I have an almost new BMC Speedfox AL Two that slips in high gear. I brought it back to the bike shop I bought it from a couple of times. They said there was nothing wrong with it. The only thing they did was take 2 links out of the chain. I’ve tried everything I can think of, but nothing has worked. Hi & Lo settings, B setting, cable adjustments, new chain, even a new rear cassette. The bike has done this since new. This bike has all Shimano Deore components. I’m a senior and I don’t ride this bike hard. Very disappointed in this bike and the shop. I have read all the articles I can to find a solution to this, but no luck. Anyone have this issue and found a fix? Thanks in advance for any help?
Shimano 12spd slips in high gear
kej53
1 - 20 of 60 Posts
I have an almost new BMC Speedfox AL Two that slips in high gear. I brought it back to the bike shop I bought it from a couple of times. They said there was nothing wrong with it. The only thing they did was take 2 links out of the chain. I’ve tried everything I can think of, but nothing has worked. Hi & Lo settings, B setting, cable adjustments, new chain, even a new rear cassette. The bike has done this since new. This bike has all Shimano Deore components. I’m a senior and I don’t ride this bike hard. Very disappointed in this bike and the shop. I have read all the articles I can to find a solution to this, but no luck. Anyone have this issue and found a fix? Thanks in advance for any help?
Joined
·
24,227 Posts
That is disappointing that the shop can't figure it out for you, much harder to diagnose problems from here. The most common cause of that problem is a new chain on an older cassette but that doesn't sound right in your case.
It's not hard to install the small cog incorrectly so I guess I'd check that first.
It's not hard to install the small cog incorrectly so I guess I'd check that first.
Thanks for y
Thanks for replying. I’m quite sure it’s installed correctly. I purchased a complete Shimano cassette with chain and at first I thought it was the solution. However after trying it a few times it slipped also. I know when it’s in the highest gear it is actually only engaging a few teeth on the 10 T sprocket. It just doesn’t seem right that a Shimano drivetrain should do this. Like I mentioned I don’t even ride it that hard.
Joined
·
24,227 Posts
It definitely isn't right and for sure something is wrong with the setup. I know you're sure the 10t is installed right but if it were me I'd triple check it. Also make sure the chain or quick link isn't installed backwards. Check all the normal stuff like hanger, b- screw, etc.
Good luck!
This is probably not the cause, but it could be easy enough to try out, a sticky chain can sometimes cause slipping in high gear (I mean the smaller cogs on the cassette) with power applied. You could try lubricating and cleaning the chain really well to see if that helps? Honestly it sounds like it could be the derailleur hangar alignment or some bad components.
Joined
·
628 Posts
Joined
·
42,655 Posts
by "skipping", what behavior, exactly are you referring to?
is the chain grabbing teeth on the cog next to it? or is the chain actually slipping from one cog to the next under power? can you share any pictures of the drivetrain? especially one with the chain in the 10t cog AND sagged, as mentioned.
is the chain grabbing teeth on the cog next to it? or is the chain actually slipping from one cog to the next under power? can you share any pictures of the drivetrain? especially one with the chain in the 10t cog AND sagged, as mentioned.
Joined
·
1,715 Posts
I'm the kind of guy who only ever knows enough to throw wild ideas out...people like JB Weld and Harold are a lot more likely to get you headed in the right direction.
But -- and again, literally throwing this out for anyone to comment on.... could it be the freehub? If it's happening with a new cassette and chain as well....
Either that or the RD. Those to me are the only things in the equation left to consider if you replaced the chain and cassette....
But -- and again, literally throwing this out for anyone to comment on.... could it be the freehub? If it's happening with a new cassette and chain as well....
Either that or the RD. Those to me are the only things in the equation left to consider if you replaced the chain and cassette....
Joined
·
4,741 Posts
"slipping" but I basically have the same question, what does it mean specifically (or do they even know? do they just feel a clunk but have never actually seen it?)
generically:
The chain ridding up onto the next cog is either caused by being out of adjustment (cable adjustment, limit screw) or often sometimes by a bent derailleur hanger. Bent hangers usually only cause issues in the middle area of the cassette. Sometimes it can be caused by just very bad chain line with the front cranks. 1X is always a compromise for chain line at the largest and smallest cogs. Usually its a "pick one" scenario where the large cogs OR the small cogs work perfectly, but not both. Many people will bias the chainring to the large cogs with shimano to prevent back pedaling issues (especially 11, less an issue with 12).
