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  1. #1
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    please can someone help with a measurement

    Hi, I am building a project bike, i have just bought a new m4 hope caliper with a G mount and tech lever to fit a rear brake, i also have a hope 203mm disc but i need an engineer to fit a 6 hole adapter to my plain hub so i can fit the disc, I will need to weld on an IS bracket to the frame, when the IS bracket is welded to the frame i need to know the standard measurement between the back of the IS bracket to the face of the disc when the wheel is fitted. Could someone please give me this measurement in MM ? Thanks John.

  2. #2
    rebmem rbtm
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    i need an engineer to fit a 6 hole adapter to my plain hub so i can fit the disc
    Buy a new rear wheel that's disc brake compatible.

    I will need to weld on an IS bracket to the frame, when the IS bracket is welded to the frame i need to know the standard measurement between the back of the IS bracket to the face of the disc when the wheel is fitted.
    140mm: http://www.hayesdiscbrake.com/wp-con...2101_5inch.pdf
    160mm: http://www.hayesdiscbrake.com/wp-con...7886_6inch.pdf
    180mm: http://www.hayesdiscbrake.com/wp-con...4/98-18646.pdf
    203mm: http://www.hayesdiscbrake.com/wp-con...4/98-17887.pdf

    Rear IS frame mounts are usually 140mm.

    What bike do you have?

  3. #3
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    Quote Originally Posted by cobba View Post
    Buy a new rear wheel that's disc brake compatible.



    140mm: http://www.hayesdiscbrake.com/wp-con...2101_5inch.pdf
    160mm: http://www.hayesdiscbrake.com/wp-con...7886_6inch.pdf
    180mm: http://www.hayesdiscbrake.com/wp-con...4/98-18646.pdf
    203mm: http://www.hayesdiscbrake.com/wp-con...4/98-17887.pdf

    Rear IS frame mounts are usually 140mm.

    What bike do you have?
    thanks cobba for the link, i'm stuck with the hub i have unfortunately, it's a 1981 mongoose with 4 1/2 inch rear stingray chopper wheels to be fitted,
    if you go to retro-goose.com and go into projects you'll see what i mean

  4. #4
    rebmem rbtm
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    This ?

  5. #5
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    Quote Originally Posted by cobba View Post
    Yes that's the one.

  6. #6
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    Quote Originally Posted by snoppy23 View Post
    Yes that's the one.
    could you tell me how thick the IS bracket is on a steel frame, looks like about 5mm but want to get it right.

  7. #7
    rebmem rbtm
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    Look at the 140mm brake mount specs, it has a thickness of about 7mm.

    The position of the brake mount in relation to the rotor is more important then the thickness of the brake mount as long as it's thick enough not to break.

    For $6 you can buy a IS brake mount.

    http://www.paragonmachineworks.com/cgi-bin/commerce.cgi?search=action&category=CM01

    For the Hope 'G' adapter to work with a 203mm rotor you'll need the IS brake mount to be set at the 140mm specs.

    You'll need to fix your hub up before you think about attaching the brake mount otherwise you won't know where to attach it in relation to the rotor.

  8. #8
    rebmem rbtm
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    You could also attach post mounts to the frame and not use the brake adapter you have.

    http://www.hayesdiscbrake.com/wp-content/uploads/2010/04/e-10722-9_RA.pdf

    http://www.paragonmachineworks.com/cgi-bin/commerce.cgi?search=action&category=CM02

    If the post mounts are set at 203mm then no adapter is needed with your brake but that also means 203mm is the minimum rotor size that can be used.

    If the post mounts are set at 140mm, 160mm or 180mm then a post mount to post mount adapter will be needed if a 203mm rotor is used.

  9. #9
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    Thanks cobba you have been most helpful, i have bought various adapters for 140,160,183 and the 203 on the caliper already, just in case i need to fit the IS onto the frame stay rather than the drop out,only because the drop out is 3mm plate, i can then use the 203 disc and use a 140 adapter which will move the IS bracket higher up the frame.
    Those adapters are nice, thanks for the link. at that money it's not worth me getting one made

