Why washer and barrel bearing design for Rear Deraileur?



FasterthanU

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Jun 29, 2004
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I just finished working on a friends SIS rear deraileur. I have to say quite frankly, I'm ****** over the way deraileur tension wheel's bearings are designed. They don't hold lube, they are subject to high friction and wear because of the poor clearance, and they require way too much servicing. I've dipped my hands into skateboard repair and don't see why deraileur wheels don't use sealed bearing cartridges-- they last forever and require no servicing. Why hasn't a change been made?!!! If you say weight savings I'll kill you! There's no way weight justifies the pathetic performance and servicing time envolved with such a primitive bearing setup. By the way, I hate Shimano's SIS line and I apologize ahead of time for not having researched the archives for past discussions on this topic. I'm needing to vent. Again, REAR DERAILEUR WHEEL BEARINGS SUCK! Please bring fourth your comments. I'd be suprised if other mechanics don't agree. Later, FasterthanU P.S.- I have a little voice in the back of my head telling me that deraileur wheels have to be able to shift slightly in order to shift efficiently. Maybe this is the primary reason of it's design? STUPID BEARINGS!!!!!!!!!! :mad: :mad: :mad: :mad: :) :) :D
 
You CAN buy after-market sealed cartridge bearing derailleur wheels. Most people balk at the relatively high price because they DON'T provide much improvement in derailleur operation, and most people don't bother to service them anyway. The existing design works well enough and lasts long enough for 99% of bikers.

Sealed cartridge bearings don't last forever, and just because they are sealed doesn't mean they don't need to be maintained.

TD
 
WOW!!!:eek: I thought I was high strung!!:D Grease 'em and leave 'em. That's what I do. So far it's worked.
 
Not high strung- just PO'd over a primitive and overlooked technical shortcoming. So far, no helpful insight into why a change has not been made. Where are the techies? Does anyone else work on other mechanical things besides bikes? Don't you see how derailleaur pulley design are so 50-years ago. Like, oh my god! -fasterthanU. :p
 
FasterthanU said:
So far, no helpful insight into why a change has not been made. Where are the techies?
It's like throwing $5 at a 50 cent problem. For one, the upper pulley needs to "jockey" (i.e. float laterally) for the index shifting to work properly, and the aftermarket sealed bearing pulleys don't address that (or at least they didn't the last time I looked at them).

The amount of drag for those pulleys is negligible, so for Shimano to make them sealed bearings would increase the cost of the RD without adding any performance benefit. I've pulled RDs apart that have obscene amounts of mileage, and those pulleys still work just fine. On the other hand, I had a Tioga revolver crank with sealed bearings that I replaced a few times.

Sometimes the simplest solution is the best one.