Chain rubbing on rear mech cage

[timbob]

Unfortunately, my first day with my shiny new bike hasn't been all roses - I picked up a new Genesis Equilibrium 30 (Campag Athena) yesterday and went for a quick spin this morning, noticing that the chain was rubbing on the front mech cage in any of the lowest 5 gears.

A bit annoyed, I thought the limit screw might be a bit out. Anyway, upon investigation I found that as well as the chain run on the front mech the rear mech hit the stops on the 2nd biggest cog, and it took two clicks to move off the smallest cog - the indexing was one whole gear out!

That's now fixed, but I have zero confidence in the LBS and the mechanic who signed off my PDI checklist.

Anyway, everything is now running fine except for using the smallest half of the cassette with the big chain ring. The chain is rubbing on the inside (closest to the wheel) edge of the very first part of the derailleur cage, before it gets to the jockey wheel. The mech is straight and the hangar is straight. Can't decide if the cage around the jockey wheels is on the slant. It looks to me like the cage needs taking apart and a pair of pliers taking to the inner side to open it out a bit, but surely that shouldn't be the case on a brand new expensive group set?!

Any thoughts?

[Get Karter]

timbob said:

except for using the smallest half of the cassette with the big chain ring. The chain is rubbing on the inside (closest to the wheel) edge of the very first part of the derailleur cage,

Any thoughts?

Not clear if it is rubbing on the front derailleur cage, or rear derailleur near the jockey wheels.

If the former, then it is most likely that the High limit screw is too far out. The outer side of the front cage should just about rub on the outside of the chain when in top gear. This will give max clearance on inside edge of cage when in big ring.

If the latter.....best case would be slightly bent hanger (only detectable by using the appropriate tool that any good bike shop will have - the tool screws into the rear mech threaded hole in the hanger and measures 360 degrees for equi-distance from rear wheel rim.) Worst case....mal-aligned frame.

[timbob]

Get Karter said:

Not clear if it is rubbing on the front derailleur cage, or rear derailleur near the jockey wheels.

If the former, then it is most likely that the High limit screw is too far out. The outer side of the front cage should just about rub on the outside of the chain when in top gear. This will give max clearance on inside edge of cage when in big ring.

If the latter.....best case would be slightly bent hanger (only detectable by using the appropriate tool that any good bike shop will have - the tool screws into the rear mech threaded hole in the hanger and measures 360 degrees for equi-distance from rear wheel rim.) Worst case....mal-aligned frame.

It is the latter - where the chain enters at the very bottom of the rear cage around the first/lowest jockey wheel.

The sprockets in the cassette and the jockey wheels are perfectly in line, however, and I've had a frame with a misaligned hanger before, so I'm pretty confident it's not that. All gears index fine with both chain rings - it's just the rub on the lower inside edge of the jockey wheel cage that is the issue.

I don't know whether to take it back to the LBS I bought it from - given their mechanic evidently cannot set up either a front or rear gear system correctly, what hope do I have with a much more nuanced problem?! Or do I take it to another LBS in the next town who I have previously used and whose mechanics have an excellent reputation.

Or I undo the jockey wheel spindles, take out the side plate of the rear mech cage and open the end out 1-2mm with a pair I'd pliers myself... I'm pretty sure all form of warranty will be out the window in that case though!!

[thiscocks]

Try altering the 'b' adjustment screw on the cage. If that doesn't do it, it must be a bent deralliuer or bent hanger...

[timbob]

thiscocks said:

Try altering the 'b' adjustment screw on the cage. If that doesn't do it, it must be a bent deralliuer or bent hanger...

No effect.

I will take it to a trusted LBS to check if the hanger is straight or if it is misaligned. I suppose the derailleur could have a bent cage too?

Is a misaligned hangar on a new bike a common thing? Is it something that a proper mechanic will set up and tweak when building up a bike from the box? Only I've bought two new bikes over the last two years, and it would seem both have had bad rear hangers!

[WinstonWolf]

Is it Shimano? There's a half click adjustment available on the lever to prevent that if you're riding on the granny ring and the smaller cogs at the rear.

[gazza285]

WinstonWolf said:

Is it Shimano? There's a half click adjustment available on the lever to prevent that if you're riding on the granny ring and the smaller cogs at the rear.

