Rear mech for 9 speed 44/32/22 - 12-36?

[Blue Hills]

Another thing that may be a problem, once you've solved the conundrums of rear mech largest sprocket and rear mech capacity may be cable pull.

If you have an indexed setup and choose an MTB mech for its wide capacity there may be cable pull incompatibility. I know nothing about this, I've just read about it. It may be nothing, but worth checking.

But if you don't have indexed shifters, that problem won't arise.

All my bikes are flat bar dogtrousers.
Interesting that some seem to have assumed that I am on drops.
But am grateful for all the help.

 

[scotsbikester]

Another thing that may be a problem, once you've solved the conundrums of rear mech largest sprocket and rear mech capacity may be cable pull.

If you have an indexed setup and choose an MTB mech for its wide capacity there may be cable pull incompatibility. I know nothing about this, I've just read about it. It may be nothing, but worth checking.

But if you don't have indexed shifters, that problem won't arise.

OP, the advice above is incorrect.

Nine speed Shimano used the same cable pull, whether the rear derailleur was described as for "mountain bike" or "road bike". I run a Shimano XT RD-M772, which is a "mountain bike" rear derailleur, 9 speed. The shifters are Ultegra ST-6510, road shifters. They are indexed, obviously.

 

[Dogtrousers]

OP, the advice above is incorrect.

Nine speed Shimano used the same cable pull, whether the rear derailleur was described as for "mountain bike" or "road bike". I run a Shimano XT RD-M772, which is a "mountain bike" rear derailleur, 9 speed. The shifters are Ultegra ST-6510, road shifters. They are indexed, obviously.

I beg to differ. The advice was entirely correct.

"It may be nothing, but worth checking." It was indeed checked, and it was nothing.

You get nothing but 100% honest to goodness correct, but slightly useless, advice from me.

 

[scotsbikester]

I beg to differ. The advice was entirely correct.

"It may be nothing, but worth checking." It was indeed checked, and it was nothing.

You get nothing but 100% honest to goodness correct, but slightly useless, advice from me.

My deepest apologies, you are of course absolutely correct.

I'm not sure the earth is a sphere, it could be flat. I may be wrong, but it's worth checking.

 

[Blue Hills]

nice over in this bit of cchat isn't it?

 

[Blue Hills]

Partial update - have had a rummage through my parts stock built up pre-plague pre-brexit and have found a brand new Alivio RD-M4000-SGS which shimano's specs tell me still has a maximum capacity of 45 (as ming points out I strictly need 46 but as discussed mr shimano can be a bit of a tease) but is listed as definitely being able to take a 36T big cog at the back. Will try this.

Hope I haven't damaged the XT (it did do a few shudders) - may have got away with it and I can keep it as a spare for the Hewitt which is unlikely to be as heavily loaded as its kinda twin built from base that cost me £21.

In case anyone else heads down this path of the mysteries of shimano specs, this may prove useful.

https://productinfo.shimano.com/#/archive

Will report back after some tinkering and test riding sometime next week.

 

[scotsbikester]

My own experience is that you can exceed Shimano's capacity specs by a lot more than one tooth.

For a while I ran 48-38-24 with an 11-34 cassette, which is a difference of, er, 47. That was with a Sora RD with a capacity of 43. In small-small the cage folded back on itself and rubbed a little. But then again it was a full length chain and in big-big the cage was nowhere near stretched flat. I'm fairly sure I could have taken a pair of links out and all would have been fine. And a rubbing chain, in a combination you never use, isn't really a problem.

I've got a feeling that sometimes Shimano gives specs just to match the other components in a particular groupset. So a RD might be said to have a capacity of 45 if the crankset/cassette for that groupset give exactly that difference. I think I read somewhere an experienced poster stating exactly that same belief.

 

[Dogtrousers]

I've never had a bike with a triple, but are the chances of accidentally cross-chaining lower with a triple? I mean - I inadvertently cross chain big-big quite frequently with my double, because I'm careless, and it's no big deal anyway. But is it less likely with a triple? If it is, and you can trust yourself to be careful, that's another reason to eat into the stated capacity.

 

[matticus]

I'm not sure the earth is a sphere, it could be flat. I may be wrong, but it's worth checking.

Definitely worth checking. (You will probably find that it is neither.)

I believe this to be 100% honest to goodness correct, but slightly useless.

 

[scotsbikester]

I've never had a bike with a triple, but are the chances of accidentally cross-chaining lower with a triple?

Probably. If you're on the inner ring, it means your want lower gears, so you'll probably be on the bigger sprockets. It would be a bit weird to be on the inner ring and end up going all the way to the smallest cog. Even if you did, you would probably get some warning in the shape of chain rub. On my set up, if I'm on the inner ring, I can use the four largest sprockets fine. When I move to the next one I get a little chainrub (on the front derailleur). I can trim it out fine, and sometimes I'll stay there, depending on approaching terrain. But usually it's a sign to move back to the middle ring.

