Ultegra 6800 rear mech rub...?

luv2ride

I have a new bike with Ultegra 6800 rear mech (medium cage) with a 11-32t 105 cassette (11sp). I'm really struggling to get clean, noiseless running across the entire cassette. If I set it up for good rear shifting from the small cog (using the rear barrel adjuster), I find it is quite noisy when in the 4th and 5th cogs (but quiet in all others). Is it possible to get quiet running across the whole cassette. Have come over to Shimano from Sram 10sp and never had this issue before.

Have discovered the front mech trim feature which has helped minimise noise from the chainring, but the cassette cog noise is separate.

Help?!!

jgsi

Dont make the basic setup with the barrel adjuster - thats for fine tuning afterwards.
Get behind the bike and check the lower jockey wheel is directly under and in alignment with the smallest sprocket.
using the 'H' limiter screw to adjust accordingly.
You may want to start with the cable detached from the mech.
Check that the other limit - biggest cog is not over shifting - you can move the derailleur with your hand to simulate shifting... you dont want to the chain thrown off into the spokes.
if it is quiet in the small cog, it should be quiet all up as well.

luv2ride

JGSI wrote:

Dont make the basic setup with the barrel adjuster - thats for fine tuning afterwards.
Get behind the bike and check the lower jockey wheel is directly under and in alignment with the smallest sprocket.
using the 'H' limiter screw to adjust accordingly.
You may want to start with the cable detached from the mech.
Check that the other limit - biggest cog is not over shifting - you can move the derailleur with your hand to simulate shifting... you dont want to the chain thrown off into the spokes.
if it is quiet in the small cog, it should be quiet all up as well.

Thanks, will give this a go later. Currently I get it quiet on 9 out of 11 cogs. Which two produce the chain noise depends on trimming via the rear barrel adjuster, so is a little frustrating. The bigger cogs and smaller cogs tend to all run quietly. Think I'll do as you suggest, release the cable and start again and see what happens. Slightly concerned the hangar might be out of alignment - bike arrived in a big box, not particularly well padded out. Will need to go in to LBS for steerer to be cut so could ask them to check alignment then I guess, assuming I can't resolve it myself through checking the limit screws, etc.

cyclozone

Be sure to check if your rear derailleur hanger is bent.

royalmile

Your shifter should move the rear mech in even steps but there are a couple of fairly common issues that can lead to inconsistency over the cassette:

If the noise is coming from the cassette and sounds like the chain isn't properly meshed or hesitating between gears:

1. Rear derailleur hanger is bent - check visually looking from the rear of the bike.
2. Inner cable is dragging on the outer cable.

If the noise is coming from the front mech - a metallic rubbing sound - adjust the H and L limit screws at the front. You may still experience some rub when cross-chaining - e.g. big front ring + big rear cog or small ring + small cog which should be avoided anyway.

luv2ride

I'm still stuck with this issue, and can only conclude its down to a bent hanger. Currently asking the supplier to send me a new hanger as a good will gesture, or at least with a decent discount (though not holding my breath). Supplying shop have so far suggested I simply "bend it back".

Am considering getting a rear hanger alignment tool, as have a few other bikes so am sure it be useful. My question is, assuming the hanger is bent, is it safe to try and strighten it in the frame?

It's a £2,500 carbon bike with flexi seatstays and through axles - not sure that makes the hanger "beefier" or just that it's more securely anchored to the frame. Anyway, do I risk damaging the frame if I attempt to bend it in situ? btw, if it's a bent hanger the bend is minimal, but the lack of clean shifting across the whole is certainly spoiling my enjoyment if the bike.

k-dog

No point getting a new hanger - it has to be straight on the bike, not on a flat surface.

sungod

Luv2ride wrote:

Am considering getting a rear hanger alignment tool, as have a few other bikes so am sure it be useful. My question is, assuming the hanger is bent, is it safe to try and bend it in the frame?

you can always check the manufacturer's info for your frame, but the vast majority of frames are fine with the hanger being adjusted - typically the hanger 'wraps' around the axle and is clamped by the qr, this is a really solid area able to take high loads, which is why hangers can be bent or even snapped leaving the rest undamaged

prior to adjusting, make sure any screws securing the hanger are tight, the wheel is fully seated in the drops, and the qr is tight

be gentle adjusting, check four points around the wheel after each tweak, you don't want to put the hanger through lots of bending cycles

luv2ride

^both. Do I need an alignment tool to confirm whether the hanger is really bent or not, or is it possibly to see by eye? I note the lower part of cage does seem to hang in board a touch, when in the "outer half" of the block, but not by much:

sungod

unless it's really badly bent you can't do it by eye, and depending on rd the cage angle can vary by design

tool will catch even slight misalignment

i've got a park tool one, it's ok though heavy, i actually made a lightweight one i could use when taking bike overseas in case the hanger got a knock...

http://weightweenies.starbike.com/forum ... 5#p1240162


btw, free photobucket hosting no longer allows cross-linking, try postimage.org instead

MrSweary

I've had this exact problem with a full ultegra set-up and I've seen it reported elsewhere - same cogs etc.

I have a hunch it is actually a cabling drag / rub problem. Will tell you if this fixes it for me!

luv2ride

Well, used the new hanger alignment tool and it seems the hanger was bent after all...
Rear shifting less noisy now, but I'm currently full of cold so resisting the urge to properly road test it.

itboffin

cyclozone wrote:

Be sure to check if your rear derailleur hanger is bent.

^ its this ^

luv2ride

Luv2ride wrote:

Well, used the new hanger alignment tool and it seems the hanger was bent after all...
Rear shifting less noisy now, but I'm currently full of cold so resisting the urge to properly road test it.

Still not completely free of the lurgy but went out for a cheeky 30 miler this afternoon. Shifting much improved after the hanger re-alignment

luv2ride

Quick Update:
Issue wasn't fully resolved with the re-aligned mech hanger. Another forumite suggested he'd sorted a similar issue after fitting a new KMC chain. I ordered one in readiness, but before fitting decided to have a further fettle. After running the B screw adjustment ALL the way out (so chain as close as possible to the cassette), i get silent shifting and running. Night and day difference.

Think it's odd I'm having to back this adjustment all the way off, given its a long cage GS Ultegra 6800 mech with a 11-32 cassette, as would have thought that this is what you'd have to do if running a smaller cassette (such as a 11-28t) with the long cage mech?

Anyway, a really quiet drivetrain has transformed the bike for now so happy enough.... ...and I have a un-used replacement chain ready for when its needed.

lesfirth

sungod wrote:

unless it's really badly bent you can't do it by eye, and depending on rd the cage angle can vary by design

tool will catch even slight misalignment

i've got a park tool one, it's ok though heavy, i actually made a lightweight one i could use when taking bike overseas in case the hanger got a knock...

http://weightweenies.starbike.com/forum ... 5#p1240162


btw, free photobucket hosting no longer allows cross-linking, try postimage.org instead

If you take an alignment tool on holiday in case you bend your hanger there is no point in asking if your glass is half empty or half full. What else do you take and how big is your suitcase?