Shimano Exage Long Cage vs. Acera Long Cage
I have a 1991 GT Timberline that came with an Exage 400LX rear derailleur (7-speed), and the shifting has been less than dreamy since I have had it. Picked it up for free from a co-worker that wadded up pretty good on it and decided he wanted a new bike if he was to to continue riding. I got the bike (minus the wheels because they were a casualty in the crash). Everything else seems pretty good.
Been using it as an 'around town' bike path sled and have been trying to smooth out the shifting for quite some time. Finally decided that the RD looked out of whack and decided to swap the Exage out for the 7-speed Acera RD that came stock on my 1996 GT Outpost that I bought new way back then.
I popped the cage apart so I didn't have to punch a pin out of the chain and got it mounted up just fine. But now there is too much slack when in the small / small combo. Not that I would ride it more than a few yards in that combo, but I need it to be set up right.
Pretty sure the Acera (RD-M291) is a long cage as it was mated to an Acera 24/34/42 triple chainring crankset. The Timberline came with a 28/38/48 Bio-Pace crankset with SG chainrings and a UG chain. I had an IG cassette on it, but swapped out to an HG, A bit confusing trying to figure out what won't supposedly work with what.
Just wondering if some of those older derailleurs came with 'super long' cages compared to slightly newer long cage derailleurs?
What pins or quick links would be used to put the chain back together if I removed a link or two?
EDIT: It has a UG51 chain, and TBH, I'm not sure exactly what pins or quick-links are needed, or even available if I did decide to just take a link or two out of the chain. I don't really want to throw much (none would be wonderful) money at it if I can help it.
Last edited by jeffj; 11-09-2013 at 07:14 AM.
I'm guessing from the above you didn't shorten the chain at all before installing it?
Generally, you need to shorten chain first. Normally by about 6 or so pairs of links.
There are a few ways of determining the length for the chain. You could count the links on the existing chain and count the same on the new one, which is easiest. Or you could set it up around the big-big combo (not through the derailleur) and add 2 pairs of links to that to allow it to run through the derailleur, or run the chain small-small and through the derailleur with enough tension so the chain doesn't run against itself through the derailleur.
Either option is fine.
You need a chain tool and the easiest way to join is to use joiner links. SRAM make them for various "speeds" of chain, though not sure about 7 speed.
Sounds to me like he didn't change the chain "I popped the cage apart so I didn't have to punch a pin out of the chain and got it mounted up just fine." so no there should be no difference. Did you hold the old derailleur up against the new one and check the cage length? Also if the old derailleur is that badly bent you should check your derailleur hanger to make sure it's straight.
Ahh yes, I misread that. Oopsy!
Originally Posted by screamingbunny
Jeffj, a photo of the derailleur from the drive side and also from behind would help us out here.
The Exage is off the bike now, but it definitely looked wonky from behind the bike. I have the Acera derailleur on there now and it looks straight and shifts well (when not in a gear that allows slack). I did take the cage apart on both derailleurs to be able to make the swap without taking the chain apart as it (a Uniglide chain) has no master link and I have no way of knowing which shimano pin will work on that chain. For all I know, that might be the original chain.
I think the UG chain that I have on there now is a 7.3mm chain width. I have had issues in the past with SRAM quick links on Shimano 8 speed chain (they don't work). SRAM 8 speed chain is 7.1mm wide and Shimano is usually 7.3 IIRC, but they may make a 'narrow' chain.
I see that KMC makes 7.3mm quick links (or whatever they call them).
As it turns out, a friend saw this post and has generously offered me a spare Exage 400 LX RD he has in his parts bin. I think I will go with that option and see what happens. Thanks for the replies.
clarity is not overrated
As it turns out, "pretty sure" is not "sure."
I came across a shimano tech doc for the RD -291 (the Acera derailleur I have), and it only shows it as a GS (long cage) and the Exage appears to be an SGS (super long cage).
I went ahead and cut three links out of the Uniglide (UG) chain and got a 7.3mm KMC quick link and put the 12-30 IG cassette back on. I am exceeding the max capacity of the RD-M291 by having the 12-30 cassette and the max total number of gears I should be using (rated for 35, and I have 38), but it seems to be working well and shifting better than it ever has. I'll add the links back in (or get a new chain) when I get the replacement Exage 400LX.
It only sees bike path duty at this time, so I won't be putting too much strain on any of it. But I do ride it fairly often these days.
Just thought I'd post this info for others that may go through similar dilemmas.
Also, lots of good info here:
Shimano Rear Derailleur Specification - Bicycle Parts at discount prices / the Buyer's Guide / Bicycle Parts at their finest! / Professional Bicycle Source / Bike Pro
Plenty of other info there too if you drill around and look for it.
Glad you got it sorted, ride on brother!
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