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#1
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Unwanted downshifts over bumps
Gears on the MTB (Shimano XT) are all set up nice, instant changes, no
noise - perfect on the road. But when pedalling over bumps (pot holes, off road etc) the chain-ring deraillieur has a tendancy to down- shift by one towards the inner-most sprocket. This is confimed in the trigger pod window as it will either have moved from 3 to 2, or from 2 to 1. To make sure I wasn't knocking the trigger I fisted the left handlebar grip - still does it. Any thoughts on where I should be looking to solve the problem - in the pod or at the mech?? Many thanks, Duncan |
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#2
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Unwanted downshifts over bumps
Duncan Smith wrote:
Gears on the MTB (Shimano XT) are all set up nice, instant changes, no noise - perfect on the road. But when pedalling over bumps (pot holes, off road etc) the chain-ring deraillieur has a tendancy to down- shift by one towards the inner-most sprocket. This is confimed in the trigger pod window as it will either have moved from 3 to 2, or from 2 to 1. To make sure I wasn't knocking the trigger I fisted the left handlebar grip - still does it. Any thoughts on where I should be looking to solve the problem - in the pod or at the mech?? Look at the cable and cable guides first of all, or flex or anything that could cause the cable to slacken. Btw, even though it's physically down to a smaller sprocket, it always seems odd to me to call shifting to a higher gear "downshifting". ~PB |
#3
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Unwanted downshifts over bumps
"Pete Biggs" wrote in
message ... Duncan Smith wrote: Gears on the MTB (Shimano XT) are all set up nice, instant changes, no noise - perfect on the road. But when pedalling over bumps (pot holes, off road etc) the chain-ring deraillieur has a tendancy to down- shift by one towards the inner-most sprocket. This is confimed in the trigger pod window as it will either have moved from 3 to 2, or from 2 to 1. To make sure I wasn't knocking the trigger I fisted the left handlebar grip - still does it. Any thoughts on where I should be looking to solve the problem - in the pod or at the mech?? Look at the cable and cable guides first of all, or flex or anything that could cause the cable to slacken. Btw, even though it's physically down to a smaller sprocket, it always seems odd to me to call shifting to a higher gear "downshifting". Maybe - but it's his front shifter which is having the problems :-) cheers, clive |
#4
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Unwanted downshifts over bumps
Duncan Smith wrote:
Gears on the MTB (Shimano XT) are all set up nice, instant changes, no noise - perfect on the road. But when pedalling over bumps (pot holes, off road etc) the chain-ring deraillieur has a tendancy to down- shift by one towards the inner-most sprocket. This is confimed in the trigger pod window as it will either have moved from 3 to 2, or from 2 to 1. To make sure I wasn't knocking the trigger I fisted the left handlebar grip - still does it. Any thoughts on where I should be looking to solve the problem - in the pod or at the mech?? The mech spring will be trying to pull towards the innermost sprocket anyway, and the only thing that restrains it is the pod. Logically, therefore, the mech is fine since it's doing exactly what it is supposed to do. (The only fault it could have would be that the spring was too strong, but that seems unlikely.) This, and the fact that the gear indicator changes as well, puts suspicion on the pod. Sounds like some clamping / restraining doohickey has worn out, but the innards of these things are not the domain of mortal man, at least not this one, so I can't offer any more insight. Shimano aren't known for making their components user- serviceable though, so I reckon you might be needing a new pod. Colin |
#5
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Unwanted downshifts over bumps
Clive George wrote:
"Pete Biggs" wrote in message ... Duncan Smith wrote: Gears on the MTB (Shimano XT) are all set up nice, instant changes, no noise - perfect on the road. But when pedalling over bumps (pot holes, off road etc) the chain-ring deraillieur has a tendancy to down- shift by one towards the inner-most sprocket. This is confimed in the trigger pod window as it will either have moved from 3 to 2, or from 2 to 1. To make sure I wasn't knocking the trigger I fisted the left handlebar grip - still does it. Any thoughts on where I should be looking to solve the problem - in the pod or at the mech?? Look at the cable and cable guides first of all, or flex or anything that could cause the cable to slacken. Btw, even though it's physically down to a smaller sprocket, it always seems odd to me to call shifting to a higher gear "downshifting". Sorry, I'd don't know what's happening to my brain these days. I was indeed thinking of rear shifting there. Anyway the advice remains the same. First of all, check for anything that could be causing the cable tension to momentarily slacken. ~PB |
#6
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Unwanted downshifts over bumps
Colin MacDonald wrote:
Duncan Smith wrote: Gears on the MTB (Shimano XT) are all set up nice, instant changes, no noise - perfect on the road. But when pedalling over bumps (pot holes, off road etc) the chain-ring deraillieur has a tendancy to down- shift by one towards the inner-most sprocket. This is confimed in the trigger pod window as it will either have moved from 3 to 2, or from 2 to 1. To make sure I wasn't knocking the trigger I fisted the left handlebar grip - still does it. Any thoughts on where I should be looking to solve the problem - in the pod or at the mech?? The mech spring will be trying to pull towards the innermost sprocket anyway, and the only thing that restrains it is the pod. Logically, therefore, the mech is fine since it's doing exactly what it is supposed to do. (The only fault it could have would be that the spring was too strong, but that seems unlikely.) This, and the fact that the gear indicator changes as well, puts suspicion on the pod. Sounds like some clamping / restraining doohickey has worn out, but the innards of these things are not the domain of mortal man, at least not this one, so I can't offer any more insight. Shimano aren't known for making their components user- serviceable though, so I reckon you might be needing a new pod. Colin You might be able to confirm this - while off the bike, try to re-create the downshift by whacking the pod only. |
#7
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Unwanted downshifts over bumps
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#8
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Unwanted downshifts over bumps
I'm not familiar with your components, but I have experienced similar symptoms, and it was down to the lever. In my scenario it was a rear derailleur changing up by itself. It was really annoying and caused a couple of crashes. It got so bad a small disturbance to the cable (like turning the bars) would change gear. Took me a while to identify the guilty component - Suntour thumb shifter - it just wouldn't stay in the 'click' positions. A workaround is to switch to friction mode instead of index mode. G. Cheers, I don't think there's a friction switch on the XT pods any more (if there ever were?). Last time I saw one of those was on my hack that had a Shimano Biopace groupset - a very nice feature too, pity they're not that common any more... Regards, Duncan |
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