Mash Master

I have replacement deraileurs and I was wondering what is the correct procedure.

I'm swapping out a shimano 105 long cage derailuer with an ultegra short cage deraileur
and an even swap of the an FSA front deraileur with the same model (I mangled the old one and "fixed" it with a hammer :-) )

1) So for swapping them out do I first shift to the inside rings of the gears first?
2) remove the chain
3) remove the rear wheel
4) Remove and replace the front derailuer (detach cable then rettach cable fully tensioned)
5) remove and replace the rear derailuer (ditto)
6) replace the chain
7) replace wheel

Adjust tension barell


Does that sound correct?

cny-bikeman

Major item is that you will have to resize the chain, but there are many more details to insure proper alignment and adjustment, particularly for the front derailleur. I would guess that Sheldon's site has a good bit of info. there are just too many items to do a good job with pure text (in my opinion).

KevinF

The Park Tool site goes into some good detail about what's required and what needs to be done when: https://www.parktool.com/repair/byregion.asp?catid=53. Sheldon's site (https://sheldonbrown.com/derailer-adjustment.html) also has an everything-you-need-to-know page. It's far too much info to type into a single coherent post.

HillRider

No. Unless he changes either the big chainring or the largest cog size, he will not have to make any changes in chain length. Chain length is determined by the big chainring and the big cog, not the rear derailleur type. His posting made no mention of gearing changes.

What may change is which gears can be used without the derailleur allowing the chain to go completely slack. If the gear range is greater than the new derailleur can "wrap", some of the smaller cogs may not be usable with the small chainring.

Al1943

There should be no tension on the cables when attached to the derailleurs. You can add tension if needed with the barrel adjustors. The front derailleur should be positioned and the low limit screw set after installing the chain and before attaching the cable.
The derailleur adjustment instructions found at https://wwwparktool.com are good. They should be done in sequence with nothing left out.

Al

Mash Master

The gearing is staying the same. so the chain should stay the same length as I understand it.

Bill Kapaun

Not exactly what the poster is trying to accomplish, but I replaced a bent SunTour Rder on my brothers bike a few weeks ago with an low level Shimano I got off a junker bike. The formerly "perfect" length chain was too short to go BIG-BIG without a severe bind.

HillRider

This sounds like a rare occurance and may be an artifact of the dropout/claw design of the old derailleur you used. The derailleur hanger design on modern frames and current derailleurs have the derailleur pulleys in an absolutely straight line when the bottom run of the chain is tight and they have no influence on chain length.

Phantoj

I guess I would leave the wheels on.

tellyho

If you have a triple up front, I'd caution against replacing a long cage with a short cage.

Mash Master

I replaced the deraileurs and kinda screwed up one small thing.... I managed to mangle the rear deraileur cable so I need to replace that. So I think I half way through the job.

Is it easy to replace the rear cable?

mozgj

Yes. But consult the service manual for your shifters before you try to rip the cable off 'em.

Al1943

It would be good to replace the cable housing(s) as well. Cable housing condition significantly effects shifting performance on STI systems.

Al