Road Bike, Cycling Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
5,524 Posts
Discussion Starter · #1 ·
Dohhhh.

I shortened a Shimano chain this weekend simply by pushing a pin part-way out and re-inserting the same pin. I see now that I should have installed a replacement pin. Is the replacement pin optional, or do I now have a weakened chain that I need to replace? If I need to replace it, can I use an 8sp chain on a 9 sp drivetrain?

Thanks.
 

·
Registered
Joined
·
10,160 Posts
Yes,

you have a weakened chain. Most new models have flush pins that don't protrude beyond the outer sideplates, like older chains. The old style could be reassembled without a special pin, but with flush pins, it's very risky. You should not use an 8 speed chain with a 9 speed drivetrain, but the other way around is usually ok.

Anyone who needs to shorten a chain makes me think they don't know how to adjust the chain length in the first place. With a shimano double or triple drivetrain, there is one chain length that will handle all road cassettes from an 11-21 to a 12-27.

Here's the long and detailed explanation for the simple process of adjusting chain length.

Two simple tests will determine if the chain is the correct length. First, it must not hang loose in the little ring, little cog combination. If there is no tension on the chain in the little ring, little cog combination; remove two links (one inch) at a time, until there is. When the ends of the chain are brought together, some movement of the lower pulley should occur, indicating tension is being applied. Two more links (another inch) may need to be removed, beyond the point of absolute minimum tension, to keep the chain from rubbing on itself or the chain guide tab as it passes under the upper derailleur pulley. If you want to see how much lower pulley movement will occur, without removing the extra inch of chain, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links. Once this is done, the chain is set to the maximum useable length. Removing additional links will do nothing but reduce the derailleur's capacity.

Second, the chain must be long enough to avoid over-extending the rear derailleur when shifted to the big ring and biggest cog combination. If the chain is set to the maximum length as described, it should always pass this test, unless your setup exceeds the derailleur's stated wrap capacity. If you deliberately exceed the derailleur's capacity and the derailleur is over-extended in the big ring/largest cog combo, then you must either avoid that combo or add another inch and avoid using the little chainring and the smallest 3 or 4 cogs (since the chain will hang loose).
 

·
Registered
Joined
·
5,524 Posts
Discussion Starter · #3 ·
Dang.... Thanks for the info.

I shortened the chain because I replaced a standard crankset 53/39 with a compact one 50/34. I used the "just tension the rear dereailleur in the small-small combo," while confirming that the big-big worked. Without removing the 1 inch of chain the rear derailleur was completely wrapped back on itself in the small-small combo.

That said, I clearly didn't know about the Shimano replacement pin system. Now I'll replace my toasted 9 spd chain with one of my supply of 8 spd SRAM chains.
 

·
NeoRetroGrouch
Joined
·
6,491 Posts
PdxMark said:
Dang.... Thanks for the info.

I shortened the chain because I replaced a standard crankset 53/39 with a compact one 50/34. I used the "just tension the rear dereailleur in the small-small combo," while confirming that the big-big worked. Without removing the 1 inch of chain the rear derailleur was completely wrapped back on itself in the small-small combo.

That said, I clearly didn't know about the Shimano replacement pin system. Now I'll replace my toasted 9 spd chain with one of my supply of 8 spd SRAM chains.
You should be able to find it, pop it out and use the appropriate 'special' pin.

Also, he said, "You should not use an 8 speed chain with a 9 speed drivetrain...", so unless you are running 8-speed, don't use the SRAM chain.

TF
 

·
Registered
Joined
·
5,524 Posts
Discussion Starter · #6 ·
TurboTurtle said:
You should be able to find it, pop it out and use the appropriate 'special' pin.

Also, he said, "You should not use an 8 speed chain with a 9 speed drivetrain...", so unless you are running 8-speed, don't use the SRAM chain.

TF
Thanks - I'll check for the pin... and thanks for the gentle correction of my reading comprehension lapse...
 
1 - 6 of 6 Posts
Top