OneUp Components launches 45t range expander sprocket for Shimano XTR

Add-on kit broadens gear range while maintaining relatively even gaps

Shimano did a lot of things right with its latest XTR mechanical and electronic mountain bike groupsets but one common gripe lies in the 11-40T cassette, which doesn’t offer up a sufficiently wide range for many riders to comfortably run a single chainring. OneUp Components comes to the rescue with a new 45-tooth add-on cog – plus XTR-specific narrow-wide chainrings – which adds 12.5 percent to the total range and puts the modified XTR setup nearly on even footing with SRAM XX1.

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As with other OneUp Components range-extending cogs, this latest version is CNC-machined from 7075-T6 aluminium plate and installed in between the cassette and rear hub. The stock 17-19T cluster is replaced with the included single 18-tooth nickel-plated hardened steel sprocket to maintain relatively even ratio jumps throughout the spread.

All of this fits on the same freehub body as the standard XTR M9000 cassette, too, meaning that the OneUp-modified XTR cassette will now also let current 10-speed riders switch to a true wide-range 11-speed setup without having to change wheels (as they would have to do with any of SRAM’s 1×11 mountain bike drivetrains).

“This gives you 11-13-15-18-21-24-27-31-35-40-45 (stock is 11-13-15-17-19-21-24-27-31-35-40),” said OneUp Components’ Sam Richards. “Everything is colour matched to the stock XTR cassette for a fully integrated look and feel.”

OneUp components says the converted shimano xtr cassette yields two distinct shifting ‘zones’ – a climbing zone with slightly smaller jumps in between gears to help maintain a smooth cadence on climbs, and a descending zone with bigger jumps to yield more explosive bursts of power when you’re moving faster:

OneUp says the modified cassette yields two distinct shifting ‘zones’ – one with smaller gaps for climbing, and one with bigger gaps for descending

According to Richards, the converted cassette will effective offer riders two distinct shifting ‘zones’: a climbing zone (comprising the 21-45T sprockets) with ratio jumps between 13 and 15 percent; and a descending zone (comprising the 11-18T sprockets) with slightly bigger 15 to 20 percent ratio jumps. OneUp’s thinking here is that it’s more important to maintain an even cadence when climbing whereas on descents, riders are typically looking for larger ratio changes per shift for bigger bursts of out-of-the-saddle speed.

Either way, OneUp says that the modified cassette will have to be set up with a single chainring only since the stock derailleur doesn’t have enough capacity to handle such a huge gear ratio spread with dual rings. That’s no problem here, as OneUp will also offer separately its own narrow/wide chainrings with XTR-specific bolt circle patterns.

The stock shimano xtr m9000 rear derailleur doesn’t have enough capacity to handle a two-chainring setup with the expanded-range cassette. naturally, oneup will also offer its own narrow-wide chainrings specifically to fit the asymmetrical xtr spider, too :

OneUp Components will also offer separately narrow-wide chainrings specifically for use on Shimano XTR crankarms

OneUp says the modified cassette will weigh 65g more than a standard XTR M9000 11-40T cassette for a grand total of 396g. For now, the 45T cog will only be offered in anodised grey to match the stock cassette but other colours may be added later. OneUp says the new range-extended XTR kits are available now, and we’ve got one on the way and will start testing immediately.

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