XC racing with 2x10 vs 3x10?

What are advantages vs disadvantages with say, 24/38 x 11-36 vs 24/32/42 x 11-36? I've always had a triple... Is it a just weight thing or what? Small-ring spread looks the same. 38 looks like middle ground?

 

you're giving up about 10% of your top end speed but gaining less crossover. I've been riding a double for a while and think it's overrated compared to a triple, assuming you have a triple that shifts well up front.

 

For me, I'm too heavy/not experienced enough/not smart enough to notice the weight, but I just like the simplicity. I really never need to go faster than my big ring/small cog combo, and have never come across a climb where the small ring/big cog combo wouldn't work. Now my heart/lungs/legs, that's a different story. After having two rings, three just seems excessive now. In fact, looking forward to a juicy job so I can go buy a 1x11!!!

 

two rings is lighter, shifts cleaner and is less likely to drop opposed to a three

 

I've only raced OTH and never found myself needing the granny gear. People use granny for xc? My opinion 2x with tall rings. But one advantage of having the granny is in case the chain falls off the middle.

 

Many of the full suspension bikes have their pedal efficiency tuned to triple cranksets, but you don't have to worry about that if you're on a HT. Turner is one of the few exceptions; he has tuned the pedaling on his bikes for 2x starting a couple years ago, I believe. I like the triple's straight forward and effective shifting strategy (ex. climb, trail, descend). 2x saves you a little weight and saves you from "thinking" about front shifts (SRAM actually encourages minimizing front shifts, staying in the big ring as much as possible, shifting down as a bail-out), at the expense of an uncommon BCD (80/120 SRAM, 88 Shimano), having the chainline adjusted, an increased tendency to want to cross chain, and limited bashguard options. I believe the ring weight savings are actually pretty small (XTR ring weights 83/43/25, SRAM 38-26 weighs 70/36) and less technologically advanced on 2x. Shimano claims 755g w/BB for their XTR 3x and 698g w/BB for their XTR 2x. As a comparison, SRAM XX crankset w/o BB weighs 650g (+10g for 28/42 version) and a SRAM XX1 GXP crankset weighs 650g (w/BB, 565g w/o) and a XTR BB weighs about 90g.

See shifting ramp, cut-out, pin, teeth shaping profiles:

SLX 2x:


XT 2x


XO 2x:


XX 2x:


XTR 3x:


Random aftermarket 3x (Straitline):


Excuse the last 2 pics, stolen from mtbr topic about properly installing chainrings with the nubs oriented correctly (straitline rings installed wrong), but you should still see the gist of how I say a lot more engineering went into XTR 3x compared to the other rings.

XX, XT, and XTR shift strategies seem to rely on minimizing the gap between the rings, guiding the chain carefully and making the trip up to the bigger ring as easy as possible. XX seems to trade a little instant shifting response to minimize chances of a failed shift, I suppose since they don't expect you to be shifting up front much. XTR 3x seems to put ramps all over for "instant" shifts, while XX seems to time them for certain areas of the pedal stroke (seems timed for 4 o'clock and 10 o'clock crankarm orientation, if I'm looking at it correctly). Chainring stiffness also has a significant role in shifting quality, and Shimano pays especially good attention to it; I personally like the grainy look of their forged rings (at least grainy on the side of the parts they didn't spend a lot of time polishing).

SRAM XO crankarms are reported to be slightly less stiff in test rigs than XT crankarms, according to BikeRadar (source).

 

I would think it just depends on your riding. I use my big ring a lot. I tried the 2x10 set up for a couple months, as that's what my bike came with. I really missed bombing speed. I don't find 3 all that complicated, but I rarely use the granny... I have also been told, "I'm not normal." :-k

 

Do you run out of gearing in any races? If so you may want to stick to 3x if not then 2x may something to look into.

 

So much mumbojumbo!!!!! None of you are world cup racers so it doesnt matter, run what you brung!

 

IME a triple is overkill for XC here in so cal. My FS bike has a 2x10 and HT 1x11.

 

True that! Personally I converted my 3x to 2x with a bash and have never looked back. I always found myself in the wrong gear and now, I never have that issue.

If 3x works for you great. If 2x works that's cool too.

 

The longer you ride and more out of shape you are, the more it seems your gearing is too high. The shorter and harder you ride and the more fit you are, the more it seems your gearing is too low. Triples pretty much have all the gearing you want, regardless of ride length and fitness level. 3x to 2x isn't really much difference. Some people just feel like they don't need some of it, and use that as excuse to drop a little weight. Going to 1x, you might lose a 115g shifter, 150g FD, cable and housing ?, rings totaling maybe 100g, several chain links. Going 2x from 3x, you lose less than 100g.

