Used tubeless ready tires leaking air (that were used previously with tubes)

Question

I recently purchased a pair of new wheels and decided to mount on them a pair tubeless ready tires that I had in my stock — the tires are one year old but barely used (about 100km when I bought them, with air chambers — I unmounted them after and kept them). The tubeless part of the install went well.

I noticed that I was loosing about 2 bars/30psi of pressure (from 4 bars/60psi) in a few hours. The tires seem properly seated then I rode 5km on gravel rough gravel to spread the sealant. I searched online and found the trick of untightening the valve, but the result was the same. Then I sprayed some soapy water and saw small bubbles forming everywhere, clearly showing that the tires themselves are permeable.

So I was wondering:

• is it possible that given that I used the tires with tubes, the tubes have a bit worn out the inside of the tire, which would make them more permeable - in 100km, that would seem very short?
• the tires are tubeless ready, not tubeless: from I understood, I should expect some leaks, that should compensated by the sealant (I added 45ml of sealant in each wheel). When I shake the wheel, I don't hear anything, like if all the sealant have been consumed (in 24h), is it possible?
• is adding more sealant the solution? If yes, how much and what is the best way to spread it?

Answer 1

Yes, lots of small leaks everywhere typically means you just need more sealant.

Tires vary quite a bit in how thin/supple versus thick/strong their casings are. Some tires simply take more sealant before they stop leaking through the casing. Usually what you find going along with the symptom you're having is there's also not much free liquid sealant left, which you need some of to block punctures. Sealant manufacturers love to low-ball the amount needed per tire because it presents the most optimistic case for weight savings, but this is an area where they can veer into dishonesty.

Everyone would like it if choosing a sealant fill or refill amount was totally prescriptive, but that's simply not the case. Add until it stops leaking and you're satisfied with the amount of free liquid sloshing around, which itself is a weight vs time-until-replenishment consideration. For a light gravel/allroad tire generally go about 25ml at a time if you're trying to be weight-conscious or 50ml if you want to just get it done. For higher volume tires doing this kind of thing I would go straight to 50ml increments. (These numbers are for Stans and Orange, which are the main sealants in my life, but should be pretty close to the same for most sealants).

Answer 2

I've tried that with Continental Race King and Cross King tires. Rode them for 6 month with tubes and then tried using them tubeless.

The sidewalls of these tires were leaking sealant at first and lots of small cuts showed up.

It should work and the sealant should close all the cuts that have been in the tire - but in my experience it worked okay for the front tire, but the back tire already had too many cuts for it to work great.

I was using Stans (which is pretty thin) and these tires had thin sidewalls, so that may have aggravated the problem.

Short answer: it can work, but for best performance you start with new or nearly new tires