As above, I have old sets of jockey wheels with perfect upper wheels as it’s only the lower one that wears out. Do you reckon I could use these as a lower? and if you’re saying ‘yes of course’ why do reckon they specify lower/upper if there’s no difference?

they dont specify on SRAM top or bottom and I have swapped without issue

As long as you change the internals they can be swapped. The upper one generally floats from side to side, where as the lower is fixed.

I think, Shimano ones are different, for the reason willyboy states.

It is a shimano mech, cheers fellas I’ll take a closer look.

Yeah on Shimano mechs the upper “guide pulley” floats and the lower “tension pulley” doesn’t.

I’d imagine you could run an upper as a lower but not vice versa.

😉

why do reckon they specify lower/upper if there’s no difference?

In my opinion this is another one of those situations where Shimano make it look like their parts are very specific encouraging you to keep buying their overpriced aftermarket spares for fear of anything else not being compatible.

The reason I say this is that jockey wheels from other manufacturers are cheaper, lighter, last longer and work perfectly on Shimano mechs yet are identical top and bottom. I have Aerozine ceramic pulleys at 10g a pair (a nice but not necessary bonus) but that are also cheaper than Shimano, more bling (obviously important), have better bearings and last longer. MT Zoom, Tacx, KCNC and a multitude of others are all worth a look.

Mt Zoom CNC jobbies here on shimano 10 speed mechs. Identical top and bottom.