Tubeless leak after hard braking

So descending today… I had an animal run in front of me. Luckily no harm but I hit the brakes pretty hard. Didn’t immediately notice any problems and I kept riding. About 20 minutes later my rear tire is flat. So, I looked for signs of damages and didn’t find anything and just re-inflated it with a co2 cartridge. Back home, I double checked pressure with a pump and now it’s sat for several hours. I went and checked it and it’s definitely slow leaking. Googling around it seems like the braking issue might be a cause for concern.

Before I start debugging this, I thought I’d ask all you super rider bike expert dudes if there is a good way to go about fixing this.

Continental 5000 tubeless (700x28) tires on Aeolus 3 rims. I have around 300 miles on them since I installed them and before today haven’t had any issue with them.

Full carbon rim brakes generate a lot of heat. Could’ve lost the bead seating on the tire or damaged the tire itself it due to the heat generation.

Sorry, forgot to mention… I do have disc brakes.


Have you got enough sealant in?

Even if you burped it by braking (in a straight line? Not heard of that before), it shouldn’t still be leaking. You could have also punctured it, either with the braking incident or some other time during the ride

  • If you mean “fixing the leak”, do the “Stan’s bounce and/or shake” to make sure you have sealant spread appropriately in the tire.

  • If you mean find the source of what introduced the leak, that may be trickier. Considering it was the rear tire, assuming downhill and high speed, the rear tire is not loaded very much compared to the front. Maybe it got just enough torque to allow the tire to slide and rotate on the rim, which “broke” a prior seal between the tire and rim? As such, I don’t know how you prevent that if it was properly installed, inflated and had sufficient sealant already.

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Reinflate the tire and submerge in a tub of water. Look for air bubbles, that is where the leak is coming from.

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I was going to spread some soapy water on the rims and valve etc. As for checking sealant quantity, anyone have a good test for that? I put the recommended amount in when I set it up. Like I was saying it’s really only been a few hundred miles… so a few weeks for me.

There is a “testing kit” that you can buy.

I just hold the wheel off the bike, let the sealant pool at the bottom, and do a mild Stan’s shake while listening and feeling for sealant. There should be some noise and feel. If you get little or none, it’s worth dropping pressure, popping a bead partially off (1/2 way) and see what’s in there.

I would say this is coincidence more thank anything.


Well I did the shake test and then compared with the front wheel. The front wheel definitely had more. I wasn’t able to detect much in the back. They were set up at the same time with the same amount so I wonder if something during todays ride caused a loss? Maybe I’ll never know. could all be coincidental.

Anyway, I just went ahead and added more and I’ll watch again in a few hours I guess. I couldn’t detect any leaks with the soapy water. Putting 2 co2 cartridges in my tool bag I guess lol.

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You can gauge sealant with a plastic zip tie, just like checking auto engine oil, If you’ve got removable valve cores. Cut off the little angled tip of zip tie so it starts at the toothed part. Then let deflated and suspended (weight on deflated tire will mess with your sealant puddle measure) wheel sit for a bit with valve at 6 o’clock, for sealant to pool. Then just dip the zip tie thru core-removed valve till it bottoms out against tire, remove and measure.

Next time you fill a tire with your desired amount of fresh sealant measure then and you’ll know how high your “full” should be.

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Can’t recommend the Milkit system enough. The syringe etc is just the usual, the valves are the sweet part. Really reduced the hassle of filling trickier fitting tires. If you use a shorter-life sealant like the Race stans you may find the syringe to draw out and measure the contents of the tire without breaking the bead to be a time/mess saver. I even put them on my fatbike.

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CO2 loses volume faster than regular atmosphere. It’s normal for a tire inflated with CO2 to deflate faster. Pump it back up with a pump.


Good point. And some sealant doesn’t like the cold burst from the CO2 as well, so it may have lead to additional issues that show different between the front and rear now.

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Seems very unlikely to be related to hard braking. You were descending, so there would have been little weight on your rear tire, and even less weight on it when you were braking.

The co2 info is interesting. Don’t know if it applies to my tire since I did refill it with air when I first got back. However, it is could be relevant pertaining to the amount of sealant left. Unsure.

In the mean time, happy to report next morning (pre-ride) it’s still pumped up hasn’t lost any pressure. So I’m chalking this one up to just low sealant in general and going to count the hard braking incident as coincidental. I guess in future I’ll monitor sealant level along with other maintenance things I do. I didn’t think enough time had gone by since I installed them to worry about it much.

Tons of good tips in here, thanks all!
(I always get the best responses on this forum.)