  10. #10
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    Quote Originally Posted by snoppy23 View Post
    Thanks cobba you have been most helpful, i have bought various adapters for 140,160,183 and the 203 on the caliper already, just in case i need to fit the IS onto the frame stay rather than the drop out,only because the drop out is 3mm plate, i can then use the 203 disc and use a 140 adapter which will move the IS bracket higher up the frame.
    Those adapters are nice, thanks for the link. at that money it's not worth me getting one made
    Would you fit the BK2005 , BK2006 or BK2007 ? frame tube is 19mm OD with a 2mm wall thickness and take into account that's a monster brake for a 20" wheel ?Also cobba where the wheel on the bmx is adjustable for the chain i may need to have a IS slotted at the same angle as the drop out slot so i can adjust when the chain starts to wear, i plan on getting the spindle just further forward than in the middle when finished. i could make the wheel fixed and then use the standard style IS bracket, i bought the claiper because of it side adjustment so i don't have to use shims, i am not interested in setting it up for 140 specs really as long as a 203 disc is always going to be available I know what you mean about fitting a 140 adapter then i can't go smaller than the 203 ,i could always fit a 160mm adapter which would let me change to a 183 disc if i choose. If i make the wheel fixed and once i'm happy with the gearing i could mount an adjustable chain roller so i can set it up with the chain a little slack and then adjust the chain by the guide roller, ideally the brake needs to adjust with the wheel though. I haven't got enough room to make a floating brake set up like on a motorcycle with an adjustable torque arm. Like you said earlier i need the disc mounted to the hub first but until i get the disc in my hand i'm not sure if the disc will even fit over the hub but one way or another i will make it work With this project most of the specs are made up as i'm building it, i have keeped the frame looking like a mongoose with the specs of the drop outs and tubing etc apart from the width, from a side view it will look like 1981 mongoose but from the rear it will make most fat bottomed girls look slim )
    Last edited by snoppy23; 09-22-2013 at 06:12 AM.

  11. #11
    rebmem rbtm
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    Why do you need a 203mm rotor?
    What sort of speeds do you expect to do on the bike?
    What sort of riding are you going to do on it, will you be riding on flat country or down long hills?

    Those IS mounts should need some modification to get the correct alignment specs on the frame.

    Anyhow, various adapters mean that you probably will be able to put the IS mount at either the 140mm, 160mm, 180mm or 203mm position when using a 203mm rotor.

    A 203mm rear adapter is basically a 63mm adapter, it allows you to increase the rotor size by 63mm on a 140mm mount.
    A 180mm rear adapter is basically a 40mm adapter, it allows you to increase the rotor size by 40mm on a 140mm mount.
    A 160mm rear adapter is basically a 20mm adapter, it allows you to increase the rotor size by 20mm on a 140mm mount.
    A 140mm rear adapter is basically a 0mm adapter, it doesn't increase the rotor size on a 140mm mount.

    A 140mm rear adapter will probably work on a 203mm IS mount with a 203mm rotor
    A 160mm rear adapter will probably work on a 180mm IS mount with a 203mm rotor
    A 180mm rear adapter will probably work on a 160mm IS mount with a 203mm rotor
    A 203mm rear adapter will work on a 140mm IS mount with a 203mm rotor

    * probably means that you should check alignments before any welding is done.

    Horizontal dropout frames usually have different IS mounts that have slots instead of holes so they are adjustable.
    Photo 1, Photo 2, Photo 3, Photo 4.

    If you're rebuilding the rear end of the bike maybe you should put some sliding dropouts on it where the brake mount moves when you adjust the rear wheel.
    http://www.paragonmachineworks.com/c...&category=ISBB
    http://www.paragonmachineworks.com/c...&category=ISBC
    http://www.interlocracing.com/frame_droupouts.html
    * the IS mounts on those are made for standard disc hubs, if your custom disc hub is spaced with different specs then extra spacing or modifying of the brake adapter might be needed.


    Have you thought about putting an eccentric bottom bracket on it, you wouldn't need to move the rear axle to adjust the chain tension.

    Put on a tube splitter, make it belt drive and you won't have a chain that needs adjusting.
    http://www.paragonmachineworks.com/c...&category=TS09

    A good article on single speeds and disc brakes: http://www.bike198.com/building-a-si...in-bike-frame/
    Some good write ups and info on custom builds: http://www.ratrodbikes.com/forum/index.php

  12. #12
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    When i bought the set it just happened to come with the 203mm rotor, the bike looks a bit overkill so i will probably go with it, as for going downhill unlikely, it is actually built for wheelies so hopefully it will be a brake that has good control, since the levers came on the scene i just fell in love with them, i may have to fit a shorter brake hose, i know the goodridge hose you can shorten, can the hope braided lines be shortened easily ? got the links thank you, photo one looks close to what i require.

  13. #13
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    Quote Originally Posted by snoppy23 View Post
    When i bought the set it just happened to come with the 203mm rotor, the bike looks a bit overkill so i will probably go with it, as for going downhill unlikely, it is actually built for wheelies so hopefully it will be a brake that has good control, since the levers came on the scene i just fell in love with them, i may have to fit a shorter brake hose, i know the goodridge hose you can shorten, can the hope braided lines be shortened easily ? got the links thank you, photo one looks close to what i require.
    Large diameter rotors on small diameter wheels are not easy to control.
    mtbtires.com
    The trouble with common sense is it is no longer common

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