Experienced gear fettler bamboozled

stevieboy

Having set countless numbers of mechs up to perfection using the excellent guide in park tools website I consider myself to be fully competant at setting up gears.

However....

The other day I bought some XT shifters, new cables an XT E type front mech and an XTR M972 Shadow rear mech.

The front is spot on, but for some reason I can't get the rear set up right when shifting to top cog.

The L limit is set in line with top cog, the H limit is set to the outside edge of the bottom cog and the indexing is set up spot on - except in top cog it seems. For whatever reason it is tight and pulling on the stop resulting in a slightly stiffer lever than the other gears.

To investigate further I temporarily loosened the L limit to discover that the jockey wheel moves past the top cog ie out of index with the other cogs.

So i'm thinking either the cassette is slightly out of tolerance on the top cog to 2nd gap or the shifter is duff.

I know the L limit prevents chain to spoke contact, but at the moment it's causing the last shift up to feel a little tighter than it should.

Any help or similar experience appreciated

nicklouse

Not wanting to state the obvious but do you have the cable the correct side of the clamp bolt?

switchback18

Definitely something to check, I've seen people set the cable in the wrong place & spend ages trying to work out what's wrong with the indexing. Also, although I've not looked at a Shadow mech, on some mechs it's possible to move the whole cable clamp assembly round the wrong way - usually on cheaper mechs though.

dunker

messed about with mine (lx) recently just for learning really, set it all up inline all shifting nicely but once on the bike i found the L limiter was'nt "over" enough and the H limiter was'nt out enough.so i've set the H limiter so it's a bit out of line away from the cassette and the L limiter more over the largest cog, seems riding that's how my lx likes it, stay quiet too. dunno if xt is similiar?

setup this way off the bike it really does'nt like shifting from 1st down to 2nd but once riding it's perfect odd, maybe it's time to fit new cables or a new mech or it's like shimano hubs, set them up loose but once there's some tension on them they just work? something similar with rear mechs and rider weight on the frame?

kegs

it wouldn't be that there isn't much clearance between the biggest sprocket and the top jockey wheel, would it?

You might need to screw out the b screw on the mech to get some clearance for it to shift.

supersonic

Top jockey wheels on Shimano mechs do float a degree to help shifting. Can make 100% accurate set up a little harder. And as much as a 16th turn of the adjuster can have noticable effects.

kegs

true, but if there isn't enough clearance for the mech to push the chain onto the top sprocket the change will feel tight at the shifter, surely?

Shadow mechs do seem to be a bit more sensitive to setup than conventional mechs.

supersonic

Like you say, B tension screw should be set. In initial set up. I wind the screw in until the skipping/rubbing just subsides.

stevieboy

Blimey - I thought I was posting late!

Right to provide further info:

The gap between jockey wheel and top cog is 6mm
The cable is in the groove and straight in line with the outer

Usually in the past i've found that cable tension alone allows the chain to shift to the top cog with the L limit screw there as a safety measure. In this case the L limit is being employed as a definate stop preventing the shifter from indexing correctly.

Im not sure if it's an issue with shadow mechs, but the older XT had very similar symptoms. Never had an issue with RD M770's or M970's before.

I'm going to try the LX shifters with the XTR mech and XT shifters with XT (shadow) mech tonight to see if I can spot the faulty part.

daddylonglegs

Hello Steve

I've been setting up rear mechs of all kinds for twenty years in the trade and at home.

I appreciate you've done a fair bit of this, but here's a few general pointers. Out of the box the rear mech limit screws will be very close to being correctly set. It is very unlikely they will need any drastic adjustment, if any at all. They are not a particularly precision part of the mech.

Assuming you have fitted the cable correctly (shifter fully released, cable tension adjuster at mech half-way out, all slack out of cable before tightening pinch bolt and as someone has already suggested, cable correctly placed), the only thing left to do is tune the indexing, which is really just a case of adjusting the cable tension with the adjuster at the point the cable enters the mech. Assuming everything is in decent nick, shifts should be virtually instantaneous and apart from the moment of the actual shift, noiseless.

