You are hereForums / By Discipline / Mountain (off road) / MTB Gear / 2 x 10 chain rings

2 x 10 chain rings

staffe's picture

By staffe - Posted on 20 April 2015

Looking at replacing my worn out chain rings and would like to change them around a bit if possible and looking for advise / experience in doing so before ordering stuff.

Running XT 38 - 26 rings and often find myself in the highest gear wishing there were one more to use. So I'm wondering if it is possible to fit a 40 big ring and keep the 26.

Looking at CRC there seems to be preset options: 40 - 28, 38 - 26 and 38 - 24 so I'm thinking that maybe the size 40 won't fit the cranks or can't be combined with a 26 inner for some reason.

If anyone has any experience in changing this around on a 2x10 setup or has knowledge around this, please advise and maybe save me from the disappointment of paying good money for gear that don't fit (yet again)


Brian's picture

I'm just curious as to where you are running out of gears. I imagine with your cassette it would mean 38x11 in the hardest gear.

I'm only curious because I run xx1 with a 32t front ring meaning I have 32x10 which seams fine. Sometimes on the road I have to spin a lot but on the trails it's good.

Brian's picture

Also, sorry as I didn't really answer your question. I don't have experience in changing the ratios on the mtb. There are sites that calculate rear derailleur cage length because you will need to make sure it can handle the difference. I think you also need to check the front derailleur as well.

You will most likely need a new chain.

staffe's picture

Yes 38 - 11, It's not that I really have to go bigger, spinning faster also works but given that I need to replace the rings (and chain and cassette) fairly soon and if I had one more gear I'd use it so it is worth exploring whether it is an option.

Good point re front derailleur - need to check if there is room to move there.

StanTheMan's picture

I run out of gears all the time while transporting between tracks
I run a 40-28 front 32-11 on the rear.

can't recall if Ive ever run out of gears while racing. Would only be on fire trial going downhill at serious pace. but 38.....I recon I'd run out. Having said that.....Ive never run a 38.
But I'm also on a 26er. Might be different on 29ers

On the other hand Brian is a serious racer perhaps he can run at a much higher cadence than I could ever dream of.

pharmaboy's picture

12 is std teeth difference for shimano but it will do 14, so 40 should be fine.

BUT, really 38 to 40 is not really something you'll notice, it's only about a third of a gear harder, cadence will make a far bigger difference than that .

On a 29er, at 80 cadence, those two rings are a 2kmh difference ie 38kmh versus 40kmh, but at 90 cadence you are doing 43 on the 38

Check out bike calc and play with it before deciding to change . If you do lots of slight downhill road riding, maybe you need a triple with a 44 upfront, or just learn to spin faster

hawkeye's picture

The only time I've come anywhere near running out of gears on the trail is fanging it down the Oaks after Black Flash.

I'm on a 29er with 39/26 on the front.

On the road, down The Spit, yeah I run out there if the traffic is light, but not on the flat.

Mamil's picture

Couple of things to watch out for...

The 40 ring will fit on the cranks ok, but does your frame/chainstay have clearance for a 40T ring in the middle position? Some will only take 38 max.

When you raise your FD to fit the 40T ring, the chain may rub on bottom of cage when in 26 ring and small sprockets. However, suspension sag and/or the fact that most people don't use this combination means it may not be such an issue.

Finally, although the current 2x10 FDs will cope with a 14T gap, it's a big jump and things may get a bit crunchy if you try and shift under load. Particularly as Shimano "pair" their 2X chainrings so they match in things like tooth phase, ramp profiles, pin locations etc. It's why for example there's two different 38T rings - one for a 26T granny and the other for a 24T granny. When I tried to run a mis-matched pair I kept on dropping the chain.

So, I'd say combination of bigger than normal gap and mis-matched chainrings would be asking for shifting problems. Not saying it won't work, but will be "sub-optimal".

uppo75's picture

I looked into this a while back.
Apparently they are optimised for that combination.
and IIRC, the 38 for the 26 is slightly different from the 38 matched with the 24.
Shimano makes no excuses for things that are not interchangeable. They are there to make things that work as best they can and to make these things interchangeable would compromise the shifting properties of their cranksets.

Jonathan's picture

Are you set on 2x10? why not drop off the front mech and shifter and go 1x10 i'm running 36x30 and although it does take a while to get used to (especially on cascades) im super happy i did it. The best would be running 1x10 on a regular 36-11 cassette then adding a 40/42t granny like hope/wolf tooth/black etc.. but in saying that i haven't done so yet, its just boosting my legs and im used to it now hahah.

At least i believe that would be the best unless you want to drop an arm and a leg and go 1x11. All the 10x stuff is super cheap now and you're all ready go with all the gear to do it. haveing clean handlebars is great!


Discodan's picture

I'm a great fan of 1 x 10 setups but isn't the OP looking to a broader range of gears not a narrower range. I think if he's spinning out on a 38t big ring then a 34t may cause an issue Smiling

Brian's picture

Yes I run 1x11 (32t) and think its more than enough but I didn't recommend it because he wants more gearing, not less Eye-wink

uppo75's picture

I have a hard tail with 38/36 x 11-36 and a dually with 30 x 11-40

staffe's picture

Seems like the sensible thing is to either stick to 38-26 or go to 40-28, very rarely do I use the lowest gear so 40-28 is most probably the better option.

Would not go 1x10 but maybe 1x11 but that seems like a whole range of stuff needs to be replaced so I'll stick with 2x10 until it is time for a new bike.

Thanks for all the good suggestions and advise.


Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Best Mountain Bike