6/8/14 2:57 PM

Threw the timing chain today. My motocross reflexes came to the rescue. (I think)

I expected it to be looser that it was when I popped it back on after some flailing. But looked pretty taught still. I jumped out of the saddle for a hard acceleration @ about 20mph and did the bike saddle spaz thing to stay on.

So is this a no no on the Tandem? Sprint level hard pushes? I hammered it, and glad slamming back down on the saddle did not include a gland incursion!

Elaine did not panic, in fact she was awesome back there until the very end of the 30 miles. Hard little up hill after a longer grade. I said push, and felt her legs say fook you to both of us and she was in zone 4. ;)

I suspect a slightly loose chain and such a long bike flexing when I jumped on it hard caused it.
I probably won't do that again...

Luckily, no damage to the bike beyond a crank scratch.

We also hit the bottom of a broken bottle I did not see, bottom up thankfully. Brand new Gator on the back, GP All Season front. Super glad the front did not flip it over for the back to get cut. Very good luck I would say.

Last edited by Sparky on 6/8/14 4:05 PM; edited 1 time in total

6/8/14 3:38 PM

I dunno, never tried it. I captained a tandem for years with my wife and others, raced on it a few times, and never tried a standing sprint. The reason was that I assumed it would be a disaster unless both riders sprinted, and could coordinate the effort, which would take practice, and we never practiced it.

If you were standing and sprinting with your wife sitting on the back, I really cannot see that ending well....

6/8/14 4:07 PM

More like a gap closing out of the saddle effort. A few seconds of drop hammer just out of the saddle. No real rocking the bike from side to side. The stoker kind of like a gyro back there pretty much.

So maybe calling it a sprint was a bit of a stretch. Startled me more than Elaine to be sure...

6/8/14 4:28 PM

I think you found one of the donts for an older steel tandem. If she stood too, I doubt it would have jumped off. This is one of the arguments for small timing chain rings, but most feel larger rings are more efficient.

I did that on a Cannondale tandem no problem, but I'm sure yours rides nicer without a suspension seatpost mandatory for the stoker.

6/8/14 8:23 PM

Should the timing chain be same tightness as a Fixed/SS ? That is what I was assuming pretty much.

6/9/14 4:06 PM

My wife and I have been riding tandems for over 30 years, and we quite frequently both get out of the saddle together - more to give our arses a rest than to purposely sprint, but the effect is the same. I can't recall the timing chain ever coming off, and we've had several different tandems over that time. Maybe your timing chain is too slack - if your timing chainrings are reasonably concentric - not always a given - then with the chain not overly tight at any point in the crank rotation, you shouldn't be able to get more than about half an inch of vertical movement in the chain anywhere else in the rotation if you try to waggle it at the midpoint between the chainrings.

6/9/14 4:25 PM

I was reading how to loosen the chain rings and tap the chain to center the rings on the spiders as best as they can get centered/reducing any eccentric in the system as much is possible.

So after reading about the techniques appropriate to center and tighten the chain properly, I realize that my comment that the chain seemed pretty tight when I popped it back on may not be entirely true. It may have been on high lobes, so to speak and be a lot looser in the opposite condition/revolution etc. So some shop time in the garage for me, and some learning the ring centering trick etc. Hope the eccentric bottom bracket is not in an un co-operative state... As in froze... I doubt it has been touched since the Tandem was new... I am sure it has not been considering it had 12 miles on it when we got it.

6/9/14 4:57 PM

Having had several new tandems, I was surprised by the timing chain stretch characteristics. They stretch in the first 20 miles to maybe 90% of what they are ever going to strecth to. After the first ride or 2, I had to retension it, but never again afterward.

I once had daVinci cranks, and they have a 1 piece spyder/chainring, and they did not have a high/low spot during rotation.

6/9/14 5:55 PM

Don't

Ride a Havnoonian for a century with JP. Thing flexed in places I didn't know a steel bike could flex.

6/10/14 8:18 AM

The eccentric BB was easily rotated after loosening the set screws. I was thankful for that and it not being stuck or anything. But it sat in the original owner garage except for two short rides before we got it.

The timing chain ring/chain high/tight spot was minimal, so I did not diddle the rings to attempt to center them additionally.

But I retract my statement that the chain was [seemed?] tight enough. I guess I am used to a much shorter run on a fixie. After Googling correct technique for tightening I realized this.

Just happy throwing it at 20MPH did not do worse things on several levels, ;)