In my experience many people don't appreciate how little movement is required in the adjuster to go from a poor, noisy under/overshift to perfection. It's a good idea to give the shifting a real hard beasting up and down the cassette to ensure that the mech won't dump the chain at either end when you're actually riding as this can be expensive and dangerous. This is really all the limit screws are there for and only have an incidental effect on shifting at the furthest limits of the cassette if they are screwed in too far.

Now the problem. It sounds like you might have a bent mech hanger. If this is the case only a very big adjustment on the limit screw is likely to help. Are you sure all the shifts are completely clean and precise? (I'm assuming cables, chain and cassette are in good order). If you have a bent hanger - even a couple of mm - quiet, reliable shifting will be impossible and it really needs to straightened (if it's steel) or possibly replaced if aluminium.

You can't always see a bent hanger and it takes a bike mechanic with an alignment tool to check it properly.

This sort of damage is very common on a mountain bike, particularly with detachable aluminium hangers which are very soft and are designed to deform to protect the frame. Just letting a bike fall on its right side can be enough to knock it out of true.

Just a thought, but I wonder how many mountain bikers are out there cursing their noisy, censored gears and who don't know they have bent hangers.

Sorry if this has gone on a bit, but I'm at a bit of a loose end this morning. Ho hum...

switchback18

List of stuff that can cause poor shifting (maybe not all apply here):

- Indexing barrel adjusters out of adjustment

- Cable not clamped properly, either loose or on the wrong side of the bolt

- Dirt in the cables, especially the bit next to the rear mech.It slows down or stops the cable moving

- Shifters worn out. Not always obvious, this one. Sometimes it's the last thing you find by a process of elimination

- Bent rear mech hanger. Oddly, can sometimes be slightly bent and mess up the shifting totally, or very bent and everything still works. If this is the problem, will never get better than indexing in one direction. Can sometimes feel the same as when the cable is dirty. This can't always be compensated for by adjustments, and does need straightening. Take it to a shop unles you want to spend £40 - £80 on a tool!

- Mech worn out. Check for play in the mech pivots, if there's too much it'll need replacing

- Chainrings/sprockets or chain worn out

- No lube

- Last but not least, everything's full of mud ...bit obvious

the high & low stop screws don't have anything to do with the indexing, they just limit how far the mech can move, so the L stops the mech giong into the spokes and the H stops it the other direction. Most people will know this, but thought I may as well put it in for completeness.

stevieboy

The only thing which is making me think that there is a problem with the shifters is that the lever throw on the final push up to top cog is longer than the others by around 4-5mm. Every other click on the ratchet is within a mm in terms of lever travel. This alone suggests that the cable is being pulled more on the final push - surely this is not right?

Thanks anyway for the above suggestions - until I check back with my old shifters tonight i'll not know what the problem is. Unless the above info jumps out at someone as being not right, in which case the shifters will be going back as faulty.

daddylonglegs

It sounds like maybe your shifter is trying to find another gear.

I realise this might be obvious, but are you sure the shifter is fully released? Try undoing the cable and then making absolutely sure the shifter is fully released and in neutral by repeatedly up-shifting (ie pressing the shifter which would usually give you a bigger gear when riding). You may be trying to set the mech up one gear over as it were.

When you're sure the shifter internals are in the correct position, re-attach the cable and try again.

I think that the indexed position in the shifter must match the equivalent position on the cassette - ie on a 9-speed, position 9 on the lever must equate to the lowest gear on the cassette. This is done by ensuring the shifter is fully released (Ie on the smallest sprocket) before attaching the cable.

Might be worth trying if only to avoid embarrassment in the returns dept.

Bleedproof

Just to add to this as I've avidly following this thread... I've just install the exact same XT shifters and found setting up the front XT mech a breeze. The rear XT shadow presents the same odd symptoms.

I've setup the bike with new cab;es and outers and made sure the shifter was in the lowest position (full released) before clamping the cable. I get a lot of adjustment from the H adjustment, but not a lot from L.

The last change feels very stunted and doesn't have the same reassuring 'click' as per the other changes.

