Maximum tyre pressures

[GSF355]

Hi all,

I've recently bought a new road bike, and the LBS highly recommended going tubeless, so I drank their cool-aid and here I am running tubeless.

I've since been told by someone who should know, to be very careful with what psi I run (carbon wheels) as too high can cause the wheels to fail in very dramatic fashion, and that I am likely running too much pressure.

I'm running Pirelli P-Zero Race (30's) on Scope S3 rims. The Pirelli website suggests 74psi for tubeless, based on my weight and weight of the bike. Does this sound ok, or is a rim about to explode at this insane pressure?

As a slight aside, my front tyre will be completely flat after a few days of doing nothing, yet the rear remains at a reasonable pressure. Is that likely to be a tyre to rim sealing issue, only solved by removing the tyre and re-gluing?

Back to an inner tube is seeming more appealing!

Thanks for your thoughts.

[warthog1]

If the wheels are hookless, 74 psi is indeed too high. Etrto guidelines for hookless limit it to 5bar or 72.5 psi.
What is an appropriate pressure for you depends on your weight and the internal width of the rims.
I weigh 76kg and with my 25mm wide hookless WR50s that pressure would indeed be too much. I run 55psi and that is plenty at my weight.
My narrower hooked tubeless (19mm int) with a 25c f and 28c r I run somwhere around that pressure.
10s of thousands of tubeless ks now and it is sooo much better than tubed I wont buy non tubeless wheels and no longer ride any of my tubed wheels.
Stans regular and orange seal regular have both worked well for me.

[Arbuckle23]

As per Warty's advice on pressures.

A bit of pressure loss is normal, it will settle after a bit and lose a bit less.
I normally check with a pump every 3 or 4 days once settled and the old finger press in between
If one tyre continues to lose more, a little bit more sealant usually sorts it.

[2wheels_mond]

I'm running Pirelli P-Zero Race (30's) on Scope S3 rims. The Pirelli website suggests 74psi for tubeless, based on my weight and weight of the bike. Does this sound ok, or is a rim about to explode at this insane pressure?

That seems pretty high unless you're a fairly heavy rider. With the same tyres, I'm running 55-60 PSI at 70kgs. This is on the recommendations of the Silca pressure calculator:

https://silca.cc/pages/pro-tire-pressure-calculator

[Duck!]

As per Warty's advice on pressures.

A bit of pressure loss is normal, it will settle after a bit and lose a bit less.
I normally check with a pump every 3 or 4 days once settled and the old finger press in between
If one tyre continues to lose more, a little bit more sealant usually sorts it.

As above. When new, tubeless tyres need a bit of time for some of the sealant to soak into the tyre to fill all the tiny pores and form a membrane on the inside of the tyre to properly seal it, so will lose a bit of pressure for a while. However, it may be possible that the tyre hasn't properly popped up into the rim's locking beads - which given the tight tolerance is not uncommon - causing a leak point.

[Andy01]

"A bit of pressure loss" over a few days is OK (maybe ±5psi per week for tubes, maybe less for tubeless ?), but going from 74psi to 0psi ("completely flat") in a few days is definitely not right. I would be taking it back to the bike shop who set up the tubeless.

[CmdrBiggles]

My TCR is running 75/75 psi, checked fortnightly and re-inflated if necessary.

MTB loses pressure over 2 months — good ol'tubes on tubeless WTB rims. Lots of interesting observations with a road bike running tubeless compared to the long-time honoured tubed MTB and touring bikes that came before it!

The biggest slow leaks can also come from the smallest unseen shards of whatever it is lying lazily on the road — microshards of glass that get picked up and unless the tyre is checked post-ride, will work their way in. If I have had to ride through a debris field, I use the palm of gloved hand to "rasp" over the tyre for 3 revolutions, but this is not so easy with the limited clearance of the rear tyre to seat tube.

"going from 74psi to 0psi"...in the old touring cyclist parlance: "you've got a flat!"

I often wonder if, like my car, there is a tyre pressure management system of some kind for bikes that can be fitted to valves and relay information to either/both on-board computer or phone.

[CmdrBiggles]

Hi all,

[...]

Back to an inner tube is seeming more appealing!

Thanks for your thoughts.

Mm-hmm. It will be very appealing when the time comes when you are looking for a quick fix over the double, double, toil and trouble of fixing up a tubeless let-down!

Whacking in a tube is better than faffing around in fading light or rain trying to find the little blighter that caused a puncture. My choice: I am not going to be doing that anywhere, so just carry a spare tube in the seat bag, along with the requisite tyre levers and C02 bulbs.

