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Old 07-18-14, 11:55 AM   #1
401flava
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Front Caliper nut threads only halfway on

Hi, I have a front caliper brake whose nut will only thread halfway onto the mounting bolt. I tried to use the nut from the back brake on the front bolt and it would not thread at all. (I had a couple other back brake nuts around and they wouldn't even thread on either...are they not compatible or do I have a bad bolt?). The brakes are new (Sram rival), I can't see anything wrong with the threads, I've cleaned both nut and bolt and lubricated, nothing. I get the nut about halfway down the bolt and it stops dead. I haven't tried to force it because I don't want to mangle anything. Any ideas on what's going on here?


Worse case: It looks like the center bolt may be removable and replaceable...is that right?




Thanks doods
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Old 07-18-14, 01:35 PM   #2
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Not seeing the brake, but based on the model, I gather that you're talking about a recessed nut.

If so the nut probably can't go farther because you're bottoming against the material pushed forward when they broached (pushed a hex peg into a round hole) the hex .

You see the same type of reduced size hole when you look at socket wrenches.

In any case, you need only about 5 threads to be engaged to achieve maximum strength, so if the nut turns 5 turns or more you're fine. The key is to use a nut of the right length to meet that 5 turns goal on your fork.

BTW- the threads on your front brake are overly long because they have to provide for longer nuts and various thickness fork crowns. More thread than necessary on the bolt give you more latitude in matching nuts and forks.
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Old 07-18-14, 04:15 PM   #3
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It is a recessed nut, I should've said. I understand why the front brake is the way it is and all that. The issue is the 'long' nut that comes with the front brake will only thread halfway down the bolt, leaving it too long to tighten into the fork. If it would tighten all the way it would probably be the right length. Now, I figured to be able to use a shorter nut to overcome this issue but the 'short' bolt from the back brake (and 2 other short bolts) would not thread on at all. So either back and front brake nuts/bolts are slightly different from each other or I guess I have a bad center bolt? I've tried 3 different short brake nuts and none will start threading, only the oem long bolt threads on (halfway)

heres a pic of the oem 'long' bolt threaded on as far as it will go:
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Old 07-18-14, 06:01 PM   #4
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Both brakes have identical threads. 6x1 has been standard for decades. Odds are there's a burr or some minor out of tolerance problem with the front bolt, and the long one is loose enough to accommodate it up to a point and the short ones aren't.

Take an eyeball down the nut, and see how far the thread goes. Or go to any hardware store and buy a 6mm bolt and nut. Use the nut to "dress" the front brake bolt's threads, and the bolt to dress the threads on the nuts. Use plenty of oil and work by degrees, 3 steps forward, one step back. Feel for heat, and if it warms more than hot tap water stop and rest it. Remember, do not force anything, gust go a bit farther each time.

BTW- you can use the same method with the parts you have, but using a commercial bolt and nut eliminates the risk of the bad part damaging the good one.
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Old 07-19-14, 12:08 PM   #5
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Quote:
Originally Posted by FBinNY View Post
Both brakes have identical threads. 6x1 has been standard for decades. Odds are there's a burr or some minor out of tolerance problem with the front bolt, and the long one is loose enough to accommodate it up to a point and the short ones aren't.

Take an eyeball down the nut, and see how far the thread goes. Or go to any hardware store and buy a 6mm bolt and nut. Use the nut to "dress" the front brake bolt's threads, and the bolt to dress the threads on the nuts. Use plenty of oil and work by degrees, 3 steps forward, one step back. Feel for heat, and if it warms more than hot tap water stop and rest it. Remember, do not force anything, gust go a bit farther each time.

BTW- you can use the same method with the parts you have, but using a commercial bolt and nut eliminates the risk of the bad part damaging the good one.
Success! I thank you sir, you are a cyclist and a gentleman. It was precisely as you said, some issue on the bolt that the longer nut was more 'tolerant' of. Threading on a bolt was enough to dress it, it did take a liiiittle force but not much. Woohoo, I'm so happy. It looks like you CAN technically replace that center bolt but it does not look like fun- it's pinned in there so it won't ever move. Now I move on to internally routing my brake and shift cables,lol, I'll be back! I don't want to make it weird on the forum, but I LOVE YOU GUYS
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