Jim’s Tech Talk
By Jim Langley
As the designated mechanic for our couples group who bike together some weekends, I run into interesting issues. Like last week, when Marc disappeared off the back and I went looking for him. He was a half mile behind standing on the shoulder trying to pump up the tubeless rear tire on his Santa Cruz.
He told me it wasn’t flat, only soft enough that he wanted to add a little air. The problem holding him up was that he couldn’t get any air into the tire with his pump.
We both checked his mini-pump by holding our hand over the head and making sure pumping created pressure. No problem there. We next made sure the tip of the Presta valve was unscrewed and the seal was open. The pressure inside the tire keeps the valve sealed until you break the seal by unscrewed and depressing the tip.
The valve seemed to be in working order, because pressing down on the tip as described produced the rush of escaping air. Since I had a pump, too, we gave it a try thinking maybe something was awry with Marc’s. No dice. My pump was useless, too.
Why couldn’t we get any air into the tire with the pumps? It was a bit of a mystery so I’m explaining what we figured out in case you ever have the same problem. And to help ensure you’re prepared to deal with related tire troubles, I’ll give some examples of other tire valve issues. They’re all relatively easy to fix as long as you carry the few small parts and tools mentioned.
Marc’s Valve
When Marc’s valve allowed air out but not in, I asked Marc if he happened to have a spare valve core. Tubeless valves usually have replaceable cores. The core is the working mechanism inside the valve that keeps the air in and allows inflating and deflating.
Not all valves have replaceable cores. Especially in the case of valves on tubes. You can tell by looking closely at the sides of the top of the valve just below the knurled tip you screw to open/close the valve. On valves with replaceable cores, there will be two wrench flats on the sides.
There are little valve-core removal tools you can buy, such as Park Tool’s VC-1. You can also use pliers or a tiny adjustable wrench to remove them. The cores are tightened enough that you can’t get them out by hand.
Carry a Spare Valve Core
I recommend always carrying a spare tube to fit your bike – even if you have tubeless tires. And, I would also always make sure that tube has a replaceable valve core. All Presta valves with replaceable cores use a universal fitting Presta valve core. So, as long as you have a core with you on the spare tube, you will have a backup if you need it. You can also purchase Presta valve cores separately.
With Marc’s bike, he was actually carrying 2 spare valve cores in his seat bag, one for his bike and one for Sue, his wife’s Santa Cruz (attaboy, Marc!). So, we simply removed the valve core from his valve and screwed in a new one with Marc’s tool. After that, it was a cinch to pump up the tire and get rolling again.
Sealant Issues
We couldn’t tell looking at Marc’s old valve core what had made it refuse to accept air. And, I don’t know if we could have fixed it if we had time to soak it in solvent or blow it out back in my shop with compressed air.
But, it’s possible that some sealant from his tubeless tire made its way to the valve, got into the end of the core and gummed it up in a way it would let air out but not in.
Tip: To prevent sealant gumming up valves, it’s best to be sure to rotate valves to near 12 o’clock before deflating or inflating sealant filled tires. That helps keep the sealant pooled in the bottom of the tire and with luck it’ll stay down there.
Dealing with Sealant Plugs
Something that happens with sealant over time is it drying and forming a skin or plug. Since the tubeless valve is protruding inside the tire, it’s a natural place for the sealant to collect, dry and create a plug or a clog.
In that event, if you try to let air out, only a small bit will escape before the air flow stops. And your pump will be useless just like ours were with Marc’s tubeless tire.
The replaceable-core valve comes in super handy when you run into this problem. What’s needed to get the valve working again is pushing out or breaking through the sealant skin, plug or clog.
To do this, rotate the valve towards 12 o’clock and remove the valve core with whatever tool you’re carrying (careful; it’s small – don’t drop and lose it!). Once the core is removed, all that’s needed to clear the plug is to poke something inside the valve far enough to push out or poke through the sealant.
