Aftermarket derailleur pulleys.
If you’ve been around a while, you’re probably in one of two schools of thought when thinking about rear derailleur pulleys.
One school of thought is that derailleur pulleys is an area ripe for efficiency gains. Some might remember the Bullseye sealed bearing pulleys from a few decades ago, with NMB 6260 sealed cartridge bearings and anodized colors. Bullseye would advertise its pulleys to save about a hundred feet of climbing in 100 miles, and the ad was effective in winning over anyone who liked the idea of $27 pulleys that came with some “free speed.”
Read the full story HERE. Find out if our pulleys are pure science or pure bullshit?