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I just replaced my rear wheel with a road tubeless (Bontrager RL TLR). Was lucky to have the bike shop installed the tyre, took two blokes to put it on the rim. Anyway, my second ride was a couple of days after I bought it and I can feel the wheel bumped a gap on the driveway. So I went back and put some more air to 90 psi.

Two days after I pumped the tyre, I checked the tyre before riding and it only had 40 psi. Is that normal for road tubeless? I only have to add air once a week with none tubeless tyre.

Follow up

I went back to the shop and they said they put enough sealant and insisted that rapid air loss is normal for tubeless. They also offered to put tube in it if it's too much a pain. Caveat, I asked how others' experience with road tubeless and they said I'm the only one with tubeless. I did see there's a stack of TLR rim strip, presumably from new Trek bikes they sold that came with Bontrager TLR wheels.

I sent a link to this question to them and trek, no response yet.

For now, I will just pump the tyres before every ride.

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Bloke, I had to look it up. –  Carson Reinke Dec 12 '13 at 13:37

3 Answers 3

You're really asking two questions here:
1) Do road tires lose air more quickly?
And 2) Do tubeless tires lose air more quickly?

First off, let's talk about the different ways that tires can (and do) lose pressure.

Obviously, they can lose pressure through a poor seal, either on the valve or where the tire seats to the rim on tubeless tires.

Tires also lose pressure through permeation. This essentially means that air molecules escape between the molecules that make up the casing (i.e., tube or tubeless tire). This is true of all tires, not just bicycle tires.

And of course, there is always the possibility of a slow leak caused by a puncture.

No matter what the reason for air loss, a tire at a higher pressure will lose air more quickly than a tire at a lower pressure. Thus, if we assume the same type of tire, materials, etc: road tires lose air more quickly than cross tires, and cross tires lose air more quickly than mountain bike tires.

Additionally, air loss is also more noticeable on smaller tires because any air that escapes represents a larger percentage of the total volume of air. So, if you have a 26x2 mountain bike tire and a 700x23c and inflate them both to the same pressure, they will initially lose the same amount of air at the same rate. However, since the air lost in the road tire represents a larger percentage of the overall volume, the pressure will drop more quickly. And as the pressure drops, the road tire will lose air more slowly, but the pressure will still drop more quickly than the mountain bike tire due to its significantly greater size.

Air loss is also exacerbated by thinner walled casings. This means that (again, assuming the same materials) lighter and thinner tubes will lose air more quickly than heavier and thicker tubes.

Now, I don't have a lot of experience with tubeless, but given that caveat...

Tubeless tires should in theory lose air less quickly than tubes due to the thickness of the casing and the fact that people typically run them at lower pressures. I have heavily stressed "in theory" here because it is certainly possible that tubeless tires are more permeable than tubes and because of this, some balance is achieved.

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On auto tires, at least, the tire itself is not particularly good at holding air. Rather, "tubeless" auto tires have a tube of sorts -- a layer of relatively soft yet air-resistant rubber -- laminated to the inside of the tire casing. I would assume the same is true of tubeless bike tires. –  Daniel R Hicks Dec 12 '13 at 4:01

Road tires have higher pressure with lower volume, and both of those properties are going to cause them to lose air more quickly than a lower pressure, higher volume tire, tubeless or not.

With that in mind, it may be the case that the tire needs a little more sealant. The stuff has to squeeze around not only throughout the casing of the tire, but also between the bead and the channel the bead sits in. If there's not enough to slosh around, the area between the bead and it's channel may never seal.

Another possibility as Lucky pointed out is that they damaged the bead during install, though this is pretty hard to do. They could have taken a hunk of rubber off of the bead to expose the carbon fiber below, but that would likely require some serious hamfistedness during the install process.

A more likely cause is that they messed up the rim strip during the install. The wheel you have does not have a solid metal outer wall but instead relies on a rim strip to seal the spoke holes. This is similar to the Stan's NoTubes solution of using tape though in my experience- albeit with brands other than Bontrager- the rim strips don't work as well (It's possible that the valley in the rim is too deep for the tape to conform to and/or they're just looking for the convenience of the rim strip, but that's somewhat beside the point). Either way, tape and rim strips can be damaged pretty easily if you're not diligent with your tire levers, and given the horror stories I've heard about installing tubeless road tires I think this is something that should be inspected by the guys that installed it in the first place.

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I don't believe the "which type loses more air" is as obvious as you make out. A 4 bar, 50mm tyre has more than twice the surface area of a 6 bar, 22mm road tyre but only 1.5x the pressure. They have very similar leaky areas around the bead and spokes. It'd be interesting to measure and I can't find any research online. But the smaller tyre will lose pressure much more quickly than the bigger one as it has less than half the volume. –  Mσᶎ Dec 12 '13 at 2:47

If the guys who installed the tubeless tire didn't clean the rim and use sealant on the rim and tire before installing it, then it is likely losing excessive air. Tubeless tires run at a lower pressure than tube type tires...about 10 to 15 pounds per square inch less, so they need more attention than the tube type tires. I'd take the bike back and explain to them about the rapid air pressure loss and ask them if they cleaned and used sealant on the rim and tire when mounting it. It's also possible that they ruined the bead when mounting this tire. Make sure that's checked out also.

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I was there when they wrestled the tyre and saw that they put sealant in it, although by pouring it rather than injecting trough the removable valve core, and heard the tyre pop as it seated the rim. I'll ask them about cleaning and tyre bead. –  imel96 Dec 11 '13 at 21:49
@imel96 - The "pop" is certainly normal for tubeless auto tires. –  Daniel R Hicks Dec 14 '13 at 14:14
Just using a sealant isn't the correct way with tubeless tires. If the wheel area where the tire must "seat" ( seal ), then any dirt or debris on the wheel will allow an air leak. I repaired tubeless vehicle tires for years, and cleaning the rim for a good seal was the hardest part. We had to use a wire brush and a cleaning solution to get a good seal. –  user4975 Jan 5 '14 at 18:38

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