Up to you if you want to adapt to your gear and take advantage of it, or to shell out the cash to adapt your gear to suit your habits, habits which likely change to adapt to the new system anyways. It's hard to beat a good balance and versatility, unless you're super competitive and you need to shed absolutely any excess you don't need to be as efficient as you possibly can. I get the feeling that people just are getting sold on it and they enjoy the process of making the change into a project... it's different, it works, it satisfies them in a fulfilling way (challenge of completing a project, meeting goals, and learning a new system successfully). Maybe because they change, they think their gear needs to change with them. Sometimes, it could be something as petty as a home mechanic changing their drivetrain since it doesn't seem to shift very well, and the LBS couldn't figure it out going off of the reported issues you've faced on the trails, who then suggest replacing some parts. Hearing opinions from others, I just can't help wonder just how much can be attributed to the placebo effect...

 

When I bought my bike last year, I assumed I would go 3x10 because I had always run a triple and liked having a wide gearing range. At the last minute, I went for the 2x10 and couldn't be happier with it. With the 11-36 in the back you still get a pretty wide range even with only two rings up front. The selling point that got me was that I could leave it in the big ring on the double and use all 10 gears in the back without worrying about problems with cross-chaining. After a year of use, they were right, I haven't had any problems running big-big, dropping the chain (w/ shadow plus r. der.), or any other drivetrain problems. I use it the way Varaxis described: I generally stay in the big ring as much as I can, and drop to the granny as a bailout. I never found a using a triple to be complicated, but I have to admit I love the simplicity of rarely shifting in the front.

And I'll admit I've used the granny plenty in XC racing at the Enduro Stuff series. I'm not strong enough to consistently make it up climbs like Mathis and Coachwhip without my small ring up front, especially on the 2nd lap. Not to mention the Dreaded Hill climb at the Whiting Time Trial. That climb was painful even with my granny gear.

Sounds like it's time to add some gearing choices to your bike demo list. Try them both and see what you like.

 

great insight. I have 3x on my SC Superlight and plan to leave it as is. I'm looking at a race bike and am considering 2x. I occasionally wish I had another low cog when I'm burnt during a race and climbing. I never run out of gears on the big end unless I'm peddling on a smooth fire road descent.

 

Well I guess since I'm not a world cup racer I should just buy my bike at Walmart and save a couple grand. World cup racer or not, one big reason we're all here reading this forum is to learn and achieve our personal bests in terms of performance AND setup. Part of most people's passion for MTB is in the search for the 'secret sauce', that combination of controllable factors that allow them to go just a little faster, and finding the right drivetrain surely is part of that search.

 

How do you tune a suspension for gear ratio?

 

2x10, no brainer, I have had both 39-26 and 38-24 up front on two different bikes, currently I use the 38-24 bike more, for racing and riding all around O.C., it is a carbon h/t 29er, with the big gear range in the back I don't miss a triple one bit, you will be fine with the 2x10 and have far less issues, there actually is a website, it's called sheldon brown's gear ratios and you can plug in all the chainring and cassette combo's you want and compare what you are gaining or losing and you will see you don't lose much on either end on the 2x10 vs. the 3x10 system

 

Niether. Go 1x11 - sram XX1 is what most top end XC race bikes are equiped with. No front derailleur no front shfter. No chain suck no dropped chains. For xc racing the gear ratio is more than enough.

Ad if you really want to improve your xc racing get a 27.5 wheeled hard tail.

 

In case anyone is interested in the math.... this is done in Gain Ratios
I did analysis back in Jan... I needed some "Trail Gears" for my 29er..

For Me: I did ride the 2x10 for a while ... it was fine for 2 hour rides for me and set a lot of PRs on my favorite loops was *very solid* and... definitely would have worked in races around here (guess that the OPs question),

but I wanted trail gears...ya know support 3-6 hour / 30+ mile rides with some steep climbs etc i.e. a real granny. I even tried the not supported 22/38... didn't work well. NOW Shimano coming out with a 22/36 2x...finally... after they said for 5+ years.. no 29er specific gearing needed nothing less that 24 on the 2x...now a 22...dorks! ...anywhoo...

Also I like the triple because I love the 32 tooth... spend a lot of time in it...on the 2x I was stuck in that damned 24 all the time... didn't like it...and could only get in the 38 when I was really moving...again just me.

The bottom chart is 24/38 w 11-36, the cross over point is between 4 & 5

(I know... More than OP asked for)

 

+1 on the XX1......however he is over 6" and a 29'er is the right sauce