Jim’s Tech Talk
By Jim Langley
This will be the last in what’s turned out with today’s article, to be a 3-part series on repairing and preventing flat tires. We provided our tips and you readers added yours with interesting and helpful tips, advice and product recommendations. Thanks everyone! If you missed the first two columns and all the great comments, here they are: Sharing Lessons From a Flat Tire Fiasco and Your Flat Tire Prevention Tips And Product Recommendations.
This week, the goal is to help a Salt Lake City cyclist named Rob who asked for our help with his leaking tubeless tire. We’ll take a crack at answering Rob and after reading our suggestions please weigh in with a comment if you have more tips for him.
Rob Asked
“Hi Jim and friends,
I have a question about tubeless tires, which I have used on my gravel bikes for around 5 years and generally like. I am still learning the tricks needed to live happily with tubeless tires. I have 50 years of experience with tubed tires and a long list of tricks, but I need to build the equivalent for tubeless.
The specific situation I am grappling with are the possible sources of the small leaks that other riders tell me are common with tubeless tires. On my regular ride, an Orbea Terra, I have replaced tires, regularly added sealant, etc, but one of the tires consistently loses 10 lbs of pressure overnight. One problem was that the valve core was not seated as well as it could be; fixing that improved things but did not fully resolve them.
I wonder if, with all the wisdom at RoadBikeRider homebase and the readers, we could gather up a list of possible sources of small leaks in tubeless tires. Ultimately, these are likely to be installation hacks, but from what my buddies tell me, I am not the only one struggling to get things ‘just right’ with my tubeless tires.
Thanks for the great content and all you do for cycling.
Cheers,
Rob
(Salt Lake City)”
My Ideas
Sorry to hear about your tubeless tire trouble Rob. To me, losing 10 pounds of pressure overnight is not a small leak. I consider that a big leak. One of the great things about tubeless tires is that they should stay sealed and inflated. You might lose air over a week or more, but usually it wouldn’t be more than a few pounds.
You wrote that only one of the tires consistently loses those 10 pounds too, which makes me curious why it’s just that one and not the other tires you’re running or have run? Maybe there’s something different about the tire or setup and if you could discover that, you’d know what to avoid next time.
Look for the Leak
The first thing you might try is filling a plastic tub with water and slowly turning the wheel, submerging one section of it at a time looking closely for escaping bubbles. You might find something stuck in the tire or the air coming out somewhere else to give you an idea what might be wrong.
Tire sweating
One tubeless leaking issue is sidewall seepage, which shows up as if the tire is sweating sealant through the casing. You would expect the sealant to clog the pores in the tire casing instead of passing through them, but I’ve seen this phenomenon more than once and it even occurred on one of my WTB tires, makers of really nice tires.
I actually don’t know if this was an issue with the tire or with the sealant. The tire held air fine even losing sealant through the casing like this. But maybe if I’d looked for a thicker sealant it would have solved the problem. I also think that since my other WTB tires didn’t do it, that maybe there was an issue with that one tire.
How the Sealant Works
The sealant is actually designed to keep working to travel to any leaks and seal them. It does this best when you’re riding, which helps the sealant travel inside the tire. Also, when riding, your weight on the tires causes the casing to flex allowing the sealant access to any pores or small voids anywhere in the tire. That’s why it’s a good idea to ride around a bit on newly installed tubeless tires.
You mentioned a loose valve core, which could cause a leak, however, once you start riding on the tire, the valve will be moving with the tire and the sealant should try to seal any leaks, even one at the valve core. So I would have expected the problem to slowly stop as the sealant did its work.
Is there enough sealant to seal the tire?
One potential issue with any tubeless tire that’s losing air is whether there’s enough sealant in the tire to keep sealing the leak. Maybe there’s a tiny leak somewhere such as from the tubeless tape not quite covering a spoke hole in the rim. In that scenario, the sealant could be working hard to seal the small leak and in the process going inside the rim, which means less sealant inside the tire. After a while there might not be enough sealant inside the tire to seal punctures anymore.
