SRAM X7 derailleur set up

richie131

I have a new MTB with SRAM X7 rear derailleur and shifters. its my first SRAM, previous bike had cheapo shimano.

despite this the shimano worked fine through full range of gears even the best avoided extreme ones, eg, big chainring, small rear cog at cassette.

the SRAM by contrast is not happy at all.

when on small chainring the SRAM will not derail to smallest 2 cogs at rear and if persuaded the lower guide wheel smashes into upper derailleur body. fine, i never use those gears anyway as the chain is way too slack and at a terrible angle.

but it also does this when on middle chainring, which i think is within the chains working range. (correct me if wrong, but the cheapo shimano never complained)

i have had it checked by 2 mechanics who seem to think this is normal for SRAM. but they can't explain why i cannot set up the B-screw adjuster to the required SRAM 6mm clearance from the upper guide pulley to largest cog on cassette.

mine is way off that, at all extremes of B-screw adjustment.

the deraiileur is shifting ok-ish but dropping onto small rear cog is best described as patchy in every chainstay configuration.

i'm stuck. SRAM guide telling me one thing, mechanics telling the opposite.

any ideas who is right?

ta, richie

.blitz

Seems odd that the B-adjuster is so far off. I used to have a (damaged) X4 mech where the B-adjuster screw had been forced off the little tab on the gear hanger and found itself a new 'home' lower down on the hanger so it was impossible to get the upper guide wheel anywhere near the largest cog on the cassette.

The damage was caused by carelessly laying the bike on its side

Edit: just remembered that the X7 mech has a rotating collar for the B-adjuster to bear on that fits against the tab on the gear hanger. Is this intact and in place?

supersonic

On the middle chainring, the derailer should drop to the two smallest cogs.

First off is the chain the correct length? Should be measured by wrapping the chain around the the largest chainring and largest rear cog, bypassing the derailers. Add two full links to wear they overlap. If you have a full sus, measure at the furthest point of the axle from the bottom barcket in the bikes travel.

What cassette are you running ie ratios? I would definitely avoid the small/small and large/large combos, but the chain length is optimised to avoid damage should you hit large/large by accident. Go smaller on the chain if you wish, but be very careful. If you want to try and use all ratios, make sure the derailer has enough capacity. And that it works with whatever largestrear cog you have.

SRAM say 6mm, but in reality a setting that just clears suffices ie adjust until rubbing stops. A longer screw may help get more clearance.

Many shifting problems are caused by cable gremlins ie mud, badly cut cables, frayed cables and ferules that don't fit correctly, so I would check all these too.

Also always check the mech hanger for alignment.

richie131

thanks for replies...

bike is: http://www.commencal.co.uk/web/bicycles ... remier-pro

so relevant drive train is:

Shifters New Sram Trigger X7 3×9
Front Mech Shimano Deore
Rear Mech New Sram X7
Bottom Bracket Shimano splined
Cranks Shimano M442 Octalink
Chain KMC 9s
Cassette Sram PG 950 9s 11-32

bike is brand new (less than month old) so has no issues with cable gremlins and i have hardly ridden. it hasn't seen any mud yet and covered less than 10 miles.

the chain length is fine, according to the mechanics who have looked at it, but its years since i took a chain off so i'm going to take their word for it for the moment. i can't imagine the factory would have put the wrong chain length on, no?

but i am intrigued by:

"just remembered that the X7 mech has a rotating collar for the B-adjuster to bear on that fits against the tab on the gear hanger. Is this intact and in place?"

i've just had a look and i can see see no such rotating collar, just a tab that it hits like the H and L screws have. no matter how much i adjust the B screw the upper guide will not go anywhere near the cassette. i can drive a coach and horses through the gap.

thats the most sensible suggestion i have heard so far, but not sure what to do now?

cheers all

richie

supersonic

Can you take a pic of the B screw arrangement? Maybe it has missed where it is supposed to fit on the hanger.

New bikes frequently have wrong chain lengths and crap cables But that would be a minor part if above is the problem.

.blitz

The rotating collar is the medium-grey part:


The b-adjuster presses on the collar and not on the tab on the gear hanger. On the X4 mech that I had, the collar was either missing or not fitted and the b-adjuster rested against the tab on the gear hanger. It was impossible to set the gap with the mech like this.

richie131

i checked all of the suggestions.

firstly, the collar is fitted and looks set up as in the diagram. the b screw is hitting the collar rather than the gear hanger. so all seems well there.

i also checked the chain length, but only by big chainstay - big cog at rear. the chain was pretty stretched out in this configuration and i don't think removing any links would be a possibility.

i pinched the chain, to improvise a shortening and it didn't look happy.

i have taken some pics if someone can explain to me how to upload them. feel a bit daft but i can't work it out!

richie

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delta5

In these situations its often best to start from scratch . . .

