help me set up my front mech please

[laurence]

first of all, i have built a few bikes before and repaired and maintained many more so why, i ask myself, is this causing me to scratch my head so much. i must be doing something wrong, so perhaps you can help.

a brief bit of background - i acquired an old (as yet unidentified) saracen and have decided to keep it as a pub/shop bike (i've been running the risk of losing my e4 for too long now by leaving it unattended) - anyway i decided to change the crankset as i had a superior one in the shed to the one that came on the bike. Now with the old crankset the shimano index shifter was happily able to shift onto all 3 rings, but with the new one i can only get 2 rings, granny and middle or middle and big - it's as if the shifter won't quite pull or release enough cable. the chainrings are the same distance apart and the same thickness on both cranksets.

So what's going on?

 

[drystonepaul]

Hello laurence and welcome to the site.
What cranks have you swapped from and to? Sounds like they may have affected your chainline.

Have a look in the thread below for some advice on setting up your front mech.
http://www.retrobike.co.uk/forum/viewtopic.php?t=53227

 

[laurence]

thanks for responding - i've had a recap on the magazine pages you suggested but i'm none the wiser really.

the old crankset is unbranded (and heavy) - 24-34-42
the new one (it's not new) is Shimano FC-M568 - 22-32-42

shifter is a Shimano ST-EF28 (combined brake/shift)
front mech is shimano but i couldn't see a number.

any further comments welcome.

 

[cce]

try the park tools website

 

[drystonepaul]

The FC-M563 cranks are low profile Shimano LX cranks from between 1994 and 1996. They will require a 107 - 113mm Bottom Bracket length.

I reckon that your other cranks may have had a longer BB spindle, so you new LX ones will sit further apart than they should. In which case this will affect the performance of your front mech.

Put some pictures up though as this often helps.

 

[CAS]

Actually this rings a bell. With my LX cranks I needed a shorter bottom bracket as I had the same problem. Shorter BB meant that I could then get all three rings

 

[kaiser]

measure from the middle chainring to the centre of the seattube it should be between 48-50mm.

 

[kaiser]

if it isn't post what it is and you can work out your bb length

 

[Xesh]

measure from the middle chainring to the centre of the seattube it should be between 48-50mm.

That's one way.

You can also check by looking down on the chainset and lining it up with the BB on the frame. If it's right the inside edge of the small ring will be level with the edge of the frame.

 

[laurence]

thanks for all your input.

measure from the middle chainring to the centre of the seattube it should be between 48-50mm.

it's more like 52 - 54mm, and on reflection it doesn't look right - the chainset looks like it should be closer to the frame.