Has anyone done it? Was it difficult? Where did you source a replacement 42T cog from? Does it cause any issues having a part worn cassette and a new 42T ring?
Cheers.

AFAIK the cassette is all one piece, at least it’s not meant to come apart. I doubt you’d find a spare cog either.

Someone somewhere makes a replacement and includes instructions. Try all the usual suspects eg wolftooth etc. Can’t remember who

AFAIK the cassette is all one piece, at least it’s not meant to come apart

I thought when they came out to allay peoples concerns over the alloy top cog SRAM said they could be replaced?

here

Considering the price of these cogs/rings, you’ll probably be better off with a new cassette.

http://int.oneupcomponents.com/products/x-cog-44t-sprocket
http://www.aribike.it/pignone%20sram%20XX1%20html/pignone_cassetta_sramXX1.htm
GCX 42T Cog for SRAM XX1/X01 cassette

Dang, your(sic) quick!!

I fitted a one up 44t new when I got my cassette as I wanted more range..

It’s reasonably easy to do if you are patient.. It just took a while to do..

Follow the instructions on one ups site, take your time and just keep tapping around each pin and it eventually goes on nicely!

Thanks for the links folks, must admit I was being a bit lazy and a quick google would have probably given me the same info.

Considering the price of these cogs/rings, you’ll probably be better off with a new cassette.

Hmm you may be right, $90 = £90 I guess by the time I take shipping and customs into account.
Wonder if Works components have one in the pipeline.

If you buy from One Up they have an International/UK Wharehouse site so there’s no customs/duty etc to pay.
CRC do them too if you have a discount code 😉
http://www.chainreactioncycles.com/oneup-components-sram-x-cog-expander-sprocket/rp-prod141745

New chain and it’s slipping? If so, round chainsaw file and reprofile the teeth. 4 chains on a Hope T-Rex when I was 10 speed, and 4 chains on an M8000 11-42t and counting.

Been there done that.

I got a wolftooth one from Chris @ Leveret (importers) for £74. (nit cheap, but a LOT cheaper than a new cassette)

Changing it is a 2 min job once you’ve got the cassette off – the only thing to watch is that there’s one wide pin on the big lump, and one matching big hole on the new cog to align with it.

I got just under 2 years of all year Peaks riding out of the SRAM 42T. The Wolftooth one is now just over a year old, and so far seems fine.

I think I’d just get one of the cheaper SRAM 11 speed cassettes instead and huff a bit over the minor weight increase