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  1. #1
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    Thread Size on Older Bike's Rack/Fender Mount

    Hey, all!

    I am coming around the final bend in my race to build my CCM Torino 76 into a sturdy all weather Afline 8 equipped commuter, and all that needs to be done now is to mount fenders and a rack. There are braze-ons aove the rear and behind the front dropouts, but they are obviously a larger diameter than the modern standard (M4?) for mounting racks, fenders, and water bottles.

    I have found in the past that some BSOs have larger holes that are threaded, but don't know what thread size and pattern they were. Does anyone know what size(s) of bolt are likely to thread into an old frame like this? It is a Made in Canada CCM Torino '10 speed' from , I think, 1976.

    I am going to try a few different sizes tonight, and I may just wind up going with an M4 or M5 with a nut, but if there is a more elegant solution I will be happy as a clam at high tide!

    Thanks,
    LASF

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    Close to 100% of threaded fender/rack mount eyes are 5x.8mm, the same as the water bottle screw.

    If you have brazed on WB mount, you might borrow that screw and confirm.
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    Quote Originally Posted by FBinNY View Post
    Close to 100% of threaded fender/rack mount eyes are 5x.8mm, the same as the water bottle screw.

    If you have brazed on WB mount, you might borrow that screw and confirm.
    I will certainly try am M5 to confirm but I am pretty sure the hole is too big for that.
    Many older and cheaper bikes (mine included) have a larger hole that M5 passes right through. In the past I have sometimes been lucky and had the correct bolt to fit customers' bikes when they had these holes. Perhaps it was the same bolt size as the long bolt normally included with fenders to mount to the crown of the fork. M5? M6? 1/4-20? 10-32?

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    Quote Originally Posted by DCB0 View Post
    I will certainly try am M5 to confirm but I am pretty sure the hole is too big for that.
    Many older and cheaper bikes (mine included) have a larger hole that M5 passes right through. In the past I have sometimes been lucky and had the correct bolt to fit customers' bikes when they had these holes. Perhaps it was the same bolt size as the long bolt normally included with fenders to mount to the crown of the fork. M5? M6? 1/4-20? 10-32?
    As I said, most threaded eyes are M5. Unthreaded eyes are usually bigger to accept an M5 screw (or bigger) and nut. M5 is fairly standard threaded eye or not, because most fenders and racks have a 5mm unthreaded hole, so that's going to be the screw of choice either way.

    Of course, there are always exceptions, so confirmation by measurement or trial and error is still the best course, which is why I suggested it.
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    Quote Originally Posted by FBinNY View Post
    As I said, most threaded eyes are M5. Unthreaded eyes are usually bigger to accept an M5 screw (or bigger) and nut. M5 is fairly standard threaded eye or not, because most fenders and racks have a 5mm unthreaded hole, so that's going to be the screw of choice either way.

    Of course, there are always exceptions, so confirmation by measurement or trial and error is still the best course, which is why I suggested it.

    Excellent. Thanks for the advice!

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    Quote Originally Posted by FBinNY View Post
    Close to 100% of threaded fender/rack mount eyes are 5x.8mm, the same as the water bottle screw.

    If you have brazed on WB mount, you might borrow that screw and confirm.
    Close to 100% of modern rack mount eyes are M5 threads (a 10-32 will also work). However, older bikes may not have the same size rack mounts. I've had bicycles in the distant past that required drilling out the rack itself so that it would fit. Those are M6 bolts. Given the age of this bike, it may be one of those rare (for today) larger bolts.
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    Quote Originally Posted by cyccommute View Post
    Close to 100% of modern rack mount eyes are M5 threads (a 10-32 will also work). However, older bikes may not have the same size rack mounts. I've had bicycles in the distant past that required drilling out the rack itself so that it would fit. Those are M6 bolts. Given the age of this bike, it may be one of those rare (for today) larger bolts.
    OK, 100% probability that it is M5, unless it is M6. Got it! TrialAndErrorVille, here I come!
    Last edited by DCB0; 09-06-11 at 12:08 PM.

