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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 06-15-08, 10:35 PM   #1
HeIncreasesMe
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I Crossed Thread By Brand New Bikes Braze Ons

I am thoroughly done w/ myself. I crossed threaded my seat stays braze ons. I just bought this bike on saturday and it is sunday. I was trying to be all cool and learn how to work on my bike and add a rear rack. I ended up cross threading the braze on...GRRR! I didn't even know what I did...I thought something was wrong w/ the bike. I took it back to the shop and they told me what I did.

Is there a simple way I can fix this? Or is it best just to wait the two weeks YES 14 DAYS..until the shop can fix my bike. Plus the ~$30 fix for this tragedy. GRRR! Not to mention the extra $35 bucks for the rack and installation.

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Old 06-15-08, 10:45 PM   #2
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You can go to the local hardware store and get a tap of the correct size. Then, CAREFULLY, re thread the braze ons. That is if the threads are not to far gone. Good luck!!
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Old 06-15-08, 10:47 PM   #3
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I don't want to sound like a jerk, but if you didn't know you were cross threading the screw, maybe you should leave the thread repair to the pros. I mean, I am an experienced mechanic (more cars than bikes), and I still hate thread repair.

EDIT- But screw your LBS, find another one. Or, better yet, take your bike to a machine shop. They should be able to fix the threads (if they are fixable).
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Old 06-15-08, 10:51 PM   #4
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Originally Posted by HeIncreasesMe View Post
I am thoroughly done w/ myself. I crossed threaded my seat stays braze ons. I just bought this bike on saturday and it is sunday. I was trying to be all cool and learn how to work on my bike and add a rear rack. I ended up cross threading the braze on...GRRR! I didn't even know what I did...I thought something was wrong w/ the bike. I took it back to the shop and they told me what I did.

Is there a simple way I can fix this? Or is it best just to wait the two weeks YES 14 DAYS..until the shop can fix my bike. Plus the ~$30 fix for this tragedy. GRRR! Not to mention the extra $35 bucks for the rack and installation.
In your case I'd wait the time, pay the money, and take this as a learning experience.

Why don't you pick up a cheap, near dead used bike to practice wrenching on? That way you can get some experience on what things should feel like (you can feel it when you cross thread a bolt), and you don't have to worry about fouling any thing up. In the end you might just have a spare bike!
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Old 06-15-08, 10:52 PM   #5
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I don't want to sound like a jerk, but if you didn't know you were cross threading the screw, maybe you should leave the thread repair to the pros. I mean, I am an experienced mechanic (more cars than bikes), and I still hate thread repair.
YOU JERK!


Why come in here telling me something that I know deep deep in my heart? Why tell me something I've been telling myself all day. LEAVE IT ALONE LEAVE IT ALONE, before you mess up something else on that bike. I've been telling myself "Stop thinking you are some type of mechanic and leave it to the professionals. Or at least get some training." Hahahahahaha! Thanks. You are sooo right. I am still trying to be Ms. Mechanic. I need to go ahead pay the 30 bucks and just consult my bike shop for any other mechanical things that go beyond changing a flat. lol. Oh I hope you get the above was straight sarcasm and said in jest. No disrespect.

This was my first major bike purchase. Trek 7.3FX. Before this..it was all walmart bikes. So I am taking this pretty hard. I know it shows.
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Old 06-15-08, 10:56 PM   #6
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You are sooo right. I am still trying to be Ms. Mechanic. I need to go ahead pay the 30 bucks and just consult my bike shop for any other mechanical things that go beyond changing a flat.
In no way am I trying to discourage you from learning to work on your bike. I am just trying to keep you from taking too large a jump all at once. Going from not knowing better about cross threading screws to fixing the damage is a little like jumping off of a tricycle right in to the middle of the Tour de France.
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Old 06-15-08, 11:00 PM   #7
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In no way am I trying to discourage you from learning to work on your bike. I am just trying to keep you from taking too large a jump all at once. Going from not knowing better about cross threading screws to fixing the damage is a little like jumping off of a tricycle right in to the middle of the Tour de France.
Yea..I totally got that feel from your post. Like I said..I am just taking this a bit hard. My first test ride on that bike I came back w/ a grin ear to ear. I searched two whole weeks for it. And now to see that I damaged it...WOW! You may have no idea how I feel. But, like you said..lets go from tricycle to training wheels and so on and so on.

I need to get a book. lol
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Old 06-15-08, 11:21 PM   #8
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I know it's 20-20 hindsight at this point but generally with threaded fixtures if you find you have to force it then there's something wrong. When you thread in a screw it's rare that it won't turn in by hand or at most with two fingers twirling the allen wrench shaft. For next time if you find there's significant resistance from the get go then stop, back the screw out and try again. Don't force it at all.

Now the exception to this is if theres paint or powder coating in the threads. If that's the case it's not uncommon to feel some drag on the screw. But as you turn it in the drag should tend to lessen as you wear away the paint rather than build to a higher level after the first turn.

As I said, offered for the next time.

As for repairing this one it depends on how far you jammed the screw in before realizing that it wasn't right. Did you run the screw in 5 or 6 turns or did it go less than 2 or 3 turns and then jam up? If the last then at least we can say that the repair is not only possible but should work quite well. The repair being more of a patch in that running a tap in there will reform the good threads slight but it'll cut away some of the bruised metal leaving that brazeon slightly weaker than before. When you put screws into that one do not tighten it up as much as the other side. I'd suggest only two fingers on the allen key and keep them fairly close to the bend. Get it so the screw head contacts the rack and is starting to feel fairly firm. Then another 1/3 to 1/2 turn only while feeling for a big increase in torque needed. In this case pinch it tight rather than reefing on it. By only using two fingers and not turning it so tight that you feel pain in your fingers from the pressure and do not leave any temporary grooves from the pressure you'll be giving it a torque value it'll withstand.

Another option would be to start a screw into the threads in the original track and mash the cross threading back into place. That can often work as well but obviously it requires a sharp eye to see if the screw is starting into the hole straight instead of following the new cross threads. You may or may not want to try this.

If you do and it starts there will be a fair degree of resistance initially as you turn the screw in. But instead of getting worse like with a cross threading it should stay the same for a few turns and then ease off on the pressure.

All of this is based on a feel sort of thing. I've tried to put it into words but it's more a skill you get from doing. And with your new toy I wouldn't blame you if you just said "I'll wait thankyouverymuch".
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Old 06-15-08, 11:31 PM   #9
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The Trek FXs use riv-nuts there, so once the threads are bungled, my preferred solution would be to replace the riv-nuts, which I suspect is what your shop has in mind. However, if you'd like to fix it yourself, one really nifty option is to get a seat collar that has built-in rack mounts Most LBSs can get you one from J&B Importers. For a Trek FX 7.3, off the top of my head, I believe you want the 31.8mm diameter: print this page and ask an LBS to get you one



Elegant, inexpensive, and considerably harder to cross-thread than riv-nuts are This would be a cinch to install, you just pull out the seatpost, lift off the old collar, plunk this one on there, and put your seatpost back in.
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