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70s fork, 2009 brake -- fit issues

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70s fork, 2009 brake -- fit issues

Old 03-26-11, 01:06 PM
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cccorlew
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70s fork, 2009 brake -- fit issues

I have a 70s bike with a 70s Columbus tube fork. Currently is has a single pivot Royal Gran Comp brake on it.

It's connects with a bolt that goes through the crown and has a nut on the back.

It really doesn't stop all that well, even with new high quality pads.

I thought I'd replace it with a Shimano 105 front caliper I got on eBay.

The 105 bolt isn't long enough to come out the other side of the fork, and the trick bolt looks like it's supposed to go inside the hole on the fork is too fat to do so.

Is there a solution for me? Would it be wise to drill out the back hole in the fork so the fancy new bolt will fit inside?
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Old 03-26-11, 01:14 PM
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The newer brake will have a socket head nut, as opposed to a hex nut, to fasten the brake caliper.

Later model brake bolts do not go all the way through the fork crown. Rather, the bolt goes part way through, and then the recessed socket head nut goes part way through also, but from the opposite end.

To make this work, on your fork, you will have to drill the back side hole to 8mm(I think that to be the size but you should measure your socket head barrel to be sure). That will allow the barrel of the nub to pass through the crown and reach the brake caliper bolt.

Does that make any sense?
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Old 03-26-11, 01:17 PM
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Yes, it makes perfect sense. I didn't want to start drilling if I didn't need to, or if it would create a problem.
Time to bust out the drill and locate (read 'go buy') a metric drill bit.

And thanks for the help!
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Old 03-26-11, 02:23 PM
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Curtis,

You don't need to buy a metric drill bit if you have a SAE set already. Just pick the closest one and be happy - there's a lip on the recessed bolt that should snug up just fine.

If you're in the neighborhood, bring it by.
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Old 03-26-11, 02:55 PM
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+1, just get a bit big enough for the bolt and smaller than that lip. Drill the back only, and you'll be fine.

I'd probably just buy six cans of local brew and go to BBM's house.
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Old 03-26-11, 03:53 PM
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When I did the brake bridge on a Trek a couple weeks ago for 6600 Ultegra I meeasured the nut at 0.31" so I drilled 5/16" (.312)
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Old 03-26-11, 03:59 PM
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Originally Posted by randyjawa View Post
The newer brake will have a socket head nut, as opposed to a hex nut, to fasten the brake caliper.

Later model brake bolts do not go all the way through the fork crown. Rather, the bolt goes part way through, and then the recessed socket head nut goes part way through also, but from the opposite end.

To make this work, on your fork, you will have to drill the back side hole to 8mm(I think that to be the size but you should measure your socket head barrel to be sure). That will allow the barrel of the nub to pass through the crown and reach the brake caliper bolt.

Does that make any sense?
I've also had to do exactly this. It is a bit of a pain but it works.
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Old 03-26-11, 04:28 PM
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I've done this before, its pretty simple and easy. Also, I've heard you can buy an extra long bolt that will reach far enough.
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Old 03-26-11, 05:21 PM
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Success!
Thanks to all! I used my non-metric drill bits and just kept going up one size until it fit. It worked and this caliper sure stops better!


105 brake on older fork by ccorlew, on Flickr
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