Crankset and bottom bracket replacement

[mackay45]

Having some issues recently with my Boardman MTB (hardtail 650B), basically with the non-drive side crank arm falling off(!) a couple of times when riding.

Quite an old bike so not sure if the problem would have been with the bike shop not torquing it up correctly on fitting it or whether I should have been checking it since then. Bike is similar to this:

http://www.bikeradar.com/mtb/gear/category/bikes/m...

Anyway I've now removed the crankset, and figured I might as well change the bottom bracket at the same time. Parts I've removed are:

Crankset:

http://www.fullspeedahead.com/products/cranksets-m...

Mine is the 42/27 teeth version.

Bottom bracket:

http://www.chainreactioncycles.com/shimano-deore-b...

Any suggestions of what to replace them with? Would rather not have to change the rear cassette too if I can avoid it!

As you've probably worked out already I'm not particularly mechanically minded when it comes to bikes, so will probably be taking the stripped down bike and newly acquired bits to a shop to get them to fit the new stuff for me!

[neenaw]

Any of the Shimano Hollowtech bottom brackets will fit. You can get XT level ones for about £10-15. If you want to spend a bit more then you can't go far wrong with a Hope one for about £60 or so.

For the cranks I'd also go for Shimano. SLX or XT would be the best bet and if you shop around you can get some really good prices on them.

[daddy cool]

Yeah, what he said ^^

But think about converting to 1x10 (with a 32T ring replacing your 42/27 rings) - its what all the cool kids do. Means you can ditch the front derailleur which tidies up the handlebars and BB area. Unless you do a lot of hills you'll likely have enough gearing, or if you do a lot of hills, you could get a new cassette (~£50) which is still 10-speed, but has a 40T cog rather than your current 36T. Nothing to be afraid of in changing the cassette, its easy if you have the tools.
Also, if the bikes done a lot of miles, check the chain hasn't stretched - if it has replace it. Last thing you want to do is ruin a new set of shiny cranks with a duff chain.

Strange the crank arm has fallen off though - presumably you have tried doing it up again with a hex key?

[chrisga]

Did the bike shop remove the cranks/install a new bottom bracket? First thing I'd do is check spacers betwen the bottom bracket and the frame. If there are too many it could be too wide not leaving enough of the axle visible on the non drive side.

Also, if the crank is like I remember, on the FSA's they have an aluminium bolt (not palstic like shimano cranks) which screws into the cranks axle to effectivey pull the cranks together. I think this is designed to purposely strip the threads if too much pressure is applied to protect the bottom bracket. The two small allen key bolts on the end of the crank arm itself are what hold it onto the axle. If the aluminium tension bolt has stripped could it be the crank isn't ont he axle far enough so when you do the two small allen key bolts up it doesn't grip the axle.

edit, sorry didn't read the thread properly. If i were you id just replace bottom bracket and buy a new fsa bolt for the cranks off ebay for about a fiver and put them back on.

Edited by chrisga on Sunday 20th November 08:58

[Black can man]

My Bordman Team carbon bottom bracket went after about a year for me too.


I got a cheap second hand full Ultegra group set & my LBS fitted it for me. runs lovely

[lllnorrislll]

Fsa crankbolts are about £3 from Evans, if there is nothing wrong with the bottom bracket or crank, would it mot be worth trying this as a fix before spending?