cptsilver

Trying to pick up a used Shimano rear derailleur, but I'm not sure if I need a long or short cage version. I'll be using it with the Shimano "Mega Range" 7-speed 14-34 freewheel. Thank you!

ColonelJLloyd 

No road derailleur will handle that 34t cog so you need to look for a MTB derailleur, the great majority of which have long cages.

ThermionicScott 

+1 on road derailleurs probably not handling it. Deore LX will, though!


(Photo is of a 13-34T "K" cassette, but you get the idea.)

cptsilver

Yea, I've been looking at used Deore XT units, sounds like I need a long cage. Thanks!

rootboy 

Hey Colonel. I'm unsure, as always, but won't a long cage like a Rally or NR, Huret Long handle it? Or, is it the amount of lateral movement a road derailleur won't handle?

ColonelJLloyd 

No, you're right. They'll handle it easily. I thought the OP was after a Shimano RD specifically, though. In which case, a GT200/LeTour/Crane long cage will shift it, but that's not where my head was when I initially read the post.

You actually might not. I would imagine any of the MTB derailleurs will shift a 34t cog. You need a long cage for chain wrap and we don't know your requirements in that regard because you didn't mention what your chainrings your crankset has installed.

rootboy 

That's probably the best choice anyhow. Those I mentioned are fairly pricy.

cptsilver

Sorry for not providing all the info... Right now, the bike has a 30x46x50 crankset, but I'd like to run the 24x35x46 Sugino XD2 crankset with the aforementioned 14-34 FW.

ColonelJLloyd 

That's a lot of chain to wrap. Long cage FTW!

cptsilver

Long it is! Thanks!

Lascauxcaveman 

I love it when this subject comes up, since I once get to drag out this bit of derailleur-maxing craziness. So the answer, as always, begins with "It depends."

With a triple up front, I can't imagine using anything but a long cage on back, unless the rear freewheel is a close ratio 'corncob' (which runs at cross purposes with the whole reason for having a triple in the first place).

Doesn't mean I'm not going to try it someday

Cougrrcj

I'm still using a SunTour VGT-luxe (long cage) on my Fuji.

Since I'm riding in the relatively flat Midwest now, I kept my 48/38/28 triple front from my touring days, and am using a 13-21 six-speed freewheel (13-14-15-17-19-21 - close to 'corncob' ). Surprisingly, there is very little gear overlap in the 'usable' gears - i.e. without too much chain angle. Now that I'm a bit 'older', I stay pretty much on the middle chainring and use the full range of rear cogs to ride at my 85-95 cadence 'normal pace' - so essentially I'm riding a 'six speed' - but if there is a 20+ headwind/tailwind, I'll use the big or little front chainrings - big for tailwinds and little for headwinds. Works for me!

Now if I was riding in very hilly/mountainous terrain, that freewheel would get changed to one that a bit more terrain-friendly Whether I would I have to go with an 'extra-long' derailleur remains to be determined. I've never done that sort of riding.

old's'cool

FWIW, I'm running the following cluster/crankset/RD combinations with no chain wrap issues (all RDs are standard cage length, per type, no long cages):

• 13-26/36-46-52/Shimano Light action (late 80's)
• 13-28/36-48-52/Shimano Altus (early 80's)
• 13-22/36-49-52/Suntour Cyclone (1st gen)
• 13-28/36-49-52/Shimano 105 (late 80's)

I never intentionally shift to big/big but rare accidental selection of big/big has not led to any grief. I never use small/small or anything close, as the gearing of the small chainring starts to overlap the middle one at the third largest cog or so.

I also have a different take on running a corncob with a triple. One of my favorite combos for fast pleasure rides is a single step plus granny combo, consisting of a 13-14-15-16-17-19 cluster with a 36-49-52 crankset. The inner chainring gets me out of the hole from a stop (& gives me a bailout, if necessary, for the steepest hills); after getting started I have a nice close ratio selection of single step gearing.

T-Mar

I be cautious about running some of the older long cage derailleurs with the 34T. A lot of them weren't designed to handle that big a cog. Whether they will or will not work often comes down to the hanger drop dimension and where you position the rear wheel in the dropout.

jimmuller 

Good timing. I paired a VGT-Luxe to a 34T 6-speed yesterday and realized that though the pulley-to-large-cog clearance is fine, the inner plate of the cage could potentially hit the 5th largest cog when it shifts to the 6th. A sufficiently short chain will keep the cage rotated enough to prevent it. S it looks like a surmountable issue, but it is one I didn't really expect. I'll have to pick the chain length carefully. (Eventually I'll use a Shimano more appropriate for this bike.)

