So, after weighing up all options I have gone with AC Wide Lighnings on my Spesh Epic Expert 29.
Contenders were AC WL, LB carbon on Hope or Novatech, Roval carbon.
The width argument seems generally settled, question is how wide. I also had some concerns re cost of decent carbon wheels relative to performance and durability.
Rovals were too expensive ($1400 - $1600 depending on width) so was down to LB and AC (both around $1100, but still more than I was prepared to pay/afford). At the 29mm internal width the AC's were lighter than the equivalent size LB by nearly 100 g (with Hopes).
I have to admit the twentynineinches (
http://twentynineinches.com/2014/07/06/american-classic-wide-lightning-29er-wheels-final-review/) articles on the AC's were pretty convincing and Bill Shook's comments (
http://www.pinkbike.com/news/To-the-Point-Bill-Shook-on-Wheel-Building-and-Wide-Rims.html) re Al Vs Carbon summarised my feelings after a pretty wide web search on the topic.
Pushy's EOFY sale was the final trigger ($850) and in Pushy's usual style, online order was quick and easy, delivery similarly.
Of the 20 odd wheelsets I have had over the years all but a few were not built by myself, so this would be only the second high end off the rack set for me (other is DT XR1450 in 26"). Price was around what it would cost for me to build up LB based wheels in any case.
Out of the box:
As you would expect for the price, the AC's are well finished. Bearings are smooth, wheels were true and spoke tension well within spec (specs on AC wbsite). Front (9mm TA conversion but without axle) weighs 764g, rear (with 142 x 12mm conversion but without axle) weighs 864g.
The 142 x 12 and 9mm through axle kits fitted easily (check fitting instructions from website, there is a trick to getting preload correct). If you buy the 15mm front version and wish to convert to 9mm TA, a cheaper option is to buy an after market adapter to put inside the 15mm axle, because that's how AC do it (at some expense).
They have a number of nice engineering aspects. The hubs are high flange but machined for minimal weight. The Al freehub has two splines faced with a steel inserts to protect it from from cassette bite and the axle tubes have adjustable bearing preload to optimise drag. The proprietary double butted spokes (AC branded) have a longer butted section than DT comps, over the spoke length the thinner section would be 75mm longer. Also the Al nipples have only 10mm showing on the outside of the rim with the rest inside with a square section drive rather than a slot. Not many weight saving opportunities have been ignored.
I was a bit worried the lairy paint on the AC's wouldn't go with the Epic red/white paint scheme, but it is more subtle in real life than photo's suggested and is fine.
My OEM Spesh rims (DT 450SL) are 18.3 internal and the WL's 29.3mm so I was interested to see the effect on my Schwalbe RoRo front (2.25) and RaRa rear (2.25), both snakeskin versions and tubed (as I would initially also run on the AC's for direct comparison). Pressures would be the same also (23psi front, 27psi rear; 95kg smooth xc only rider).
Tyres fitted up easily, the well in the rim is generous, but I found I had to soap up the beads and pump to 45psi to get them seated in AC's bead well.
Tyre size:
On the old rims, the 2.25 RoRo measured 54mm across the tread and 53mm at the widest point of the carcas. On the AC's this grew to 56mm across the tread and 58mm across the carcass.
On the old rims, the 2.25 RaRa measured 55mm across the tread and 55mm at the widest point of the carcas. On the AC's this grew to 56mm across the tread and 59mm across the carcass.
The final carcass dimensions for the RoRo on the AC's match the 2.35 version of the tyre (on 18.3mm internal rims), so AC's claim that the wide fitment takes a tyre up one size seems to hold, albeit in volume only as the 2.35 tread width is 60mm (and a bit more aggressive).
Initial impressions:
Thanks to indifferent weather, I have only had a short ride on flowy singletrack (Hans/Candlebark in Melbourne) so far. As you would expect with a 400g reduction in wheel mass, they spin up faster and make the steering (indeed the whole bike) more lively and responsive.
Grip and ride improvements are immediately noticeable. Grip is particularly noticeable ridding through ruts and channels where the tyre seems to be able to hang onto the side of the valley better and seems less fussed generally with off camber and rock edges. The wheels are also much stiffer than the spesh ones (the front of which also has 32 spokes and DB spokes) and the bike points more confidently in corners. Ride is improved over small stutter bumps and square edge hits.
As others have mentioned, the freehub pickup is slower than some. I had an 18pt on the DT XR1450 when I got them and the upgrade to 36pt was noticeable (but not earth shattering and not worth the $100 it cost).
The OEM spesh wheels have 24 point and the AC's feel the same. I'm happy with it at this stage.
The tyre is so stable I will try dropping a few psi for the next ride. After that I will probably succumb to the the lure of more performance and lower mass (another 160g lost) from tubeless (rims are tubeless ready and come with nice valves).