Chain too short?

noidea · May 2010

HI, I have recently upgraded complete gearset (accept the front mech) on my bike to the following:

XT hollowtech cranks FC-M752
XT 9 speed cassette 11-34T
XT 9 speed chain HG93 9spd
XT Rear Mech 9spd M772
Deore shifters
Stock front mech for now (cheapo Shimano C50)

I have followed video tutorials to setup my front and rear mechs but I still find that on the rear, I have trouble selecting some gears and they require the shifter to be clicked and then held for a few seconds untill it shifts. The H and L adjustment screws have been adjusted as best as I could to the but where if I either tighten or loosen them half/ quarter turn it just makes it worse.

I followed the Park Tools guide to shorten my chain (around both biggest cogs without mechs and add one inch) but when in the largest gears the chain looks way too short:

The chain was brand new and shortening it to what its supposed to be the correct lengh only needed about 4-5 links being taken out. IMO it looks too short and could this be causing the rear shifting problem?

My old rear mech had a cable tensioner but the new XT one wasn't supplied with one but it is second hand. I have looked on pinkbike, some XT mechs have one and some don't.. any ideas?

Please bare with me, this is the first time i've upgraded an entire gearset.

Radioactiveman · May 2010

Big Big is not a combination I would ever use. It usually resorts in mech death ime. As for setting chain length that is the correct way afaik If you add any more chain when you are in small small the mech will be slack and cause even more problems

I set the mech stops(L & H) without the chain on as it allows you to see the alignment between the mech and cassette better.

Also the L&H purely set the mechanical stop at either end of the cassette. Cable tension ensure it indexes correctly between gears.

Hope this makes sense,if not I am sure someone more eloquent will post shortly.

glauciaregina9 · May 2010

Sounds like you followed a well tried and trusted method of working out the correct length for the chain, so I can't see an issue with that.

Are you using the existing cable? Does it move smoothly in the outer? The cable could be sticking due to dirt or something, which is causing the delay in shifting...

glauciaregina9 · May 2010

And...

The H & L adjusters will only affect shifting onto the smallest or largest rear sprocket.

If you're having issues with shifting to any sprocket, it'll be the cable sticking or indexiing isn't set up quite right yet (use the barrell adjuster on the mech or shifter to tweak the cable tension).

noidea · May 2010

Thanks for clearing that up guys about what the H and L screws actually do. As Radioactiveman said, im never going to use that gear combo anyway and the chain seems fine in every other gear so im going to leave that as it is.

All thats left to do is adjust the cable tension, im using brand new inner cables but with old outers. Im thinking about going for new outers that are completely enclosed rather than leaving sections of cables exposed as its setup now to help keep the cables running smooth.

However, my rear mech doesn't have a cable tensioner. I bought it second hand from ebay and the cable just attaches directly to the mech. Looking at other bikes, some XT mechs dont have a tensioner whereas others do.

Searching the model number, it appears that the M772 doesn't need one?

Random google image

Once I had cleaned/replaced the gear outer cables, would the tension adjustment at the shifter end be enough?

Chunkers1980 · May 2010

Nope, you're right - 'shadow' mechs don't have a mech barrel adjuster. Your chain length looks fine.

Try small/small does the mech soakup all the chain slack?

supersonic · May 2010

The chain length looks perfect. Don't touch it.

Replace the outers, and then set up the derailer as per instructions on park tools.

cee · May 2010

looks ok...

as a general rule...

good chain line combinations are....

big front ring...smallest three cassette cogs.
middle front ring....probably ok in all cassette rings.
small front ring biggest three cassette cogs...

so i would never be in the big ring big cog combo....anyways...there is some overlap, so middle ring, middlish cassette cog will give you a roughly equal gear inch to the one in your photo.

apologies if that makes no sense...it kind of makes sense to me in my head...but heyho!

Chain too short?

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