[Duck!]

Chucking a tube in has always been the recommended course of action for a puncture that's beyond the capability of the sealant to close. Tubeless does have a few detail tweaks to rims and tyres to get the sealing to work, but fundamentally they are still normal clinchers. ALWAYS carry a spare tube and necessary tools to fix a flat, even if running tubeless!

[warthog1]

I would say if you don't have much in the way of maintenance skills tubeless may not be for you.
Yes ime it is pretty effective at reducing the incidence of punctures. However you need to be able to problem solve a bit in setting them up and seating them.
Slapping a tube in and just inflating is an easier process, you don't get the benefit of latex sealant dealing with smaller holes, but it is simple to set up.
I have a decent storage tank compressor at home that will blast enough air quickly enough to seat almost any tyre once I whip the valve core out. Makes it pretty trouble free.

[GSF355]

Thanks all!

I'm approx 78kg, and the rims are hooked.

It sounds like the front tyre needs some more attention either more sealant or refit.

I like the theory of tubeless, but if my scenario was considered a normal compromise of a tubeless setup I'm not interested.

[Nobody]

I have a decent storage tank compressor at home that will blast enough air quickly enough to seat almost any tyre once I whip the valve core out. Makes it pretty trouble free.

I managed to bead seat a rear motorcycle tyre with the valve in and a standard floor pump. So it reads like the bead seat sealing may be looser on bicycle tyres if you need the valve out and a compressor to do it.

[Mr Purple]

You'll always lose pressure on a new tubeless setup, but fortunately you have two tyres so can compare the pressure loss on both - if they're roughly equal you've either stuffed them up equally or it just needs time to settle.

I've had a few occasions where one tyre has behaved exactly as yours - there was always a reason for it. The biggest trap I noticed was that you have to clean and fit the valve exactly correctly otherwise you lose pressure and you'll never find it because you're basically just pressurising the interior of the wheel.

The other reason is always 'not enough sealant'. If it's a brand new setup check the valve is tight enough (finger tight is fine) and then just add 15-20ml more sealant and ride it a bit more. It'll probably fix the problem.

Your wheels themselves aren't going to fail with 74PSI. Plenty of idiots still running 110PSI on tubeless setups and carbon wheels and the biggest risk apart from a tyre potentially popping off is that any puncture won't seal. And your butt will hurt.

[GSF355]

You'll always lose pressure on a new tubeless setup, but fortunately you have two tyres so can compare the pressure loss on both - if they're roughly equal you've either stuffed them up equally or it just needs time to settle.

I've had a few occasions where one tyre has behaved exactly as yours - there was always a reason for it. The biggest trap I noticed was that you have to clean and fit the valve exactly correctly otherwise you lose pressure and you'll never find it because you're basically just pressurising the interior of the wheel.

The other reason is always 'not enough sealant'. If it's a brand new setup check the valve is tight enough (finger tight is fine) and then just add 15-20ml more sealant and ride it a bit more. It'll probably fix the problem.

Your wheels themselves aren't going to fail with 74PSI. Plenty of idiots still running 110PSI on tubeless setups and carbon wheels and the biggest risk apart from a tyre potentially popping off is that any puncture won't seal. And your butt will hurt.

Thanks Mr Purple. I'll check the valve and investigate topping up the sealant. I don't mind losing pressure over time, as with most tubes, but fully flat after a few days seems excessive, and the rear wheel looks to prove that the front is not behaving normally.

Can sealant brands be mixed, or should I try and find out what the LBS used? Sadly I haven't been happy with the LBS since buying so I'm reluctant to go back to them, I'd rather start over with another shop...

[Mr Purple]

I'm not the most mechanically adept person on the planet but it didn't take me long to get the hang of tubeless - I actually find fitting a tubeless tyre easier than a tubed these days (there's no tube to get caught so you can be as brutal as you want).

Sealant brands shouldn't really be mixed as a rule but odds are you'd get away with it. I wouldn't do it because I'm paranoid, particularly with front tyres.

A proper tubeless setup in my experience doesn't lose pressure any faster than a tubed setup. There is always that week or two when you install new tyres though were you're wondering if it'll ever actually seal! Usually just before you give up and reinstall it, it magically sorts itself out.

I suspect in your case that there's just not enough sealant in it. When I bought my Checkpoint my rear tyre was losing slightly more pressure than the front over the first 800km or so. Fortunately I flatted at that time so removed the tyres to inspect to find that there was literally no sealant at all in the rear. That'd be the culprit. Since then I don't trust shops to do anything properly.