You don’t want to risk puncturing the tire, so don’t use anything too sharp. I like to use a 2.5mm allen wrench. It only needs to be long enough to reach through and into the tire. You could make a tool out of almost anything that fits through the valve.
Tip: It’s possible to poke something too small or too pointed into the valve plug and then still have trouble getting air in. That’s because it made too small a hole in the plug and the air sealed it again. If that happens, poke something larger into the valve to enlarge the hole.
Don’t Break the Bead Seal
In most cases, if you’re careful and work as described, you should be able to inflate the tire again and finish a ride after replacing a bad valve core or poking open a sealant plug. But, with all tubeless tires with sealant, you want to try to avoid breaking loose the beads of the tire from the rim.
When properly installed, tires are what’s called “seated” on the rim. This means that the edges of the tire on both sides and all around the rim are in the perfect position to seal any air from escaping. Since you are only working on the valve and not the tire, it will stay seated like this unless you make the mistake of trying to remove the tire.
And, as long as the tire remains seated, you should be able to inflate it and have it hold air – even if the sealant inside has dried up inside and there isn’t much left in a liquid state to help seal the tire.
If you mistakenly unseat the tire bead(s) on tubeless tires you may have trouble getting it to hold air again if there isn’t sufficient wet sealant inside remaining to help seal the tire. If you run into this situation, you need to add sealant if possible.
Ride total: 9,247
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.
Another excellent “war story” that makes life simpler. The only thing I’d add is that if you’re running tubeless tires installed by a shop and you get a flat that won’t stay pumped up you need to swap in your spare tube. But, if you don’t have a wrench to remove the valve stem (sometimes tightened so much you need a tool to remove the ring) you’re not going to be a happy camper.
BTW: Langley’s incredible streak of ride days continues to amaze. Me? I haven’t ridden a bike in over a month having been in Cabarete kitesurfing but hope to get out today here at home if it’s not too windy.
I’ve run into this problem too! You have to get that tubeless valve stem on tight enough that it seals, and then when you need to remove it by hand later you find that you can’t. I love tubeless when it works, and then I absolutely hate it when it doesn’t. Sometimes I wonder why I use it on anything other than cyclocross / gravel or mountain bikes.
Here’s a solution: https://boydcycling.com/shop/accessories/offset-wingnut-for-valvestems/ Not used it myself, but seems like you aren’t the only ones with this problem.
I’m trying to inflate by bike tire with the help of bicycle pump… But when i pump it down…it bounces back toward me. Tire has a shrader valve and the pump connector properly connected their.. but I failed to inflate the tire.. what is the reason behind that? And how can I solve this problem?
Yet another example of why tubeless is not ready for recreational riders. Too much maintenance and work for minimal benefit. Most recreational riders won’t even notice a few less psi. And whats the point if you still need to carry a spare inner tube. Is it just a method to make up for inadequate riding skills? Do riders today even know how to pick the smoothest line or do they just slam over obstacles with their long travel bikes? I raced MTB with the Army in Germany for ten years and never once had the need for tubeless, and it’s one of the muddiest places in Europe and I was no slouch, top 5 or better. I’ll stick with the security and reliability of inner tubes, at least until they come out with a better sealing system. I tried sealant in my road bike once, only once and it was a disaster when I had a puncture, sealant everywhere except where it needed to be….the puncture. I spent half a day removing dried sealant from my bike and components. Bah!!
Depends on the situation. My commute (45-70 miles round-trip depending on which route I go and 99% on bike path, no less) is littered with goatheads for whatever reason. I’ve had occasions where I’ve had three flats on a single ride. Not really too much fun. I’ve gone tubeless on my commuting bike and have not since had a problem. They can be a bit of a pain setting them up, but once they’re good, they’re good for a long time. I think the ability to ride with low pressure is much less of a consideration for road bikes than for MTB.
little too much chest pounding dont you think/
I think the name says it all.
Agreed! By using latex (yes I know I have to top up more often & they cost more) I have the benefit of lower rotational weight like tubeless and as to lower pressure; I use the optimal pressure for road riding at my weight and I see no reason to be lower than optimal as higher or lower equals higher resistance.