Actually skipping OVER the cog is usually caused by wear or mismatched chain and cogs, but that seems not to be the case here (I am assuming the cassette and chain are genuine shimano and not 3rd party or ebay counterfeits)
Mixing new and old parts can cause a problem. If the chain is ruined for example and skipping, and you buy a new one, the cogs may now be too worn for the new chain, which makes the new chain skip. This then destroys the chain, but you think its the cogs so you buy new cogs, and the cycle continues. Small cogs are the most prone to wear if you use them a lot, and also the most prone to skipping a worn chain if you DONT use them a lot. It is a chicken and egg thing. This is why they tell you to replace them both at the same time. Now obviously "most of the time" it is fine and no one does this, but you might just have a peculiar gear usage that makes things show up that others really don't see.
More fussy things are:
B tension will reduce or increase the wrap around the bottom cog. With a 10t, you want as much wrap as possible. If it is not wrapping enough it could skip over under high load so you want the b tension looser (wound out) most likely. Some things to look for specific to shimano 12 is that the b screw plastic piece is actually on the right side of the derailleur hanger. it can easily be installed wrong, although I would HOPE a shop mechanic would notice. When it is installed wrong the derailleur can pull forward too much cause all manner of bad things.
Because of the huge offset on the upper pulley on 12s, REMOVING chain links will actually reduce the wrap around the bottom cog, and possibly make things worse. 12s is a bit fussy, and you kinda need the exact right chain length. You should not be fudging it longer or shorter to attempt to correct something.
The clutch can be bothersome sometimes. A sticky clutch can cause the cage to keep a very high tension on the chain, which in turn could cause the chain to ride up on the cogs. The motion of full suspension can tighten and loosen the clutch causing it to behave badly intermittently.
Last, when you have the clutch OFF there can be a very noticeable kick back because of the mass of the derailleur assembly when you pause pedaling or back pedal or when the suspension moves. You feel this most in the smallest cogs. This can cause the chain to derail and you would "feel" a clunk as it goes back into place. In this case, this is just annoying, but not actually a problem. You mostly want to keep the clutch ON on an FS bike.
I expect you or the shop has already checked most of these, but I would start with the hanger alignment, checking the b screw plate position and checking the clutch motion. It may also be worth a quick check on the actual frame alignment. 99% likely it is fine, but I have seen some TERRIBLE "high end" FS bikes on here (and one of my own).
Joined
·
582 Posts
True beefcakes can make a chain slip in the 10t cog. Buddy of mine was a power lifter who could do this. I told him to shift down one cog and if he’s so damn strong upsize your chainring. There’s no correction for this that I’m aware of, but this seems like a parking lot test to me and doesn’t happen in real world riding.
I agree with JBW; pretty hard to diagnose over the interwebs, but if we're bored, and throwing **** at the wall, I'll offer this:
Sticky/burred chain link. It only happens on the 10T because the chain needs that much articulation to hit the offending spot in the link.
Try back-pedaling in that gear while the bike is in a stand and look for a jump in the chain.
Sticky/burred chain link. It only happens on the 10T because the chain needs that much articulation to hit the offending spot in the link.
Try back-pedaling in that gear while the bike is in a stand and look for a jump in the chain.
Joined
·
4,741 Posts
Multiple chain and trips to the dealer makes a stiff link pretty unlikely. But you did remind me... shimano 12 chains of course are directional and the link needs to be the right direction as well. Maybe it is backwards and on the 10 it is lifting due to needing to articulate more.
Valid point.
Joined
·
660 Posts
Good point, but if the bike mechanic doesn't know Shimano 12 speed chains/links are directional, the OP needs to find a better mechanic 🤷♂️
Joined
·
4,741 Posts
Possibly, but it seems that there may be a mix of diy and shop work here.
Joined
·
24,227 Posts
I don't think that's normally true but even if so the op say's he's a senior who doesn't ride hard.
Joined
·
42,655 Posts
I'm not big on power, but IME, a poorly adjusted b-gap will allow the chain to skip over cogs, but when it's adjusted correctly, it holds well.
Joined
·
1,451 Posts
Point remains.
Joined
·
2,836 Posts
I once had similar symptoms and the culprit was the derailleur hanger was not screwed in tightly to the frame. I'm talking like quarter turn more needed on the 2 screws that fixed it to the frame.
1 - 20 of 60 Posts
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
