This, along with the Continental Mountain King, are my go-to tires. My 29er hardtail has the 2.2 in the rear and 2.4 in the front, and I can swap it out for the 2.2 front when I do not need the additional traction. My 27.5 FS has 2.4 front and rear, typically with the X-King in back and Mountain King in front for additional control and cornering. Grip is good, if not great depending on the condition. This isn't the ideal tire for all conditions, but I ride in all seasons, weather, and mixed terrain from sandy beaches to gravel to rocky single track. While I'd love to have five wheelsets with varous tire combinations, that's just too expensive and cumbersome.

The tires are very durable - the only time I get flats is when the sidewall is so deteriorated from use that the sealant seeps through, and that is after 600-800 miles on the rear, 1200+ on the front (depends on the time of year and trails). See the attached pic - still held air pressure at this point.

The knobs hold up very well. When the start to wear out they turn out to be great gravel tires for another 200 miles.

These are not the lightest or most aggressive tire, but they are a perfect compromise for me. I want something that can be ridden hard on all terrain and not swap tires every two months or when the trails are dry or wet. While I would definitely race on them, however I'd prefer to be more selective based on the trail conditions. Then again, there's something to say about not having to worry about the tires and just go.

I have not had a problem setting these up tubeless.

I typically run the following:
2.2 X-King front and rear for smoother trails and gravel (29 hardtail)
2.2X-King 2.2 Rear with 2.4 X-King front all around setup (29er hardtail)
2.4 X-King front, 2.4 Mountain King for general trail riding (27.5 FS)
2.4 Mountain King front and Rear for most aggressive trail (27.5 FS)

I purchased these tires as a last alternative as I had a ride scheduled and needed tires bad. This is what was in stock in the needed size and price range. I was stoked at the performance they delivered compared to a set of Racing Ralph's I took off, (not that the Ralph's are a bad tire, just not good for my use). My every day ride has about 4 miles of pavement and 16 miles of CA High Desert which consists of hard pack, decomposed granite, sand and jagged rocks. The X-Kings perform great on all of these surfaces and with the protection side wall, I have yet to even see a mark from the rocks! i'm running these on a carbon hard tail 29er and have found that 28-30 psi give me good dry grip and still rolls good on the pavement. I can easily say for my are these are great tires.

PROS: Light Weight, Low Rolling Resistance, Quiet On Street

CONS: none

BEST USES: Loose, Hard Pack

It's not perfect, but compared to other tires (Maxxis, Schwalbe), it's less costly for the protection version, lasts longer, rolls as good or better, and is more cut resistant. I've had 6-8 of these tires, and keep coming back. I did have one warranted for an out-of-round carcass. The 2.2 looses knobs easier than the 2.4 because the 2.2 has a smaller radius where the knob attaches to the tire. One 2.4 I've had never did seal up real great, but overall they've been better than the competition. The tread hasn't lasted as long as the Mountain King though. Mostly use the X-kings as a back tire now. Not a good mud tire at all.

PROS: Rolling Resistance, Fit On Tlr Rims, Cut Resitance

CONS: Looses Some Knobs

BEST USES: Racing, Mountain Biking

I really like the design of the overall tire - lightweight, good traction, corners well, climbs very well and looks good. I purchased this tire to be used as a rear on my trail bike and within 200 miles the tread was very worn and I punctured the sidewall. Purchased another thinking maybe badluck but again within 200 miles tread was wearing fast and I again punctured a sidewall. Decided to run a tube to get some more life out of the tire and managed to get about 100 miles more before I moved on to another brand...

PROS: Lightweight, Easy To Install

CONS: Sidewall Puncture, Tread Wears Fast

This tire has not held up well. I have put about 30 miles on it. One tread block completely came off on the side wall. I have 3 more that have started to rip off. This is not a cheap tire but it has performed like one.