This problem is happening to me with tube tires. No sealant being used.
Hi Jan,
It’s probably a problem with the valve. So you would replace the core if you have a replaceable one in your tube’s Presta valve. If you can’t replace the valve core because your tube doesn’t have replaceables, then you would replace the tube. There are defective valves that fail after awhile. And Presta valves can get damaged and stop working, too. So a new core (if possible) or a new tube with new valve should fix your problem.
Good luck,
Jim Langley
I think I know the answer to that this, but is there a valve core “standard”; i.e., a single size core that fits all stems? I suspect the answer is yes, but given how bike manufacturers are always trying to “reinvent the wheel” (literally and figuratively)…
Yes, Richard, the valve core in Presta valves is a standard size. That goes for tubeless valves and the valves on inner tubes with Presta valves. So if you carry valve cores, they will work to fix both bikes with tubeless tires and bikes with tubed tires.
Hope this helps,
Jim Langley
I don’t run tubeless on my road bikes because I seldom flat (Continental Grand Prix)… I have run tubeless on my mountain bike for the past two years and would never consider returning to tubes on it,. I use Orange Seal sealant and every four months I remove the valve core and check the sealant level with the little di;p stick that comes with OS sealant. Lot’s of thorns on the dirt trails where I ride and used to be plagued by flats. Have lost count of the number of thorns I have removed from my Maxxis tubeless tires and (knock wood) not a single flat in two years. Good sealant works! Will soon be adding a gravel bike to my battery and it will wear tubeless tires..
I had a similar problem about 40 years ago when I first started using Presta valves. The valve would not open even with the shaft depressed. I ended up intentionally puncturing my tire with a pin so I could change the tube. A short time later it happened again. I finally realized I was damaging the valves by over-tightening the tiny thumb nut at the tip of the valve shaft.
More recently I had a problem a slow leak so I change the tube. A week or two later, the new tube also started to seep air. Initially, I could not find any holes in either tube and the tire was free debris and damage. I then pumped air into the tubes and dunked them in water where I found tiny bubbles coming from the removable Presta valves. It took me awhile to figure out the valves were being loosened by the chuck on my floor pump. I typically rotate my wheel so the stem is short of vertical before clamping the air chuck to the stem. When I let go of the chuck to start pumping, the weight of the air hose was enough to pivot the chuck down about a quarter of a turn. The chuck fit so tightly it served as a wrench to loosen the valve.
Great tips, John! Thanks for sharing!
Jim Langley
I use a Schrader adapter for inflating my presta valves. Releases less air on removal of the pump chuck and less likely to damage the presta core. For a dollar and couple of seconds I find it worth it. Also gives redundancy if I need to use a “standard” inflation source.
Another problem to watch for is the core coming loose. I was installing brand new tubes and still getting flats. This happened multiple times before I checked the presta valve cores, they were loose out of the box. Now I check every valve before I install it and periodically check all my cores. I was putting blue 242 Loctite on them to help keep them from coming loose, but if you use too much it causes the valve to stick, it still works it just takes a little more pump pressure to pop it open.
If the sealant gets into the stem, rotating the stem to the 12 o’clock position before removing the core may result in sealant leaking out. Yes, most of the sealant should be at the bottom of the tire. To avoid gumming up my valve cores, I prefer a 7 or 8 o’clock position to the 12. Placing my stems this way while I mount my Garmin, lights, water bottles allows the sealant to pool at the bottom of the tire including any sealant hanging out in the stems. This prevents most plugged cores.
Jim –
Great article about a problem I’ve experienced several times. My current strategy is to discard the clogged core because there seems to be no way to mechanically remove the coagulated sealant.
In the article, you mentioned using solvent to clean the clogged core. As with some of the other commenters, I use Orange Seal; do you know what is an appropriate solvent for dried OS?
