# MTB Drivetrains 101: What’s the Big Deal About 2×10?

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SHARES

You have probably heard terms like 3×9, 2×10, or 1×9 thrown around in discussions about mountain bike gearing. In case you are not familiar with the jargon, here is a quick review.

When someone says 3×9 (pronounced “three by nine”) they are referring to the setup of the chain rings and cassette on their bike. The number 3 is how many chain rings they have on the front and 9 is the number of cogs on the cassette. Therefore a 1×9 would be 1 chain ring and a 9 speed cassette, etc. You get the idea.

A typical 3×9 crankset from RaceFace.

Additionally, chain rings and cassettes come in different sizes. Both are measured by the number of teeth they have, and if you’re mathematically inclined you can use this info, along with the wheel diameter andlength of your crank arms, to calculate your total effective gear ratio. I am notmathematically inclined, so let’s just skip that part.

For years mountain bikes have employed a triple front chain ring and a 7, 8, or 9 speed cassette. This is a tried and true design and it gives you an extremely low granny gear for long, steep climbs, and a decent big ring for haulin’ the mail on flat or downhill sections.

However, there are some limitations to this setup.

Weight: Three chain rings weigh more than two … or one.

Clearance: When crossing logs, rocks, etc, the big ring can scrape, and bent or broken teeth are generally the result. (On the chain ring, not necessarily your teeth.)

Crossing Your Chain: This is discussed at length in this forum post but here are the cliff notes. Every rear derailleur has a range of gears that it can handle. It is usually expressed as a number of teeth, and on a typical 3×9 system it will be somewhat less than the difference between your largest chainring and smallest cog, or vice versa. Shifting into one of these extremes will result in poorpedaling efficiency and will accelerate wear on your chain and gears.

Derailleur Cage Length: The greater the difference between your large and small gears, the longer your derailleur cage needs to be to take up the chain slack. The longer the derailleur cage is, the more likely it is to get whacked on stuff.

One obvious solution is to just get rid of the big ring and maybe replace it with a bashguard. Many riders, especially here in Colorado, have done just that, leaving the small and middle rings. This is a workable solution, however without that big ring, long stints on the flats can be really tedious.

A ‘ghetto’ 2×9 setup with a bashguard installed.

So what is a modern mountain biker to do?

Enter the 2×10 setup!

But wait, isn’t that essentially what the bashguard setup is?

Not exactly…

A typical 3×9 setup will have something like a 44t-32t-24t chain ring setup, (t = number of teeth) and an 11-34t cassette. There are some variations such as older 8 speed cassettes with 11-30t or 32t, and newer 10 speed cassettes with 11-36t. The latter is the norm on most 29ers.

So what those clever bike engineers have done is take the traditional triple chain ring and “split the difference” with a two ring setup. The current offerings from SRAM employ a 26t-39t setup, whereas Shimano has a 26t-38t or a 28t-40t.

Okay, I get the concept, but why do I care?

Admittedly, a 2×10 setup is the very definition of compromise, as there isn’t as big of a big ring and the granny gear is a little less granny and a little more gear, but there are some advantages.

Weight: Comparing otherwise identical Race Face Turbine crank sets, the double shaves 55 grams off the weight of the triple.

Clearance: While not as radical as the old school two ring setup, the new style 2 speed cranks are still smaller than the traditional big ring so it will scrape less (and yes, there are bashguards for a 39t big ring).

Crossing Your Chain: This is my favorite feature. On a 2×10 setup you can use all 10 gears with either chain ring; there is no chain crossing. On the trail this simplicity is awesome.

Derailleur Cage Length: Depending on your exact setup, you can most likely get away with a shorter, mid cage rear derailleur.

I recently made the switch from 3×9 to 2×10 and I am completely sold on the concept, however, it may not be for everyone. The slightly smaller big ring isn’t much of an issue, but out here in the mountains the lack of a true granny gear is very noticeable. I found myself needing to keep up a slightly higher cadence in order to avoid stalling out when climbing. It was brutal at first, but once I got used to it, I really liked it. And after a month or so, I found myselfsignificantlyfaster on climbs.

There is nothing wrong with a traditional 3 chain ring approach or a homebrew 2x with a bashguard, but if you’re bored with your current setup and want to shave a little weight while losing some complexity, then you should definitely give 2×10 a try.

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SHARES

Having grown up riding and wrenching on BMX bikes, Corey discovered mountain biking after moving to Colorado in 2004. An IT worker by day, he now spends most of his free time following the bike industry and trying to keep up with his teenage daughter out on the trail.

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• Jeff Barber

When SRAM first came out with their 2×10 drivetrain it was limited to the high end but now it’s filtered down to entry level components which is great for everyone.

