Well, ideally you have good purchase on any kind of interface, but force wise ordinarily it's just the chain tension created by the spring of the derailleur, me thinks? Of course you could hit a bump or a pothole and the whole thing gets slapped up and down ... Not sure ...
Nice, will have a look.
Thanks Pascalo!
So you think I’m right to be cautious?
That bit needs to withstand a lot of pressure, so does need to be strong?