My hub gears wont shift - what's up?
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- Location: Maastricht, Netherlands
My hub gears wont shift - what's up?
This picture shows the inside of my bike hub on the side of the brake. In the centre is a nut thing that holds in the gubbins on the other side, where the rear sprocket is located. It is a hub with internal gears and there is another nut located on the other side (the sprocket-side) which keeps the sprocket and splined-sprocket holder in place, on top of a couple of springs and sets of ball-bearings. My problem is that the gears are not shifting (and the shifter lever is difficult to move) and I'm having trouble determining how tight each nut should be. It moves to the lowest gear easily enough, but if I want it in high gear, I have to keep back-pedaling and going over bumps. Too tight, and it seems to stop the wheel from being able to turn at all, and too loose and the gears stop working. Does anyone have experience with these fickle internal gear systems? It's a SRAM super 7 and the clickbox is fine.
- 7_lives_left
- Posts: 798
- Joined: 9 May 2008, 8:29pm
- Location: South Bucks
Hi seanspotatobusiness
I have a SRAM Spectro S7 Hub on my old bike. I suspect this is similar,
if not the same. Mine is without the hub brake however.
I have never dismantled it, the exploded view in the manual page on the web
was scary enough to discourage me from trying that.
When I had problems with gear changing after refitting the back wheel,
I found it was one of two things.
First was I had the chain tension too high. This made the gears stick.
I could change up to a higher gear, but changing down was troublesome.
Second was mis-seating the red plastic clip that slides over the axle and
that also mates with the click box. I failed to get the red clip to slide in to
the keyway/collar that surrounds the tiny rod in the center of the axle
that selects the gear. The symptom was that the gears were totally jamed,
couldn't change up or down.
Neither of these sound like your problem though.
These nuts you are tightening, are they the outer most nuts holding the
wheel in the drop outs? I never had a problem with these being too tight.
The bike has horizontal drop outs, so the tighter the better in my case,
to stop the wheel shifting.
I have a SRAM Spectro S7 Hub on my old bike. I suspect this is similar,
if not the same. Mine is without the hub brake however.
I have never dismantled it, the exploded view in the manual page on the web
was scary enough to discourage me from trying that.
When I had problems with gear changing after refitting the back wheel,
I found it was one of two things.
First was I had the chain tension too high. This made the gears stick.
I could change up to a higher gear, but changing down was troublesome.
Second was mis-seating the red plastic clip that slides over the axle and
that also mates with the click box. I failed to get the red clip to slide in to
the keyway/collar that surrounds the tiny rod in the center of the axle
that selects the gear. The symptom was that the gears were totally jamed,
couldn't change up or down.
Neither of these sound like your problem though.
These nuts you are tightening, are they the outer most nuts holding the
wheel in the drop outs? I never had a problem with these being too tight.
The bike has horizontal drop outs, so the tighter the better in my case,
to stop the wheel shifting.
- hubgearfreak
- Posts: 8212
- Joined: 7 Jan 2007, 4:14pm
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- Joined: 9 Jan 2007, 2:44pm
I have a Sachs Spectro 7 (predecessor of the SRAM) I've never really had any problems at all ( so long as I got all the bits and pieces correctly positioned after a puncture or similar) and I'm not sure I understand your problem but when I got mine, the nice chap at Roman Road Cycles who were then the distributors explaned there could be problems if there was too much packing on the axle on the clickbox side. He said the best way was to discard the washer and treat the protective arm as the washer.
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- Joined: 8 May 2008, 6:01pm
- Location: Maastricht, Netherlands
7_lives_lighter: no, the nuts I'm talking about aren't holding the hub in the fork, but rather holding the ends of the hub together. If you remove the drum brake section (on mine, not yours), you reveal a nut that holds the cogs 'n' stuff inside the hub. It's the same on the other side, but a different design of nut.
Gearfreak: I've always tightened the clickbox grub screw as tight as I could and not had this problem, but I'll bear it in mind. I'd imagine that in different designs, this may not be an issue.
thirdcrank: There could be something in that. I think I might have already lost the washer (if I had it in the first place) and the protective arm does indeed function as the washer. However, this problem first occurred in its seemingly unsolvable form (I've had it before but only needed to tighten something, which now isn't solving it) when I added a chaincase which involves extra packing on the clickbox-side. I'll try that next (there may be a delay, since I might have done something to the bearings while trying to fix this...)
