How to install a Hope 40T-REx

The Hope 40T-REx is one of a new generation of drivetrain bits. Designed for people who want to run a single chainring up front but still retain a decently wide range of gears at the back.

It’s not adding a gear (making 10 speed into 11). It’s simply extending the range of your 10 speed cassette.

The idea is to replace a sprocket of your existing cassette and bung on a massive largest sprocket. It’s adding an extra significantly easier gear at your top end.

1. Check your rear mech can cope with the increased range. The vast majority will be fine but if your mech is a of a Downhill variety (Shimano Saint, Zee etc) then you may struggle.

2. Remove the cassette lock ring using a chain whip, a large adjustable spanner and a cassette lock ring tool.

3. Remove the cassette from the hub. Sometimes this can take a bit of force if the cassette has been on there a long time. Try tapping around the back of the cassette with a flat blade screwdriver and a rubber mallet to get things moving.

4. Take note of the position of any spacers.

5. While the cassette is off, take this opportunity to give it a really good clean.


6. Remove the individual sprocket (probably the 17T) that you wish to discard and its adjacent spacer.


7. Put the Hope 40T-REx on to the hub, making sure you’re using the correct spline location.

8. DON’T put a spacer on.

9. Put the existing cassette back on to the hub.

10. Re-install the cassette lock ring with a cassette lock ring tool and a large adjustable spanner.

11. Put the wheel in your bike.

12. Put the chain on the 40T-REx sprocket. If you find your chain isn’t long enough, you’ll need to put a new chain on (unless you have a few spare links of chain lying around that can attach). Remember that full-suspension bikes need a bit of ‘extra’ chain length, so a chain that fits around the rings but ends up really taut will still be too short.


13. With the chain off the 40T-REx sprocket, adjust the rear mech’s B-tension screw so that the top jockey wheel doesn’t touch the T-REx but does sit quite close to it (5-8mm gap). If your B-tension screw isn’t long enough, remove it and use the 20mm screw that comes supplied with the Hope 40T-REx.

14. You shouldn’t need to adjust your gear indexing or stop limit screws but you may as well give the system a once over while you’re there.

If you’ve not done so already, you should think about getting a new chain-retaining chainring for your cranks too. No more faffy chain devices! Happily, Hope also make these things – Hope Retainer Rings.


Have a look at the Hope 40T-REx ratio expander sprocket on Merlin Cycles.


  • Benji Haworth

    Benji has been around the cycling industry for over ten years now. He started in ad sales for magazines before jumping the fence over into editorial. He writes words and takes pics about pushbikes, both for his day job and in his spare time too. Bike addict. Benji’s interested in all kinds of cycling but has a particular obsession with mountain biking

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