Advice on chain and poss chainring/cassette replacement, pls

[unkleGsif]

Just be careful on the BCD of the rings you buy.... lookis like your spesh cranks are 110, while the ones linked to Spa Cycles are compact...

G

 

[Dead Rats]

Just be careful on the BCD of the rings you buy.... lookis like your spesh cranks are 110, while the ones linked to Spa Cycles are compact...

G

good point, and some Spesh cranks have unusual granny ring BCD, though that might only be the four bolt ones I can't remember for sure

 

[xerxes]

Everything you ever wanted to know about BCD:

http://www.sheldonbrown.com/gloss_bo-z.html

http://www.sheldonbrown.com/cribsheet-bcd.html

 

[GingerSpeshster]

Great, cheers!

BCD is 64.7mm on a 5 hole -> 110.

If I'm going to change this, would I get away with going to 52T as I'm running out of gears at the mo running a 46/12 ratio?

 

[Dead Rats]

Great, cheers!

BCD is 64.7mm on a 5 hole -> 110.

If I'm going to change this, would I get away with going to 52T as I'm running out of gears at the mo running a 46/12 ratio?

you could try but it might be fiddly:

there would be less chainring / chainstay clearance

it would mean a big jump between middle and outer rings

it would increase capacity demand on rear mech, meaning you'll need a longer chain (unless you run it short which means NEVER using big to big else you'd snap the rear mech!)

a 52t outer ring's curve would not match curve of your front mech as well existing 46t ring

 

[xerxes]

Possibly, but you may find that the front derailleur cage isn't long enough, so when you move the front mech up the seat stay to clear the larger ring, the bottom of the cage is too high, so that the chain rubs on the cross piece when you use the granny ring. If you never use the granny ring, you can adjust the low screw so that it stops at the middle ring and remove the granny ring if you like.

 

[Dead Rats]

Possibly, but you may find that the front derailleur cage isn't long enough, so when you move the front mech up the seat stay to clear the larger ring, the bottom of the cage is too high, so that the chain rubs on the cross piece when you use the granny ring. If you never use the granny ring, you can adjust the low screw so that it stops at the middle ring and remove the granny ring if you like.

agreed... if 46/12 is too low for you I imagine you're not using the granny much!

 

[unkleGsif]

When I went up to 48 from 46, I noticed a dramatic improvement in gearing. 52 would be s step too far IMO


G

 

[xerxes]

Have a mess about with this: http://www.machars.net/bikecalc.htm

52x12 at a cadence of 80 is about 30mph, that's the same speed as the boys in the TDF peleton, have you thought of going professional.

 

[gtRTSdh]

First thing to do is measure your chain.

Put the chain in a combination of gears so that the chain is straight.
Apply some tension to the chain with the pedals by hand.
The links are 1/2" pitch so using a 12" rule a new chain will line up on 12" pin to pin, if your chain is measuring more than 12 & 1/16" then it needs changing.

I should mention, that changing the chain at the +1/16" point is to protect the cassette and chainrigs, not absolutely neccessary, however if you let it get to +1/8" (1%) there's a real concern a new chain could slip/skip under load. At the worn point sometimes it's just better to cut your losses, run the whole drive train into the ground & accept the fact you'll have to buy all three at a later date.

Ps) This talk of changing chain and chainrings is very odd to me, cassettes always go first in my experience. . .