Gearfreak: I've always tightened the clickbox grub screw as tight as I could and not had this problem, but I'll bear it in mind. I'd imagine that in different designs, this may not be an issue.
thirdcrank: There could be something in that. I think I might have already lost the washer (if I had it in the first place) and the protective arm does indeed function as the washer. However, this problem first occurred in its seemingly unsolvable form (I've had it before but only needed to tighten something, which now isn't solving it) when I added a chaincase which involves extra packing on the clickbox-side. I'll try that next (there may be a delay, since I might have done something to the bearings while trying to fix this...)
- 7_lives_left
- Posts: 798
- Joined: 9 May 2008, 8:29pm
- Location: South Bucks
@seanspotatobusiness
I had a look at the SRAM tech manual here
On page 59, top right hand corner, there is a table titled "trouble shooting".
One of the entries in the table reads:
Probelm | Cause | Remedy
Shifting Difficulties | Too much additional axle attachments between hub and axel nut | Begining of axle thread must be visible in front of axle nut.
What do you think?
I had a look at the SRAM tech manual here
On page 59, top right hand corner, there is a table titled "trouble shooting".
One of the entries in the table reads:
Probelm | Cause | Remedy
Shifting Difficulties | Too much additional axle attachments between hub and axel nut | Begining of axle thread must be visible in front of axle nut.
What do you think?
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- Joined: 8 May 2008, 6:01pm
- Location: Maastricht, Netherlands
7_lives_left wrote:@seanspotatobusiness
I had a look at the SRAM tech manual here
On page 59, top right hand corner, there is a table titled "trouble shooting".
One of the entries in the table reads:
Probelm | Cause | Remedy
Shifting Difficulties | Too much additional axle attachments between hub and axel nut | Begining of axle thread must be visible in front of axle nut.
What do you think?
Thanks for looking that up for me. I have now only the nut and protective arm between the fork and the clickbox (the thread is thus visible before the axle nut). I can now shift between gears 1-3/4 (three or four) but not higher. The gear lever works with little resistance (no more than usual, I think) but moving the lever to the higher positions doesn't translate to a gear beyond three or four. I wonder if the hub is now in the wrong place on the axel.
Has anyone any idea how the gear changing works? There are two pins, one inside the other with a slit in the other one, which a nubin on the red plastic clickbox guide thing fits into. How do the pins translate into gear changes? Do they always move together or does one move one increment and then the next one follows on the next gear?
It is possible that I have moved the hub too far on the axel, away from the clickbox (this goes back to those nuts I was talking about tightening on the hub - hub nuts? - If I loosen the "hub nut" at the brake-end and tighten at the clickbox-end, then I'm shifting the entire hub on the axel. I'm not sure what the optimal alignment is though. If I tighten those nuts too much, the whole thing seizes up and wont turn on the axel but if the nuts are too loose, the two ends wobble on the axel (so the whole wheel wobbles). It seems impossible to get right, especially since while putting the wheel in, the nuts seem to loosen sometimes.
- hubgearfreak
- Posts: 8212
- Joined: 7 Jan 2007, 4:14pm
seanspotatobusiness wrote:It is possible that I have moved the hub too far on the axel, away from the clickbox
i don't think so, the click box is positioned by the red thing isn't it. the red thing sits on a band machined into the axle, and the clickbox onto it. therefore the CB cant go in (towards the centre of the hub) too far
just out of interest, how many miles have you done & how old is it?
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Well, the clickbox certainly can't go too close to the middle, but (I'm guessing that) the hub itself could move too far from the clickbox? Somewhere along the axel must be something that gets prodded by the pins (which are in turn molested by the clickbox). That something that gets prodded by the pins must transmit somehow to the magic bits inside the hub and if the hub is moved too far towards the brake-side (away from the clickbox side), I surmise that this could reduce the number of gears that I can access? Not sure.
Anyway, I bought the bike second hand nearly two years ago. I'm not sure how old it is or how to find out. I know only that it is a Batavus (make) Cambridge (model) and I must have gone a very, very long way on it (not as much as a cycling-enthusiast does in two years but still). I have no cycle-computer so I might guestimate two to three thousand miles? I use it for getting to university and for my shopping (it has a pannier on the back). Actually it's Dutch and I'm attending university in the Netherlands to avoid the high tuition fees in the UK.
Anyway, I bought the bike second hand nearly two years ago. I'm not sure how old it is or how to find out. I know only that it is a Batavus (make) Cambridge (model) and I must have gone a very, very long way on it (not as much as a cycling-enthusiast does in two years but still). I have no cycle-computer so I might guestimate two to three thousand miles? I use it for getting to university and for my shopping (it has a pannier on the back). Actually it's Dutch and I'm attending university in the Netherlands to avoid the high tuition fees in the UK.