Campag Athena, as mentioned in the OP.

[WinstonWolf]

gazza285 said:

WinstonWolf said:

Is it Shimano? There's a half click adjustment available on the lever to prevent that if you're riding on the granny ring and the smaller cogs at the rear.

Campag Athena, as mentioned in the OP.

I speed read through the brackets

[timbob]

Shop say hanger isn't bent, but it looks it to me. It's hard to tell by eye as I think it's only slightly out - jockey and tension wheels look to be pointing slightly outwards.

You can see in the image above the chain rubbing - looks like the cage is angled outwards to me?

[timbob]

Shop say hanger isn't bent, but it looks it to me. It's hard to tell by eye as I think it's only slightly out - jockey and tension wheels look to be pointing slightly outwards.

You can see in the image above the chain rubbing - looks like the cage is angled outwards to me?

[Get Karter]

Did the shop use one of these to ascertain the hanger is not bent?

If not, then they can't be sure.

http://www.chainreactioncycles.com/park-tool-mech-...

I'd get a second opinion from another bike shop, if possible.

ETA - doesn't have to be a Park Tool branded tool!

[Nighthawk]

In that image the mech appears to be twisted, could be a funny angle with the camera so recommend the hanger is checked etc.

[thiscocks]

From the image the inboard part of the cage does look closer to the chain than it does on my campag mech, and mine certainly doesnt get near touching whatever gear im in. Id take it back to the shop you bought it and show them the problem and tell them to sort it. Suggest they put another mech on I think.

Not great pic(frame and hanger look bent in pic but are vertical!):

Edited by thiscocks on Thursday 14th May 11:59

[Matt_N]

My Campag has two clicks for front mech trim before it shifts onto the big ring, you do need to trim up when moving down the cassette to stop it rubbing, are you using the trim function?

[timbob]

Get Karter said:

Did the shop use one of these to ascertain the hanger is not bent?

If not, then they can't be sure.

http://www.chainreactioncycles.com/park-tool-mech-...

I'd get a second opinion from another bike shop, if possible.

ETA - doesn't have to be a Park Tool branded tool!

I'm unsure - I took it in to a local bike shop, showed them the exact problem asked whether the hanger could be misaligned and could they sort it for me. They rung me to say it was ready, I picked it up the next day ("all sorted, no problems") they said, yet the exact same problem persists. You can hear the chain rub in the highest 5 or 6 gears...!

The reason I took it to a second shop, rather than taking it back to the shop I bought it from is that when I picked it up from brand new:

- The little chain ring was unusable (front cage rub - limit screw waaaay out)
- The rear derailleur was set totally wrong - it took two clicks to move out of the smallest cog, and I ran out of clicks to get into the granny gear (all gears set one out)
- Brake blocks with varying degrees of toe in or out (only the very rear corner of one brake block even touched the rim)

So I'm not trusting them to fix something much more finicky! I'm disappointed the second (locally very well regarded) shop hasn't fixed it either.

I've ordered the Park Tool alignment tool and will check the alignment myself!

[timbob]

Well, the repair hanger was not straight. With the tool touching the rim at the rear, swinging it round to the front left a half inch gap...! All straightened now.

Still not convinced all is well - in the higher gears the chain rises and then falls and twists as it enters the cage at a slight angle to the jockey wheel and settles onto each tooth. I think my cage is twisted.

Still unsure what to do... The shop I bought it from set it up so wrong to start with, and the second shop charged me for a full set up and didn't even check the hanger was straight.

[outnumbered]

timbob said:

Well, the repair hanger was not straight. With the tool touching the rim at the rear, swinging it round to the front left a half inch gap...! All straightened now.

Still not convinced all is well - in the higher gears the chain rises and then falls and twists as it enters the cage at a slight angle to the jockey wheel and settles onto each tooth. I think my cage is twisted.

Still unsure what to do... The shop I bought it from set it up so wrong to start with, and the second shop charged me for a full set up and didn't even check the hanger was straight.

It does sound like the mech must be twisted. I wonder if the bike has fallen over at some point, and bent both the hanger and the mech? Lousy job from both shops, I'd be looking for a refund from the second lot...