OneUp components has released a conversion kit for Shimano 11-speed cassettes that increases the gear range by 12.5 per cent. The kit includes a 45-tooth sprocket and an 18-tooth sprocket.

Unlike the recently released SRAM kit, which replaces the largest sprocket of the XX1 cassette, the 45 tooth sprocket on the Shimano kit will sit behind the current 40 tooth sprocket to give added climbing range. The 18 tooth sprocket will replace the current 17 and 19 tooth sprockets, keeping the total number of gears at 11.

This gives a cassette progression of: 11-13-15-18-21-24-27-31-35-40-45.

The full OneUp cassette

OneUp claims that this splits the cassette into two separate zones – climbing and descending. The climbing zone works between the 21 and 45T sprockets and has small 13-15 per cent jumps. OneUp believes these small increments will allow you to maintain climbing cadence more easily.

The descending zone operates between the 11 and 18T sprockets. This has 15 – 20 per cent cassette progression. OneUp hopes that this will reduce double tap shifting and provide better burst acceleration.

Performance difference with OneUp installed

The conversion will be compatible with the XTR M9000 cassette and the newly released XT M8000. It will add 65 grams of weight to the stock Shimano cassette.

The big question mark is over compatibility with rear derailleurs. New Shimano XTR and XT 11-speed derailleurs only have to work with a max 42T sprocket as standard, stretching another three teeth could leave the mech vulnerable to damage.

The 45T sprocket is made of aluminium and the 18T is made from hardened steel, they are both colour matched to XTR. The kit retails at $90 (£58.99), for comparison an M8000 cassette costs £74.99 and an M9000 costs £189.99.