If like me, you like to do as much training as possible off-road, then you might have had a 1X cassette/chainring combination conundrum.
Too small a ring and you run our of gears on when going downhill on hard 2x20 or VO2 intervals, too big a ring and your easy gear is not easy enough...
I have the same problem on the road too; rather than a dedicated road bike I have a Crockett set up with a 48t oval ring and a SRAM 11-36 cassette and it has worked pretty well. The 48/36 is close to to a Sub-Compact 36/28 so steep hills are ok, and the 48/11 is obviously a little smaller than a Compact 50/11, so also spins out on hard down hill road intervals.
For ages I've wanted SRAM to make a 10-36t 11s cassette to give me that bigger gear with the a 40t ring for off-road or the 48t ring on my one bike to do it all - but to no avail.
Their new 10-34t 12s cassettes look interesting, but for off-road, the replacement cost of an AXS mech does not make sense to me. And the 10-40+t of their XD MTB cassettes makes the jumps between sprockets just too big for me.
Enter the e*thirteen XCX Plus Cassette range...
e.thirteen are known for their MTB components but they have a 9-34t cassette that looks like it could answer the problem (they also have a 9-39t and 9-42t versions).
Yes - you did read that correctly 9 tooth!
They have a unique fitting where the aluminium 34t sprocket first attaches to a SRAM XD/XDR freehub with a pinch bolt, then the single piece, machined steel, 9-30t sprockets slots on / attaches to the 34t.
It is a really simple and effective design, I was a little worried when I first saw it - but it has been solid so far.
The sprocket sizes are 9,11,13,15,17,19,21,24,27,30,34.
In use, the rear mech stops did not need adjusting, which is good for wheel swaps, but the indexing did need a small adjustment compared to the SRAM 1170 11-36t.
The gear changes are similar to SRAM with a positive clunk type gear change.
It weighs in at 275g, just 4g more than e*thirteen claimed weight, and nearly 100g lighter then the 1170 11-36.
I've been using it for a couple of months now, the black coating coating is wearing off in places, much like it does on SRAM MTB cassettes, but there is no noticeable wear or lip on the teeth and the 9t only gets used on those few downhill sections, so far I'm happy with the wear.
It is an expensive cassette - at £189 RRP! You can find them for £125 if you do a google shopping search.
You'll need an XD or XDR freehub body. I used an XD so that there was no spacer involved in fitting the 34t sprocket.
How long will the 9t last...? watch this space, I'll update as wear progresses.
The 34t pinch bolt and the lock screw between the aluminium sprocket and the one piece steel sprockets are very small. Being M3 I think they would be sensitive to regular changes.
Although expensive it is a truly unique cassette. The smaller sprocket really opens up chainring selection and 1x training options - it is a really cool addition.
Link to the e*thirteen fitting instructions.
Gear size table, useful for comparing chainring and cassette combinations (source http://bikecalc-staging.herokuapp.com/gear_ratios).
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