Is 1mm too tight a clearance between the chain stay and the crank arm? - London Fixed-gear and Single-speed

bigben · 24th August 2008

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/i...a-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.

100 · 24th August 2008

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

BringMeMyFix · 24th August 2008

1mm - sharp intake of breath...

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

bigben · 24th August 2008

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...

hippy · 24th August 2008

Quote:

Originally Posted by 100

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

fruitbat · 24th August 2008

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

asm · 24th August 2008

shorter cranks? probably more costly than a new bb.

BringMeMyFix · 24th August 2008

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.

lpg · 24th August 2008

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

100 · 24th August 2008

Quote:

Originally Posted by hippy

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.

100 · 24th August 2008

Quote:

Originally Posted by BringMeMyFix

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 (??)

BringMeMyFix · 24th August 2008

Quote:

Originally Posted by lpg

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.

Dammit · 24th August 2008

Quote:

Originally Posted by lpg

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!

fruitbat · 24th August 2008

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

bigben · 24th August 2008

!@£$%^&*( £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.

bigben · 24th August 2008

Sorry, make that 110mm so 1.5 extra.

bigben · 24th August 2008

Or this one at £15 from campag.

http://www.totalcycling.com/index.ph...urrency&id=GBP

Archi Pelago · 24th August 2008

Quote:

Originally Posted by Dammit

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

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

lpg · 24th August 2008

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.

Quote:

Originally Posted by BringMeMyFix

Bareknuckles are pretty rigid, and you are feeble.

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

asm · 24th August 2008

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.

fruitbat · 24th August 2008

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.

BringMeMyFix · 24th August 2008

Quote:

Originally Posted by lpg

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.

the-smiling-buddha · 24th August 2008

tight clearances make the bike look better

asm · 24th August 2008

tight clearances make everything look better

mr_tom · 24th August 2008

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.

Dylan · 24th August 2008

mine is pretty close but i had no problems so far and I've probably cycled around 500miles on it so far so good.

bigben · 25th August 2008

Quote:

Originally Posted by fruitbat

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.

Now I'm really confused... Surely that would mean 106mm BB? 68+19+19?
Here is an image of the clearance, bear in mind that it is an 3 arm TA crank so might flex a bit. OH an weight wise, 107.6kg dressed and improving a bit, down to 103.1kg in the noddy.

100 · 25th August 2008

Quote:

Originally Posted by bigben

Now I'm really confused... Surely that would mean 106mm BB? 68+19+19?
Here is an image of the clearance, bear in mind that it is an 3 arm TA crank so might flex a bit. OH an weight wise, 107.6kg dressed and improving a bit, down to 103.1kg in the noddy.

Shorter cranks will do the trick.

VelocityBoy · 25th August 2008

A bit of duct tape on the chain stay, and replace it when it's worn through.

It will strike the chain stays occasionally, and it will wear off the paint there. But it's a bike, signs of usage are beautiful things.

fruitbat · 25th August 2008

Quote:

Originally Posted by bigben

Now I'm really confused... Surely that would mean 106mm BB? 68+19+19?
Here is an image of the clearance, bear in mind that it is an 3 arm TA crank so might flex a bit. OH an weight wise, 107.6kg dressed and improving a bit, down to 103.1kg in the noddy.

Ben your calculation here doesn't allow for the thickness of the BB cups. On the TA BB these are (from memory) 4.5mm left and 3mm right.

fruitbat · 25th August 2008

http://www.sheldonbrown.com/harris/i...a-bb-axles.gif

So the original measurements would be 17 + 4.5 + 68 + 3 + 19 = 111.5mm
I'd go for a campag 109mm. (68 - P - 120)

bigben · 25th August 2008

Cranks are already 165 and gorgeous so no way am I buying another set. Fruitbat, can I get away with the miche 110mm at £16 or do I really need the £35 campag? VB, I've indulged myself on the spec of this bike so if and when it gets scratced well and good thats use, but no way am I gaffaing the chain stay at the start.

bigben · 25th August 2008

Ah, didn't see your reply, why the campag instead of the miche? Both are the correct taper no?

fruitbat · 25th August 2008

Miche should work fine, I know from experience that campag works.
Didn't know that Miche did a 110

bigben · 25th August 2008

Many thanks to all of you for the advice, might manage to change out the BB in time for easties on Wednesday.

Fruitbat, just texted you re: work.

24th August 2008	#1
bigben	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/i...a-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.
	quote reply

24th August 2008	#25
mr_tom	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. Last edited by mr_tom; 24th August 2008 at 22:19.. Reason: Read the question. C-.
	quote reply

24th August 2008	#3
BringMeMyFix	1mm - sharp intake of breath... How powerful are you? How stiff is your frame? What year is it? Who's the president?
	quote reply

24th August 2008	#6
fruitbat	TA BB's are asymmetric. 111 is the correct size if you find a TA 314. Next best option is a Campag 109.
	quote reply

24th August 2008	#23
the-smiling-buddha	tight clearances make the bike look better
	quote reply

24th August 2008	#26
Dylan	mine is pretty close but i had no problems so far and I've probably cycled around 500miles on it so far so good.
	quote reply

25th August 2008	#29
VelocityBoy	A bit of duct tape on the chain stay, and replace it when it's worn through. It will strike the chain stays occasionally, and it will wear off the paint there. But it's a bike, signs of usage are beautiful things.
	quote reply