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Chain slipping from chainring after conversion to apex 1x11

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Chain slipping from chainring after conversion to apex 1x11

Old 09-26-20, 11:06 AM
  #1  
nioann
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Chain slipping from chainring after conversion to apex 1x11

Hello everyone,
I have a cboardman hybrid pro. The bike was originally set up with a 10 speed 11-28 cassette and two chainrings 50/34 at the front. These were very worn after many years of use, so I decided to convert the bike to 1x11 drivetrain. I got a mechanic to swap the cassette, shifter and rear derailleur with the SRAM apex 1 and the two front chainrings with a single 46T FSA Pro combat chainring, that is compatible with my current five bolt crankset. I also used the 114 links chain that is used for the SRAM apex 1. Note that the full apex 1 drivetrain has a 44T front chainring. The new single chainring has been positioned where the old small chainring was, with spacers. The tension on the chain seems fine to me and the mechanic.

The problem is that now the chain slips off the front chainring when the torque is high, e.g. corners or staring on a high gear. Reinstalling the front derailleur didn't help at all. Also the chainring has scratches and broken teeth after 45 mins of riding in the city, which doesn't seem right to me.

The mechanic is trying to be helpful but seems a bit puzzled, so I'd be very helpful of any help on what should we try.

Thanks!
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Old 09-26-20, 11:31 AM
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Originally Posted by nioann
The new single chainring has been positioned where the old small chainring was, with spacers.
The problem is that now the chain slips off the front chainring when the torque is high, e.g. corners or staring on a high gear.
Also the chainring has scratches and broken teeth after 45 mins of riding in the city, which doesn't seem right to me.
At first blush, this sounds like a chainline problem, which is not uncommon when going from a double to a single. This article might help.

Last edited by Rolla; 09-26-20 at 11:35 AM.
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Old 09-26-20, 01:36 PM
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Get yourself a narrow-wide chainring. If you have a 46T FSA Pro Road chainring (as the internet cannot locate a Pro combat chainring) then it's pinned and ramped for shifting-- which is basically the worst option. USAMade can have you sorted on the cheap. Plenty of other options if you want to spend more.
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Old 09-26-20, 03:17 PM
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Originally Posted by DrIsotope
Get yourself a narrow-wide chainring. If you have a 46T FSA Pro Road chainring (as the internet cannot locate a Pro combat chainring) then it's pinned and ramped for shifting-- which is basically the worst option. USAMade can have you sorted on the cheap. Plenty of other options if you want to spend more.
The ramps are probably what appear to be broken teeth.
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Old 09-26-20, 06:43 PM
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Along with a new chainring, you may also want to get a new mechanic.
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Old 09-27-20, 12:34 PM
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Good lord, I skimmed right over the part where a mechanic had looked at this. Yikes.
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Old 09-27-20, 12:45 PM
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Where does the plane of the front ring hit the cassette? If you have your bike in a stand you can just turn your front wheel to look through the spokes and sight across the chainwheel to the cassette. Should be about the middle of the stack, maybe one cog either way at most.

And a couple other questions........
  • Which side is it falling off?
  • You aren't shifting gears while in those high torque situations where the chain falls off are you?
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Old 09-27-20, 01:47 PM
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Drisotope has it right. You need a narrow wide ring. To be on the safe side add a chain guide. Done this conversion a few times at the shop and it works well with the narrow wide and chain guide.
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Old 10-19-20, 06:34 PM
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nioann
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Thank you for all the pointers!

Sorry for the late reply, I was out of London so couldn't check the bike.

If anyone knows a good mechanic in London I'd be grateful for the recommendation.

I don't have a stand, but as far as I can tell, the chainring is not far off from the middle of the cassette. The mechanic said it's placed where the old small chainring was placed.

I went for a ride yesterday, and unfortunately in addition to the chain falling off at high gears, it also doesn't change to the two lowest gears while climbing.

The chain always falls outwards, towards the pedal.

Is it possible that both the gears not changing the chain falling off caused by a short chain? I have a 114 sram apex chain that is meant for a 44T chain ring, while the one I have is 46T.

I'll definitely try the chainring suggested, if anything else can't help.

Thanks again for all the help!
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Old 10-20-20, 11:59 AM
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This is a single narrow/wide chainring installed on an Apex double crankset. It is installed in the outer position with the proper chainring bolts for a single chainring. The 1x11 drivetrain shifts perfectly and the chain never comes off the chainring. Installing the ring in the inner position is wrong and adding spacers makes it worse, so I'm not surprised that your chain falls off to the outside. Your shifting problem is most likely the result of a poorly adjusted rear derailleur.

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