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flexy bottom bracket messing with gears

Old 05-11-21, 02:21 PM
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flexy bottom bracket messing with gears

I ride a Bianchi megatubo Titanium that has a very flexy bottom bracket. Many of my gears cause chain rub on the fd. Is the only way around this bending the (Campy) fd cage?
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Old 05-11-21, 02:29 PM
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Can't say w/o seeing the bike in person. Who knows whether the derailleur is adjusted correctly or not? I find it hard to believe the frame is flexing that much...how much do you weigh?
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Old 05-11-21, 06:17 PM
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Originally Posted by cxwrench
I find it hard to believe the frame is flexing that much...
Could there be play in the bottom bracket bearings?
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Old 05-11-21, 06:50 PM
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Sure, could be. I'd think (hope) that would be painfully obvious but I know how things go.
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Old 05-11-21, 07:21 PM
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Having used Ergo levers since the mid 1990s and many different ft ders with them I understand that the detent steps, shifting response and chain rub can be a fine line sometimes. One thing I've done is to not use very narrow ft der cages. the other is to set the cable tension so that the lever settles into that last detent (of ft der travel) completely but no more travel can be had. This is done after setting the cage arrangement WRT the large ring and high gear combo.

But I have a very good skill/technique when shifting the front and almost never drop a chain or can't get the chain to shift. I know that this is not what many people experience or can do. (and the trend to eliminate frt shifting altogether is the result of so many riders not being able to grasp and learn how to shift the front well).

Back in the day with friction levers, symmetrical ring teeth, straight side plated chains, not sculpted cage plates and flexible frt ders we would tweak cages all the time. These days I see FAR less need and it's a rare set up that needs it. lastly I'll mention that when front indexing was being brought out (by Shimano) a little piece of instructional paper was included in the new bike packet (although not always made it's way to the rider) which diagramed the ring/cog combos where chain rub was to be expected.

Lastly I'll say that if the system can be biased somewhat to not rub is certain combos, although at the cost of other combos being worse rub prone. Andy
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Old 05-11-21, 07:24 PM
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Use the trim function of your front derailleur & quit cross-chaining.
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Old 05-11-21, 08:00 PM
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Originally Posted by base2
Use the trim function of your front derailleur & quit cross-chaining.
Looks like you missed the memo. Big/big is perfectly acceptable these days and every drivetrain is designed to let it happen. Small/small, no.
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