BMX Bottom Bracket Problem

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BMX Bottom Bracket Problem
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Posted: Jul 13, 2010 at 15:24 Quote
I have a 2008 Intense Clutch which comes stock with an American Unsealed Bottom Bracket. However I seem to go through one of these every 6 months and would like to put in a sealed bottom bracket. I took it into one bike shop and they said it couldn't be done because the bottom bracket isn't machined or something. Can you get press fit bottom brackets for American bottom brackets? The inside diameter is 38mm.

Thanks

Posted: Jul 13, 2010 at 16:00 Quote
I'm giving them the benefit of the doubt and guessing they misunderstood you.

They probably thought you meant putting a sealed bearing inside the current cups, which you obviously can't do because the bearing surfaces aren't machined for that type of bearing.

However, yes you can get a whole new sealed American BB and hammer it in and ride on. For instance when you switch from a 1 pc crank to a 3 pc crank, the majority of the time you have to convert from an unsealed to a sealed American BB so yes it can be done with the right parts.

Posted: Jul 15, 2010 at 21:07 Quote
It would work just fine as long as the interface on the bb spindel is the same as your crank arms.

Provided the 2 fit together, buy it. When it shows up take your pedals off, then pull off the crank arms.

Undo the nut that holds the bb spindel on, unscrew the berring race and pull the old axle out.

Remove berrings, then take an old seat post or something like that and place it on the inside of the berring cup.

Then hit it with a hammer. Switch and hit the other side.

Put a little grease on the inside of the bb shell, place one of the sealed berrings on the edge of the shell. And if you don't have a berring press, hit it with a hammer.

Switch and repeat.

Install new spindel, and reinstall the crankarms and pedals.

It should only take 1/2 an hour at the most. Last one i did took me 6min from start to finnish.

Posted: Jul 16, 2010 at 19:22 Quote
I've just bought a new bottom bracket and crankset off danscomp. Thanks for the help

Posted: Jul 19, 2010 at 23:38 Quote
But now I have a new problem. I found out that in fact my bottom bracket is not an american size (despite being told so by a Rep), it is actually a mid size. But I don't have the right surface inside the bottom bracket so i can fit the bearings. Is it possible to get a spanish bearing set that can fit a mid size bottom bracket?

Posted: Jul 20, 2010 at 3:51 Quote
What exactly do you mean by "doesn't have the right surface"?
If it is mid then it should just be the frame, no cups or threads. The bearings are press fitted, aka we use a rubber mallet hammer them in or a bearing press as mentioned above.

Posted: Jul 20, 2010 at 4:33 Quote
The 08 Intense Clutch has a mid bb, if you bought the American bb kit the bearings you got should just press into your frame and you won't need to worry about using the cups supplied with the American bb kit.

Posted: Jul 20, 2010 at 9:28 Quote
These guys got it bang on. Just pop the berrings out of the cups by lightly clamping it in a vice upside down. Then just use a socket and a hammer to tap them out.

After they're out of the cups they should fit just fine.

Posted: Jul 20, 2010 at 22:28 Quote
But shouldn't there be something inside the bottom bracket to stop the bearings going in too far?

Posted: Jul 20, 2010 at 22:41 Quote
There should have been a berring spacer included with the kit that you bought. But if there wasn't it's not that hard to make one. All you need is a bit of pipe that fits over your spindle, and is wide enough to stop the berrings from pushing to far into the frame.

Should look like this:Unsecure image, only https images allowed: http://sgbmx.files.wordpress.com/2009/02/primo-bb-us.jpg

Posted: Jul 20, 2010 at 22:52 Quote
I bought the blue American/mid one off danscomp.

http://www.danscomp.com/456065.php?cat=PARTS#

So there isn't any need for a race of some sort to be inside the bottom bracket?

Posted: Jul 21, 2010 at 3:33 Quote
bolmaing wrote:
So there isn't any need for a race of some sort to be inside the bottom bracket?

not sure what you mean by race, but hammer in one bearing, turn your frame around, put in the spacer tube, hammer in the other bearing, make sure the spacer is lined up with the bearings, press in your spindle and you're good to go.

Posted: Jul 21, 2010 at 3:50 Quote
Ok. My bottom bracket is just a flat piece of tube. It doesn't have any work done to the inside of it e.g machining. Is that what other bmx bottom brackets look like?

Posted: Jul 21, 2010 at 4:12 Quote
bolmaing wrote:
Ok. My bottom bracket is just a flat piece of tube. It doesn't have any work done to the inside of it e.g machining. Is that what other bmx bottom brackets look like?
Just watch this...
http://bmx.transworld.net/1000078750/videos/how-to-install-a-bottom-bracket-with-jim-bauer/

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