Chain ring crank arm is binding BB?

pbracing
pbracing Posts: 231
edited April 2011 in Workshop
Hi all, hope someone can help me please. i've had a search but can't see an answer.

I run a (Campag) square taper bottom bracket on my old steel training bike. It all works fine, though occasionally I have to nip up the crank bolts (too many track stands waiting for my boy en route to nurasery :lol: )

This latest time however, when I nip up the chainring crank bolt (just barely tight) it binds up the bottom bracket- as in the cranks won't spin freely.

I've loosened off the BB lock nut and adjuster on the opposite side and then tightened the crank but it still binds.

Any thoughts welcome. For now it's got loctite on it and no torque.

Cheers
Why not? My bikes.
Summer & dry days
http://i396.photobucket.com/albums/pp47 ... /Trek1.jpg

Wet winter days & going the shops runaround
http://i396.photobucket.com/albums/pp47 ... rello1.jpg

Comments

  • redvee
    redvee Posts: 11,922
    Is the chainring catching on the chainstay? Is it a single ring up front?
    I've added a signature to prove it is still possible.
  • pbracing
    pbracing Posts: 231
    No, it's def binding on the BB. It's a double with 7 speed cassette. It's got me puzzled.
    Why not? My bikes.
    Summer & dry days
    http://i396.photobucket.com/albums/pp47 ... /Trek1.jpg

    Wet winter days & going the shops runaround
    http://i396.photobucket.com/albums/pp47 ... rello1.jpg
  • Monty Dog
    Monty Dog Posts: 20,614
    Sound like the tapers on the cranks are f*d
    Make mine an Italian, with Campagnolo on the side..
  • pbracing
    pbracing Posts: 231
    Monty Dog wrote:
    Sound like the tapers on the cranks are f*d

    Is that in reference to the cranks coming loose, or the binding issue?
    If the former, they're not worn as the cranks only very occasionally need tightening - and to be honest I've never torqued them just given them a firm nip.

    If you're referring to the binding, please can you elaberate a bit on how worn tapers will cause it as I'd like to understand the problem.
    Cheers, Pete
    Why not? My bikes.
    Summer & dry days
    http://i396.photobucket.com/albums/pp47 ... /Trek1.jpg

    Wet winter days & going the shops runaround
    http://i396.photobucket.com/albums/pp47 ... rello1.jpg
  • Monty Dog
    Monty Dog Posts: 20,614
    Unless the BB spindle is broken, then I can't see how an increase of axial load will load the bearings unless the crank is bottomed-out and even fouling the cups / frame. I'd strip the whole thing down to check the condition of all the parts. You may have already deformed the tapers if riding the bike with the cranks loose - it's a bit more than a nip but less than a heave!
    Make mine an Italian, with Campagnolo on the side..
  • John.T
    John.T Posts: 3,698
    If it is an Italian BB it may be coming unscrewed in the frame. This causes the LH crank to bind on the BB shell. Check for this and also that the drive side is butted up tight to the BB shell.
  • pbracing
    pbracing Posts: 231
    Hi John, thanks for that. It is a Campag BB. It's the right side that's binding, but that makes sense if it's unscrewing to the left and pulling the right crank arm closer to the BB housing/ frame.

    Indeed, I'd already had another look this morning and noticed how very close to the frame the right crank arm is.

    I wondered if wear on the tapers would allow the cranks to pull on further and bind on the frame in the same way. There is no wear in rotation though, so not sure if they'd wear inward before then.

    Think it's time for a strip and service of the BB and check it all properly for wear and fit.
    Thanks for all your answers. Pete
    Why not? My bikes.
    Summer & dry days
    http://i396.photobucket.com/albums/pp47 ... /Trek1.jpg

    Wet winter days & going the shops runaround
    http://i396.photobucket.com/albums/pp47 ... rello1.jpg
  • John.T
    John.T Posts: 3,698
    An Italian BB would unscrew to the RH (drive) side due to using a RH thread unlike English ones that use a LH thread on the drive side. If it is the RH crank binding then I would suspect worn taper on the crank. You are right to strip and check everything. It never does any harm anyway.
  • pbracing
    pbracing Posts: 231
    Thanks John, great stuff. Now off to the garage (and I can't hear the sound of crying babies from there either - bliss).
    Why not? My bikes.
    Summer & dry days
    http://i396.photobucket.com/albums/pp47 ... /Trek1.jpg

    Wet winter days & going the shops runaround
    http://i396.photobucket.com/albums/pp47 ... rello1.jpg
  • pbracing
    pbracing Posts: 231
    mmm Should have been obvious really. The right crank arm is worn on the taper.

    In my defence, I've got 6 week old twins and I'm a wee bit tired. Ahem, I'm sure I'd have sussed it sooner else :wink:

    Thanks for the help.
    Why not? My bikes.
    Summer & dry days
    http://i396.photobucket.com/albums/pp47 ... /Trek1.jpg

    Wet winter days & going the shops runaround
    http://i396.photobucket.com/albums/pp47 ... rello1.jpg