Slight phase difference a problem?
When I was loading my tandem on the car rack last Saturday, I noticed that the cranks were slightly out of phase...maybe a chain link or two.
Is this something I should bother correcting, or is close enough not to be a problem?
I think the stoker's crank is slightly behind the captain's.
That's too bad. If you hadn't noticed, you wouldn't have to bother with it and it wouldn't matter. Now that you have, it'll drive you crazy until you correct it. If it was my bike, I'd have to fix it.
Originally Posted by tornadobass
Exactly! I'm probably going to check in my garage tonight to see if I have the right tools...just an allen wrench and a pin wrench...right?
Originally Posted by Retro Grouch
The job entails...I'd guess:
1. loosen set screws, turn the eccentric to loosen chain, remove timing chain from front crank set
2. align cranks with bottom tube
3. replace chain
4. adjust eccentric to tighten chain, tighten set screws
5. check crank alignment and chain deflection
6. find something new to worry about
The repair strategy might not work. As you take up the slack with the eccentric adjustment, the crank may rotate relative to the other.
Lazy oaf/idjit that I am, once I've turned the eccentric enough to get slack to hop the chain over a tooth, that's what I do, in the direction of the needed adjustment. Then you rotate the eccentric back to see if you got it right, do it again if needed or tighten up the setscrews. Wear gloves and you won't slime your fingers. Removing and replacing the chain will drive you crazy.
Micromanagerial types note that it is easier to get closer to perfect synchronization with larger timing chainrings, but that can introduce a number of other frame clearance problems, so it has to be considered carefully.
That's pretty much it. The hardest part is figureing out which way you need to move the front crank relative to the chain. You'll probably only have to move the chain one or two teeth. It's easiest if you keep the chain in the same place on the rear crank and try to adjust the chain on the front crank as little as possible.
A quick/fast/unauthorized way to get chain off crossover: Use a thin bladed screwdriver at chain/chainring junction. Pedal backwards. Chain pops off. Align both cranks where you want them. Re-install chain same way, but have someone hold up back end of tandem and move pedal forward and chain gets seated.
Or, loosen eccentric, etc.
However we on purpose have our cross over chain set up with pedals 90 degrees out of phase. Reason: there is always a power stroke going 'over the top.' Easier climbing (for us). Quicker get-away from lights. Stoker stays seated at stops and provides instant over the top power as we push off. Also, less tandem sway when stomping on the pedals as we do not both push hard with left foot then both with right foot, but we alternate that motion by being 90 degrees out of phase.
Yes some people say we are 'goofy footed' but been doing it successfully for over 29 years.
Pedal on TWOgether!
Rudy and Kay/Zona tandem
We are new to tandem riding and know practically nothing about it, but while we were climbing a hill a guy who was passing us on a single suggested that we move the pedals out of synch in order to have at least one of us on the power stroke more of the time. Later that day the timing chain broke, so when I replaced it (with bombproof single speed chain) I decided to give it a try. I didn't want to go too far for fear of losing cornering clearance or making standing too awkward, but I did offset the pedals by 10 or 20 degrees. It didn't seem to affect our ability to stand smoothly and we both felt like our stroke became smoother and more powerful all the way around (although this is, obviously, pretty subjective). Even if we were imagining it, at least it made us FEEL stronger and smoother -- and we didn't seem to pay any penalty for it.
So long as you are leading, it's not a big deal. In fact, I always make sure my cranks are about 1 link ahead of Debbie's.
Originally Posted by tornadobass
As for the out-of-phase vs in-phase, there's a bunch of posts in the archives and elsewhere that address the topic. Some folks love it, others don't and many of them have never even tried it.
Lift the rear wheel of the ground. Derail the timing chain off one set of cranks by turning the pedals. Line up the cranks. Re-rail the chain by turning the pedals. This works if the timing chain is not over-tensioned.
Forgot about this thread...the manager of my LBS said it was intentional to just be a couple of links off to avoid dead spots. I've never changed it and it's never been a problem.
OTOH, I rode a RANS Screamer with cranks 90 degrees out of phase and it was really hard to get started because my foot would never be at the right spot by the time I got my foot way up to the pedal. I'd want that bike in phase if i rode it again.