Bottom Bracket problems

Scarbery Rdr · **Posted:** Wed Jul 29, 2009 9:02 pm

So I blew up my bottom bracket hitting a big double,(it definatley didn't happen while I was riding down to check the surf) and I have a few questions about replacing it. I have a Giant STP with a Howitzer external bearing BB, on the BB cartridge it has "68/68e/78/73e shell." I'm assuming that's refering to the diamiter/radius of the bikes bb shell, is the width measured between the bearings or the width of the spindle? any help is apreciated.

qpcr8tiv · **Posted:** Thu Jul 30, 2009 12:00 am

Scarbery Rdr wrote:

So I blew up my bottom bracket hitting a big double,(it definatley didn't happen while I was riding down to check the surf) and I have a few questions about replacing it. I have a Giant STP with a Howitzer external bearing BB, on the BB cartridge it has "68/68e/78/73e shell." I'm assuming that's refering to the diamiter/radius of the bikes bb shell, is the width measured between the bearings or the width of the spindle? any help is apreciated.

The width of the BB is measure at the frame. Those numbers refer to the Frame's bottom bracket widths that it's designed to work with -- those are standard sizes. You should have plenty of options available.

OffRoadie · **Posted:** Thu Jul 30, 2009 7:58 am

There are two numbers on bottom brackets. The smaller one is the width of the BB shell on the frame. Take a ruler and measure it. The larger one is the width of the spindle. As long as you get the correct shell width, it will fit in the frame.

68x110 is 68mm shell width, 110mm spindle.

EBasil · **Posted:** Fri Jul 31, 2009 6:01 am

Hey, just so you know: it wasn't the double that blew the BB unless you've got a bent spindle/crank axle. If it's your bearing(s) that went bad, that took some time and doing.

These things happen, and if the crank is okay, all you might need to do is to either swap new bearings (think: EnduroBearings.com) into the cups or to swap in a new set of bottom bracket cup/bearing combo. Either is easy and affordabler than a whole new crankset.

PacMan · **Posted:** Fri Jul 31, 2009 7:04 am

OffRoadie wrote:

There are two numbers on bottom brackets. The smaller one is the width of the BB shell on the frame. Take a ruler and measure it. The larger one is the width of the spindle. As long as you get the correct shell width, it will fit in the frame.

68x110 is 68mm shell width, 110mm spindle.

True, but correct me if I'm wrong--don't frames also need a certain spindle width so chain line isn't too affected? I was under the impression that not every 68mm BB will run smoothly in every 68mm frame. Same goes with 73mm frames/shells.

stang · **Posted:** Fri Jul 31, 2009 7:41 am

Ya that is true about chain-line. But typically there are spacers with the BB to help setup the chain-line/width. Front derailleurs on the other hand are chain-line sensitive.

OffRoadie · **Posted:** Sat Aug 01, 2009 7:09 am

PacMan wrote:

OffRoadie wrote:

There are two numbers on bottom brackets. The smaller one is the width of the BB shell on the frame. Take a ruler and measure it. The larger one is the width of the spindle. As long as you get the correct shell width, it will fit in the frame.

68x110 is 68mm shell width, 110mm spindle.

True, but correct me if I'm wrong--don't frames also need a certain spindle width so chain line isn't too affected? I was under the impression that not every 68mm BB will run smoothly in every 68mm frame. Same goes with 73mm frames/shells.

The chainline is dependent on the spindle length and the crankset, so it depends on the cranks that you have.

Bottom Bracket problems

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