Author Topic: Why don't my gears work properly?  (Read 1385 times)

Why don't my gears work properly?
« on: July 20, 2020, 03:28:15 pm »
10 speed Shimano hub, cassette, mech and STI shifters.  Work perfectly when the bike is upside-down.  Even pushing the brake lever right over, it's impossible to get the rear mech to touch the spokes.

Ride it up any hill in the 28T sprocket, and the mech pings off the spokes.  Always has done.  It's not the wheel - I sold the rather underbuilt DT set and built some very tight 32-spoke conventional wheels.  Something is flexing under the torque of riding, I think.  I'm not talking about bar-snapping levels of effort here either, just any kind of incline.  AFAIK the frame (Boardman Team Carbon) isn't cracked, the QR is tight and the bearing cones are properly adjusted.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

LittleWheelsandBig

  • Whimsy Rider
Re: Why don't my gears work properly?
« Reply #1 on: July 20, 2020, 03:56:10 pm »
Start with the stuff you have already checked:
Hanger straight?
Spokes laced to maximise clearance?
Wheel meet again, don't know where, don't know when...

Re: Why don't my gears work properly?
« Reply #2 on: July 20, 2020, 03:56:41 pm »
apols if this is obvious but frame flex can cause the gear cable to 'pull' and if the limit screw isn't limiting the RD in the right way It can move.  Also when setting the bike up on the workstand, you should grab the RD and try and push it into the spokes; if it touches the spokes then, it'll do the same when you are riding the bike.

Also if the spokes are uneven tensions or the crossings are not braced in the right way, the RD can touch the spokes when the wheel is loaded.

Finally if the 10s cassette isn't fitted with the spacer at the back of the cassette, it'll be that bit closer to the spokes than it should be.

cheers

Re: Why don't my gears work properly?
« Reply #3 on: July 20, 2020, 04:13:17 pm »
Does a 10 speed cassette on a 10 speed hub need the 1mm spacer?  The cassette instructions (CS-6700) say no, not if you have a 10-speed freehub.  The freehub instructions (FH-5700) say yes.  Shimano can't make up their minds...
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Why don't my gears work properly?
« Reply #4 on: July 20, 2020, 05:48:29 pm »
Does a 10 speed cassette on a 10 speed hub need the 1mm spacer?  The cassette instructions (CS-6700) say no, not if you have a 10-speed freehub. 

It's referring to a "10 speed *only*" freehub, which are rare beasties with splines that are too short for a 8/9 speed cassettes. I don't think the FH-5700 is one of them. So you probably need a spacer.

Re: Why don't my gears work properly?
« Reply #5 on: July 20, 2020, 07:29:10 pm »
+1 ^^^

Re: Why don't my gears work properly?
« Reply #6 on: July 20, 2020, 09:43:12 pm »
Spacer in.  It's still pretty close to the spokes.  The bike has never been dropped or crashed but the mech does seem to be at a bit of an angle.  I will try a new hanger as they are super-cheap.  I have a known good mech, too.

FWIW, I always do RH pulling spokes heads-in, as do most builders (Hewitt, Pete Matthews, DT, slope OTP!).  The heads-out thing seems mainly to be a Sheldon Brown thing and even he admits it doesn't really matter, as does Jobst Brandt.  Derailleur clearance has never been an issue before.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Why don't my gears work properly?
« Reply #7 on: July 20, 2020, 09:48:11 pm »
I saw the title and wanted to suggest it must be due to dirt somewhere. :demon:

More helpfully, the only time I’ve had similar the axle had cracked. It span fine on the workstand and easy pedalling. Put some effort through it and it started to give.

LittleWheelsandBig

  • Whimsy Rider
Re: Why don't my gears work properly?
« Reply #8 on: July 20, 2020, 09:51:05 pm »
I almost always lace rear wheels with pulling spokes heads out, both for better derailleur clearance and to minimise spoke damage if the chain overshifts.

