New chainset, but chain is slipping under load. Can't work out why
This is my Carbon Topstone, have done 15,000km or so, and replaced the chain + cassette 3 or 4 times, and the chainrings twice now.
Last week I replaced the lot again, was overdue. New 48/34 FSA chainrings, 11-34 Shimano 105 cassette and KMC 11s chain, identical spec to the last setup.
Anyway, put it all back together, went for a ride. All absolutely fine, until I put some juice through the pedals and the chain came off. Tried different gear ratios, happens on both rings and across the block when I'm going north of 250w or so.
Feels like the same way the chain slips when there's a mismatch of old/new rings and an old/new chain but both are brand new.
Struggling to work out what else could be causing the issue.
It's not the freehub, have given that clean up too.
I torqued the crank bolt back to 40nm when I replaced it so don't think it could be that.
Any other ideas?
Comments
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Chain sized correctly?
I know you have cleaned up the freehub but have you inspected it, no damage or misalignment of the pawls at all?
Barring that, I am a bit stuck too, considering it is all new gear.
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I'm confused too. Had a look at the videos and played them at slowest possible speed on my biggest screen.
I cannot see the rear cassette or chain move in those shots. I'm not saying it doesn't but I can't see it. If the chain and chainrings are brand new it should be physically impossible for the chain to skip like that.
I can only think that the freehub is failing but that would cause movement. Perhaps get some Tippex or white paint and put a blob on a chain link and a blob next to it on the next sprocket on the cassette; same at front on the chainrings and repeat your video. That way you'll know what is skipping an where. Deffo not your cranks as they would be at a weird angle to each other if that happened.
Sometimes. Maybe. Possibly.
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It certainly looks like it is slipping on the front chainring as the chain seems to be stationary. Very strange.
Stupid question but is the chain/chainring on the right way around (i dont think its generally possible to get the chainrings wrong anyway)?
Correct chain length & derailleur tensioning the chain?
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Agree with the two comments above, it seems to defy logic - in the 2nd video specifically the chain and cassette very much appear not to move as the crank goes round.
The only way I could see that being possible is if the chainring was loose and was not turning, whilst the cranks were - but that would be blatantly obvious.
Felt F70 05 (Turbo)
Marin Palisades Trail 91 and 06
Scott CR1 SL 12
Cannondale Synapse Adventure 15 & 16 Di2
Scott Foil 180 -
Inner ring wrong way around, leaving too big a gap, chain falling between the rings?
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in the videos it looks like you are smallest chainring and smallest cog, i.e. worst possible way to cross-chain, possibly the chain is laying on the fd cage due, combination of that position and low tension
if you're on the smallest chainring, i'd avoid using any but the largest 3-4 cogs
may be due to the bad cross-chaining, but it looks like there's little/no tension on the chain, some rear mechs have a tab on the mount that presses against a bit on the hanger, if it's in the wrong position there's no tension, if you refitted the rear mech, check that it's correct
if all that's correct, try posting a video showing it slipping when it isn't so cross-chained
my bike - faster than god's and twice as shiny0 -
In a very non stalker-ish way 😉 i think I recognise that barn too.
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Rear derailler dosnt look like it's pulling back to put tension on the chain ,it looks like it's sagging, check all the pivots are working ,most likly the one where it bolts to the frame ,make sure its in it's proper position too ,looks too far forward ,what RD is it ?
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It's not cross chained. Looks to be 4th cog on the cassette.
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Shimano 105. Says do in the post. Those do get sticky, but I don't see how the non tensioned part of the chain can be the cause.
Nor is it the free hub pawls slipping, I don't think.
Still best bet something to do with chainring spacing, is my guess.
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You say it's non-stalkerish, but how do we know for sure?
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Well I'm currently about 1500 km away so I think he's safe for now.
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If tge chain is hanging then it won't be engaging properly on the front part of the front chainring .Pic shows the chain with a droop and by the chain position the RD looks too upright for where it is on the cassette imo
Chainline is possible but you would think it would find 1 gear that would suit it somewhere on the block the op says it's every gear ,least that's how I read it .
