Is it time for a new shock cord?

[GreenStratMan]

Hi chaps, I’ve just got my new spring balance and checked the tension of the shock cord. It initially read 1.5kg. I’ve had to shorten the cord by about 10 inches on each side to get it to read 2.5kg. Does this mean there is insufficient elasticity left in the cord?

Many thanks.

[Nomath]

I don't think there is something wrong with a cord tension of only 1.5-2.5 kg (more correctly: 15-25N) as long as there is no slack in the chain during the recovery. The main purpose of the shock cord is to keep the chain tensioned on the sprocket wheel during the recovery. A well-oiled chain can do with less cord tension. Excess cord tension is just working against you in the drive phase.

You will probably need a higher tension with a high stroke rate.

[Ombrax]

As NM says above, the only reason to replace your elastic cord is if the chain doesn't retract fast enough on the recovery. If it does, then it really doesn't matter how low the tension is at the handle.

[Carl Watts]

You cannot shorten it, if its low tension on its factory length then its stuffed. Get a new cord and make sure its not a white one.

[Ergmeister]

I've found the best indication of a bungee needing replacement is chain slapping on the recovery when you are at 34+ strokes/minute. This assumes that your hands are smooth and not "rowing over a barrel" - which means your hands are sliding back and forth on an even plane on drive and recovery. Many coaches will put a piece of white tape on the side of the slot where they want the chain to be on drive and recovery. It is helpful. Taking 10" out of each end of your bungee is huge and I'd definitely replace it if it were me. Just out of curiosity, what color bungee cord is on there now and what color "tape" is on the cut ends?

[GreenStratMan]

I've found the best indication of a bungee needing replacement is chain slapping on the recovery when you are at 34+ strokes/minute. This assumes that your hands are smooth and not "rowing over a barrel" - which means your hands are sliding back and forth on an even plane on drive and recovery. Many coaches will put a piece of white tape on the side of the slot where they want the chain to be on drive and recovery. It is helpful. Taking 10" out of each end of your bungee is huge and I'd definitely replace it if it were me. Just out of curiosity, what color bungee cord is on there now and what color "tape" is on the cut ends?

Thanks chaps.

I’ve just ordered one. It’s a 20 year old model C, I don’t know it’s service history. It only had 1000k on the clock when I got it in March. But elastic stuff can break down over time.

The cord in it is either black or dark grey. There is no tape on the ends.

I got the machine for nothing so it owes me nothing;-)