EddyR

On my 1997 Cannondale with Ultegra I am running the original 8 speed short cage with a big gear 34 tooth and have no problems. I did buy a long cage but tried the stock short one before mounting the long cage and never had to use it. I converted a Centurion Expert to this same 8 speed combination and the 600 short cage would not make the shift.
Ed

ctmullins 

Specs published over at the disraeligears site lead one to believe that a large number of long-cage vintage derailleurs can easily handle a 34-tooth cog...

SvenMN 

May not be relevant to the OPs 7-speed freewheel set-up... is an option possibly friction-shifting a newer Shimano long-cage?

Just installed a few hours ago, and have not ridden yet. Ultegra long-cage, SRAM 36-12 cassette, SRAM Rival compact crank. B-tension screw all they way in.
Just had the ace mechanic at LBS check it and he says ride it!



This is my bail-out for Horribly Hilly Hundreds 200K.

jimmuller 

Did you or that mechanic check the big-big combination, in case you shift there accidentally? That looks like it could be a stretch for the derailleur. Yeah, I know, you don't intend to shift into biug-bitg, but it can happen accidentally.

SvenMN 

Sure did. Bottom jockey pulley is at about 4:30 when in the big ring (50) and the big rear cog (36). As expected, severe cross-chaining... and of course you will drop the chain while in this combination if you unwisely go to the small ring (34). This gearing is intended for a day of climb after climb. When the road goes up, the front goes down to the small ring.

Small-small is also a concern and the long cage soaks up all that extra chain.

I'd say an 11-36 cassette (which is available) with the compact would be at the max for this set-up.

jimmuller 

Interesting gearing. A 12-36 7-speed, you say? I wonder whether you'll ever do any traditional crossover shifting. That's a 20% average jump per cog.

Most of my bikes are fairly conventional, 48-34 front, 14-28 6-speed rear for a 15% jump per cog. The rear jumps are reasonably small and I tend to use the front as a range selector.

Thanks to the NR's 144mm BCD, the Masi is 47-42 front and 14-34 (IIRC) 6-speed rear, for 19% jump per cog. It gives me an good half-step arrangement and a high that I can actually use (instead of the useless high that so many bikes used to come with). But the rear steps are so far apart that the half-step crossover is nearly essential. The result lets me keep spinning on New England's highly variable terrain as long as I'm willing to shift frequently. It would not be as nice without the half-step crossover.

Just something to think about.

aramis

usually the problem isn't the cage being able to take up the slack (so you can use small/small as well as big/big) but the ability for the upper derailleur pulley to not ride on the large cog. Changing the cage doesn't change the derailleurs ability to not ride on the cog. The rear derailleur placement, btrim and all that fun stuff determines if a big cog will make it on those shimano derailleurs intended for a 28 or 30t max.

When I put a 11-32 on my ultegra di2 by putting on a longer cage I had to fiddle with the btrim and put a smaller tooth upper derailleur pulley to keep it off the cog and needed a new chain. But can shift from anything to anything without fear of dropping the chain or breaking anything.

SvenMN 

Jim: Sorry, no. Unlike the OP, my set up is with a non-C&V modern drivetrain... 10 speed cassette with compact crank. I have plenty of options with the 12, 13, 15, 17, 19, 22, 25, 28, 32 and 36 cogs. On the flats I am typically big ring with 15 or 17 cog. When I start a climb I shift the front to the small ring and as my momentum/cadence drops start shifting to the bigger cogs.

SvenMN 

Agreed. I've been running a 11-32 cassette, and thought I'd give the 12-36 a try. I was quite amazed when the B-Tensioner gave me a few thousandths clearance between the top pulley and the 36 cog.

T-Mar

Many of those couldn't, in practice. Manufacturers have a history of presenting their products in the most favourable light. For instance, during the early 1970's boom, claimed bicycle weight was typically the weight of the smallest size. The consumer rarely got a bicycle as light as what was claimed.

Things were the same with derailleurs. Manufacturers used clever advertising copy to provide the most favourable ratings. They weren't necessarily lying, but they were optimized. For instance, if you looked at the mid-1970s, Suntour long cage derailleurs, you'd think they capable of handling a 34T cog. They were, but only with the shown, long adpater claw. Remove the claw and install them on a SunTour touring dropout and they were down to 32T. Put them on a short hanger racing droput and you could probably only manage 30T.

The bottom line is that derailleur specs do not necessarily reflect what you can achieve. It will all depend on your particular set-up, as it may not reflect the manufacturers' test conditions. Sometimes you'll get more and sometimes you'll get less. However, you are more likely to achieve the spec rating on relatively modern derailleurs, as manufacturers have become more conservative with their ratings due to consumer outrage over what viewed as misleading advertising.