Here you go. For sale:
http://weightweenies.starbike.com/phpBB2/viewtopic.php?t=23440
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That’s pretty cool.
I’m thinking of stealing the Pulleys from my son’s Trek 820 to make one up.
jaretj
The general attitude towards this modification seems dismissive by the ‘tech elite’. However, given how efficient chain drives are, it seems reasonable to me to speculate that a major portion of drivetrain efficiency loss is due to the chain wrapping around the derailleur pulleys, so this would seem an area that one might be able to save a little bit of wattage.
I could see how larger pulleys might result in less chain friction since the chain wraps around at a less acute angle. Someone in the thread mentions a half watt, this is not very encouraging, that’s not much power. That would put this pretty low on the list of cost-effective upgrades.
I would think that it would not be hard to devise a test that would evaluate the effectiveness of this modification, but a powermeter won’t work, half a watt is too small to measure with a PM.
Looking closely at the pic on your link, it appears to me the upper pulley is actually smaller than normal while the lower is larger. Wonder if this would “average out” any benefit. But hey, it LOOKS cool and it could be an excuse to spend money. 
the Shimano megapulley system uses 13tooth top and 15tooth bottom pulleys. This custom system appears to be similar. I’m wondering if the Shimano unit can be upgraded with better bearings. Might pick up one of the cheap Shimano derailleurs with the megapulleys just to play with.
Maybe a little off topic but I’m thinking ahead to 2007. Currently I have an Ultegra rear derailleur.
If I upgrade to a Dura Ace or higher grade bearings/pulleys would it make any real world difference or is that like a fraction of a watt difference?
Anybody know?
Thank you. I was interested in these.