Let’s go over what’s great: MTB 2×10 Drivetrain, 29ers, Titanium, Pushing limits, Supporting small businesses. But, nothing is without its pitfalls.
With the introduction of the 2×10 drivetrain we’ve also been introduced to the 80/120 Chainring BCD. Limiting the smallest ring to a (some would say) gigantic size of 26t. Paired with the new 36t cassette makes for a bigger (harder) granny gear, compared to the typical triple crankset set up with 22t little ring and 34t in the rear. And the big ring…well, if you’re spinning out a 42-12, this doesn’t matter to you.
If having more options and dialing in your bike interests you click on to read and see more…
Introductory Math:
22×34 = 0.65 (11:17) – typical 3×9
26×36 = 0.72 (13:18) – small 2×10
Put in simpler terms, the 2×10 granny gear is about the same as one gear harder then your granny with your 3×9 setup. So what? Big deal, you say. Tell yourself that in the middle of that 30 min climb everyone warned you about that you didn’t realize just how steep it was. Not everyone can roll up the climbs with an Ulrich-like cadence. Some of us really need that easy, wimpy gear ratio! I’m sure anyone who has ever been mountain biking can recall a time when they went to shift to the granny gear, just to realize that they were already in the granny. Bummer! Point being, even though the new 2×10 granny gear is just slightly harder then what you’re used to, harder is still harder.
Not everyone is interested in upgrading to a 2×10. I certainly wasn’t. But… when someone says to me “I’ve got an new XX/XO drivetrain for dirt cheap. Do you want it?” Hell yes I do! What about the harder gear? I did my homework and the math when the 2×10 hit the market. For this price…who cares! I can deal with it. And I did…for 2 months. After the novelty of the great deal wore off, I realized I was stuck with a harder gear that I couldn’t and didn’t want to push. So, I did what any other self respecting mountain biker would do… I asked the MTBR forums. That’s where I was introduced to many custom machinists who make chainrings.
More Math:
22×34 = 0.65 (11:17) – This is my old set up, I want to get as close to this as possible.
Keeping the new 36t cassette as a constant:
26×36 = 0.72 (13:18) – Got it. Don’t want it
25×36 = 0.69 (25:36) – Pretty good!
24×36 = 0.67 (2:3) – Almost exactly the same!
Then I was told by all the machinists contacted that the smallest possible chainring with a 80 BCD is 26t. I knew by looking at the XX ring on my bike that there was a pretty good chance a 25t could be made, so I contact Mattais, a Swedish engineer that likes to experiment with a lighter, faster, better approach to whatever bike part he feels like working on. How does he make a living? I don’t know, maybe Sweden’s got a high bank-rolling weight weenie crowd? I inquire about either a 25t or 24t possibility. He said 24t is questionable but 25t…he could definitely make!
€55.00 ($76) and 6 weeks later, I’ve got a sexy 25t titanium chainring made for an XX crank!
It’s may seem like an expensive endeavor but, if I’ve already put a ton a money into my bike, skimping now would just be ridiculous. It’d be like dining at a fancy French restaurant and not ordering wine. How much is my happiness worth? Since I’ve already tricked myself into believing that all the cash I spend on bikes and such is a good “investment” in my health, the $76 is an easy spend for me.
The SRAM XX chainring are based on a 1:1.5 ratio, with ramps and such in specific places to make them the best shifting chainrings in the world. And they are!! Suddenly changing that 1:1.5 ratio is a concern. Will it still shift crisply? Will I have to shorten the chain? Will it shift like a neglected Bio-Pace ring set? Actually…it works really well. Sure there’s probably a very slight difference that Princess-and-the-Pea riders could notice but, to me, it shifts at least as well as my previous triple crankset.
Mattais either forgot or didn’t want to countersink the crankbolt holes, and the clearance between the chain and chainring bolts is so slim it’s laughable. But hey, clearance is clearance, and that’s all that matters.
Noticing the difference between the 26t and 25t is instant, for me at least. Riding my usual trails, taking my usual lines proves to be a good test for comparison. Now…nothing is without downfalls. Just as soon as I thought I was getting used to riding a double crankset, I have to get used to it all over again. It turns out that the ratio gap gets bigger when you put a smaller little ring on your crank. Hmmm…who knew? Which means I’m now shifting from little to big, big to little noticeably more to find the gear I like. Less gear redundancy: a plus! Shifting between chainrings more often: you be the judge.
For me, I’ll take it. Having the gear I so want, I so need, I so love…is well worth an extra shift here and there.
Mattais’ Site: http://hellore.se/experimentalprototype/
