Paul Melvin Chain Tensioner

Want to build a singlespeed without buying a dedicated frame? The Paul Melvin bolts on where the rear derailleur normally goes and lets you run a singlespeed rear wheel on bikes with vertical dropouts, including Boost and fat bikes. Made in Chico, California.

Two sealed-bearing aluminum pulleys give it 20 teeth of chain wrap, so it can also handle a double or triple up front (chainrings up to 20 teeth apart). Spacers on the mounting pivot let you adjust chainline, and the pulleys float side to side to quiet small chainline differences. The cage is wide enough for 1/8" chains.

• Material: 6061 aluminum, anodized
• Weight: 108g
• Chainline range (135/142 rear spacing): 44-52mm
• Largest rear cog: 20 teeth
• Chain wrap: 20 teeth
• Chain compatibility: current Melvins (made after 8/12/25) fit most 6-12 speed chains
• Chain tip: for 1/8" cogs Paul recommends the SRAM PC-1; for 3/32" cogs, any 8-speed chain
• Mounts to a derailleur hanger; not for fixed gear use