I always assume it’s going to take a fair amount of sealant to travel around and seal the tire, so I always put more sealant in tires than the recommended dosage.
Rim Tape Issues
A common cause of rim tape issues is tight tire installation. If it’s a struggle to get the tire beads up and onto the rim, it’s possible for the bead to grip and push the rim tape and if this exposes a spoke hole, it might be impossible to see it with the tire in place. There are different types of tubeless rim tape and strips and they come in different widths too.
If you suspect there’s a leak related to the tubeless tape, you’ll want to remove the tire, sealant and old rim tape, clean everything well and start with new tubeless tape. Be sure to get the right width for the width of your rim. If the tape is too narrow it’s more likely to move out of position. And be sure to apply it carefully, avoiding air bubbles and wrinkles, which can lead to leaks.
Summing Up
If I were you Rob, I would try to fix the tire that’s losing 10 pounds nightly by adding sealant to it and seeing if that fixes it. Be sure to ride around slowly for a while to give the sealant a chance to seal the leak.
If that doesn’t work, I’d take the tire off and look inside for something causing the leak, such as a too-narrow tubeless tape or a bad tape job or an opening to the rim from a cut. I would look closely at the tubeless valve too and replace it if it didn’t look like it sealed properly against the rim or if the base of the valve looked damaged or cut. If the rim has sealant in it, it’s usually getting in there through the spoke or valve holes. Good luck and let us know how it goes.
Jim Langley is RBR’s Technical Editor. A pro mechanic & cycling writer for more than 40 years, he’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Tune in to Jim’s popular YouTube channel for wheel building & bike repair how-to’s. Jim’s also known for his cycling streak that ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.
I have more issues with tape than anything else when it comes to slow leaks. I have been running tubeless on road and gravel bikes exclusively for >5 yrs now. I seldom find that tape will last much more than a year, with some notable exceptions. Recently I observed that if I spray soapy water over the vent hole on my Zipp rims that a very slowly developing bubble may form from the air that is leaking slowly into the inner rim space. I have an old set of Mavic aluminum hookless wheels with undrilled rim beds that are total no-brainers because they do not need rim tape. This is such a frequently overlooked and undervalued feature! My next set of wheels will be Fulcrum for this same reason
My wife’s bike had a worn out valve core which caused a similar problem. Replacing the core did the trick.
Same for me! I live with the problem by inflating the tyres before every ride. My Xiaomi electric pump is invaluable. I think that my problem is that my tyres (Continental Terra Speed) are not very puncture resistant. I live in the Philippines where exploding truck tyres leave an abundance of very small metal shards on the roads. They are by far the biggest cause of punctures on my tubed gatorskin tyres.
Overnight my Terra Speed tyres become quite blotchy – damp patches. I suspect that I have a lot of micro punctures. To be honest, my life isn’t perfect so I live with the problem. It doesn’t detract my riding pleasure. I have very limited tyre clearance so I can’t fit any other tyres (650b)
If you have damp patches maybe micro punctures are the issue?
Hopefully you can enjoy your cycling despite this
I’ve seen one case where air leaked from the seam in an aluminum rim that wasn’t properly welded.
Regarding tubeless tires “sweating”, I have Maxxis Ravagers on my gravel bike that do it constantly, though they don’t lose significant air pressure. I’m happy with the tires otherwise, but I won’t be buying them again, as Maxxis refuses to cover them under warranty..
Yes, I have had Michelin tubeless tires that would leak sealant through the sidewall as well. I changed to a different sealant and the issue went away. I would check the rim bead to make sure it is totally clean. If it is dirty or has imperfections, air can leak from there. Other than that, check that the valve seals off well at the rim.