I’m still not entirely convinced 2×10 is the way to go for me personally – I’m pretty used to running 1×9. I have a 2×10 on my FS bike and I find myself shifting the front derailleur a lot – guess I’m always looking for that “middle ring” sweet spot. ðŸ™‚

^^that’s what I wonder about Jeff. 99% of my trail riding is in the middle, 32t ring, and I use the whole cassette. I only use the big ring on gravel/pavement between the singletrack, and the granny only gets used when I head to the mtns, or one or two super steepies on my local trails. If I had a 2x without my 32t ring I’d be shifting on the front a whole lot more, which I don’t think I’d like. That said, I still want to try a 2×10.

• mtbgreg1

Great post madd! For me the shifting simplicity is the biggest advantage. Also, I remember hearing that SRAM had 3 chain ring combos available. I checked the site but only found 2 2×10 ratios: 26-39 and 28-42. I just think it is important to note that there are options available to suit almost any need!

@dgaddis, you sound like the perfect rider to test out a HammerSchmidt crankset!

@mtbgreg, nice catch, I could only find the Sram in the one gear combo. Where did you find the 28-42? (Which I will NOT be running here in the mountains, by the way!)

• mtbgreg1

Found it on the website under x9. I’ll see if i can find any info on that other combo I heard about.

• Jeff Barber

@madd – I’m content with 9 gears for now. To me it’s not worth the expense and hassle of changing everything out for just one more gear. However, if I were starting from scratch I would definitely consider it.

• element22

I converted all the bikes to 2×10 or 1×10….They now have a bashring to protect 2×10 bikes without loosing a ring…

I like the 2×10 on my trail bike…I find with an 11-36 on the back i can still deal with most everything….((most))…on my DH rig’s I run 1×10’s and a short cage..((All about clearance there)).

• 8valvegrowl

All my bikes are 1×9.

32T x 11-32.

Works well for me and is dead simple/reliable. I use a BBG sandwich and a Blackspire Stinger to keep things taut. Midcage Deore XT Shadow rear with an XT shifter pod. Fast precise shifting. I wouldn’t be opposed to moving up to 1×10 at some point.

• fat_billy

Great post madd. Clear, understandable and didn’t require a whole beer to read it. Thanks.

• AK_Dan

Very nice write up, thanks.
I tried the 2×10 on a couple bikes @ Outerbike and was fairly happy with it, but all the riding was on sweet Moab singletrack and I can see its advantages for such riding. Because I ride such a wide variety of terrain including the occassional long & flat I am still keeping the 3 on my trail bike. That 2×10 may very well end up on the commuter bike though.

I have forced myself to shift on the front rings more over the last couple years and after getting used to it, it really has improved my riding effecientcy and overall speed. Dropping or climbing one ring vs. craming 4 or 5 cogs in a tight spot is much more efficient. Getting the proper timing with crank strokes has been the learning curve but all in all works pretty well.

AKDan – that’s why I use gripshifters – I can shift the whole cassette with just a twist of the wrist.

GRIPSHIFT FOR LIFE!…or, at least, as long as it’s available lol ðŸ˜€

On a 2×10 the front shifts a lot better (no middle position). As my 2×10 bike is down for it’s winter service, I’ve been riding my 3×9, have only found one long steep climb that I can make on the 3×9 that I can’t on the 2×10. (both bike weigh the same) Do occasionally miss the big ring but I’m not on singletrack when that happens so no big deal. Been riding at Ray’s in Cleveland this week; have 26 gears I’m not using

• AK_Dan

Them grip shifters are a hot comadity here in Alaska as people use them in the winter – much easier to shift with large gloves on than trigger types.

• steve32300

I had grip shifters on my first mtn biike and actually liked them,although when I started riding more and more technical trals,the more aggressive I rode the more I would accidentily shift.I got a dropped big ring with a bash gaurd in place so I still only have the ghetto 2×10 mostly because I like my granny gear at my weight(300 pllb.)and the steep front range climbs here in colorado,I think I would like to try the factory 2×10 though to see if it would work for me.

• seamus560

Personally I think the 2×10 is a great concept for 26’rs. But I rode a Rip9 as a demo with the Sram 2×10 and I hated it. It was not low enough for long steep climbs. I think it would be great for the average mountain biker on your average trail but here in Colorado we have some steep trails. When you are going up a thousand feet plus in elevation that 26t plus the larger 29″ tires makes for a tiring ride.

• thegrover

Love Grip Shifts, they are on all my bikes. So fast and simple. Never had a problem with accidental shifting. Look better and cleaner than a bunch of levers hanging off the bike. The clincher is I have arthritis in my hands and I could not ride without them. If I ride a bike with shift levers after about twenty minutes I am in a lot of pain.

• chiefwfb

I first tried a 2×10 on a Yeti ASR-5 in Winter Park and loved it. Came back to AZ and went getto removing the upper chain ring and replacing it w/a bash guard. Had the LBS make some adjustments on my limits for shifting and it worked well. Then I bought a new Ibis HD w/a Race Face sixc 36×24 crank. Love it for the type of riding I do.

• David_Trent

I just chanded from a 3×8 to a 2×8 and haven’t had a chance to get out. I don’t know if i have the proper gear setup yet. 22-32 chainring and 12-32 cassette. Has anybody else tried the 2×8 setup on singletrack?

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