Originally Posted by
peugeot84
Hi new to bike building so need some help please. Project is a Peugeot 531 P frame and sourcing appropriate components. Got 48 T / 36 T chainrings a 6 speed freewheel 12 T - 17 T, rear mech is a simplex SX610 which seems to working ok. The chain tension is correct when on the big chainring but way too slack when on the small ring. Is the rear mech not working properly or is it not compatible with the gearing I've got ? Any advice appreciated.
You have a 12 t difference up front, a bit large, but not unprecedented.
Very close out back.
My guess assuming that the rear derailleur mount is aligned… is that you could remove some length of chain, the goal to get the upper jockey wheel closer to the cogs while still allowing the 48-17 and 36-12 to have reasonable capacity. I would gamble and take out three links of chain.