By Jim Langley
This week’s tip is the result of an email from my buddy Seth. We’ve actually never met in person but have been email pen pals through our RBR comments section and outside it, too. Seth hails from Tucson and one day when I’m there he’s promised to pace me up Mt. Lemmon. Can’t wait.
The note Seth sent that spurred today’s topic was about his recent crash. Only four miles from home, banking into a turn, a sudden loss of tire pressure made his bike slide out from under him. Seth hit the deck slamming the back of his helmet into the guardrail. But, like any good roadie he was more interested in his bike’s condition than his own.
Said Seth, “My tire simply lost pressure probably from the lack of sealant. It’s fine now and the bike is none the worse from the fall.”
Tubeless Tires and Pressure Loss
Lots of things can cause a tubeless tire like Seth’s to go soft or even almost flat. For me, it happens more often on my mountain bike than on my roadster. That’s because there are more obstacles creating opportunities for what’s called “burping.”
Burping is the tire unseating in one spot, which lets some air out, sometimes a lot of air. The last time it happened to me I had attempted to manual up and over a ledge. In case manual is gibberish to you, here’s a how-to: https://www.pinkbike.com/news/how-to-manual-with-duncan-shaw.html.
When I did it, I cleared the ledge with my front tire but brought the front end down to one side causing me to strike the rear wheel and tire crooked on the ledge, which created a peeling force that unseated and burped the knobby. Suddenly I had a flat. But it wasn’t really a flat, rather a loss of air. Adding air got me back on the trail.
Sealant Doesn’t Last Forever
The role of sealant in tubeless tires is to travel to any air leak and seal it. It can and will do that as long as there’s enough inside the tire.
I used Stan’s No Tubes as a reference here because they’ve been in the tubeless game since the beginning and I’ve used their products since then. They recommend 2 ounces (60ml) of Stan’s sealant for road tubeless tires.
And, for maintaining sealant, they say “The sealant should last an average of 2-6 months depending on factors such as: temperatures and humidity in your area, how often you ride, where you store your bike (cooler is better), tire casing thickness, number of punctures the sealant has already sealed that you never knew you had, etc. A good preventative maintenance schedule for most riders is to check/refresh your sealant quarterly (every three months).”
Refreshing Sealant
In order to check your sealant level, you would need to remove enough of a tire to look inside. That means breaking the tubeless bead lock on tubeless-ready rims, which you may not want to do. Because if you only have a floor pump, you might not be able to inflate the tire enough to get it to reseat.
An easier approach is to just assume you need a little more sealant and squirt it into the tire through the valve. To do this it helps to have a valve core removal tool. I like Park Tool’s Valve Core Remover: https://amzn.to/3tBu5tN.
With the tool (or you can carefully do it with pliers – don’t ruin the valve core!), you can hold and turn the tubeless valve’s core counterclockwise to remove it. First, be sure to rotate the wheel so the valve is at about 10 o’clock or else some sealant could come out along with any remaining air that leaks out.
It’s also a good idea to lift the wheel off the ground before removing the valve core. That way the floor/ground can’t push on the tire and unseat it from the bead lock, which is unlikely but might happen.
Dealing with a Clogged Valve
Because sealant’s job is to travel to where the air escapes, it’s likely that it may have created a skin inside the tire over the valve hole. If that’s the case, when you try to squirt sealant in it won’t go in because the skin will block it.
To prevent any chance of this happening, once you’ve removed the valve core, especially if no air comes out, poke something harmless into the valve core to break the skin (nothing pointed because you might puncture the tire). A handy item for this that you probably already have in your shop and that will fit in any seat bag is the applicator tube/straw that comes with cans of spray lube.
Simply poke that into the valve until you feel that there’s nothing blocking the valve hole anymore.
Inserting Fresh Sealant
There are injector tools for putting sealant into valves. But, it’s easy to do it with the nozzle that’s built into Stan’s No Tube’s 2 ounce size of sealant, too. This will fit in a seat pack, too. Once it’s opened, you can push the nozzle into and hold it onto the valve and squeeze the tube of sealant to squirt it all into the tire. If you buy a supply of sealant in larger containers you can keep refilling the 2 ouncer and use it again and again.