I mean - I inadvertently cross chain big-big quite frequently with my double, because I'm careless, and it's no big deal anyway. But is it less likely with a triple? If it is, and you can trust yourself to be careful, that's another reason to eat into the stated capacity.

When I first built up this bike I lived on the middle ring. As I get stronger and dare I say it, a better cyclist, I'm using all three rings a lot more. In fact I try to use the other two partly to even out the wear. And the nice thing about a triple is you can keep a far straighter chainline - there are three dead straight combos (though if that makes much difference in terms of wear is another question).

As I said, I originally built this bike well outside of the stated RD capacity and was actually quite pleased that I could go through all 27 combinations just fine. I didn't actually notice that small-small rubbed, presumably because I only ever went into that to prove I could.

The inner on most triples is the "get out" granny gear, and you'll be very well aware you're in it, so unlikely to completely cross chain, small to small.

The outer ring is the more dangerous one, in that big-big without enough capacity can break things, including the rider. But so long as there's enough chain to allow big-big I don't think it's a big problem, I don't think that rubbing with small-small has ever thrown anybody off.

These days I'm running 11-34 with 48-38-26 and an XT RD-M772, so I'm bang on the stated capacity of 45. I'm tempted to move up to 12-36, which would put me one outside capacity.

PS "You" in this post means "one", as in somebody riding a bike in a given scenario. Thought I better be clear. I know how sensitive some people are to perceived personal "insults"

 

[roubaixtuesday]

so long as there's enough chain to allow big-big I don't think it's a big problem

This. As long as big/big operates without catastrophe, and gears you actually want to ride in work well, all else is detail.

 

[Blue Hills]

Update.

Instead of the new Alivio I mentioned upthread, I ended up fitting a good-condition second hand Deore RD M592 which I had in the spares box.

Same capability - unlike the Alivio though it doesn't have its own adjuster.

Just shows that "lower" level bits can be just as good. Will keep the XT as a spare for the Hewitt.

On the stand at least it seems to run just fine - will test ride in the next day or two.

Have never actually fitted a shadow mech before, though my Ridgeback Expedition came with one.

Was a bit dubious but think I possibly prefer - no outer loop at the end to collect crud.

Thanks for all the posts and help folk.

 

[Blue Hills]

I've got a feeling that sometimes Shimano gives specs just to match the other components in a particular groupset. So a RD might be said to have a capacity of 45 if the crankset/cassette for that groupset give exactly that difference. I think I read somewhere an experienced poster stating exactly that same belief.

Possibly other reasons as well. I have a very nice by now old-school ultegra rear mech. I think the specs say max big cog of 27. It will take more. One theory was that shimano said 27 as they thought its target market wouldn't take kindly to having a mech that might imply they had trouble with hills/weren't the powerhouses they liked to think.

 

[Dogtrousers]

Possibly other reasons as well. I have a very nice by now old-school ultegra rear mech. I think the specs say max big cog of 27. It will take more. One theory was that shimano said 27 as they thought its target market wouldn't take kindly to having a mech that might imply they had trouble with hills/weren't the powerhouses they liked to think.

Maybe people were better clued up in the days of your old-school mech, but these days I rather doubt most riders know the capacity or max sprocket of their rear derailleurs. It's something you only bother digging out if/when you're doing a build. And then you forget it.

 

[scotsbikester]

Update.

Instead of the new Alivio I mentioned upthread, I ended up fitting a good-condition second hand Deore RD M592 which I had in the spares box.

Same capability - unlike the Alivio though it doesn't have its own adjuster.

Just shows that "lower" level bits can be just as good. Will keep the XT as a spare for the Hewitt.

On the stand at least it seems to run just fine - will test ride in the next day or two.

Have never actually fitted a shadow mech before, though my Ridgeback Expedition came with one.

Was a bit dubious but think I possibly prefer - no outer loop at the end to collect crud.

Thanks for all the posts and help folk.

If you want to build up spares, new M592 and M591 (the non shadow version) are still available. I've got two on their way to me right now! You won't find new XT 9-speed anywhere I don't think.

I just changed from Sora to XT M772. I like the straighter cable. I like the whole feel of the M772, but maybe that's just because of how much I paid for it! Shifting is flawless.

I've got down-tube cable adjusters, but I think IRD make an adjuster designed for RDs without built-in adjusters, if you've no adjustment anywhere else. Yes, here it is:

https://southerndistributors.co.uk/product/barrel-adjuster-rear-bike-derailleur/