The other gears are indexed properly and ascend and descend fine. It also make it to the last position but not in the same way as the others.....

Bleedproof

duplicate... sorry

Bleedproof

duplicate... sorry

stevieboy

It's not just me then....

That's the same symptom I get - gears indexed perfectly - limit stops set. But the last change up feels, as you say, stunted or restricted slightly.

Either we're both being pickey over lever feel - or the Big S has not quite got this Shadow melarchy right. Never been an issue with traditional mechs.

Just out of interest, I can confirm the shifters are fine, the LX produce the same symptom - highly unlikely lightening would strike twice with dodgy shifters.

It's be interesting to here from other Shadow users - the only thing I can see with the cable pull mechanisim is that every pull bar the last one takes place with the cable clamp lower or level to the line of the hose exit point. The last shift takes the cable over / above this line. Could it be that these mechs are flawed in that the cable pull arm has not been designed correctly?

daddylonglegs

I would so like to get my hands on this!!

Can I check something: When you back off the low limit screw does the situation improve? If not, none of the below applies!

I know what what you mean by a tight heavy shift when moving onto the largest sprocket, but in my experience, this is almost always due to the low limit screw needing adjustment. In a situation like this I would back the screw right off right off until the mech strikes the spokes or starts to lift the chain into the wheel (care!). I would then screw it back in until the chain reliably stays on the sprocket. (It's important to check this by whacking the gear from several sprockets out up onto the biggest cog, several times and fast as you can - You can also do this by hand by releasing the cable and physically manipulating the mech body to attempt to force the chain off the sprocket). If it stays put you're in business - at least from a safety point of view anyway. Bear in mind, this is all a lot easier with a workstand.

The only other explanation if we are discounting knackered parts, bent hanger and the various other suggestions we've had is a mis-match between cassette, mech and shift lever, where the cassette is sitting slightly too close to the wheel. It's unlikely these problems are down to bad design.

daddylonglegs

None of this may be news to you: http://www.bikemagic.com/news/article/mps/uan/5511

Then again...

kegs

Can't say I have had any problems at all with my shadow mech, especially not the ones you are describing.

Got it set up easily, I did need to screw in the B-screw a bit to get some clearance with the largest sprocket, but the indexing has been rock solid since, apart from when I had a stiff chain link.

It might be the b-screw, or a slightly bent hanger. B-screw would be the first thing I'd try, obviously.

Because they do seem a bit more sensitive to set up you could well have a very slightly bent mech hanger, which is affecting the shadow mech, but conventional mechs cope with fine.

It must be frustrating trying to get the damn thing sorted.

daddylonglegs

I agree with the bent hanger possibility having just read up on this mech, it's possible that it is less tolerant of a mis-aligned hanger than a conventional mech. If nothing else works, it might be worth checking this.

Bleedproof

I never had a problem with the change with LX shifters. The problem here doesn't stand with the chain moving onto the cog, but the feel of the change. There seems to be nothing left on the shifter movement... just enough to get the chain across and picked up by the teeth.

It may just be the way it's designed, but I would have thought the last shift should be a good as the other 7?

It's a good upgrade to combine the XT shifters and mechs.... I'm already feeling the benefits, but I'd like to think I have it all sorted.... hmmm

I'll have a play this weekend and see what I can discover.

stevieboy

All sorted

I've not had my mech hanger checked as I've never dropped the bike or even so much as put a mark on the previous mech. However, although the hanger looked as straight as can be I decided to give it a little tug outwards, literally a tiny change in position of no more than 1mm.

As a result of this I have been able to find the sweet-spot that is oh so small on these mechs and got the top cog shift perfect.

I'm tempted to get the hanger aligned properly, but as the shifting is sorted I think i'll leave it be.

So my lessons learned are -

don't trust that on a nearly new bike everything is as should be
shadow mechs are sweet pieces of kit but require a perfectly aligned hanger
my gear fettling skills are up to scratch

And....

This forum is full of top people when it comes to knowledge and advice

Right - i'm off to go play with my XTR shadow (work of art) equipped scale

Thanks again