Squeeze the sealant in with the valve at about 9 o’clock or 3 o’clock so that the liquid can drop down into the tire. Once it’s in there, screw the valve core back in. Then reinflate the tire.
To ensure the new sealant seeks out and stops any air loss, spin the tire a lot. It also helps to ride around, which flexes the tire casing and helps the sealant seal any pores and gaps that need it.
Hopefully, refreshing your sealant on a regular basis will prevent any sudden tubeless tire pressure loss and especially any crashes from them.
Please share your favorite road tubeless tire sealant tips for preventing these issues as there are lots of choices in sealants, tubeless tires and maintenance tools and techniques.
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.
Call me an old dog unwilling to learn new tricks. But all the problems noted don’t happen with basic years dependable tubes. A friend I ride with has had several tubeless flats on rides. It takes twice the time to fix by inserting a tube . I do get the occasional tube flat which takes 5 minutes to replace if I’m going slow. I’ve been buying good guiltily tubes in bulk, 50, for just over $2 each and splitting them with another rider. I’m not bothering with patching at that price. So to each his own. I’m sticking with tubes. As an addendum I remember a big group ride when a tubeless got a large flat and sprayed sealant all over the bike and rider on its way to flat.
I started putting sealant in my mb tubes a couple of years ago. No flats and very little air leak when I check check my inflation before I ride.
tubeless == WAY TOO MUCH TROUBLE
who needs diva tires?
Exactly!
I’m not interested in tubeless tires. I’m an early adopter of much new technology. I only have road bikes, no mountain bikes and I don’t think the advantages of tubeless outweigh the negatives.
Dave: Would you provide a link to where you can buy tubes in lots of 50 for $2+ each?
Thank you
Check Excel Sports (https://www.excelsports.com/). I have purchased Conti Race tubes from them in bulk, although not 50 at a time! Last time I bought 5 for $14 so $2.80 each, but the price may have increased since then.
Jim, thanks again for another informative article. After reading it, it seems to me that Seth’s diagnosis of the source of his problem (lack of sealant) can’t be correct. Am I right in saying that lack of sealant cannot cause an air leak – it just won’t be able to seal an air leak that was caused by another source, like burping, or a puncture from an object, i.e. things caused by external forces, not lack of sealant. So what really caused Seth’s leak? Did he pick up something while banking into the turn? I’d be more concerned that maybe his tire might not be properly sized to his rim. What do you think? Thanks again, Pete
Thanks for the comment and questions, Pete. Yes, the lack of sealant didn’t cause the flat but you can see how someone could blame the sealant if it wasn’t able to stop a flat, too. I don’t know what really caused Seth’s flat. He might have had a puncture and slow leak and there wasn’t enough sealant to stop it. To me that’s the likeliest cause. I doubt that Seth had any tire fit problems because he rides quality wheels and tires and knows how to mount them properly.
Thanks again!
Jim
Jim and Pete, allow me to elaborate as to why I think it was a lack of sealant. First, Pete, size was not an issue, I’ve been running 700 X 25mm Conti GP 5000 tubeless (Jim’s favorite — NOT!) on these rims for a while and
…I’ve been using tubeless only for 7 years. My mistake on this ride was not reacting to a different sound I heard ride over some gravel on the tarmac. I had topped-off the pressure before the ride. Visually, all looked good with the front tire. It did not feel like it was losing pressure, but I must have hit an expansion or rut which knocked the remaining air out just before the sharp turn where it flatted and I went down. When I got home and inspected the tire here’s what I found: No puncture, the valve was intact, no sealant (!), the tire never lost its seal with the rim (that’s a first — great wheels) and I was able to blow-up the tires by hand, checked for leaks with a spray bottle and all was good. Not what I expected. So, by the process of elimination I concluded it was the lack of sealant exacerbated by burping, etc. Whatever the case, I should have known better and stopped after hearing unfamiliar sounds. No question this was user error. Let me know if you have further questions.. Seth
I’m currently using Sunlite #63741 700×18-23 available on eBay 50 for $113 free shipping.
