NewbieIATandem

Ok, as in the name, we're newbies. We have a new Trek T900 and have a slightly strange sound coming from our timing chaing. At least that is what we think.

It happens when the left is down so it happens quite often. What is weird is that it sound like the tire rubbing, but since it happens at various speeds and only when the left s are down...

Any clue as to what might be wrong? Should I maybe be looking for warped, bent, unaligned, etc. etc.

Could take it to the LBS, but seems so trivial to make the trip.

Thank you for helping us previously non-cycling tandemists.

Brian

Bent or worn chainring maybe? If it was my bike, I'd inspect them first. If nothing seems amiss, remove the chain and rotate each crankset to try and isolate the source.

galen_52657

Check the chain tension all the way around by rotating the pedals a complete revolution. Chain wear is uneven, so it should be adjusted at the tightest spot. Once the tightest spot is located, make sure you have a half inch or so of vertical play in the timing chain. Also try cleaning and lubing the chain. Timing chains get short changed on lube lots of times because we forget about them...they just go 'round and 'round and don't shift any gears.

Retro Grouch 

You say that it happens when your left is down. Are you saying that it happens when you are coasting with your left feet down? Or are you saying that it happens when your left foot is down on every pedal stroke? Can you tell if it seems to be coming from the front or rear of the bike?

Maury Cohen

Do make sure your timing chain is correctly tensioned. If it's sagging noticeably it's probably loose.

stapfam

Its that tyre noise that throws me, and other than a tyre rubbing, I can't think of any noise similar. One of the common problems is the cranks not being tight enough. I mean really tight. This is a problem that I know about, and it is surprising how many times I get a sound coming from the cranks at a certain part of their revolution. It is now part of my monthly check on all my bikes, and it is surprising how often an extra 1/4 of a turn can be got. The only other thing I can think of is a rubber pedal degrading or catching on a part of the frame.

Daft Punk

Get that fixed straight away! A broken timing chain will likely result in severe engine damage - bent valves and scored piston heads...

...oh wait...

...wrong timing chain.

Marco

aggie_grad

This may sound like a strange sugestion, but I did notice it on my bike. My feet are large and the crank arm would barely rub on the inside of my shoe on every revolution. It would just barely rub and I could not feel it. It will only happen when that foot is down. I shifted the cleat over and the noise went away. Just something you might look at. It could make all different sounds depending on the type of shoe you have.

Aggie_grad

NewbieIATandem

Thank you for all your suggestions. I am not the most mechanically inclined, but we think we may have it more localized to the rear . We only go about 5 miles a day, in town, and topped out at 15 mph (oooh). Doing an 18 mile leisure Sunday, so hopefully I can see something by then. I will continue to look at it.

So far:
Yes, it is when the left foot is down (or right foot is up).
Does not occur when coasting.
Have put it up on the stand and pedaled by hand, everything looks straight and doesn't seem to happen when pedaling by hand.
Might only be manifesting itself while riding as we are a combined 400 - 420 lb team, so things may not be quite so straight when we are one the bike.
The looking did help me find a slightly dragging rear brake which I adjusted.

Seeing as we only have 58 miles on the bike and no drops I don't think it is a wear issue, but certainly could be a setup, bent, adjustment issue. We really appreciate all the support and great ideas we have found on this forum.

TandemGeek

Part of what you're paying for when you buy a tandem from a dealer is their expertise and support. You're also usually entitled to at least a free 30-day / 100 mile tune-up on a new bike from most bike shops. If you're having ANY trouble with that new tandem, real or perceived, let them help you diagnose the problem as it may be one of those things that could require a "spotter" to see, e.g., someone from the bike shop riding along side.

Tandems are fickle machines that sometimes won't replicate a problem unless they are being ridden by the same riders who were on the tandem when the problem appears vs. checking it in a workstand or while a lone captain or perhaps a vastly different team combination take the tandem for a check ride.

Bottom Line: The fewer annoyances you can eliminate from a new tandem the sooner you'll be able to focus all you attention on enjoying the riding experience. If a trip to the shop isn't too much of a logistical event, it could help you and yours get to tandem-nirvana sooner rather than later.