Last century, Mavic did a comparative study of wheels laced up a bunch of ways and found that pulling heads in spokes required somewhat less maintenance but there was very little in it.
Wheel meet again, don't know where, don't know when...

Re: Why don't my gears work properly?
« Reply #9 on: July 20, 2020, 10:30:44 pm »
I almost always lace rear wheels with pulling spokes heads out, both for better derailleur clearance and to minimise spoke damage if the chain overshifts.

IIRC that is the reverse way from shimano's recommendation.  I know that both ways have their advocates.  One observation is that if laced the other way (pulling spokes 'outside' or heads in) you get 'early warning' by contact that occurs only under high load, eg when climbing. Unless the rider is half-asleep, this ought to trigger some inspection/maintenance before catastrophe ensues.    Whether that is really 'better' than the alternative I'm not sure.

FWIW there is something to be said for building using aero spokes on the driveside.  One of my mad ideas is to modify round spokes so that they are flatter at/near the crossings, just to get a bit of extra clearance on 10s/11s wheels.  I guess using a slightly wider OLN and/or using an asymmetric rim gain you a bit of extra clearance for nothing too.

I also note that most shimano RDs in recent years couldn't be better designed to dive into the spokes, often with jaggy bit just next to the guide pulley; what happened to the 'spoke barrier cage' design that was on shimano mechs in the 1980s....?

cheers

LittleWheelsandBig

  • Whimsy Rider
Re: Why don't my gears work properly?
« Reply #10 on: July 20, 2020, 10:39:36 pm »
I know it is the opposite of Shimano’s recommendation, which matches Mavic’s findings. I figure that handbuilding makes up for a slight deficiency in spoke arrangement. I almost never need to true wheels, so it seems to work.

I have seen too many wheels with jammed chains behind the cassette (usually from a bent hanger), which almost never happens when spoked my way. The advantages of my arrangement tip the balance IMHO.
Wheel meet again, don't know where, don't know when...

Re: Why don't my gears work properly?
« Reply #11 on: July 20, 2020, 11:20:25 pm »
I honestly don't have a very strong opinion on which is the best way. I happen to have mostly done it the other way but I've seen good wheels built both ways and I've seen all kinds of horrors (both ways) when the chain comes unshipped too.

If the chain gets in the gap it will tend to jam with OP (outside pulling) spoking and more likely to skate round with IP spoking. I dunno which is more likely to cause severe damage to the spokes; I have seen bad damage to the spokes both ways.  However there is a certain type of rider that will not fix their bike if they can get the chain out easily, so repeat episodes are perhaps more likely....   I also note  that with worst jams/tangles occur with freewheels rather than cassettes and the very worst of all occur with modern shimano freewheels such as MF-TZ21, ...31...500 etc where the chain can get into a proper tangle in the back of the freewheel because there is a space there for the chain to go into.  I note that the latest versions of MF-TZ500 etc can have built-in spoke protectors, attached to the largest sprocket; seems like a good idea and maybe 'posher' cassettes could benefit from something similar...?

I also note that with modern 10s/11s systems the chain going left of the largest sprocket is often accompanied by the mech going in the spokes; this being the case something that jams quickly might be an advantage, if it helps mitigate damage arising from other sources; however very often when looking at the mangled remains, it is difficult to tell what happened first, and what caused what, exactly....

cheers

LittleWheelsandBig

  • Whimsy Rider
Re: Why don't my gears work properly?
« Reply #12 on: July 20, 2020, 11:42:42 pm »
I rarely build wheels for cheap freewheels, so no problem.
Wheel meet again, don't know where, don't know when...