BTW – for commenters who want to tell the rest of us how lame we are for using tubeless tires, all I can say is be thankful you haven’t yet developed arthritis in your hands. Once you have, you tune about Tubeless (and large volume) tires is probably going to change..
Exactly the reason I switched to tubeless. My hands can’t remove tire anymore and if I’m alone on a ride I’ll have to call for a ride.
I like the 7 or 8 o’clock position for letting air out. And always carry a mini u-shaped valve-core wrench, especially if you have a screw-on hose-type mini pump that can loosen the valve core. And a 2.5 mm hex for unplugging the valve.
Thanks so much. Your excellent article has solved my problem. But how much air do I pump into my road bike tires to achieve good pressure?
“Tip: To prevent sealant gumming up valves, it’s best to” forget about tubeless once and for all.
Lubricating the valve and stem with a coat of silicone grease may help to prevent sealant buildup and valve failure. This is speculation: I haven’t tried this idea with tubeless tires, as I don’t have tubeless tires on my bike. I do suspect that tire sealant won’t adhere to silicone grease.
However, I do use silicone grease on my tube’s valves. I discovered this because I was occasionally, and randomly experiencing slow leaks on older tubes. I eventually found the leaking was coming from the tube’s Presta valves. After removing the valve, cleaning the stem inside with a small swab, and wiping the valve clean, I applied a coat of silicone to all the valve working surfaces, and inside the stem. The problem immediately disappeared.
Background: I use latex tubes, patch them, and typically get long service life from the tubes. This allows the tube’s valves to see enough service to need cleaning and lubrication.
Perhaps this solution will also be useful for those with tubeless tires.
A way to help minimize the chance of sealant gumming up the valve is when you put your bike up after a ride, just try to ensure that the valves are in the 10-2 o’clock position. That way any sealant in/around the valves should drain out to the bottom of the tire (that which is in the 4-8 o’clock position). I have always done this since I switched over to tubeless tires/wheels a number of years ago on my primary bike (and I do still always carry spare tubes just in case – just be sure that the valve stem of the tube is long enough to extend beyond the wheel (i.e., a tube w/a stem of 2.5cm won’t do you any good if your rim is 3+ cm deep)).. If you hang you bike, your wheels will likely want to rotate to where the valves are in the 6 o’clock position, so the sealant is likely covering the bottom of the valve stem. To counter this, just rotate the wheel 180ᵒ so the valve is around the 12 o’clock position and put something that weighs more than the valve (a small rag, a sock, gloves, a towel, etc…) at the 6 o’clock position of the wheel and that will keep the valve up high so any sealant therein hopefully drains out without any issues. I do a light wipe down of my bike after every ride (a wet rag wipe and then a dry wipe w/two shop rags) and would use the two shop rags; one on each wheel.
Additionally, there is a hack, albeit a slightly risky one for piercing the valve (into the wheel) is the sealant has formed a cover/seal over the bottom of the valve and air won’t pass through. With the valve stem removed, take a skinny, firm object with a fairly sharp point (e.g., a paper clip, a toothpick, a twig, etc…) and slowly poke/force through the sealant blockage. Just be careful though, because you don’t want to use so much force that when you poke thru the sealant that you also push it through the shell of the tire and create another problem; and maybe this time one that’s too big for the sealant to fix.
I found that coating the valve core with silicone grease will keep sealant from clogging the valve core.
Just one more reason if I needed it that my “tubeless ready” Giant tires will never be tubeless. Like self driving Cars and a lot of other things, just not ready for prime time. Great for my auto’s and motorcycles through. I like the newest technology but only if the advantages exceed the disadvantages.
For those running tubes, try tire liners if you’re getting too many flats.
For problems with valve core installation and removal, try a valve core removal tool. Stan’s makes a good one.
https://www.amazon.com/NoTubes-AS0015-Core-Remover-Tool/dp/B001S98NLU/ref=sr_1_3?crid=UAJ9KGE6K5YZ&keywords=bicycle+valve+tool&qid=1674764533&sprefix=Bicycle+valve+%2Caps%2C146&sr=8-3