The tires roll incredibly fast and are quiet for being quite knobby. I was riding home last night on a paved trail and noticed that the center treads handle most of the work while on hard surfaces (the tires were covered in mud and only the center 1/3 of the tire seemed to contact a wet road, showing me where the tire was hitting the pavement). I think this is why they roll so quickly as the longer side knobs don't come into play unless you need them.
At the On the Rocks @ French Creek, I put the tires through the wringer with a number of rocky downhills, sharp corners, some steep, rocky uphills and all with some lack of technical expertise (as I'd been off my mtb for 7 days prior to the race).
|Standing on the tires while cornering at French Creek|
Plus, I could descend with little tire pressure (I had a valve leak and rode for part of the race on 10psi or less) and the tire sidewalls held up without any issue.
|Mike at French Creek on the X-Kings|
|Mid-way through a 102 mile ride - great on mixed terrain|
|John rolling through the rocks on the X-Kings|
6.12.12 Update - I took the X-Kings to a Super-D event this past weekend and pushed them hard on the downhill, hitting almost 42mph (67kph). The tires held well in the corners and traction was far better than other low knob tires that I've run in the past. I was able to hit a higher top speed in the downhill and brake far later into corners than in years past, dropping 35 seconds off my time in a 3 mile course. Plus, they handled all of the rocks without a problem. A lot of other riders crashed on the day, but the X-King was predictable in when it was getting close to losing traction and I could back off the speed a bit. A good test!
7.3.12 Update - I've been riding a set of Race King 29x2.2 ProTection tires for the past two weeks. These might be the easiest tires I've ever installed on a set of Stan's Crest rims. No mess of sealant going all over the place, no fuss and they instantly inflated and held air with a floor pump.
I initially used the Race King on the rear wheel at the central Pennsylvania Stoopid 50 mile race in tons of rocks and roots. Traction was great and they roll extremely fast, but the sidewalls took a beating on the rocks. The casing is more of a rounded shape than the X-King tire and thus, when going over rocks, the sidewall rather than the knobbies take a lot of scuffing from rocks. I would recommend the Race King tires for situations where there aren't as many rocks - rocky terrain is a better fit for the X-Kings (between the two tire types). In loose over hardpack type terrain, I've found the X-King on the front for cornering traction and the Race King on the back for speed works well for me.