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

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.

Or this one at £15 from campag.

http://www.totalcycling.com/index.php/product/bbc6_centaur.html?action=currency&id=GBP

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.