# 90 degree timing ??



## ignacious (Aug 23, 2008)

Our, like most, tandem has Captain and Stoker cranks 'in phase' for timing, aka 2-banger or 2-stroke. Does anybody know anything about 90 degree timing, 4-banger, 4-stroke? I can understand the concept that this would smooth out stroke inefficiencies, rounding out the up-down pedaling. Does this pose any kind of adverse torque on frame members or bottom brackets. Could it improve average climb output by conserving momentum? I can obviously see that coordination adjustments would be required. Anything other than just gimmick?? Thanks in advance.


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## wooglin (Feb 22, 2002)

Never tried it. But more than half the people who do try it stay with it so it can't be all bad. Certainly its not bad for the frame. From your other post you might want to advance the stoker cranks so when she's in the dead spot at the bottom of the stroke you're putting down the power. 

Can't hurt to try.


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## danl1 (Jul 23, 2005)

ignacious said:


> Our, like most, tandem has Captain and Stoker cranks 'in phase' for timing, aka 2-banger or 2-stroke. Does anybody know anything about 90 degree timing, 4-banger, 4-stroke? I can understand the concept that this would smooth out stroke inefficiencies, rounding out the up-down pedaling. Does this pose any kind of adverse torque on frame members or bottom brackets. Could it improve average climb output by conserving momentum? I can obviously see that coordination adjustments would be required. Anything other than just gimmick?? Thanks in advance.


There has been a lot of discussion on this topic on the tandem section of bikeforums.net. One of the major posters is a big advocate, the other is pretty firmly against.

You seem to hit on the advantages. It's also argued to be easier on the final drive train, and easier rather than harder on the frame. 

The one thing I find interesting is the emphasis that sometimes is placed on whether the captain or stoker is leading. As I see it, both generally have two legs, so it's not going to matter all that much one way or the other, will it? It would seem to be best decided on start-leg preferences, etc. 

I don't have any experience with it - to date, my stoker hasn't been willing to make the experiment. One of the supposed advantages is easier starting, but I confess I don't get that. It seems like it would also be more challenging to coordinate butt breaks, etc. My guess is that it has a higher likelihood of being 'right' if you spend relatively more of your riding time on the tandem, and so can become more accustomed to the quirks. If a significant amount of time is spent on singles, in-phase will probably translate more easily, with fewer differences to remember between the bikes.


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## sine (Mar 16, 2007)

Much depends on how you ride.

If you corner hard, stand to climb/sprint and both are experienced riders, in phase is best. 

It might benefit some teams and doubt it adds any more stress.


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## Keeping up with Junior (Feb 27, 2003)

*Try It*

Change your cranks and try it. This is a basic mechanical operation you should have the tools and knowledge to do on the road in case you drop a timing chain. Learn how your eccentric works.

We tried it for a couple of weeks and did not like it. I would suggest that you probably ought to have similar cadences if you are going to suceed with it. As you are testing one thing you might try also is to have the captain 3 or 4 teeth in advance of the stoker, thus maybe 7(?) degree timing. Might work for you if you are trying ot even out the power portion of the revolution as I am not sure the weak points are 90 degrees apart. 

You are not going to hurt your frame doing this unless you crash because you fail to have adequate pedal clearance in a tight corner.



ignacious said:


> ...Could it improve average climb output by conserving momentum?


I doubt it. Having your cranks in time (even) allows one or both of you to effectively stand as well as rock the tandem a bit. If you are slow at climbing I really doubt it relates to the timing of the cranks but instead has more to do with the riders style and ability as well as gear selection.


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## buck-50 (Sep 20, 2005)

We tried it, found one major problem- less power when starting from a dead stop.


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## ignacious (Aug 23, 2008)

I'm sorry, KuwJ, for sounding like I have no idea what I'm doing, if that is the impression you have taken. I am quite comfortable with maintaining and reparing all of my bicycles, thank you. We have a fairly major event coming up in less than 2 weeks, and I am also smart enough that I shouldn't be tweaking stuff so near an event, for both physiological and mechanical reasons, just for grins. I do, however, appreciate the information. I learned early on in my riding that understanding and maintaining my bicycle anywhere, anytime, anyhow is a very important skill. I once had to be creative enough to replace a chain pin using my multitool, a rock, and the bus stop booth.


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## Keeping up with Junior (Feb 27, 2003)

*Annoyance*



ignacious said:


> I'm sorry, KuwJ, for sounding like I have no idea what I'm doing...


Probably my poor wording and just general annoyance at folks that do not know how to maintain/repair their bike. Just a reminder to average roadside mechanics that the eccentric is fairly unique to tandems and taking that pin spanner or appropriate tool is a big help on the side of the road. Was just riding this weekend with a LBS employee whose bike I had to work on to shift into the big ring.


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