Changing Spring Tension in a Shimano rear mech

JustinLeeAtkinson

I want to alter the spring tension in a 105 rear mech. Having just googled it, Park Tools are suggesting that you have to dismantle the derailleur body to get at it http://www.parktool.com/blog/repair-help/rear-derailleur-overhaul

Is this the only way?

dgunthor

why would you want/need to do that?

JustinLeeAtkinson

I'm converting to a single front chainring for cyclocross. Tighter spring tension will help to stop the chain from unshipping (together with a narrow/wide chainring).

dee4life2005

(I'm referring to Ultegra 6700, but 105 should be same/similar)...
If it's the upper derailleur pivot you're wanting to adjust the tension for then yes, you do have to dismantle it as you can only put the spring into the next hole (making it tighten) when it's disassembled. I've done it a few times now, and it's relatively straight-forward following the guide ... so long as you tighten it back up in the correct direction so as not to damage the spring - and it helps to have a third pair of hands (or a bench-vice) to help with re-assembly (allen key in vice, and place the deralleur on that, leaving two hands free to finish assembly - its the easiest way).

dgunthor

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19683886#p19683886]JustinLeeAtkinson[/url] wrote:

I'm converting to a single front chainring for cyclocross. Tighter spring tension will help to stop the chain from unshipping (together with a narrow/wide chainring).

ah, ok. not sure what you mean by "unshipping" though? if you mean chain slap etc what about a MTB shimano rear mech that has a clutch on it? (need a nine speed MTB one if you have 10 speed road shimano, 10 speed MTB has diff cable pull) (stops the chainslap)

JustinLeeAtkinson

Thanks. It is as I feared then, damn. A faff.

When I say unshipped, I mean the chain coming off. But, the narrow/wide chainring, and a stiffer spring are said to work. I wont be going to MTB stuff as it's not quite compatible as you acknowledged.