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Cross Chain Gears

Old 07-03-21, 09:31 AM
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Cross Chain Gears

I was noticing during the time trial stage of the TDF that some of the Pro Tour riders seem to use the big - big gear surprisingly often. Today I have been watching Tadej Pogačar climb like an angel in the big - big gear, It makes me wonder if we have oversold the otthodoxy regarding cross chaining or is modern race bike technology more tolerant? If is just a matter of chain wear I guess the pros don't care how quickly they wear out. They certainly care about efficiency, even if it is a tiny bit of difference.

For touring, I'd think we all care about both.
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Old 07-03-21, 01:13 PM
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Zinn has written a few times about the reduced friction on bigger chainrings and sprockets because the chain links rotate on the chain pins by a smaller angle compared to the friction on smaller sprockets and chainrings. And when you are on a bigger chainring, there is less tension on the chain. Here is an example of some of his comments.
https://www.velonews.com/gear/gear-i...x-drivetrains/

So, maybe the coaches tell them to avoid smaller chainrings? Or, maybe in the heat of competition, that is the last thing he thought about.

Many of us tour on 9 speed chains, I tour on 8 speed chains. I suspect that the wider 8 or 9 speed chains do not appreciate cross chaining very much but the pros are using a lot more gears than 8 or 9 speed cassettes and have narrower chains. I would expect those narrower chains to withstand cross chaining better than the wider chains. And like you say, they probably don't care about chain life like the rest of us do.

One of the reasons that I prefer bar end shifters for my derailleur touring bikes is that when I feel my hand on the lever, I get immediate feedback that tells me if my rear derailleur is on the small sprockets or big sprockets, and that helps me avoid cross chaining.

My rando bike has a brifter for the rear, my road bike has brifters for both front and rear. I get no feedback from the shifter to warn me if I am cross chained or not. And I find I often cross chain on those bikes because I am not specifically thinking about avoiding it.
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Old 07-04-21, 10:02 AM
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Maybe with the advances in 1x drivetrains they've worked out some of the kinks and have migrated to 2x systems (pun intended).

I know that the main problem I have with cross chaining is binding the derailer or very slack chains as I often swap out narrow range clusters for more wider range cassettes. The chain length difference between small small and big big is just too great.
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Old 07-04-21, 12:51 PM
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The first derailleurs had complicated mechanisms to keep the chainline straight - but the chains of the day wouldn't really flex out of line.

https://www.disraeligears.co.uk/site...railleurs.html

Time marches on; clever folks invent clever things. One hundred and twenty-five years later we have amazingly flexible chains. The tests I've read on driveline efficiency say any increased friction from lateral chain deflection is down in the test data noise (when making use of modern, high quality poly-gear chains, natch).

Originally Posted by Tourist in MSN View Post
Zinn has written a few times about the reduced friction on bigger chainrings and sprockets because the chain links rotate on the chain pins by a smaller angle compared to the friction on smaller sprockets and chainrings. And when you are on a bigger chainring, there is less tension on the chain.
That was my thinking: Rohloff 56x21. Should help with chain life, too.


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Old 07-04-21, 04:24 PM
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Riders have been crossing for a long time. Quintana was doing it while in the lead group in today’s alpine stage. Including over one HC climb.
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Old 07-05-21, 04:13 AM
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Originally Posted by indyfabz View Post
Riders have been crossing for a long time. Quintana was doing it while in the lead group in today’s alpine stage. Including over one HC climb.
Yeah, I have been noticing it a lot in recent times and more often than just that it is likely to be a lack of care in shifting. These guys are pros and are selecting the big big for long climbs and long sections on time trials where efficiency would really matter. So I suspect they are after reduced friction of larger diameters mentioned in MSM's post.
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Old 07-05-21, 05:22 AM
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Originally Posted by staehpj1 View Post
Yeah, I have been noticing it a lot in recent times and more often than just that it is likely to be a lack of care in shifting. These guys are pros and are selecting the big big for long climbs and long sections on time trials where efficiency would really matter. So I suspect they are after reduced friction of larger diameters mentioned in MSM's post.
I assume these guys are using electronic shifting, and I assume the shifters could be set up to prevent cross chaining if they wanted to. I would not be surprised if they were aware of the friction testing and set up the shifters to allow big and big, but specifically exclude the small and small combinations in an attempt to minimize the higher wattage loss combinations.
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Old 07-05-21, 06:03 AM
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As stae said, there's the heat of the action going on, one less thing to deal (front shift) so time saved, no chance of dropping a chain with a front shift
And add in all the tech advances of chain technology and race doubles,and it just must not be a watt losing issue, or they wouldn't be doing it.

but Joe Public we see doing it have no clue, don't clean their drivetrains, and either accept or are surprised and complaining when a bike store tells them they need a new chain and cassette.
And or don't understand why their chains dislodge or jam when back pedalling or moving their bike around in the big big.

oh Stae, I also noticed the big big stuff going on while catching up on stage news so far.

Keen eyed bike nerds need only apply
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Old 07-05-21, 06:53 AM
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Originally Posted by djb View Post
And or don't understand why their chains dislodge or jam when back pedalling or moving their bike around in the big big.
Apparently when Mark Cavendish crosses the line in one of those 40+mph sprint wins and throws his hands in the air, he inadvertently whips his cranks backwards and pops the chain off.


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Old 07-05-21, 07:06 AM
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Originally Posted by tcs View Post
Apparently when Mark Cavendish crosses the line in one of those 40+mph sprint wins and throws his hands in the air, he inadvertently whips his cranks backwards and pops the chain off.


that's pretty neat.
did that happen at one of his two recent stage wins?
I've never heard commentators mention this before with sprint finishes, but that certainly doesn't mean it doesn't happen.

PS looked up and read some stuff about these incidents.
yup, pretty neat and curious combination of quick events doing this.

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Old 07-05-21, 09:03 AM
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Originally Posted by djb View Post
that's pretty neat.
did that happen at one of his two recent stage wins?
I've never heard commentators mention this before with sprint finishes, but that certainly doesn't mean it doesn't happen.

PS looked up and read some stuff about these incidents.
yup, pretty neat and curious combination of quick events doing this.
Yes it was in one of his two recent tdf wins. I saw another picture with his chain off from a previous sprint where the same thing happened. The article seemed to imply that it wasn't an unusual occurrence for Cav.
https://www.businessinsider.com/fast...ing-off-2021-7
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Old 07-05-21, 10:17 AM
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If I backpedal my folding bike with the chain on one of the bigger sprockets, it will drop the chain. Folding bikes have short chainstays, thus the side angle on the chain is more extreme when cross chained and also my chainline is a bit off. Most common when I come to a stop at a stop light and then backpedal to put my pedal in a downstroke position for when the light changes.
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