take off chain
loosen off gear cable at derailleur
turn shifter barrel adjuster all the way in, then back off 1 full turn
check that cable is running smoothly (clean and lube if necc) and shifter is working correctly

check that the hanger is straight and fitted properly
check that derailleur is mounted properly, can rotate smoothly on its pivots at the hanger, and is running straight in line with the cogs all the way across its range. Just move it with your hand to check this - it should move smoothly towards the biggest cog against the spring tension. Make sure its does move smoothly and evenly. Lube the pivots and parallelogram joints if it is at all sticky (I'd lube them anyway!)

if okay so far, set up the H and L screws:
the centreline of the upper jockey wheel should line up with the outside edge of the smallest cog (H screw)
the centreline of the upper jockey wheel should line up with the centreline of the biggest cog (L screw)

replace chain on middle chainring and smallest cog.
adjust the B screw to give roughly 10mm gap (you can close this gap later) (hopefully it will adjust as required now )
move shifter to 9;
pull cable taught and secure it.

spin pedals and change up and down through the gears.
Gears should now change through full range - but you still need to set the B screw for clearance at the biggest cog, and use the barrel adjuster to fine tune the top jockey wheel alignment to get smooth chatter-free chain flow.

On the X7 I sometimes also need to finally re-adjust the H screw just slightly to get nice smooth chain flow onto the smallest cog. It works well to shut eyes and listen carefully to the sound from the chain running onto the cogs . . 1/4 turn either way can make a difference.

Good luck!

richie131

do you really think starting again from scratch will close up the rear mech clearance issue with the large sprocket?

i had considered it, but it was supposed to be all dialed in by a bike mechanic. i assumed he did all that. i certainly asked him to. then again he may have just twiddled a bit and not done it properly.

i think i'll call him tomorrow and find out.

i am not best pleased with the bike store who sold it to me. this isn't the only mistake they made. fortunately i spotted the others and sorted them.

richie

supersonic

There are instructions on how to upload pictures in the classifieds area. Basically you upload to another host in link to here.

cooldad

richie131 wrote:

do you really think starting again from scratch will close up the rear mech clearance issue with the large sprocket?

i had considered it, but it was supposed to be all dialed in by a bike mechanic. i assumed he did all that. i certainly asked him to. then again he may have just twiddled a bit and not done it properly.

i think i'll call him tomorrow and find out.

i am not best pleased with the bike store who sold it to me. this isn't the only mistake they made. fortunately i spotted the others and sorted them.

richie

That's all very well, but easier to do it yourself, only takes a few minutes.

delta5

richie131 wrote:

do you really think starting again from scratch will close up the rear mech clearance issue with the large sprocket?

i had considered it, but it was supposed to be all dialed in by a bike mechanic. i assumed he did all that. i certainly asked him to. then again he may have just twiddled a bit and not done it properly.

i think i'll call him tomorrow and find out.

i am not best pleased with the bike store who sold it to me. this isn't the only mistake they made. fortunately i spotted the others and sorted them.
richie

Can't guarantee it will solve it, but I really think it's your best bet for getting to the bottom of the problem. It can only be caused by a limited number of things - either bad setup (possibly chain too short, or too much gear cable tension, like it might have been clamped while in 7th not 9th?) or something is damaged / bent / faulty. Starting from scratch and checking everything along the way eliminates most of the these gremlins.
BTW, meant to say, double check your chain length!

FWIW, I went through a similar thing on Tuesday night: After riding on Sunday I couldn't get into 9th anymore, and my shifter was already on the big cog when it said '2'. Loosened off the H screw, still wouldn't go to 9 . . B screw didn't seem to behave correctly ether. In the end it turned out that the cable was too tense, combined with a sticky parallelogram.

2 mechanics who seem to think this is normal for SRAM. but they can't explain why i cannot set up the B-screw adjuster to the required SRAM 6mm clearance from the upper guide pulley to largest cog on cassette.

This is definitely not normal for SRAM. I have X7 rear, and both middle and granny ring work fine over the full range of the cassette (although I choose to avoid middle-biggest and granny-smallest combos). Frankly if these are the mechanics who made the other mistakes you've mentioned, and they can't even be bothered to diagnose your problem properly, there's a good chance they also didn't bother to set your gears up correctly or do the work you asked for. :?

supersonic

I agree, starting from scratch is always a good way of trouble shooting.

Ideally any one of us here would like to look at the set up. To an extent we are shooting in the dark. So starting afresh, step by step will hoepfully nail the problem.

richie131

firstly, thank to all. excellent forum this..

i agree. its about time i got down and dirty and refreshed my skills as an amateur mechanic. i did it all when i was a teenager so i am sure i can manage it now i'm all grown up.

i have been less than impressed with all the mechanics i have used so far so i have nothing to lose. at least i can set it all up correctly and then i can troubleshoot as i go along.

and then see what happens.

fingers crossed i'll sort it and then have a good complain at the mechanics!

richie