When the chain comes off during folding, the cause must be found before riding again. For the chain coming off when folding the folding bike, the causes are: chain tension, derailleur position, and chain length. The chain dropping off during folding is usually a sign of incorrect tension or a derailleur that is not secured.
Cause 1: Chain Tension
A chain that is too loose can come off when folding. For the chain tension on the folding bike, the chain should have about 10–15 mm of slack. A chain that is too tight stresses the bearings; too loose and it comes off.
Cause 2: Derailleur Position When Folding
If the bike has a derailleur, the chain can come off when the frame is folded. For the derailleur position when folding, check whether the derailleur cage touches the frame or the chain. Some folding bikes require the chain to be placed on a specific chainring before folding.
Cause 3: Chain Length and Wear
A worn or incorrectly sized chain can come off. For the chain length on the folding bike, check the chain for wear with a chain checker. Replace the chain if it is stretched beyond 0.75%.
| Cause | Symptom | Solution |
|---|---|---|
| Chain too loose | Chain falls off easily | Tension the chain, check the tensioner |
| Derailleur position | Chain comes off when folding | Place the chain correctly before folding |
| Chain wear | Chain skips, comes off | Replace the chain |
| Chain length | Chain too long or short | Adjust chain length |
Preventing the Chain from Coming Off
For the prevention of chain dropping on the folding bike, check the chain tension regularly, place the chain correctly before folding, and replace worn chains in time.
Frequently Asked Questions
Why does the chain come off when folding?
Usually because of incorrect chain tension, the derailleur position, or a worn chain. Check all three before riding again.
How tight should the chain be on a folding bike?
About 10–15 mm of slack. Too tight stresses the bearings, too loose and the chain comes off.
Can I ride with a chain that keeps coming off?
No. A chain that comes off can block the wheel or cause a fall. Find the cause before riding again.
How often should I check the chain?
Every few hundred kilometres with a chain checker. Replace the chain when it is stretched beyond 0.75%.
