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Bottom Bracket Tech Help


cant_ride
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Hey all just a quick one.

I built my Marino yesterday and as most of you cab probably guess, frames handbuilt in a shed in Peru have a distinct lack of quality control. My BB bottoms out on 'something' inside the bb shell leaving about a 3mm gap between the drive side flange and the frame. What is the absolute worst thing that can happen if I ride with it like this? I used to work as a bike mechanic but I never came across this so I have no idea. Instinct tells me it's a bad choice but it's tight as it can get an the bottom bracket as a whole is tight and smooth.

I think it's a case of either risking buggering the threads or take it out (which might also bugger the threads) and file down whatever it is inside the frame stopping it screw in the whole way.

Let me know your threaded bottom bracket horror stories.

Ta!

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Sounds like the BB shell isnt threaded deep enough, I wouldnt ride with it as is as the BB will be constantly loose. As long as the l/h crank clears the chainstays then I dont see any problems with just putting a BB spacer behind the drive side cup; your LBS should be able to sort you out with a spacer :)

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Or if they've got a tap, they could maybe tap the threads in a bit further? I wouldn't run it with it sticking out a bit. They generally work a bit loose on the first couple of rides anyway, which wouldn't help...

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As Mark has said, take it to a bike shop and get them to chase the threads through to ensure they're cut nice and clean and to make sure that they're cut far enough into the BB shell. You want everything butted up and torqued as it should me, don't want to knacker the frame by running it incorrectly installed!

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Check for swarf in the threads from where the BB shell is pierced for the chainstays to weld on. I've seen this on other brand new steel frames (Mostly because they tap the threads before welding the BB in and painting), so it's not just Marino that can have this problem. Get a local shop to chase the threads and make sure the BB you have is the correct width for the BB shell.

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Yeah I thought that would be the outcome. I was pretty sure before it's because the chainstays have intruded slightly inside the shell I just really can't be arsed to 1. Take it to a bike shop and 2. Pay for them to do it! Although that would be better than paying for a new BB/Frame when the threads commit suicide!

The BB I got is the right length for the BB shell its literally just a case of the flippin' dodgy welding.

Cheers for the help.

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I just really can't be arsed to 1. Take it to a bike shop and 2. Pay for them to do it! Although that would be better than paying for a new BB/Frame when the threads commit suicide!

The BB I got is the right length for the BB shell its literally just a case of the flippin' dodgy welding.

Cheers for the help.

Don't think it's a case of dodgy welding at all really, you see this on a lot of steel frames, lealone ones made in a shed in Peru! I tend to get all my BB threads chased through, it's the one thing you can't afford to ever knacker really. Get off your lazy arse and sort it! :P

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