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Yeah I can't rule that out. But I've run with a rear mech that is way more fooked than that without issues. Also, for one reason or another, used a short cage campag rear derailleur with a compact chain set. Chain was slack in the lower 3 gears on the 34t. Again, there's enough chain wrapped over the chainring to preclude that jumping from happening.
Suspect the OP has fixed it, incidentally, because he's gone quiet.
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Or @monkimark isn't really 1500km away as he claims and has the OP and his chain slipping bike held hostage in that barn 😉
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Suspect OP hasn't fixed it. Went for a ride. Chain slipped on a climb where he was putting out 1100 Watts for 5 minutes, caused a crash now he's at the bottom of a ditch?
Sometimes. Maybe. Possibly.
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Shhhhhhh
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Unresolved. Took everything apart today and reassembled.
Noticed this weird interaction with inner ring and chain. Cleaned and relubed the (brand new) chain, didn't help.
Haven't got time to further investigate currently so going to admit defeat and book a mechanic. Sure it's something spectacularly simple.
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I'd head out the back if I were you. Dawn raid.
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That's the chain catching the ramps on the inside of the outer ring. It could be that the skipping is because the chain tension when you put the power down is enough to start a phantom shift, which then fails.
Could be the rear mech is maladjusted - should be easy to see if it is rubbing on the chain. If not, something is wrong with the chain line. Did you take the cranks off when you did the work?
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That vid certainly looks like it's lifting on the outer ring ,which would suggest the spacing between the 2 ,are they exact matches to what was on ?
Also has the crank been done with a proper torque wrench if its been off ,31 to 40nm for cannondale iirc
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looking at the last video, i also wonder if it's the wrong way around
but it looks like there're other alignment issues...
there's a pip showing on the inside of the inner ring, i'd expect that to be aligned with the crank arm, inner ring needs to be refitted 90 degrees further clockwise
the large ring looks like it is 180 degrees out of position - the blocking pin should be under the crank arm (unless the ring has two pins like some sram ones)
my bike - faster than god's and twice as shiny0 -
Haha! You've got everything on back to front! That spider is on wrong for a start. Flip it over. The big chainring needs flipping over too and rotate 180 degrees. The big chainring bolts go in from the outside.
See this pic for ref..
Put it back together properly then send us the vid you muppet - (obvs meant in the nicest possible way) 😉
Sometimes. Maybe. Possibly.
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Just to add - if the Spider is on in reverse then the grooves might not mesh properly with the crank arm and thus when force is applied to the pedal the slipping we are seeing is the crank slipping against the Spider.
See pic
Sometimes. Maybe. Possibly.
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I can't see the chain rings moving laterally, so it's not that I don't think. Nor is the position of that pin (which is there to stop the chain getting jammed inside the crank arm) necessarily significant if the rings are on the spider correctly.
If the bolts are in the wrong way around, it's possible they are sitting proud on the inside face, and the chain is catching them.
Alternatively, there are several spacer options available, so easy to have too few or put them on the non drive side. If the chain line is badly wrong that could also be a cause. On this, I have to say if you are 3 or 4 teeth up the cassette (looks like 4 to me) and the chain is rubbing hard on the inside of the big ring and trying to shift without the front derailleur, that's very much not right.
I know you "shouldn't" cross chain. But it should be at least possibly to do so without ending up crushing your knackers when the chain jumps.
I can do so on all my road bikes. That's a cross bike so the chain stay should be even longer - means it's way off l, I think.
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yes, looking at the images, it does seem an improbably ugly design
being installed back to front would explain this 😀
my bike - faster than god's and twice as shiny0 -
Thought you were right briefly, but I've got the 4 bolt spider, both inner and outer rings bolt to it from the inside. The chain catcher pin wasn't aligned with the crank as it apparently should be, but it is now and it's made no difference.
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You need to check the crank installation to rule that out. What you are showing is definitely a phantom shift, and the chain has to be rubbing the big ring. If that rubbing is happening further up the cassette than previously this is because the crank is closer to the bearing.
Can I ask if it still does it further up the cassette? My guess is not.
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If the pin on the outer ring is off I'm guessing the inner is too ,it needs to be on a certain way too .Has it been checked ? And is tge chain the correct speed/size for this set up ?
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OP says " happens on both rings and across the block " .
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