Re: Why don't my gears work properly?
« Reply #13 on: July 21, 2020, 07:59:34 am »
The theory AIUI is that outside spokes have an easier life because the elbow is wrapped around the flange and not hanging in space, so it makes sense to have the "pulling" spokes laced that way.  It doesn't matter as much for the LH side.  This is probably why Mavic found they require less maintenance (I'm purist on this: spokes should require NO maintenance, and if they do, it is a crap wheel).
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: Why don't my gears work properly?
« Reply #14 on: July 21, 2020, 11:32:54 am »
All this esoteric discussion on the merits or wheel building is possibly missing the heffalump on the sofa, namely are the pivots of the rear mech worn?

If the cable is pulling hard against the limit screw and there is any slop in the pivots then the cage will bend in towards the spokes. What mech is it?
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Re: Why don't my gears work properly?
« Reply #15 on: July 21, 2020, 11:47:50 am »
It's a 105 and probably only has 1000 dry miles on it.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Torslanda

  • Professional Gobshite
  • Just a tart for retro kit . . .
    • John's Bikes
Re: Why don't my gears work properly?
« Reply #16 on: July 21, 2020, 12:09:21 pm »
In which case I haven't got a scooby and will STFU.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

FifeingEejit

  • Not Small
Re: Why don't my gears work properly?
« Reply #17 on: July 21, 2020, 12:52:55 pm »
It's a 105 and probably only has 1000 dry miles on it.

Aye but... how many soaking miles  ;D :P

zigzag

  • unfuckwithable
Re: Why don't my gears work properly?
« Reply #18 on: July 21, 2020, 12:59:18 pm »
my guess is that the hanger is not aligned as it should be. fwiw, campag derailleurs are even closer to spokes (by about 2mm) and would definitely foul the spokes - which is not right.

or spokes really loose and the wheel floppy - but i hope not.

Adam

  • It'll soon be summer
    • Charity ride Durness to Dover 18-25th June 2011
Re: Why don't my gears work properly?
« Reply #19 on: July 21, 2020, 07:20:49 pm »
Work perfectly when the bike is upside-down.

Have you tried testing it right way up in a workstand?
“Life is like riding a bicycle. To keep your balance you must keep moving.” -Albert Einstein

Re: Why don't my gears work properly?
« Reply #20 on: July 21, 2020, 08:07:02 pm »
I recall a similar issue which turned out to be a faulty limit screw.  For some unfathomable reason it would slowly undo itself.  I noticed one day that the screw had gone walkabout.  Fortunately I never had a mech/spokes mash up mainly because of my cable adjustment.

A screw salvaged from an old mech sorted it

Re: Why don't my gears work properly?
« Reply #21 on: July 22, 2020, 12:02:26 am »
limit screws on some mechs these days come with preapplied threadlock paste on them. If this fails or comes off the screw will tend to move in a bad way.

Buying a new gear hanger is never a bad idea (good to have a spare) but is no substitute for checking the alignment properly; if the frame is a bit pony, a new hanger can sit at a funny angle and create running issues too.

I had another thought also, which was that there might be a little free play in the freehub bearings...?  This can force you to set the RD up slightly differently from when there is no such free play.

cheers

Re: Why don't my gears work properly?
« Reply #22 on: July 22, 2020, 04:30:42 am »
They all do that sir. I have a Boardman Pro Carbon which I bought way back in 2014. It’s always done what you describe there. I’ve never had it actually go into the spokes to the point it wrecked the mech, but it seems to be a bit of a ‘quirk’ with those frames.
Loving life with a beautiful Bianchi.

Re: Why don't my gears work properly?
« Reply #23 on: July 22, 2020, 06:59:35 am »
They all do that sir. I have a Boardman Pro Carbon which I bought way back in 2014. It’s always done what you describe there. I’ve never had it actually go into the spokes to the point it wrecked the mech, but it seems to be a bit of a ‘quirk’ with those frames.
That rather suggests the "direct power transfer"* stays are as stiff as wet spaghetti!

*Boardman bikes are absolutely covered in naff logos and acronyms
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Why don't my gears work properly?
« Reply #24 on: July 22, 2020, 08:14:01 am »
flexible plastic bike...?

Surely not..... ::-)