Resources for what disc rotors fit which forks?
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Resources for what disc rotors fit which forks?

This is a discussion on Resources for what disc rotors fit which forks? within the Technical forums, part of the Caferacer.net Forums category; Okay- I got the disc brake upgrade for the CM250C (CMX250 fork legs, triple tree and brake caliper; fork seals are dead and caliper needs ...

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  1. #1
    bunnyman's Avatar
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    Resources for what disc rotors fit which forks?

    Okay- I got the disc brake upgrade for the CM250C (CMX250 fork legs, triple tree and brake caliper; fork seals are dead and caliper needs rebuilt, but $2.98 total BEFORE shipping makes it a bargain), I need to know where I could find compatiblity for wheels and brake rotor diameters. I guess what I am saying is that I would rather not use the Rebel front wheel if I don't have to. I know that there was a set of 5 spoke cast wheels for the 250 Nighthawk in limited quantities. I know- I still need compatible brake lever and master cylinder.

    If there was any cross-compatibility between the CM400 and the CMX250, I have a line on a sweet set of wheels.

    The big bonus is that my investment in these parts is pretty minimal. I am hoping I have a few options in the means of wheels.

  2. #2
    Senior Member Geeto67's Avatar
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    if you go to your shop manual there should be a spec on rotor thickness, use that and a tape measure to figure our what size rotor you have/will need. It isn't enough that the rotor be the right diameter, it must also be the right thickness to work with the caliper.

    BTW, it is always easier to get the whole front end of the bike whose wheels you want and figure out a way for the neck to take the stem rather than re-engineer disc brakes.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
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  3. #3
    bunnyman's Avatar
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    Yeah- I may just have to be happy with a Rebel front wheel.

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  5. #4
    Senior Member HackAsaw's Avatar
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    so what is it exactly that you want to do?

    likely there are wheels that nearly bolt on but certainly there are many that can easily be adapted.

    would the scope of your capabilities go beyond a simple bolt up if somebody told you the magic wheel, brake and axle combo?
    Accidental inventor of the worlds fastest wearing rocker arms and other edible engine parts! Try my yummy blue cheese camshafts!

  6. #5
    Senior Member HackAsaw's Avatar
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    'always' and 'nevers' can sometimes be real bears.... even when one is actually seasoned with enough hands on experience to know better than to make such statements

    especially true if adapting ultra modern to vintage.... even if the modern-ish trees ain't scary ugly

    or the forks aren't too big and/or heavy

    you ever try plugging trees off a modern zipper bike with a lower stem diameter in excess of 35mm onto something much smaller or vintage


    sometimes axle work is much easier

    and rotor diameters & caliper juggling can be easier than chitting in the well and not nearly as dangerous

    quote:Originally posted by Geeto67



    BTW, it is always easier to get the whole front end of the bike whose wheels you want and figure out a way for the neck to take the stem rather than re-engineer disc brakes.
    Accidental inventor of the worlds fastest wearing rocker arms and other edible engine parts! Try my yummy blue cheese camshafts!

  7. #6
    Senior Member Geeto67's Avatar
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    I noticed you are a bicycle guy....and I think that may be your hindrance when it comes to working on old motorcycles. Unlike bicycles where there are standard sizes in which most if not all manufacturers adhere to, most of the motorbikes in the 1970s were engineered by their factories from wheels to mirrors (ie bottom to the top). Some things used common suppliers (carbs, sometimes wheels, wiring, etc), but mostly bike stuff is kinda random as to what fits what and if there are two things that are interchangeable among different models it is more often a happy accident. yes there is some parts bin robbing that goes on but most of that is proprietary information. That was a very long way of saying the list you are looking for does not exist.

    Take measurements of your wheel: brake bolt spacing and pattern, width, etc....and then carry a set of measuring calipers and a tape measure with you. Go and measure most of the bikes you come across (remember to ask first). There are lists of neck bearing sizes and fork seal sizes around that can give you some idea as to what bikes have what front ends but really you are not going to find a wheel interchange manual unless you make it yourself. Even same model same year bikes come with different wheels that don't interchange (see the 1977-78 cb750K vs cb750F for an example)

    The good news is that it looks like you have somethingin the way of fabrication skills, at least for bicycles, so you can probably make something work or fit if need be. Talk to Mr. Fischer, as he can tell you how to redrill discs or wheels, and you can always make bushings for axles and mounts for newer calipers.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
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  8. #7
    bunnyman's Avatar
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    My fabrication skills are okay, but my Mac Guyvering is top-notch!!! Seriously, I would rather have thing readily bolt together, no doubt; however, I know that some stuff would have to be, how do I say this? Rigged.

    While I did not do my own machining of metal parts when I produced a limited number of bike frames, stem/handlebar/aerobar combos and the like, I did have to do some hacking and drilling to make things work. And believe me- the if the front end of a bicycle fails, it is likely to end in the same fate as if a motorcycle front end fails. I can also mitre tubes in the correct angles to build frames from metal or carbon tubes. My welding is a bit suspect, however. I can tack weld fine. I can glue and wrap carbon so much better.

    I have only seen real parts bin robbery in the CM/CMX/CB250 realm in the world of Honda. Everywhere else has no real parts bin robbery. Answers in this thread has proven this.

    And my answer for Mr. Hacksaw is "yes", the scope of my mechanical abilities go beyond a simple bolt up.

    But like I said earlier if I can't do it myself, I can certainly find someone who can.

  9. #8
    Senior Member HackAsaw's Avatar
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    well wheel swaps and such should be easier than a vaselined cakewalk for you.....

    remember to ask first

    yuk yuk

    my guess is you'll find a drill or transfer punch set much more useful than a tape measure when searching for donors & subsequently adapting

    but what would I know.... I just like to type anything that makes me look like I know motorcycles from stem to stern

    and I'm just eleventeen years old










    Accidental inventor of the worlds fastest wearing rocker arms and other edible engine parts! Try my yummy blue cheese camshafts!

  10. #9
    bunnyman's Avatar
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    That's why I be aksin' y'all about dis stuff.

    Anything is easier than a vasolined cake walk.

    Eleventeen? I am twenty-seventeen.

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