this shows things well. This is with the brake cable detached. That's maximum clearance between pads and rim.
    Bradley

  5. #5
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    Those pads are stupid close to the rim.

    If the rim is in fact, 26.2mm, and your 25mm tire on that rim actually measures 28mm, then switch to a 23mm tire (which may measure a "working width" of 25mm on that rim) or try borrowing a wheel with a narrower rim. Install your tire on it, and see what happens.

  6. #6
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    You need a smaller tire, the brakes look lllike they clear the rim. Putting a narrower rim on is going to give you more brake clearance, but tire clearance, ..no.

    If you want brake clearance, just take those pads off and grind them down as required.
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  7. #7
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    Yes, they are stupid close.

    But switching tire sizes doesn't address the lack of adjustability between the rim and the pads, which is the real problem, at least what I consider the problem. I can pull the wheel off with the tires inflated, I just have no room for adjusting the feel or modulation in braking. The slightest pull on the brake lever and they are all but full force on. They feel hard as a rock. Seems like Shimano should have built something that can be adjusted, other than by wearing down the pads.
    Bradley

  8. #8
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    What model brake is that? 8010 or 6810? I'm wondering if older generation has less clearance.

    Edit: Nevermind the question about 6800 vs 8010. But the document for 8010 brakes shows that recommended alloy rim size is 20.8-24 mm. 26.2 is larger than that. For carbon rims, different brake pads are used for 20.8-24 mm rims vs 24-28 mm rims.

    See page 20:

    https://si.shimano.com/pdfs/dm/DM-RACBR01-03-ENG.pdf

    Looks like those rims are actually 24.2 mm at the brake track, maybe it'll work for you as-is but with a tight fit...
    Last edited by jetdog9; 03-16-2020 at 07:06 PM.

  9. #9
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    It's an 8010. I've read through that pdf manual looking for anything, but i didn't find that 24 mm number, but it wouldn't surprise me. Ah well, I prefer a softer brake but I guess I'm going to have to adjust to a stiffer feel. I earlier swapped out the Cane Creeks after losing a spring on the road. However good the Cane Creek brakes are, the spring set up was a disaster in the making.

    Thanks!
    Bradley

  10. #10
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    Quote Originally Posted by bleckb View Post
    It's an 8010. I've read through that pdf manual looking for anything, but i didn't find that 24 mm number, but it wouldn't surprise me. Ah well, I prefer a softer brake but I guess I'm going to have to adjust to a stiffer feel. I earlier swapped out the Cane Creeks after losing a spring on the road. However good the Cane Creek brakes are, the spring set up was a disaster in the making.

    Thanks!
    Measure the width of the space between the brake pads, then remove the brake from the bike and measure again. If the brake gets wider when completely off the bike then there likely was some sort of installation issue. If the brake won't open any wider when off the bike, then study it's mechanism as you flex it by hand to see what is the limit to its opening width. It would be unusual for a caliper brake to be so limited in width, but it might be a design issue.

  11. #11
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    Thanks Kerry. I had considered that but hadn't yet done it. Shouldn't take but a few minutes to give it a try and see how it goes. Nothing to lose but those few minutes. Since I'm working from home for the foreseeable future, I can try it during a work break. I'll report back.
    Bradley

  12. #12
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    Quote Originally Posted by jetdog9 View Post
    .

    See page 20:

    https://si.shimano.com/pdfs/dm/DM-RACBR01-03-ENG.pdf

    Looks like those rims are actually 24.2 mm at the brake track, maybe it'll work for you as-is but with a tight fit...
    Finally saw that. Even with an additional 2mm, still seems pretty dang tight. We'll see how it goes after I try Kerry's suggestion.
    Bradley

  13. #13
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    Followed Kerry's suggestion. Measured the width between the pads on the bike and got about 27mm. Took the brakes off and measured as best I could, as the calipers operate independently of a central pivot point, and still got about 27mm.

    I then fiddled with the centering adjustment after putting the brakes back on. When backing out the centering screw, I got quite a bit of movement on the non-drive side (see image) and very little movement on the drive side. Of course, leaving it as the image shows results in a lot of deflection. I won't be riding it like that. I didn't measure, but based on the previous image, there has to be a good bit more than 27mm total between the pads. Still stumped.

    IMG-1088.jpg
    Bradley

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