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    DCBO: I rebuilt an old Schwinn Collegiate which was tapped for M6X1 rack and fender hardware.

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    Quote Originally Posted by dsbrantjr View Post
    DCBO: I rebuilt an old Schwinn Collegiate which was tapped for M6X1 rack and fender hardware.
    Good to know. M6 is starting to sound like a possibility, too!

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    I just did a frame up build on an old CCM and here is what I found. Front fork fender stay mounts were m5x.8, two holes on either side on the rear dropouts, one for fender stays had an unthreaded hole that an m5 bolt would pass through, and a rack mount hole that an m6 bolt passed through.
    I ran an m6x1 tap through the fender stay hole, and it worked out great.
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    Quote Originally Posted by Dan Burkhart View Post
    I just did a frame up build on an old CCM and here is what I found. Front fork fender stay mounts were m5x.8, two holes on either side on the rear dropouts, one for fender stays had an unthreaded hole that an m5 bolt would pass through, and a rack mount hole that an m6 bolt passed through.
    I ran an m6x1 tap through the fender stay hole, and it worked out great.
    Good to know. However, the rear dropouts look kinda thin, so if they aren't already threaded I think I will just use a nut... there is plenty of room with the IGH - not like a 10 speed cassette where a nut on the inside would interfere with the chain.

    Thanks for the info!

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    DCBO: If you end up using a nut, an elastic stop nut will resist loosening due to vibration if there is no room for a lock washer. Blue Loctite is another possibility.

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    Senior Member bikeman715's Avatar
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    You can also put the bolt in backward (the head of the bolt inside the frame ) so there will be clearance for the chain . Just put the nut on the outside of the rack or fender .
    bikeman715

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    Quote Originally Posted by DCB0 View Post
    I will certainly try am M5 to confirm but I am pretty sure the hole is too big for that.
    Many older and cheaper bikes (mine included) have a larger hole that M5 passes right through. In the past I have sometimes been lucky and had the correct bolt to fit customers' bikes when they had these holes. Perhaps it was the same bolt size as the long bolt normally included with fenders to mount to the crown of the fork. M5? M6? 1/4-20? 10-32?
    The vast majority will be M5, a small number are unthreaded or M6.

  15. #15
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    Quote Originally Posted by bikeman715 View Post
    You can also put the bolt in backward (the head of the bolt inside the frame ) so there will be clearance for the chain . Just put the nut on the outside of the rack or fender .

    If I had limited clearance I could certainly use button head bolts on the inside of the stay, however there is a tonne of clearance between the dropout and the cog on the IGH so this shouldn't be an issue.

    Quote Originally Posted by dsbrantjr
    DCBO: If you end up using a nut, an elastic stop nut will resist loosening due to vibration if there is no room for a lock washer. Blue Loctite is another possibility.
    I don't think I will be able to get 'elastic stop' nuts (do you mean nylon insert nuts or something else?) I will be using simple stainless hardware that is lying around. But I do have blue locktite to I will probably use that. I find is is effective as a threadlocker and as an antisieze.

    Thanks, lads!

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    Quote Originally Posted by JohnDThompson View Post
    The vast majority will be M5, a small number are unthreaded or M6.
    Excellent. I will make sure I have a selection of both and I will fill you chaps in later!

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    DCBO: An advantage to your suggestion to put the bolt heads on the inside is that if you should happen to shear off one of the bolts you will be able to easily drive out the remaining piece of the bolt.

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    So I (I am also DCB0) got a selection of bolts and checked the frame and fork... all the holes are just big enough to accept an M5, but they are not threaded. I could not scrounge up any M5 nuts so I will have to wait until I do to mount the rack and fenders. Luckily, the Torino 76 is replacing a perfectly functional bike that I have on long term loan from my young sons, so there is no urgency to the repair. Thanks to all who replied!

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