Richbiker

Check the chainring bolts (the 4 or 5 small bolts that hold the chain ring to the crank arm). You will need an allen wrench and a special little wrench to keep the back side of the bolt from turning (called a chainring bolt spanner or wrench)

True recent story: my timing chain was also making a funny noise. I decided it was a little slack. So I did some maintenance before our next trip out, and while I was loosening the bolts for the eccentric on the captain's bottom bracket, I happened to notice a chain ring bolt missing in the front crank. Then 2, then 3 bolts were completely gone. Of the remaining 2, one had almost completely loosened, and the other was starting to loosen. That was the source of the funny noise. I have no idea why they loosened, or how long I had been riding while I was gradually dropping chain-ring bolts.

Had we gone out the door that day with the problem un-noticed, we would have had a long walk back as the chainring certainly would have fallen off. My 6 year old stoker can't steer the thing while I pedal, and I doubt she has enough power to move both of us forward.

rich

NewbieIATandem

OK, I'll break down and take it to the LBS. They are nice folks. They are just a bit out of the way. (OK, I'm whining, only about 25 miles.)

stapfam

Easy, Ride the tandem there, have it prearranged to have the lbs to check it, and then ride back to see if they have cured it.

Think you are taking the right decision as the noise that cannot be traced will annoy you until it stops when the vital part falls off.

beatle bailey

Where is there a timing chain on a bicycle**********? I only have one chain on my trike, and have never had anyone refer to it as a 'timing' chain!!

Daft Punk

I'm new at this. However, I figure from context that the timing chain is what connects the captain's (front rider) sprocket to the stoker's (rear rider) sprocket. Methinks it's called a timing chain cuz one should make sure captain and stoker pedals are lined-up - or timed - when the chain is put on.

Peace.

Marco

TandemGeek

Unless you ride a tandem trike like a Troika or Greenspeed... and I'm thinking you don't ... then you wouldn't have a timing chain. Only tandems (including triplets, quads, quints, and other multi-seaters) will have a timing chain or timing chains. Like the timing chains or belts on a combustion engine, the job of the timing chain(s) on a tandem is to cause the pedal strokes of each rider move through their respective power stroke in the correct sequence at the correct time, noting that the cranks on tandems can be placed in-phase (synchronized) or out-of-phase in a variety of configurations for a variety of reasons.

NewbieIATandem

MYSTERY SOLVED!

We finally got the tandem down to the LBS for the 100 mile tune up and took it out for a quick spin to see if the intermittent rubbing sound went away. Well, it almost did.

The guy from the LBS who has his own tandem hopped on as stoker and we went for about a 450 foot test ride and he said, "stop, I know what it is".

He had looked down while we were riding and saw only a sliver of clearance between the rear wheel and the double legged stand. He adjusted things a little more and the problem is solved!

So, it turns out the right being up was just a coincidence. It had to do with just a little bit of frame flex (hey, we're a big team). The snugging up of things at the 100 mile tune up and the shifting of things in the rear to allow for this normal flex (it looked to be about 1/16" or less while unmounted) solved the problem.

Again thank you all for your suggestions. (In particular we had a good laugh at the suggestion we ride to the LBS, get it fixed and ride it home. at somewhere in the neighborhood of 20+ miles one way, we have had one 13.5 mile ride at a stretch. Our normal rides so far have stretched from 5 to about 5.9 miles. Neither one of us was a cyclist to start, we just wanted to ride together. Maybe someday we'll do RAGBRAI, but for now, we are slowly but surely going farther and faster with more confidence. Someday we'll ride 20-30-100 miles, but right now we are still getting a feel for the great sport of tandeming and loving every minute of it. [Our kids, son 13 daughter 11 have started riding our $80 POS tandem, if they get so they want to ride tandem more than single, we will probably go much further and faster. We call our son, Captain Speed, our daughter would have to be Stoker Fear, I think I need to take Captain Speed out for a little... Captain etiquite training.])