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Old 05-23-07, 01:32 PM   #1
leunkstar
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FD doesn't reach outer chain ring



The situation:

- I've got an older type Shimano 600 front derailleur (FD-6207) getting it's cable from the bottom.
- I've got 3/7 STI shifters (RSX).
- I've got an older Shimano crankset (dont have the number here), a double
- I don't know exactly about the bottom bracket but it is a Shimano MH BC137 (aug '88) 1.37x68mm with a square tappered axle

At first, with an old Koga branded SR Sakea crankset it worked perfect. Than i replaced the crankset with the above one and now the FD can't reach the outer chainring. I did try loosen the limiter screws but i think the FD just can't reach that far, thus:

- the crankset isn't far enough at the axle due to incompatibility or
- the FD is not suitabel or
- i do something wrong

Any clues?
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Old 05-23-07, 02:09 PM   #2
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Likely the crankset needs a bottom bracket with a shorter spindle.
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Old 05-23-07, 02:41 PM   #3
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Quote:
Originally Posted by leunkstar
At first, with an old Koga branded SR Sakea crankset it worked perfect. Than i replaced the crankset with the above one and now the FD can't reach the outer chainring.
Then you say:
Quote:
Originally Posted by leunkstar
- the crankset isn't far enough at the axle due to incompatibility
If the derailer can't reach the outer chainring, then the chainrings are TOO FAR!
As the poster above said, you need a BB with shorter axle to adjust the chainline to what it was originally.
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Old 05-23-07, 03:03 PM   #4
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I have some other BB's in my gear box of the same 68mm diameter.
Is there a way to measure which axle lenght i need?
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Old 05-23-07, 03:43 PM   #5
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Quote:
Originally Posted by leunkstar
Is there a way to measure which axle lenght i need?
Calipers. BB spindles are typically 107 (or less) to 118 mm (or more?) long. I have a couple of Sugino 103 mm BBs, for those especially hard situations.

EDIT: I found this nice little explanation on the intarnetz:

Quote:
Originally Posted by http://www.pricepoint.com/helpDesk/ProductHelp/Cranksets&BB.htm
To find the length of the spindle, first remove the crank arms. Then measure the length of the spindle in millimeters from end to end. If your cranks are attached with nuts as opposed to bolts, do not measure the extended threaded portions of the spindle.

If you are replacing a BB and are using your old crank, you'll want a replacement BB with the same spindle length. If you are installing a new crank, you will want to use the spindle length recommended by the crank manufacturer.
EDIT 2:
This article is excellent. I highly recommend it:
http://www.sheldonbrown.com/bbsize.html

Last edited by wroomwroomoops; 05-23-07 at 04:02 PM.
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Old 05-23-07, 04:08 PM   #6
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Sorry - no advice on your problem. Sweeeet machine, though!


... Brad
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Old 05-23-07, 04:37 PM   #7
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ah thx for the compliment and thx for the add ons.

i know how to measure the spine but i want the opposite
Know how long it need to be

Ah the Sheldon "who else" brown article shows what i want but.. both cranksets arent in the table

well i'll try to guess than i am afraid (trial and error)
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Old 05-23-07, 06:09 PM   #8
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Measure your chainline as it sits. For ease of measurement, measure from the center of the seattube to the inner chainring. Lets assume you measure 45mm. The measurement you need is 41mm (giving you a 43.5mm chainline). Measure your spindle, lets assume it's 120mm and symmetrical. You'll need a symmetrical 112mm spindle [120-(2*(45-41))] or as close as you can get. (113 is common)

Just as a guess, your older double Shimano crankset will need a 113/5mm spindle. (Colnago really threaded BSC, not Italian?)

Last edited by vpiuva; 05-23-07 at 06:23 PM.
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Old 05-23-07, 07:02 PM   #9
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Quote:
Originally Posted by vpiuva
Measure your chainline as it sits. For ease of measurement, measure from the center of the seattube to the inner chainring. Lets assume you measure 45mm. The measurement you need is 41mm (giving you a 43.5mm chainline). Measure your spindle, lets assume it's 120mm and symmetrical. You'll need a symmetrical 112mm spindle [120-(2*(45-41))] or as close as you can get. (113 is common)

Just as a guess, your older double Shimano crankset will need a 113/5mm spindle. (Colnago really threaded BSC, not Italian?)
I'm pretty sure that Colnagos of that vintage use only italian BBs.

Just one comment: it's really difficult to measure "from the center of the seat-tube", because you can't reach it with a caliper. Better measure the seat-tube diameter (say, D) and then from the opposite side of the seat-tube to the middle part of the inner chainring (which can be reached with a caliper - just aim for the tip of the teeth), say D1. Then the chainline is, if my math is not fuxored, Chainline = D1 - D/2
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