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How To Fix A Cross Threaded Bottom Bracket


Matt Vandart

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I don't know if this is the right place to post this but ho hum.....

I got my loverly new middleburn bashring (£0.99 ebay!) today and so the time has finally come that I could put my middlebeurn cranks on my bike (they used to be on a planet x jackflash which had a bash guard so I only had a spider) replaceing my crappy onza ones.

So I resprayed the frame while I was at it.

At 9pm I started rebuilding the bike.

In my excitement to get my loverly middleburn cranks back on my goat of a bike, the slight damage hidden by overspray in the thread and the fact that I was half cut I managed to miss thread (cross) it in. And I mean really cross thread it, the other side of the BB was touching the frame it looked like an eccentric BB.

Stupid I know but being used to doing up massive bolts on my job (threads 2"+) and being half cut on JD I just rammed it in without noticeing until it was too late.

Oh shit I thought, it was too late to phone my mate Nick (a most fabulous bike mechanic ) to see if he had a tap for it and being too impatient to go to the bike shop tommorow. I thought how the f**k will I fix this.

So this is what I did:-

1. Screwed in the threaded spacer that is on the non drive side until it was all the way in (The outside face about 1/2" inside the BB shell)

2. This then acted as a guide for the BB to go in square as the bearing is sitting in the spacer as it should.

3. Started screwing in the drive side.

4. when it came up a bit tight I unscrewed the non drive side a bit.

5. Continued to screw in the drive side till it became a bit tight.

6. Unscrewed the non drive side.

7. Repeated this until the BB was fitted tidy in the shell.

8. Unscrewed to check that I hadn't just bent the axle.

9. Voila one totally mended BB thread.

10. Fitted it all again the proper way

11.Spun the cranks, Loverly

12. Smiled.

13. Typed this post

14. Back to the JD and coke and finnish my bike building ready for a wet rainy ride tommorow (I had better check it in the morning though!)

I don't know if this is teaching anyone to suck eggs, but I just thought I would share it in case it helps someone out in the future, say if they had drunk half a bottle of Jack and decided to put their bike back together.

My god this post actually looks readable with one eye shut.

Matt

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Matt

Sounds like it could be of use,perhaps if you take it off to check in the morning, take some pics, and do a mock up of what you did, just so we can see what your doing(kind of hard to visualize, although ive got the idea, just can see some people not understanding)

little note: youve probably damaged the threads cross threading it though, so in future you will have to be careful screwing it in, as its nowhere near as strong as it was i should imagine

little note 2: use spellcheck when drunk.

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ok sounds ideal, you fixed a problem with a good idea

problem i can see is upon "retaping" your bb with the bb have you may have ripped the threads out

i recon if you do the bb up real tight it will rip the threads right out of the shell

if it doesnt then ideal but i would be real careful on that frame because i think if you have a heavy landing you will put too much stress on the bb and rip whats left of those threads right out

sorry to knock on you fix

maxxis26

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ok sounds ideal, you fixed a problem with a good idea

problem i can see is upon "retaping" your bb with the bb have you may have ripped the threads out

i recon if you do the bb up real tight it will rip the threads right out of the shell

if it doesnt then ideal but i would be real careful on that frame because i think if you have a heavy landing you will put too much stress on the bb and rip whats left of those threads right out

sorry to knock on you fix

maxxis26

All he's doing is using the bb as a guide to make sure the cup goes in dead square to the thread. It's surprising just how well this works on even really mangled threads. Provided you back off the other side cup before it gets too tight, it wont do any damage to the frame.

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Aren't you supposed to fit BBs like that anyway? So you don't ruin the threads?

That's what I've always done when building my bikes...

I sort of guessed otherpeople had done this before but I thought I would post anyway just in case, theres nothing like the feeling of realiseing you could have f**ked your bike up. :angry:

Yeah I think I will be fitting them like that from now on too.

I checked the thread this morning and it's sweet as a nut and amazingly the brakes work fab too, when I got up this morning/afternoon I had a right feeling of dread but it all turned out Ok.

Except I fitted the wrong BB, I fitted a cheapy isis instead of the loverly new FSA I had ment to put in.

Doh.

But I had to check the threads anyway so In the new one went, sweet.

Matt

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