I have come to the conclusion that for road bikes, tubeless tires are a solution in search of a problem. I can change a flat clincher in about 5 minutes. But if a tubeless tire goes flat, it’s a much longer production. Yeah… I get that the sealant can seal small punctures before the tire goes flat. But often the “cost” of this is getting sealant sprayed all over you, your bike, and other riders. And replacing a worn tubeless tire is much more hassle than a clincher, to say nothing of having to check and top up sealant regularly. I’ve tried tubeless… and I’ve gone back to clinchers. Thanks, but no thanks.
And let’s not talk about “hookless”, and potential safety issues with those…
I too had issues with sidewall seepage on my gravel bike. I ride Specialized Pathfinder Pro tires with natural sidewalls. I switched to Muc-Off sealant (was using Stan’s), and the problem went away. Muc-Off and Silca sealants are probably the most viscous sealants I’ve used. They do a great job of sealing, especially larger punctures.
In my experience, the source of leaks often comes from the base of the valve (not the core) where it extends from the rim. It’s essential to use the correct size rubber washer — too big and it will not cover the opening; it should fit snugly against the rim with the nut, but it shouldn’t be overly tight. I have found that hard plastic nuts work better than metal ones, since they can flex to match the contour of the rim.
Over time, sealant can gum up valve cores causing them to leak even when closed. Try replacing the valve core.
Really did my best to work with Tubeless, but after a number of issues (yes I know that they can be solved and are undoubtedly user error) I have embraced TPU, Honestly cannot tell the ride difference (on road or gravel) Mountain…well yes. But going out on my daily commute, or just for a weekend ride, I am secure in the fact that my tires seldom need topping up (daily with TL) and I can quickly address a flat (have not had one with TPU in the 8,000km or so since I made the switch, slightly disappointed because I cannot use my nifty new electric pump. and yes, I am using the cheap ali express $3 rainbows, pink, orange, green, they are all the same. YMMV
I ride Rene Herse tubeless. Orange Seal goo didn’t work great for sealing the tires. Panaracer works great, seems to have more and larger particles.
The tires have sealed multiple small leaks, usually without too much goo spray. New tires often need some riding to close the pores.
I’ll lose a few pounds air each week, more in the summer. For that amount of care I find them worthwhile.
I have tubless tires iput tubes in side’ have had only 1 flat in 5 yrs. I ride at 80 lbs pressure. I normally use the pump every 2 or 3wks. Keeping Fit, Gary B.
What kind of wheels are they? I once had a tubeless tyre losing pressure through a small crack in a carbon rim.
I’ve been using tubeless road tires since 2011 to reduce flats for the following 2 reasons.
One reason is when I race I do not have support to replace a wheel if I get a flat, and the other
on long brevets so I don’t have to deal with flats on a cold or rainy night or at least reduce the possibilities.
However, I have found the following drawbacks using them.
1. The sealant leaves a “gummy” residue on the tires and rims which is difficult to remove. Some are easier to remove than others.
2. I have had rims corrode from the sealant-alloy combination so much that had to be replaced during the early days.
3. This residue accumulates so you have to clean the tires and rims at least once a year.
4. After you clean the tires and rims they are difficult to seal again even with a compressor. So I sometimes end up replacing the tire even though it’s not worn.
5. If you get a flat, and for some reason it does not seal itself, and you have to install an inner tube it’s a mess.
6. When you have to install an inner tube on the road you need a small pliers to loosen the valve ring. I had it tight so it wouldn’t leak.
Since the above 2 reasons do not apply to me anymore I have switched back to tubes.
Robert Hunter
Rob again, reporting on the latest in the leaking tire saga. I took Jims’s advice and filled the tire with air then submerged it in my bike-shop sink. What I saw was almost bizarre: small beads of air leaking from a swarm of about 20 small holes in the sidewall of the tire. I cannot imagine how one could get a puncture like this from natural causes and this was a tire that was only a few months old. I filled the tire with a double-dose of sealant and made sure lots of it settled on that side of the tire. I gave it a few hours, pumped it up, and it has been good enough since then.
Ideas? I can only think it was a defective tire (anyone from Schwalbe reading this?) and I will likely replace it soon. But at least the mystery of the leak was solved!