Salsa Beargrease Carbon Frameset XS BlackSalsa Beargrease Carbon Frameset XS Black. The Beargrease is Salsas racing fat bike. After five successful years the first production carbon fat bike has been redesigned to be better than ever. Increased tire capacity now allows the Beargrease to accommodate up to 4. 6" tires on 100mm rims and most 27. 5 x 4" tires. The Beargreases influential ride and handling characteristics are preserved while the chainstay length (440mm) remains unchanged. Rear