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Cervelo BB width (2018 model)

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Cervelo BB width (2018 model)

Old 02-19-18, 07:57 AM
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reqm
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Cervelo BB width (2018 model)

I've recently been having some problems with my chain getting jammed in-between the BB and the inner chain ring.
It seems to be a new problem that arose with the new Cervelo R5 frames (2018) getting wider at the downtube/BB area, leading to less clearance for the chain when it drops. The chain really gets stuck in there and requires me to unlink the chain to get it out. It's already done a lot of damage to the paint and I'm seriously getting concerned about possible cracks

My question is.. are other owners of the 2018 models having similar issues? If not, what crankset are you using? I'm currently using a Rotor 3D+ crank with Q-rings and wondering if switching to another crankset like Shimano's would create more clearance.

I've also tried 3 different chain catchers (installed by a mechanic) to stop the chain from dropping, but it hasn't helped at all =/

PS - I thought it'd be more appropriate to ask this question on Cervelo's own forum, but my membership request still hasn't been approved, despite multiple requests over the past 4 years.
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Old 02-19-18, 09:25 AM
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noodle soup
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If you are dropping your chain often, there's probably an adjustment issue.
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Old 02-19-18, 09:26 AM
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Chain catchers can be installed but unless they are stood off 1mm or so from the inside chain ring bolt retainers that are slightly proud of the chain ring plane, the chain can slip through.


Larger question is, why is your chain dropping off your inner ring to the inside of the BB? This is invariably due to an inner front derailleur stop that is too opened up which allows the FD to traverse too close to the seat tube inboard. So you have two issues. Incorrectly adjusted chain retainer if the chain falls off inboard...and...FD inboard stop set too loose which makes the chain literally shift off the inner ring inboard when effecting a shift from big ring to small ring presumably. You don't need different hardware...but rather better adjustment of what you have. Always set the inboard stop of your FR to almost slight rattle of the cage when on small chainring in front and biggest cog in back.
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Old 02-19-18, 12:23 PM
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Q rings have a reputation for dropping chains, but another note, my s2 and s3 had this issue with dropping chains off the small ring(perfectly adjusted) I changed the chain rings from fsa and rotor to shimano chain rings and havnt had a issue since, guess they just work better with their own group set?
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Old 02-19-18, 06:28 PM
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Get a chain catcher.
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Old 02-19-18, 07:49 PM
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Originally Posted by noodle soup View Post
If you are dropping your chain often, there's probably an adjustment issue.
The initial chain drop issue, which seemed to have been caused by several links getting bent when they got jammed in-between the BB/inner ring in the first place, has been resolved. Unfortunately, Q-rings inevitably drop once in a while, maybe once every few hundred shifts. I'm afraid that some of the links will end up being bent again when the chain gets jammed in there again, so I'm looking for a way to make more clearance in that area.
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Old 02-19-18, 07:57 PM
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Originally Posted by Campag4life View Post
Chain catchers can be installed but unless they are stood off 1mm or so from the inside chain ring bolt retainers that are slightly proud of the chain ring plane, the chain can slip through.


Larger question is, why is your chain dropping off your inner ring to the inside of the BB? This is invariably due to an inner front derailleur stop that is too opened up which allows the FD to traverse too close to the seat tube inboard. So you have two issues. Incorrectly adjusted chain retainer if the chain falls off inboard...and...FD inboard stop set too loose which makes the chain literally shift off the inner ring inboard when effecting a shift from big ring to small ring presumably. You don't need different hardware...but rather better adjustment of what you have. Always set the inboard stop of your FR to almost slight rattle of the cage when on small chainring in front and biggest cog in back.
Thanks for the detailed description on setting up the chain catcher + FD effectively. I'm terrified of doing my own installations, but I'm certain that the mechanic did the setup properly. He did all the installations on my other bike and that one works perfectly. The chain drop issue has been resolved for the most part now, but I'm looking to create more clearance in the BB area just in case the chain drops and gets jammed in there again in the future.
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Old 02-19-18, 08:04 PM
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Originally Posted by Dopefish905 View Post
Q rings have a reputation for dropping chains, but another note, my s2 and s3 had this issue with dropping chains off the small ring(perfectly adjusted) I changed the chain rings from fsa and rotor to shimano chain rings and havnt had a issue since, guess they just work better with their own group set?
Right.. Q-rings tend to drop once in a while no matter how well they're set up. My other bike has the same set up but I used to experience chain drops maybe once a year. Shifting consistency seems to vary from frame to frame.

Round rings, especially Shimano's, appear to be more reliable, so I'm thinking of switching back.
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