Owner's Manual

12
Transmission chain tension on Rohloff equipped Thorn cycles
There is always a “tight spot” on all chain drive systems; when setting chain tension there must
always be some slack in the chain at this “tight spot”. A slack chain will do no damage whatsoever, if
it is allowed to become very slack the only danger is that it may fall off. By contrast, a chain which is
too tight wears prematurely, causes premature wear to the bottom bracket assembly (possibly to
the hub too) and causes unnecessary expenditure of energy in use.
1) Do NOT re-adjust the chain tension until T1 - T2 reaches 40mm (T1-T2=40mm). The
“crude but simple, reliable and effective” system we use for locking the eccentric
depends upon the points of the screws being able to bite into the alloy eccentric… if
unnecessary chain adjustments are made, the holes created by the points will be
too close together and the eccentric will simply slip back into its previous position.
2) The chain should be adjusted before T1 T2 reaches 60mm (T1-T2=60mm). Failure
to do this makes it possible for the chain to become slack enough to fall off the
chain ring (or sprocket).
3) With a new chain (and especially a whole new transmission), it may not take very
long for 40mm of slack to become 60mm of slack but please don’t worry…this
situation will improve dramatically with the passing of the miles.
How to readjust the transmission chain tension on Thorn Rohloff
cycles (not Mercury models)
The following pages (13 and 14) show how to correctly adjust the position of the eccentric to
readjust the transmission chain tension.