Standard 11-speed road cassettes need the slightly wider freehub body that Shimano introduced when they moved past 10 speeds. The CS-HG800 sidesteps that limitation by borrowing the cantilevered largest cog design from Shimano's mountain bike cassettes, which means it fits both 10-speed and 11-speed freehub bodies. Install it on a traditional road hub with the included spacer, or drop it directly onto an MTB hub without any adapters. This cross-compatibility opens up wheel-swapping options between bikes and makes the HG800 a practical choice for riders building around older wheelsets or sharing wheels between a gravel rig and a hardtail.

The 11-34T range delivers climbing gears that standard road cassettes can't match. Paired with a compact 50/34 crankset, you get a 1:1 ratio that makes steep gravel climbs and loaded touring manageable without grinding your knees into submission. The tradeoff is larger jumps between some cogs compared to a tighter 11-28 or 11-30 cassette—the progression runs 11-13-15-17-19-21-23-25-27-30-34, which means a 3-tooth jump from 27 to 30 and a 4-tooth jump to the 34. Riders coming from closer-ratio cassettes notice these gaps initially, but most adapt quickly once they're using the low gears on terrain that actually demands them.

This cassette requires a medium-cage (GS) or long-cage (SGS) rear derailleur to handle the 34-tooth large cog. Short-cage road derailleurs don't have the capacity. If you're running Ultegra R8000 or Dura-Ace R9100 Di2, the RD-R8000-GS or equivalent medium-cage derailleur works well. Mechanical Ultegra and 105 derailleurs in GS configuration also handle the range without issues. The B-tension screw may need adjustment to ensure adequate clearance between the upper pulley and the 34-tooth cog, but that's a quick setup item rather than a compatibility barrier.... Read More