- 7_lives_left
- Posts: 798
- Joined: 9 May 2008, 8:29pm
- Location: South Bucks
I am note sure I expressed myself clearly in the earlier post. You can download a copy of the SRAM manual from their web site using this this link here
No I think seanspotatobusiness is on to something. Yes the click box and the red clip are positioned by the band machined on the axle. That will happen so long as you have enough axle sticking out. But there are also 'bits' halfway along the axle that have to line up with matching 'bits' attached to the inside of hub casing. If the hub nuts (over locknuts?) have shifted along the axel over time, maybe the axle and hub casing no longer line up. I'm looking at the figure on page 53 but I can't see a dimension that shown the position of the axle relative to the casing or the hub nuts. Perhaps I am wrong.
I don't know what's wrong, but that is an interesting result. I'll try and explain. The hub has 7 gear positions. However it only has 3 planetary gears inside. By some trick that I don't understand, each of the three planetary gears gets used twice. In positions 1, 2 and 3 they
gear down. In positions 5, 6 and 7 they gear up. We skipped position 4, that's direct drive or a ratio of 1:1 where none of the planetary gears are used but the sprocket turns at the same rate as the wheel.
If positions 1-4 are working it looks like gearing down and direct drive work, but gearing up doesn't. But I don't know why.
It's not that complicated. The inner pin is the important one. It slides the planetary gears along the axle to select the gear position. The outer pin with the slot in it doesn't actually move. It is just there to guide the arm in the clickbox that pushes the inner pin in and out so that the arm does not slide off the end on the inner pin.
That just about covers all my knowledge of hub gears I'm afraid.
hubgearfreak wrote:seanspotatobusiness wrote:It is possible that I have moved the hub too far on the axel, away from the clickbox
i don't think so, the click box is positioned by the red thing isn't it. the red thing sits on a band machined into the axle, and the clickbox onto it. therefore the CB cant go in (towards the centre of the hub) too far
No I think seanspotatobusiness is on to something. Yes the click box and the red clip are positioned by the band machined on the axle. That will happen so long as you have enough axle sticking out. But there are also 'bits' halfway along the axle that have to line up with matching 'bits' attached to the inside of hub casing. If the hub nuts (over locknuts?) have shifted along the axel over time, maybe the axle and hub casing no longer line up. I'm looking at the figure on page 53 but I can't see a dimension that shown the position of the axle relative to the casing or the hub nuts. Perhaps I am wrong.
seanspotatobusiness wrote:Thanks for looking that up for me. I have now only the nut and protective arm between the fork and the clickbox (the thread is thus visible before the axle nut). I can now shift between gears 1-3/4 (three or four) but not higher. The gear lever works with little resistance (no more than usual, I think) but moving the lever to the higher positions doesn't translate to a gear beyond three or four. I wonder if the hub is now in the wrong place on the axel.
I don't know what's wrong, but that is an interesting result. I'll try and explain. The hub has 7 gear positions. However it only has 3 planetary gears inside. By some trick that I don't understand, each of the three planetary gears gets used twice. In positions 1, 2 and 3 they
gear down. In positions 5, 6 and 7 they gear up. We skipped position 4, that's direct drive or a ratio of 1:1 where none of the planetary gears are used but the sprocket turns at the same rate as the wheel.
If positions 1-4 are working it looks like gearing down and direct drive work, but gearing up doesn't. But I don't know why.
seanspotatobusiness wrote:Has anyone any idea how the gear changing works? There are two pins, one inside the other with a slit in the other one, which a nubin on the red plastic clickbox guide thing fits into. How do the pins translate into gear changes? Do they always move together or does one move one increment and then the next one follows on the next gear?
It's not that complicated. The inner pin is the important one. It slides the planetary gears along the axle to select the gear position. The outer pin with the slot in it doesn't actually move. It is just there to guide the arm in the clickbox that pushes the inner pin in and out so that the arm does not slide off the end on the inner pin.
That just about covers all my knowledge of hub gears I'm afraid.
- hubgearfreak
- Posts: 8212
- Joined: 7 Jan 2007, 4:14pm
7LL, i am amazed at your knowledge, it goes much deeper than mine, certainly. thanks for the lesson, i know only that mine works, and works well.
both here have a date stamped onto them. has yours not?
it may well be 20 years old and have covered 10s of 1000s of kms. i would be tempted to either take it to a specialist (easier for you if you attend uni in the nederlands) or buy a new hub or even wheel
where do you study?
seanspotatobusiness wrote: I'm not sure how old it is or how to find out.
both here have a date stamped onto them. has yours not?
it may well be 20 years old and have covered 10s of 1000s of kms. i would be tempted to either take it to a specialist (easier for you if you attend uni in the nederlands) or buy a new hub or even wheel
where do you study?
