Hey guys im unsure what i should do with my scott i want to get a power meter and have been looking at the sram s975 meter but i was also wanting to eventually change from ultegra to full sram groupset.
My question is should i just get the s975 crank and use it with my ultegra or should i save up more and get the 2013 sram red groupset and the red power meter as that only works with the yaw deurailer of the new groupset where as the s975 crank can be used with my shimano gear.
Does the s975 crank work with the 2013 groupset with the yaw deurailer?
Thanks for any advice . sorry if it doesn't make too much sense!

"only works" is marketing BS. It's levels of working. Look at the 2011/2012 Red threads where people are mixing and matching with great success SRAM will say that Shimano cassettes won't work with SRAM bits; Shimano will say that SRAM cassettes won't work with Shimano bits. Nonsense! I have a bike with Ultegra cassette, 105 chain, Rival shifters, Rival crank, Ultegra front derailleur, and Rival rear Derailleur, works just fine (and, amusingly enough, I like the Ultegra front derailleur over the Rival bit on another bike...). Pardon the rant. I reallllllllly hate marketing BS.

You can get the Red powermeter or the S975 and it'll work just fine with your Ultegra. It may not be as smooth shifting as your current crankset (when is anything as smooth as Shimano front shifting?), but it'll work just fine, and, odds are, you won't even notice a difference.

I've got full DA 7900 (shifters, FD and RD), Ult cassette and FSA SL-K crank. I replaced the crank with an S975 Quarq and the Ult cassette with the older RED cassette, not the new one. My observations are as follows:

The S975 does not like to cross chain as much as the SL-K. Maybe it's the ramps, or the chainrings are every so slightly closer, or something else, but when I'm in the 34-11 crosschain combo, the chain somewhat hiccups on the outer ring. I can ride like this, it doesn't misshift or anything, but it creates noise where it used to be quiet. I generally avoid this anyways so not a big deal. I do however run the opposite cross chain frequently, 50-25. The chain sounds awful, but mostly coming from the rear. It goes quiet when I swap the cassette some it's not a crank based problem.

Like the other poster said, it's a lot of marketting. So many people mix and match things. Now if you want the new RED PM for left right balance, then I'd say wait for it.

s975 are really good powermeters(i have experience with the srm version, but friends are using quarks and don't tell me anything bad about them). big advantage is whenever you change frame or maybe crank length you can swap crankarms easily and pretty cheap. i have a set of gxp and bb30 arms and can use it on every bike. the longer you work with a powermeter, the more intresting it will be to mount it on a tt bike once, or during winter/snow on the cross bike, so versatility is a plus.

I've got an S975 GXP Quarq on my BB86 Scott Addict. Works great.

That said, there is no way, no condition, I'd buy an S975 over the new Red Quarq.

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2013 Wilier Cento1 SR || 2009 Ridley Crossbow || 2011 Yeti AS-R 5 Carbon