• Hi Guys,

    Slight hiccup on the jackson build up.

    TA track crank, 68mm BB shell, 107mm miche BB.

    I've about 1mm clearance between the chain stays and the crank/pedal arm.

    I've got this print out from Fruitbat along with a diagram of campag BBs:

    http://www.sheldonbrown.com/harris/image­s/ta-bb-axles.gif

    The chainline seems pretty damn sweet (running a Phil on the back), what do you guys think, go to a 109 or even a 111 (which seems to be what the diagram suggests)? How close is too little clearance?

    Cheers Y'all.

  • There is very little lateral movement in a decent crank arm, you should be fine.

  • 1mm - sharp intake of breath...

    How powerful are you? How stiff is your frame? What year is it? Who's the president?

  • I'm 107kg, I'm worried its going to flex, frame is a Bob possibly from the 80s, 531 etc. President is still unfortunately the retard...

  • There is very little lateral movement in a decent crank arm, you should be fine.

    There's more than the crank likely to be flexing though.. older steel frames are notorious for flexing like a biatch.. this is why I heart alu xxooxx

  • TA BB's are asymmetric. 111 is the correct size if you find a TA 314. Next best option is a Campag 109.

  • shorter cranks? probably more costly than a new bb.

  • If it does graze the stay due to flex, it's going to happen on the up stroke (opposite the side where you're putting the power down at 2-3 o' clock IYSWIM), and I don't think it would actually hit it fully enough to come to a jarring halt.

    I expect you'll lose a bit of paint.

  • my bareknuckles similar, hardly any clearance .. it hasn't scraped the chainstay yet, so i dont think it'll be a problem.

  • There's more than the crank likely to be flexing though.. older steel frames are notorious for flexing like a biatch.. this is why I heart alu xxooxx

    Yeah, I though of that (particularly the BB + BB shell) but when the cranks are leveled - the point which they might contact the stays - the forces acting on the cranks/frame/BB shell are unlikely to drive the crank arms inwards - if they are deformed (or their supporting structure is deformed) they will be driven downwards.

  • If it does graze the stay due to flex, it's going to happen on the up stroke (opposite the side where you're putting the power down at 2-3 o' clock IYSWIM), and I don't think it would actually hit it fully enough to come to a jarring halt.

    I expect you'll lose a bit of paint.

    Good point, the upstroke may cause some twist in the BB/BB shell (??)

  • my bareknuckles similar, hardly any clearance .. it hasn't scraped the chainstay yet, so i dont think it'll be a problem.

    Bareknuckles are pretty rigid, and you are feeble.

  • my bareknuckles similar, hardly any clearance .. it hasn't scraped the chainstay yet, so i dont think it'll be a problem.

    If you weigh 107kg I'll eat my tyres!

  • Ben, go for a longer bb and space the cog to correct chainline if you need to

  • !@£$%^&*( £55 for an 111mm campag pista BB, anyone got a pointer to a cheaper alternative? Fruitbat, what do you reckon if I go for a 109 miche (£15)? Pushes the crank 1mm further out and won't mess with the chain line.

  • Sorry, make that 110mm so 1.5 extra.

  • If you weigh 107kg I'll eat my tyres!

    If he weighs 107kg, he'll probably eat your tyres for you!

  • I still dont reckon the cranks would bend inwards, only because of the 3/9 o' clock position that they're in. I love the shorter q-factor anyway.

    Bareknuckles are pretty rigid, and you are feeble.

    hey, i nearly beat you in a race! no love for silver medalists!? ;)

  • ben i'd go for the miche (unless tim is opposed), because the cups are all internal so you can fiddle the chainline out a little more if necessary by screwing the cups in a bit further.

  • Ben, the link in your OP tells you all you need to know. The left hand cup on the original TA BB is 1.5mm wider than the right. If you use a symmetrical BB then you need 19mm of protruding axle on both sides.

  • I still dont reckon the cranks would bend inwards, only because of the 3/9 o' clock position that they're in. I love the shorter q-factor anyway.

    hey, i nearly beat you in a race! no love for silver medalists!? ;)

    I don't race. I think I told you, Paul, I'm a lover not a fighter.

  • tight clearances make the bike look better

  • tight clearances make everything look better

  • I had a clearance that tight with my old IRO. It was fine, although that was aluminium and I am feeble.

    The other option is to get a smaller chainring.

    Edit: Unless you actually have the problem you describe and not the one that I thought you had.

    You might have problems with your heels hitting the chainstays, though.

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Is 1mm too tight a clearance between the chain stay and the crank arm?

Posted by Avatar for bigben @bigben

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