The valves are threaded 48mm and work fine on my 40 mm carbon rims. Any larger rims would not work with this length stem so be careful.
Thanks Jim. You have just provided me with other reasons why I don’t & won’t use tubless tires.
Shimano does not recommend Stans due to interior rim corrosion. Use one of the others.
Hi BFC – could you provide a source or link for your Shimano statement please? Thank you!
Rim corrosion with Stan’s is no longer an issue. It was a problem years ago when Stan’s had ammonia in it.
Thanks for pointing that out, Brian. Yes, that was a problem years ago and not now.
Jim
While burping is not uncommon with low-pressure, off-road tires, it seems really unlikely that it would occur on higher pressure road tubeless tires, assuming that they’re properly inflated. Did Seth indicate whether he had checked his tire pressure before the ride? Starting out with low pressure could result in burping, but it still seems unlikely during normal riding and cornering.
Did he say what tires and rims he has? There are still compatibility issues with road tubeless that you don’t see with off-road tires and rims. A poor fit is another likely cause of sudden air loss.
Did he check the tire to see if there was any evidence of sealed punctures? Perhaps he had a leak that lowered his tire pressure during the ride, before the sealant plugged it (I know he mentioned “lack of sealant”, but does that mean he didn’t have any or was it just in need of renewing?).
From my experience of running sealant for 15 years or so, sealant manufacturers typically recommend using 2-3 times as much as you actually need. Remember, they’re in the business of selling sealant. I never use more than an ounce/30cc in road tires. Two ounces is plenty for MTB tires. Using more sealant than necessary has drawbacks, such as cost, weight and an increased likelihood of developing “Stanimals” or “oysters” (clumps of congealed sealant) in your tires.
For me, personally, vibration induced joint pain is the limiting factor on the duration of my rides. I love tubeless because it allows lower inflation pressures – a god send for arthritic hands.
Road Tubeless technology has improved significantly since my 1st (unsatisfactory) experiences over a decade ago. About 5 years ago, I discovered the combination of Compass Tires (now Renee Herse), and Orange Seal, thanks to my LBS. Since then, I’ve ridden tubeless with ALMOST no problems on multiple bikes. I did have a bad crash when my rear tire ‘burped’ on a fast gravel descent. Upon examination, there was no sealant left in the tire. It had been about 4 months since my last ‘top-up’. Now I set a calendar reminder to check sealant levels every 3 months.
However, I’ve also noticed that the rate of sealant evaporation varies greatly between tires/wheels, and seasons. Consequently, I measure sealant levels prior to ‘topping-up’. This is easy – just as Jim recommends, elevate the wheel and remove the valve core. But then, rotate the tire so the valve is at the 6 o’clock position. Then, clean the valve (I use a pipe cleaner) and insert a small plastic zip-tie (black is best). The Zip-tie is your ‘dip-stick’ – they have tiny horizontal ridges which catch the sealant – and provide an unambiguous visualization of sealant level. That helps guide the amount of sealant I need to add to each wheel (usually closer to 1 ounce than 2).
While this appears complicated, after a few cycles the entire exercise on 3 bikes takes less than a half-hour (including wheel inspection and light cleaning).
Sealant – or lack thereof – has nothing to do with burping, it simply seals punctures.
I have eight bikes and one of them had tubeless tires. I sold that bike after one year. After 42 years and 365,000 miles of riding and who knows how many flats with tubes, I found the tubeless system to be a complete waste of time. If I ride 12-13,000 miles this year I may get two or three flats that I can fix in 5 minutes. I was getting punctures on the tubeless that weren’t always sealing. Try removing that tire from the rim and then getting a tube installed so that the tire doesn’t have a hump or dip in it. Try pumping up a tubeless tire with anything other than an air compressor or a pump with the air compressor chamber. Having to deal with the sealant in general was just another pain in the neck with these. I’ll stick with tubes! The bike manufacturers do have a way of solving problems that don’t exist. Disc brakes would be another example: bleed them, replace the pads, replace the entire shift lever when the seals fail, etc. Rim brakes. Tubes. Cable shifting. They meet the KISS principle which the bike is, or was, based on.