[Nobody]

So they actually need sealant to seal the bead as well? Obviously different from car and MC tyres which don't.

[Mr Purple]

So they actually need sealant to seal the bead as well? Obviously different from car and MC tyres which don't.

No, they don't need sealant to actually bead. I always bead without sealant and add the sealant later.

Depending on the tyre/wheel combination in some cases you'll almost get away without sealant. Hence how my Checkpoint ran 800km without sealant in one tyre with the only clue being that it lost pressure slightly faster than the other tyre.

The sealant just seals the gaps that the tyre/wheel combination always has. Presumably cars get away with it because of their more rigid sidewalls and the fact they have much more volume so any air loss occurs relatively slowly for the volume.

[warthog1]

I have a decent storage tank compressor at home that will blast enough air quickly enough to seat almost any tyre once I whip the valve core out. Makes it pretty trouble free.

I managed to bead seat a rear motorcycle tyre with the valve in and a standard floor pump. So it reads like the bead seat sealing may be looser on bicycle tyres if you need the valve out and a compressor to do it.

Depends on the rim/tyre combination.
I have found Panaracer gravelkings most difficult to seat.
Put a new 30c Schwalbe pro one tle on my rear hookless WR50 today. Inflated with a track pump easily.

[warthog1]

You'll always lose pressure on a new tubeless setup, but fortunately you have two tyres so can compare the pressure loss on both - if they're roughly equal you've either stuffed them up equally or it just needs time to settle.

I've had a few occasions where one tyre has behaved exactly as yours - there was always a reason for it. The biggest trap I noticed was that you have to clean and fit the valve exactly correctly otherwise you lose pressure and you'll never find it because you're basically just pressurising the interior of the wheel.

The other reason is always 'not enough sealant'. If it's a brand new setup check the valve is tight enough (finger tight is fine) and then just add 15-20ml more sealant and ride it a bit more. It'll probably fix the problem.

Your wheels themselves aren't going to fail with 74PSI. Plenty of idiots still running 110PSI on tubeless setups and carbon wheels and the biggest risk apart from a tyre potentially popping off is that any puncture won't seal. And your butt will hurt.

Not necessarily. I always add the sealant after it is seated and then put the wheel on its' side and wobble it around to coat the inside of the carcass with sealant. I do that on both sides. Generally it holds pressure much better after that.

[warthog1]

A proper tubeless setup in my experience doesn't lose pressure any faster than a tubed setup.

Had a rear conti gp5ktl losing pressure overnight a while back.
Had a good look at the tyre. Pulled out 2 bits of tyre wire out of the tread area. Rotated to the bottom at each point. Went back and reinflated later. Nothing else needed to be done with that tyre until it wore out and was replaced. That sold me on tubeless.

[Mr Purple]

I should have said that with the caveat that 'it may not be much'. I've had a few occasions where I literally didn't notice anything, but in most cases it's about 'twice as much' for the first week.

Mind you, we're talking 10PSI over the course of the week as opposed to the usual 5PSI. And considering you lose roughly 4-5PSI every time you check it that's not really worth mentioning.

To be honest I was losing as much tubed as tubeless anyway.

[CmdrBiggles]

Chucking a tube in has always been the recommended course of action for a puncture that's beyond the capability of the sealant to close. Tubeless does have a few detail tweaks to rims and tyres to get the sealing to work, but fundamentally they are still normal clinchers. ALWAYS carry a spare tube and necessary tools to fix a flat, even if running tubeless!

Tools...??
I have a spare tube, No. 3 scalpel w/ No. 11 blade, Park patch kit, a tiny bag of talc, 2 levers and gloves. And jelly beans.
Anything else?

[Duck!]

Chucking a tube in has always been the recommended course of action for a puncture that's beyond the capability of the sealant to close. Tubeless does have a few detail tweaks to rims and tyres to get the sealing to work, but fundamentally they are still normal clinchers. ALWAYS carry a spare tube and necessary tools to fix a flat, even if running tubeless!

Tools...??
I have a spare tube, No. 3 scalpel w/ No. 11 blade, Park patch kit, a tiny bag of talc, 2 levers and gloves. And jelly beans.
Anything else?

A pump usually helps.

[CmdrBiggles]

Tools...??
I have a spare tube, No. 3 scalpel w/ No. 11 blade, Park patch kit, a tiny bag of talc, 2 levers and gloves. And jelly beans. Anything else?


A pump usually helps.

Right side Jersey or windbreaker vest pocket, with Co2 bulb attached, +1 one in seat pack.

Pump has its own concealed hose; only really need Co2 if I am impatient to get going again!