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  1. #1
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    Different caliper reach front and rear

    I'm in the process of converting a 1989 Trek 8500 mountain bike frame to ride on 700c wheels with dual pivot caliper brakes. The frame has 6mm bolt mounts on both the front and rear but they have different reach lengths. The front is 51mm and the rear 59mm. Ideally I would like them to match, does anyone know why they don't? The dropouts are resting on the axle.

    Second, does anyone know of an affordable brake set with a reach range that covers both the front and rear of my frame. I would like the brakes to match and I don't want to use the brakes with 55-70+ range.

    Third, what do you think about filing the rear drop out to decrease the rear reach to a more common 57mm?

    Thanks.

  2. #2
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    I'm far from an expert but I have noticed that the rear 700c tire is very close to the seat stay on my hybrid bike and if you filed down the slots, i would imagine that you might even hit the tire to the seat stay.

    I would say that filing the dropouts is best done to correct slight frame alignment issues rather than allowing for brake reach unless its required.

  3. #3
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    Non matching brake reaches were par for the course for many decades. One reason has to do with the sliding a wheel into horizontal dropouts vs. the fork's vertical entry. That went away as vertical became normal for the rear, and bike and brake companies wanted to simplify things by using the same brake front and rear.

    Even then it isn't rare for the reaches to be different, but at least within the range of a single brake, which yours might be if you buy 47-59 reach brakes like these.
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  4. #4
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    Quote Originally Posted by FBinNY View Post
    Even then it isn't rare for the reaches to be different, but at least within the range of a single brake, which yours might be if you buy 47-59 reach brakes like these.
    Thanks for the fast reply.

    I was looking at the brakes that you linked to earlier but the Tektro website calls the "57 mm long reach arms" but then list the dimensions as 47-59. Can the dimensions of the brake be different than the reach?

    Thanks for the information about the non matching brake reaches. The frame has vertical dropouts but it's good to know that it used to be common.

  5. #5
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    I expect your 8500 was built for cantilever brakes and the 6 mm holes in the fork crown and brake bridge were intended mostly for fender mounts, not caliper brakes, so Trek didn't pay a lot of attention to "reach".

  6. #6
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    Quote Originally Posted by HillRider View Post
    I expect your 8500 was built for cantilever brakes and the 6 mm holes in the fork crown and brake bridge were intended mostly for fender mounts, not caliper brakes, so Trek didn't pay a lot of attention to "reach".
    FTW.

    Also, the 8500 was designed around 26" wheels. Bastardizing it with 700c wheels and caliper brakes might be do-able, but you shouldn't be surprised if you have to run non-standard parts or jury-rig it to get it all to work.

  7. #7
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    Quote Originally Posted by alb1987 View Post
    Thanks for the fast reply.

    I was looking at the brakes that you linked to earlier but the-[Tektro Website]lists "57 mm long reach arms" but then list the dimensions as 47-59. Can the dimensions of the brake be different than the reach?
    Can't speak to the specifics, could just be a typo as they load data into different places on the site. Unfortunately it could be make or break (no pun) for you, so either ask Tektro the question directly for confirmation, of look at other options.

    Also be aware that there's a difference between front and rear brakes that can affect reach measurements, so you have to be careful. On the front wheel the rim rises ahead of the fork reducing the actual brake reach slightly. On the rear wheel of many bikes the opposite is true, increasing the reach. Unfortunately for you that can increase the disparity possibly causing you to have to mix brakes. Not a crisis, but makes shopping a bit harder.

    BTW- if your bike has canti brake bosses as Hillrider suggests it might, you're probably better off with canti or V-brakes depending on the lever throw.
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  8. #8
    Constant tinkerer FastJake's Avatar
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    +1 Those bridges were never meant for brakes, so that's why the reach is different. I have never bastardized a 26" frame to 700c but it's so tempting due to the availability of old cheap MTBs. I have been unable to find a cheap hybrid in my size for commuting, something like an old Trek 720 Multi-Track.

    If you go through with this project I'm curious to see how it turns out. I was looking up long reach brakes the other day, they're expensive! For the price of the brakes you might be able to just find an old hybrid and ride that instead.

    Quote Originally Posted by FBinNY View Post
    BTW- if your bike has canti brake bosses as Hillrider suggests it might, you're probably better off with canti or V-brakes depending on the lever throw.
    Yes, it has canti studs but those are designed around 26" wheels, not 700c wheels. OP is planning to put on 700c wheels and switch to caliper brakes.
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

  9. #9
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    I should have the first sentence more carefully. That's a horse of an entirely different color.

    The OP has a choice. He can go caliper and live with the reach issue without complaining. Or he can use the Mavic adapter 26" to 700c canti brake adapter (if they still make it) or a similar item from another company. I know a number of people who use these and they're all pretty happy. Some even report better braking than the original.
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  10. #10
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    Thanks for the input, everyone.

    I couldn't believe that the mounts were meant for caliper brakes, it makes sense that they're for fenders.

    FastJake - You're right they are expensive and since the frame cost me 10 dollars it's probably not worth it.

    FBinNY - I never heard of 26-700c canti brake adapters. I think that's the route I'll take.

  11. #11
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    Quote Originally Posted by alb1987 View Post


    FBinNY - I never heard of 26-700c canti brake adapters. I think that's the route I'll take.
    Mavic used to make them, but I don't know who else did. I got a friend a pr. from mavic about 2 years ago, but haven't seen them on their site lately. You might want to call Mavic in Massachusetts and ask if they still exist and how to buy them.

    here's a picture of a set, I think not by Mavic, but at least you'll see what you're looking for.
    Last edited by FBinNY; 02-13-12 at 09:25 PM.
    FB
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    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

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    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

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