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I'm trying to change the BB on my Rockhopper 2008 comp disc, so I checked the spec on the Specialized website and it says 68 * 118 - so I've got one of those, but I've just taken the old one out and it's a 73 * 126?
Can I just fit the 68 * 118, and will I have to fiddle about with the front derailleur?
Any help / thoughts much appreciated...by teh way, both old & new BB's are Shimano ES-51
Are there any spacers?
You might find there's three 2.5mm spacers to give you a better chain line
Edit - ignore that. It's octalink not ht2. Sorry
The first number is the BB shell width. Your new BB is too short at 68mm to fit in the 73mm shell of the frame. The second length is the axle length. While you might get away with this one with an adjustment of the front mech you will alter the chain line and which may result in more chain sucks and poor shifting. Really you need to buy the correct sized part.
There seems to be a spacer each side, maybe 2 - 3 mm thick. I was thinking I'd need to remove them , but wouldn't that affect the chain line?
Is it square taper? If so, buy the right size.
Thanks Nixie - I'm not sure why the spec on the Specialized website says 68 * 118 though?
cyclistm - no, it's octalink....
That's odd. Is the one you removed original?
I had it replaced a few years ago at my LBS, but I don't know enough about it to know whether they might have changed it from one size to the other (or even if that's possible)?
Measure the width of you frames bb shell, if its 68 buy the 68 one, if its 73 buy the 73 one.
Sounds like they've fitted a 73mm with spacers on a 68mm frame. I'm guessing but possibly they didn't have a 118x68 in stock the time?