As many of you know, we beat this topic to death last year. However, Lynn and I recently upgraded the wheels on our Mountain Bikes, which led to some playing around. First of all, here's where I started.
1. My primary goals are avoiding dealing with flats (either pinch-flats or real-flats) with as little rotational inertia and rolling resistance as possible.
2. What the racers are riding and the pressures they are using has little relevance to me. They are wanting to win races, I'm not wanting to fix flats in the middle of the poison ivy and mosquitoes, and I certainly don't generate enough power that i have trouble getting it to the ground.
2. I didn't want to deal with the hassle of Bushwacka's ghetto tubeless or with Stan's approach to making regular wheels tubeless. No educated reason behind this other than the requirement for a "high-volume" air source to seat the tire, but it just didn't excite me.
3. I bought a slime tube last year and tested that on the front of my mtb. No flats last year, but I pinched it when we changed wheels this year and it didn't heal itself (and it was a small hole). Discarded Slime Tubes as a viable way of preventing flats.
So once we decided to buy wheels that happened to be Mavic UST compatible, I decided to play with tubeless. The two tires we are using are the Continental X-King RaceSport (me) and the Kenda Karma (Midwif). The Karma is a 460 gram tire with "very supple" sidewall that seems to work well for her.
All of the X-King's are tubeless compatible (meaning they have a tubeless bead) but only the UST model is truly tubeless. The Racesport and Supersonic have a lot of web traffic about how porous the sidewalls are, but that they seal quite nicely with Stan's.
- X-King 2.2: 3 plies / total 84 tpi / 580 grams
- X-King Racesport: 3 plies / total 180 tpi / Black Chili Compound / 490 grams
- X-King Supersonic: 3 plies / total 180 tpi / Black Chili Compound / 460 grams
- X-King Protection: 4 plies / total 240 tpi / Black Chili Compound / 570 grams
- X-King UST: 3 plies / total 330 tp / 780 grams
And then I realized that, even with tubeless, I was still going to need Stan's (or similar) in the tire to deal with punctures. And if that were the case, then why lug around the 290 gram difference between the UST version and the RaceSport version? They would both need the Stan's anyway.
Test A. I mounted the front tire tubeless. I found that the CO2 cartridge inflator I carry for my road bike does a great job of inflating the tubeless tire. I stuck the tire in a sink full of water and was amazed (but not surprised) at the sidewall porosity -- I was surprised at how quickly the Stan's sealed everything up. The next morning I still had an inflated tire, I went for a 12 mile ride that evening and it worked fine. I lowered the air pressure some, but any difference in the ride characteristics was minimal. I pronounced that a successful test; tire + Stan's was 30 grams less than tire with tube and I felt that it would seal any punctures.
Test B. I did the same with the rear tire. This was a little bit easier, because I was careful to only unseat the bead on one side (to get the tube out). After inserting the valve stem and pouring in the Stan's, I manually worked the loose bead closer to the rim. I managed to inflate this one with just the hand pump (and immediately patted myself on the back). Did the same routine with water in the sink, this tire didn't seal up quite as well. Next morning it was flat -- the next evening I aired it back up and rode the neighborhood slowly figuring that was a good way to circulate the Stan's. By the end of the ride it seemed good, and next morning it still had air in it. WOW, I'm a genius. Lynn's bike happened to still be down here, her tire is next.
Test C. I did the same with Lynn's front tire. Her tires are not UST anything. Did the same trick when I removed the tube of not loosening the bead on one side of the tire. Had to use the cartridge inflator for air volume, but the tire popped right into place and I inflated with the hand pump. Stuck the tire in the water. Her sidewall (on a tire that is now three years old) didn't leak air at all like mine -- however, her tire did have a lot of leaks around the bead. These didn't seal until after I rode the tire around some the next day.
Real World Test. This past weekend we went riding in the 14,000 acre Ten Mile River Boy Scout Camp. Started out on level asphalt getting to the camp, and rode a loop that ended up with us coming down a long hill on asphalt at 27 miles per hour. In between was lots two lane rock covered jeep trails that the hunters and Boy Scout maintenance trucks use. I would still say that I really never felt much difference in the performance of the tires, except that we both found ourselves bombing down some sections at 18 miles per hour with enough control to pick which parts of the road we wanted to ride on (avoiding the mud and standing water in lots of sections of the trail). That may show a better level of control than before, in places where we have used the brakes to slow down in the past. (or maybe we are just getting more "one with the bike").
CONCLUSION: After the ride and then sitting two days, my tires were way down on pressure, but I'm ok with pumping them up before each ride (we have to do that for the road bikes anyway). The sink full of water seems to confirm my guess that the flexing of the sidewalls (especially over the really rocky trail) resulted in some really slow sidewall leakage when the tire was just sitting (no sealant being spread around).
I'm pretty pleased with the results thus far. In fact, I'm planning on ditching the air pump that I carry on my bike -- but I might add a CO2 inflator to my back pack.
CONCLUSION 2: I think there may be building acceptance of tires that are tubeless ready but that rely on the sealant to truly hold air. I've seen that in Continental and WTB and Svend was mentioning the new SCT (Sealant Compatible Tubeless) categorization for Kenda tires.