So I just bought a pair of second hand wheels in fantastic shape - a pair of DT Swiss GRC1400. Pretty much looked brand new, rolled 500km.
When I got them there was some dried up sealant in the wheel bed, looked a bit messy especially around the valve stem.
I have realised that I need to top up the air before every ride, so was wondering what normal pressure drop over night is? (this is after I also did a ride the day before)
Yesterday I pumped in 2.6 bar (38 PSI) before the ride, and this morning I had around 2.3 bar (34 PSI) when checking. Is this normal, or should I take everything off, do a really good clean of the wheel, replace the tape and stem etc?
Just wondering before I take some steps to fix it, since its kind of a lot of work to fix everything with the sealant and all.
Possibly a slow leak, are you measuring with a digital pressure gauge? Remember, every time you measure you’re loosing a bit of air and if you’re going by the pump gauge it’s likely off a bit. Any any case, cleaning the wheel (if dry sealant is obstructing the rim bead) and/or re-taping the wheel will likely fix the issue.
I’d say it is normal. I always have had to pump up my tires before every ride for all my tubeless bikes. How much depends on a lot of things, like how porous the sidewalls are, how fresh the sealant, etc. 4 psi overnight doesn’t seem like a big deal. My guess is it doesn’t leak 4 psi every night because the pressure kind of equalizes a bit and the leakage will slow way down.
I would say it sounds pretty normal for a new install and you can expect it to get better over time after the sealant has worked its way everywhere - if you are still getting that amount of loss in say a month or so then I’d maybe look at your valves etc.
I’ve never had a tubeless tyre hold pressure as well as a butyl inner tube though.
On my gravel tires, I’ve found that it improves with every top up of sealant.
For a road bike tubeless set up 4psi loss is minimal and not concerning; I’ve no idea about MTB tyres though.
tan walls also leak more than black rubber - losing a few psi is normal and I find it varies significanty day to day
Tire porosity is something I just hadn’t realised until I got Schwalbe Pro Ones. My Conti GP5000TL don’t seem to be at all porous. The Schwalbes I’ve been running for a couple of months and there’s still tiny beads of sealant oozing through all over the place. Don’t seem to be losing pressure - similar loss rate to a butyl tube and certainly a lot less than latex tubes. Assume this is normal? Does it ever stop?
It will actually get worse possibly. I haven’t really experienced it with road tires as much and I run the Schwalbe Pro Ones. However, if you have a set of the OG tubeless, aka, most mountain bike tires. After a few months, you can dunk those puppies in a water bath and it looks like soda water fizzing out of the side walls. I’m not sure if the rubber degrades, but it’s a thing.
On my first set of gravel tires I had horrible seepage and would have to pump up tires daily. I was using TruckerCO sealant. I finally switched to Stan’s sealant and things improved tenfold.
Vittoria Mezcal 2.35 MTB tire doesn’t loose air pressure. I can go a week and loose a couple PSI maybe.
EDIT: I use Stan’s Race Sealant… which has bigger particles but drys up faster.
Your tires can have a big influence, especially if they aren’t tubeless ready or it’s the first time you have run them tubeless. If either of those is true, then you will also go through sealant faster this first time as some will be absorbed into the tire to seal any pores.
Some tires are much better sealed than others. I have had Schwalbe TLR Racing Ralphs hold significant pressure for more than a year, but that was after being topped up on sealant several times.
My blackwall Panaracer Gravelking SKs with Muc-Off sealant hold air every bit as good as tubes. Even hanging in the garage over the winter for nearly 4 months I could have jumped on and ridden away, okay maybe not that great but they went from about 55 → 35psi
Same with my 2.25’s. I didn’t ride it much from Feb-April and it probably dropped from ~19 to ~12/13.
On my road bike with Vitorria Corsa Controls I’ll probably lose a couple PSI over night but nothing that I couldn’t ride on. But I do find that like once a month I’ll go downstairs and one of my tires is flat for no reason. I’ll just pump it back up and it holds fine again. It’s very weird.
After you pump it up, pump it to max PSI for the rim and tire. Spray soapy water (I just slosh it with a sponge and soapy water) around the bead of the tire, the valve, and the nipples all around the wheel.
Look for bubbles, and concentrate your wheel shake at that area (to distribute sealant all around inside). If no bubbles, no significant leak.
4psi is probably ok, can’t really say I bother to check to that degree.
Are you actually losing air or is it just the air filling up the gauge?
Fill up your tires, take your measurement, detach the gauge and then take a new measurement. It will likely decrease especially if you’re using a gauge on a pump since it takes a lot of air to pressurize the hose of a pump.
The sealant around the valve stem might have plugged a few small gaps. But your fresh sealant should refill them.
I’ve found that adding a bit more sealant after a while on a new install help reducing air loss.
38psi to 34psi overnight is fairly normal. Yes, it can be better, but it can also be much worse. I’d leave it alone for now.
There are many potential sources of leakage:
- Tire porosity / bad seating
- Rim tape gaps
- Seal between the valve stem and the rim
- Seal between the valve core and the valve stem
- Old sealant being less effective - either too dry or too watery
- And of course, small punctures
On high mileage wheels like on my Roubaix, I’ll just overhaul the entire wheelset (Roval CLX64s) every year with fresh tires, tape, sealant, and valve stems.
This is even more true if you are just relying on your pump’s pressure gauge. When you attach the pump a lot of air will flow from the tire into the pump’s chamber, and if you are using a pump with a holding chamber (used for seating tubeless tires) this effect will be amplified.
FWIW I always notice a small amount of air loss on my tubeless setups over a few days, but don’t lose sleep over it. Checking my tires pre-ride is a small price to pay for the huge reduction in ride-ruining flats vs. tubes.
It can be especially bad with thin sidewalls. Here’s a Rene herse tubeless standard casing with over a thousand miles on it. It constantly seals after shaking and replenishing sealant( orangeseal endurance) and the opens up again as the sidewalls flex etc