CONS: Durability

I was able to mount these tires with no tools on tubeless rims. Aired up, tight seal, ready to roll. I had them out on wet, and dry conditions, grip good on both, especially cornering. I would buy these again, and recommend them to any off road enthusiast.
Scott

this are one of the fastest tires there are, when on the road, i´ve been able to hang out with roadies, nit bad traction on hard packs, and they have survived couple of rock gardens.

Have used the X kings for several years now mostly on my rear tires on both my 29er and my 650b. I have used them here in FL, the mountains of NC, and in CA. I find them to have excellent grip and are very durable. The only con is that they are a little narrow for their size.

PROS: Easy To Install, Durable

Love the 2.4 for the front and back. Perfect to run 24-26 psi, great grip, and they corner well on the descents.

Fast rolling tire with great traction. I recommend the 2.4 vs the 2.2in

PROS: Smooth Ride, Handles Well, Great Components, Lightweight

BEST USES: Single Track, Casual Trails, Cross Country

Lightweight for x country biking

Great tread pattern, and excellent traction. I don't have many miles on yet, but they seem very durable.

Very stiff sidewall, would not recommend using these with tubes.

The actual width is around 2.0, not 2.2 as stated.

PROS: Durable, Easy To Install

CONS: Narrow Vs Stated Width, Narrow

BEST USES: Racing, Mountain Biking

tires tread wore rather quickly but finally I found a tire I could actually wear the tread out ok before the sidewalls gave out. size runs narrow compared to other conti tires I've used.

PROS: Attractive Design, Durable, Lightweight, Easy To Install

CONS: Tread Wears Quickly

BEST USES: Mountain Biking, Racing

I know that seems like opposite thoughts. They were easy to get to pop on the bead. I am having a little trouble getting them to hold air after the rides. Might need to add more sealant. When I mount new tires, I always folloe the way tubeless is supposed to be set up to the T.

PROS: Easy To Install

CONS: Difficult To Install

I use this on the front, I like it better than the Maxxis Ardent.

I have had the same issue with Mtn Kings as well- huge pain installing tubeless in the 2.4 size. The bead just will not set. I have no experience with their small tires so I can't comment.
Basically the only way I have been able to get them to work is to run tubes for a couple weeks then use a Stan's liner. Way too much effort for tires that performance wise are not any better then other brands.

As for the tire once I used them as I wanted they grip well in hard pack to loose over hard pack and wear well. Used as a front.

I will not buy again due to the pain of tubeless install.

PROS: Durable

CONS: Difficult To Install

This is a GREAT tire. It's hard to install as tubeless. I spent about a week removing the bead and re-seating the bead to get the tire to seal correctly. It has tons of pin-hole leaks on the sidewalls and hopefully stans no-tube liquid will fix that over time. Over all I like it, but I don't like to think I have to check my tires EVERY time I ride now.

BEST USES: Mountain Biking, Racing

I'm not mtb expert, mud builds and sticks to the tire and lose traction. Heavy rolling resistance, cant figure out the right tire pressure setting for my ride, i have not tried on dry trail yet. Again maybe i'm doing it all wrong.

I used the tire on the front for a full season on various terrain. It corners really well, has great rolling resistance, sheds mud well and seems to like high PSI. It's not great in rock gardens due to its narrow profile but it has been very durable.

PROS: Attractive Design, Lightweight

CONS: Difficult To Install

BEST USES: Racing, Mountain Biking

Jensons is the best

PROS: Attractive Design, Easy To Install, Durable, Lightweight

BEST USES: Casual Riding, Racing, Mountain Biking

Casing is too porous for tubeless, just won't hold air. Tread is fast and great for all conditions (around here). I've raced these hard with predictable handling and good speed. They need to design a 120 tpi version, the casing is a bit stiff. Sidewalls show threads very quickly and the "protection" appears cosmetic to me. Decent tire, but better alternatives exist.

CONS: Sidewall Wears Quickly, Forget Going Tubeless, Limited Compatibility, "protection" Is A Gimmick

BEST USES: Casual Riding, Mountain Biking