The 39 tooth chainring on my SRAM X0 2x chainset on my carbon fibre XC race bike is worn out and needs replacing, as is my cassette and chain, so I thought I’d look at going 1x, which I already have on my full-sus bike (SRAM X01).

I’m looking at going XT M8000 for rear mech, cassette and shifters, but I need a 38t or 39t narrow/wide chainring to give me the gearing my super-fast bike demands with an 11-40 cassette (I currently use a 11-27 Dura Ace cassette and don’t run out of climbing gears, only sprinting gears).

My confusion lies in whether I can fit a direct mount narrow/wide chainring to the SRAM X0 cranks and, if so, which ones will work, what offset do I need and what else do I need to look out for? And how do they actually fit?!

Thanks for your help!

You should be able to fit a direct mount chain ring, just remove the spider by undoing the 3 bolts on the back of it. The direct mount ring then bolts on in its place. As for offset, I’ve no idea.

Oh, and narrow / wide rings have even numbers of teeth 😉

And you don’t need one that big unless you’re using it on the road!

Thanks guys, and yes I do need it that big. My Cannondale F29 is very fast and I can climb all of the hills in southern England plenty fast with a 1:1 ratio bottom gear. And I run out of ratios with 39×11 on the local trails. On the other hand, I’m very happy with 32×10-42 on my full-sus, which gets ridden much more slowly but comes into its own in Wales and the north. It’s horses for courses.

you also may struggle putting up to 38t ring on due to clearance, i’d speak to a cannondale distributor before buying, also absolute black website is good for info as to what ring for what cranks

And I run out of ratios with 39×11 on the local trails

are your local trails roads?

39/11 is about 27mph, where you doing that off road?

I wish I could climb all the hills in Southern England. There are trails round here that I struggle up with 30:40, even when the traction is perfect. You must have thighs like Hoy.
Reckon somewhere between 30t & 34t is about right for trail riding, maybe a bit bigger if it’s a race bike.

It’s amusing that people are questioning the need for a 38t chainring when we all had 42t-44t big rings with something like 11-28 on the back up until relatively recently! And people complained about maxing out 44×11 at a lot of the races I attended and were fitting enormous rings.

And why is 27mph considered too fast for off road? These are strange comments, presumably made by people riding 30+lb full sus bikes. 90% of my riding is on and around the South Downs, which is fast, not overly technical with some decent climbs. 27mph is not especially fast on some of these trails. I rarely switch out of the 39t ring on the Downs despite having a close-ratio 11-27 cassette installed – climbing is my thing.

It’s always dangerous to assume that everyone rides trails and bikes like you. We’re all different and riding in different places. I generate 360W at threshold, am 6′ 2″ tall so have long levers and weigh 70kg, which helps me ride the local trails fairly aggressively. As I mentioned before, when I’m on my full-sus, riding in Wales, the Dales and the Lakes, I’m very happy with the 32×10-42 range on that bike, but the F29 is 4 minutes faster up a local 1.7 mile climb, which gives you some idea of how much slower a 30lb full-sus trail bike is compared with a carbon hard tail XC race bike!

I’ve got one of these spare, fitted but not used, it bolts straight on and is offset to give a 1x chainline.not narrow wide but if you wanted to try it £20 posted.
http://www.wiggle.co.uk/renthal-ultralite-sr4-chain-ring/?lang=en&curr=GBP&dest=1&sku=5360580093&ci_src=18615224&ci_sku=5360580093uk&utm_source=google&utm_term&utm_campaign=UK_PLA_Components&utm_medium=base&utm_content=sagAPebKj_dm%7cpcrid%7c67090789502%7cpkw%7c%7cpmt%7c%7cprd%7c5360580093uk