In the power meter arena, StageOne does only do that on aluminum crank arms as far I see.
It pretty much do most better road cranksets not usable, I think they use strain gauges glued on the crank arm itself.

For MTB Hollowgram series is the only one for me, tranferrable to road, which is a deal winner here.

For SRM, Quarq, and others, it´s a another game.

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Experimental Prototype

Ok, good idéa and very nice and light cranks.
I know you disagree, but i still like to try the XX1-concept. Do you know if the XX1-spider fits Hollowgram cranks? I guess not...
And second question. Do you think it is possible for you (EP) to create a XX1-spider for Hollowgram cranks?

Maybe Cannondale or Sram will create one themselves as for the Specialized cranks. I'm thinking of if/when the World Cup-XC racers like Fontana and Fumic will start to run XX1. I'm sure they will try to keep their nice Hollowgram cranks, if possible.

Edit: Changed XX-spider to XX1-spider

The XX rings don´t fit any other BCD, they have their own properitary BCD which is something like 76mm with two offset bolt holes as far I know.
I CAN do spiders if there´s enough demand, Hollowgrams is the best aluminum cranks out there, nearest competitor is far behind, a good buy at 500-700 usd for cranks only.

IF and only IF the XX1 front rings work well and no need for chainwatcher, I would recommend them, they have logically spent a lot of time and money in R&D than most of us together.
I have seen the rings in real life, a lot of CNC machining and specific teeths for inner and outer links, maximum chain holding but no chain suck.

They come in a variety of sizes too so spiders for these rings are a good opportunity to widen the use of XX1 rings.
I will get a XX1 crankset to make a spider for it very soon.

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Experimental Prototype

Ok, Great!

Sorry, my misstake in my last post. I'm only writing about the XX1-spider with 76mm BCD + offset on two bolt holes for easier dismounting of chainrings.

I know a guy who runs Garmin Vector power on his mountain bike w/o problem (it's an early field unit, not for sale). Only downside is he uses Look Exustar road pedals, so it encourages him to keep pedaling more and unclip less. Then again, maybe that's not such a down side... As far as I know it works fine.

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Fuji SL/1
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Hopefully Cannondale will make a spider for XX1 in time for 2013 riding season.

What would be very cool is if someone used the same principle (wide and thin teeth, tall teeth) to create a spiderless chainring for XX1 and other cranks like hollowgram and specialized. Homebrewed components makes spiderless chainrings, but if they improved them to make dropping chains a non issue, That would be the ideal solution in my mind.

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My Bike:
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It would be great if HBC would make spiderless rings with tooth profiles like XX1 to prevent dropped chains.... but they seem to be having trouble delivering anything at all, let alone designing new products.

I just got two orders on hollwgram spiders that are for these XX1 rings.
Will be out soon, as I finish other projects.

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Experimental Prototype

I'm running a MTB quarq at the moment. Best option I could find was to get a singlespeed rimg made (homebrewed components can make a 33t ti singlespeed front ring) and a lightweight chain keeper. Rest of the XX1 groupset wasnt a drama.

Although to be honest I'm on my second MTB quarq after the first one failed and am having trouble with this one as well. Think I may get a refund on the quarq (I have them on my roadie and cx bikes and love em but the MTB version needs some refining methinks) ang just get an XX1 crank and put a stages X9 arm on it - I think the L/R balance thing isn't such a big deal on the MTB - there's so much other 'noise' happening in the mtb files that I think it'll get lost...

If there was to be a hollow gram XX1 option I'd be on that like a shot! The bike is a scalpel 29er so would work well

I hope Cannondale custom a spider to use XX1 chainrings with the hollowgram cranks. I don,t want to change my hollowgram crankset.

According to this article, that should work:
http://www.pinkbike.com/news/sram-xx1-ride-11-speed-2013.html

"The XX1 cranks themselves are actually the same carbon arms as used elsewhere in SRAM's lineup, but use a different aluminum spider with a more compact bolt pattern that allows for smaller diameter rings to be fitted."

No options yet?
Rumors?
Nothing?
What if you have an 2x10 SRM, could be converted to take XX1 chainrings?

Now there is good news for all Hollowgram owners. XX1-spiders is beginning to arrive at webshops. First out (what i know) seems to be Leonardi Racing. Experimental Prototype is also working on one, and i think more will follow.
Then hopefully Stages Cycling will release their Hollowgram crankarm powermeters soon. But it will only be sold in the us & canada at first. So bad news for me i'm afraid. But maybe i should start saving for a pair of SiSL 2 Hollowgram XX1 cranks.

I sent a message to Sram/Quarq because I'm in the process of building up a new bike right now - here's the response I got. Seems a bit weak and seems quite surprising that their World Cup riders don't use/want power on the mtb. I get the whole thing about not promising etc. etc., but it would be a bit irritating to buy cranks twice if they are actually in the works.

January 7, 2013
"Unfortunately we do not offer a spider that is compatible with the XX1 Group."

Incidentally, I also checked with Chris King about upcoming hub availability for XX1 and heard from them:

January 15, 2013
"We will not be making a Driveshell for the XX1 system. At this time it is just not anything we have plans for. Basically there is a really small bearing in the cassette and the axle tapers, so he didn't want to make it until we can figure out a way to make it more durable."

The rotor power meter crank?
Alhoa