To help avoid the sealant forming a skin over the valve I turn the wheel so the valve is a 12 O’clock when I get done riding
When will a quality airless tire take over. I have to patch my tube on the trail every now and then, no big deal. Air pressure adjustments to conditions are easy on the trail. Like more pressure for smooth pavement to use less energy and less for off road dirt and gravel to have more predictable handling. Seams to me technology isn’t far from being able to change the firmness of something through magnetic applications. I think a tire that can change it’s firmness and tread structure on the fly would be a huge advantage on any vehicle. Probably expensive. But I bet it would sell.
Tubeless sucks, you have to carry a tube anyway, plus a tire plug and the tools to insert said plugs if you need to repair a puncture. I’ve tried sealant in my road bike tubes about 12 years ago and when I did get a puncture the sealant covered the the rear of the bike and the back of my calves. Dave is right, tubeless is too messy, fiddly and a PITA, especially on high pressure tires. I don’t think the “positives” out weight the negatives.
I don’t run tubeless on my road bikes but for a mountain bike it ranks up there with full-suspension, drop seat and 1X drive train. For about six years, I have been riding a Santa Cruz Hightower with Maxxis 17.5 plus tires with Orange Seal sealant. Air pressure is 15 psi front, 16 psi rear, I weigh 180 pounds, am a rather aggressive rider and have never experienced a so-called burp flat which is usually caused by underinflation. Like someone else has already noted, sealant is for sealing minor punctures on the go and does not secure a tire to the rim. . During my days of tube tires on a Specialized Stumpjumper, I was constantly plagued by flats. Never happens with tubeless—best thing since sliced bread!
I’ve been running tubeless on both my road and Mtn. bikes. On my road bike for last two years with no problems. On one of my regular group rides last year someone had thorn tacks on the road. As the group rode thru the tacks 5 of the six of us got flats. Some one & some two flats. All the other guys were running tubes except me. They all got flats but except me. The tacks were stuck in my tires but did not flat. The front had two tacks. They all had to change out their tubes. I left the tacks in until I got home before pulling them out. As I pulled them out the air did seep out a little until they sealed off. I’m still riding on those tires today. Have not had any flats on them. Don’t know how many flats I might have had if not for the sealant. I can say that I did pull out a small sand burr once but not sure if it had gone all the way through the tire. I’ve been running tubeless on my mtn. bike for probably last eight years. I will say tires have gotten a lot better in the last couple years than they had been previously. I really love riding tubeless tires. They can take a lot more abush plush run lower pressures, corner better and a lot less flats. Like I said tires have gotten a lot better the last couple years I can’t recall the last time I’ve had a flat on my mtn. bike. It’s been several years and then I just added a plug. aired back up and kept going. Most people run tubeless on mtn. bikes but the few that still do are still having flats and are running higher pressures making for harsher rides. There’s no way I’d go back to tubes unless that’s all that was available. Kinda like going from mechanical shifting to electric shifting and going from rim brakes to disc brakes. I’m an old guy that’s been riding a long time and most all the new technology makes riding more enjoyable. If you don’t know what you’re missing then you just don’t know. Thank God for forward thinking people who develop newer stuff so we don’t get stuck in the mindset the old stuff is better than the newer stuff, always trying to find a reason way it’s not better, or just crap.
I had the same experience as Seth. While going 22 mph in a turn, I heard the rim on the pavement and seconds later saw my bike slide away from underneath me and I landed in the middle of the road unable to move. Thankfully the police were nearby and the EMT’s took me to the ER with three fractures. After I got my bike back from the police station, the tire was off the rim and I did not find any trace of sealant. New tire and sealant in July 2022, accident in November. Fast forward to August 2023. New tire and sealant plus air liners to prevent the same issue from happening again. Turning at an intersection under 10 mph, the tire lost all its air again but this time I had installed Vittoria air-liners that kept the tire on the wheel and I was able to complete the turn. So two complete loss of air and I am now going back to tubes. On another note, both my Garmin Edge and Apple Watch incident detection failed to detect my fall even though I hit the pavement hard enough to crack the handlebar and damage the cassette.