After less than 2 years my pulleys are dead and my B spring is probably dead. Never seemed to do much anyway, but isn't it supposed to pull the derailleur forward? It barely seems to do anything at all. Can you replace a B spring on a 105?

And if you bought a new derailleur what pulleys would you use if you wanted them to last a long time in very harsh weather?

I'm not intimately familiar with Shimano RDs, but If they have springs in the upper body, it pulls the RD back, not forward. Otherwise no upper spring is needed because the chain tension in the lower loop pulls the RD forward. BTW that lower loop tension comes from the Cage spring in the lower body. If your RD isn't being pulled forward, odds are it's related to the cage spring.

As for pulleys, I find that cheap/basic plastic pulleys running on brass plain bearings (bushing) are the toughest. One drop of oil once in a lifetime (seems that way) is all they want, and they last until worn out.

Where do you get those pulleys? And would a campy rear derailleur work with Shimano 10 speed shifters? I wonder if they last any longer.

I know that many mix bands of RD and levers, often using a "travel agent" to make it work. I've never seen the need to do things the hard way, so decide on RDs and levers as a system based on what I care about.

As for the pulleys, Shimano RDs need upper pulleys with float, whereas Campagnolo uses (used?) the same pulleys upper and lower.

Shop around keeping the basic type in mind and you'll find plenty of choices.

Yes you need a c spring for your DR to work fulley and correctly exspecialty on anything nine plus. Sense you have a mid lelvel Shimano I would say buy another DR new ones start at $25 and a good used is $15-20.

Where are you getting 105 for $25?

And when you say float, what do you mean? This thing floats, but it squeals and seems like it floats too much side to side.

Campagnolo upper pulleys have floated since at least the 9 speed era and have "upper" molded into the top one.

I think 8 cog setups worked the same but it's been too long since I owned one.

My recent B spring woes have taught me that you can replace the B spring on a 105. It's not particularly easy, but I imagine since your 105 isn't too old, you can probably still pick one of these up through a Shimano dealer, or online. You just remove the C clip that secures the B-spring tensioner plate, pull it off (be ready for it to flick around a bit) and you'll have access to the spring. You can replace it, stick the plate on with the spring end in the hole, push it down over the main bolt, and basically you'll have to turn it until the little tab on the plate can catch the notch on the mech again -- requires a fair bit of effort as you need to be pushing it down as well as twisting it. Probably useful to have a vice of some sort.

Long winded explanation, but hopefully of some use.