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I'm sure hubbers is right.
I think the problem in the UK would be finding a bike shop that knew anything about these at all. I'm not saying such places don't exist, just that they are the exception. Even if you found somebody who knew, they would say that spares are not easily available in the UK.
I fancy that Holland would be the opposite.
I think the problem in the UK would be finding a bike shop that knew anything about these at all. I'm not saying such places don't exist, just that they are the exception. Even if you found somebody who knew, they would say that spares are not easily available in the UK.
I fancy that Holland would be the opposite.
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- Location: Maastricht, Netherlands
I study in Maastricht; one of the south-most municipalities.
I have more information that might yeild a solution. When I back pedal the bicycle upside down, it turns the wheel backwards. Something is too tight, but I don't know what... if I loosen up the hub then the whole wheel be wobbly?
There's also this cover around the clickbox-side hub-nut which is loose. It rattles while turning the peddles, and when it moves away from the hub, the drive disengages and the peddles jerk forwards. It covers some ball bearings. I made this image to make it clearer (my camera is rubbish). How do I keep that cover in place? The bike shop doesn't open until Tuesday (national holiday on Monday) so I'd like to try to fix it before then.
[/url]
I have more information that might yeild a solution. When I back pedal the bicycle upside down, it turns the wheel backwards. Something is too tight, but I don't know what... if I loosen up the hub then the whole wheel be wobbly?
There's also this cover around the clickbox-side hub-nut which is loose. It rattles while turning the peddles, and when it moves away from the hub, the drive disengages and the peddles jerk forwards. It covers some ball bearings. I made this image to make it clearer (my camera is rubbish). How do I keep that cover in place? The bike shop doesn't open until Tuesday (national holiday on Monday) so I'd like to try to fix it before then.
[/url]
- 7_lives_left
- Posts: 798
- Joined: 9 May 2008, 8:29pm
- Location: South Bucks
I removed my wheel from the frame then removed the dark grey plastic dust cover. I get a view just like in your figure. The piece in purple is attached to the red part. I am guessing it is some kind of cover to keep dirt out of the bearing. Perhaps it's just a press fit. It's strange that it should have come away. Is that a ball race behind the purple piece? Is it intact? Is there any marking on the inside of the purple piece that might explain why it has become detached?
I think Hubgearfreak and Thirdcrank are right, this is one for your friendly neighbourhood bike mechanic.
That's an impressive drawing you did, what software did you use to make it?
I think Hubgearfreak and Thirdcrank are right, this is one for your friendly neighbourhood bike mechanic.
That's an impressive drawing you did, what software did you use to make it?
I think your problem is that nut on the right, actually a bearing cone, has come unscrewed a bit. It should not be loose at all, but should be screwed up tight against a shoulder on the axle inside the hub. The loose dust cover has also most likely been dislodged by excess movement of that nut/cone.
This nut can be loosened if the axle rotates in the frame when you're pedalling. This can happen if the anti-rotation washers are not fitted correctly or if only one is fitted and the tab (that is supposed to engage with the dropout slot) fails under the force of pedalling, which in some gears exerts a very strong reaction torque on the axle. Even with both washers correctly fitted, there is a likelihood of some slight axle twisting, taking up any slack permitted by the washer, the first time you push hard after fitting the wheel. (However the direction of twist would loosen the nut in high and tighten it in low gear, in which you are likely to pedal hardest, so it ought not to matter). As you have removed one such washer already, your hub is more vulnerable to this sort of thing.
You need to unscrew the nut on the left a bit, to create enough slack in the bearings so you can srew the right nut fully home. Snag is, there's not much of a spanner flat to get hold of to turn it with.
This nut can be loosened if the axle rotates in the frame when you're pedalling. This can happen if the anti-rotation washers are not fitted correctly or if only one is fitted and the tab (that is supposed to engage with the dropout slot) fails under the force of pedalling, which in some gears exerts a very strong reaction torque on the axle. Even with both washers correctly fitted, there is a likelihood of some slight axle twisting, taking up any slack permitted by the washer, the first time you push hard after fitting the wheel. (However the direction of twist would loosen the nut in high and tighten it in low gear, in which you are likely to pedal hardest, so it ought not to matter). As you have removed one such washer already, your hub is more vulnerable to this sort of thing.
You need to unscrew the nut on the left a bit, to create enough slack in the bearings so you can srew the right nut fully home. Snag is, there's not much of a spanner flat to get hold of to turn it with.
Chris Juden
One lady owner, never raced or jumped.
One lady owner, never raced or jumped.