Hope T-Rex 40t sprocket.

Another mega-sprocket designed to bump your current 10-speed cassette up so that it’s compatible with a 1x drive system – as long as it’s 11-36T and splits in the right places. This sounds limiting, but in practice the compatible cassettes (Shimano XT, XTR and SRAM PG1030, PG1050 and PG1070) are probably what most folk in this position are likely to be using at the moment anyway.

Fitting is a simple matter of whipping off the cassette, taking out the 17T sprocket, adding the SRAM or Shimano 40T T-Rex, then refitting the cassette – and here the fiddling starts, because you’re going to have to stretch the rear mech’s B-tension screw to (and possibly beyond) its limits in order to accommodate the cassette’s range. I’ve been running the T-Rex in conjunction with a mid-cage SLX Shadow mech and it just about offers enough adjustment – there’s the barest whisper of chain rub in the 40T, but in practice it’s not really noticeable unless the drivetrain is really mucky. This is the main benefit of going for a 40T sprocket instead of a 42T – it’s more likely to work with your existing mech set-up, and you’re less likely to have to hunt out a longer B-tension screw or carry out a bodge. Of course another reason to go 40T is the smoother shifting between gears and though personally I found that the 17T sprocket I’d ditched actually turned out to be my most-used ‘cruising speed’ and I consistently missed it, elsewhere in the gear range there are no unacceptable glaring gaps.

As far as wear and tear goes, the T-Rex does look to be wearing a little quicker than the steel sprockets of the existing Shimano cassette it’s running with. There are noticeable burrs and flat spots appearing on the teeth after only three months of use. I’d have expected it to last at least as long as the cassette, but it looks as though it’s going to go first, instead.

Overall: Another way to grab a bit of the one-by zeitgeist. Predictably tidy engineering from the Lancashire CNC masters, but longevity perhaps not quite what I’d expected.

Review Info