Bicycle Mechanics - Jockey wheel replacment

Hi

I need to replace a jockey wheel on my Shimano 105 rear derailleur. Is there any reason to spend extra to upgrade to 2 new wheels and ceramic bearings and if so what brand do you recommend ? TIA

IMO, there's no reason to spend more than necessary for OEM quality wheels. If a pair (upper and lower) is a bargain compared to each separately go ahead and buy the pair, and either replace the lower or hold the new one back until needed.

RD pulleys are low load parts with very little loss to bearing friction. Even the simplest bronze bushing models are so close in performance to the most expensive ceramic bearing versions, that there's no way to justify an upgrade other than cool factor.

Just get another Shimano set... the top one is different from the bottom,
to make up for minor mis synch of index scheme, being on opposite ends of the cable..
top pulley has side float.

may feel you upgraded if you get Dura Ace pulleys , just to spend up a bit.

These are what you need. http://www.tacx.com/producten/derailleurwieltjes/index.dot Steel or Stainless, no need for ceramic. They have sealed bearings (I'm not positive that the steel are sealed but I believe they are) so no lubing necessary, last as long or longer than Shimano and can be found cheap on Amazon, Ebay, Discount bike sites, etc.

I've had problems with duraace pulleys. There is a steel shim and two aluminum spacers the spacers embed themselfs into the shim and cause drag. XT pulleys with the ceramic bushing tend to crack. There is no excuse for this shimano is big enough to buy custom made sealed bearings eliminating 6 parts. The problem with after market pulleys is they will only sell you two pulleys of the same size. Count your teeth.