Tubeless tyre loses seal with rim, fix?

[Wycombewheeler]

I've been running tubeless for a while now and my frequency of issues by the roadside is well down but I have had the following occur a few times on rides (about once/year) and can't work out what the fix is.

Occasionally, I will hit a pot hole and the tyre will shift on the rim creating a leak between the tyre and rim. The rim is not dented, but the tyre which had previously sealed will no longer hold air. No amount of sloshing sealant around at the critical area seems to resolve this. Removing the tyre and refitting will resolve the issue, but this is a job to be done at home with a proper pump.

Has anyone else experienced this?

Obviously not hitting potholes is ideal, but following other riders, riding in the dark, riding through puddles can lead to the occasional incident.

Is this a flaw with the hookless rims beloved of the wheel manufacturers to save a few pounds at manufacture? (i.e. the bead going up against the rim hook would be far more likely to seal?

Is there a way of fixing this in the field? Obviously I can resolve the issue with an inner tube, but this requires great care in ensuring the tyre is free from sharps. Is it a case of more pressure (perhaps with CO2?) or more patience with the sealant at a low pressure?

[robgul]

From feedback from customers when I managed an LBS I would suggest this is a common issue - exacerbated by running at low(er) pressure on wide-ish tyres.   

Fitting a tubeless tyre and getting it to seat needs quite a bit of pressure, even if the tyre is only partly unseated - IME a pump you carry on a bike is unlikely to cut the mustard - a CO2 might work out on the road.

I have one bike with tubeless (25mm Schwalbe Pro One) and run at pressures as if I had an inner tube . . .

[Ian H]

I had that with 25mm tyres, resolved by increasing the pressure from 70 to 80psi.

Other suggestion is to add one or more extra wraps of rim tape to make the tyre a slightly tighter fit.

[Hot Flatus]

Never experienced that, but then I tend to run road tyres at almost the same pressure as tubed.

I do have sone 38mm tyres that I run at about 45psi, but no issues yet with burping

[Wycombewheeler]

Thanks

helpfully ZIPP 303s have a max pressure of 5 bar (73psi) so I'll try to inflate to 70psi every time, (currently go for 60psi which I find comfortable on 30mm tyres.)
otherwise they will become my off road wheels with wider tyres

Never experienced that, but then I tend to run road tyres at almost the same pressure as tubed.

I do have sone 38mm tyres that I run at about 45psi, but no issues yet with burping

I do wonder if the pressure inside the inner tube is 90psi (for example) how much less is applied to the tyre because some of the pressure will be resisted by stretching of the inner tube. So is 90psi with no tube equivalent to 90, 85, 80 or 75 with a tube?

[Dickyelsdon]

Hookless rims are designed to seal by being tight against the shelf of the rim, not the sidewall of the rim.  Its also what holds them on with there being no hook. (pic for descriptions)



Are you saying the tyre is pulled off the shelf and into the centre well/recess  of the rim?  Youd only really expect that through excessive cornering at low pressure (i.e. Cyclocross or mtbing).

It might be that the tolerance of the tyre and rim is not a good match, with MTB tyres this used to happen as tyres aged, not sure if this happens with road tubeless as their bead tends to be stronger to handle higher pressures.

You could look to either take up some of the tolerance with an extra wrap of tubeless rim tape, or go belt-and-braces by creating a sealing hump on the rim shelf using a thin strip of tape in the middle and a full width piece over the top.

Many (MTB) tubeless rims use a flat shelf as its easier to fit (and remove) a tyre, and is usually safe.


Most road tubeless have a 'hump' on the side edge of the shelf to help hold the tyre bead against the flank/side

[aidan.f]

Never had a problem, Schwalbe 30's 3 bar on kilnin rims. Upwrong trike, if you have seem me cornering you will realise that side loads are extreme.

[ElyDave]

Not had this issue yet, with 2+ years of Terravail Canonball running at ~45 psi, but on my recent fettling, I think I have those humped rims, Hopes.

[RichForrest]

I had a similar issue with a set of gravelking tyres, they'd be fine when fitted but any slight deflation would unseal them and the sealant would come out all around the rim.
I haven't had one problem with the Schwalbe tyres in 9 months.

[Hot Flatus]

I had a similar issue with a set of gravelking tyres, they'd be fine when fitted but any slight deflation would unseal them and the sealant would come out all around the rim.
I haven't had one problem with the Schwalbe tyres in 9 months.

This is why I wondered whether the OPs tyres are lossing pressure without him realising.

It happened to me with Gravelkings until I put a load more sealant in.

[Cudzoziemiec]

Gravelkings not seating are pretty much the reason I gave up on tubeless. I'm not sure if they're just not a good design or just bad luck (I like them running tubed). I'll perhaps give tubeless another shot when I get some new tyres.

[Hot Flatus]

All it took was a bit more sealant. Once seated they maintain their pressure better than any other tubeless I've used

[Ian H]

All it took was a bit more sealant. Once seated they maintain their pressure better than any other tubeless I've used

Similarly, I've had very little trouble with the 38mm version.  I've never had them unseat - running VO rims which have a slight lip to hold the bead.  I can also mount them without tools.

[Wycombewheeler]

Hookless rims are designed to seal by being tight against the shelf of the rim, not the sidewall of the rim.  Its also what holds them on with there being no hook. (pic for descriptions)

Are you saying the tyre is pulled off the shelf and into the centre well/recess  of the rim?  Youd only really expect that through excessive cornering at low pressure (i.e. Cyclocross or mtbing).

No, the tyre is still tight to the rim, definitely not in the centre well, that would be flat, not a leak. But a small leak had developed at one point where there hadn't been for the last 1000kms. I could see the sealant coming out, but it wasn't sealing. If the tyre seals to the bed all the way around the rim, I don't see how it could move away from being sealed.

When I take the tyre off I will look for the sealing humps. I might try applying some rim tape. Or maybe look for different tyres. Of course the tighter the tyre is to the rim bed the harder it will be to fit.

[robgul]

Hookless rims are designed to seal by being tight against the shelf of the rim, not the sidewall of the rim.  Its also what holds them on with there being no hook. (pic for descriptions)

Are you saying the tyre is pulled off the shelf and into the centre well/recess  of the rim?  Youd only really expect that through excessive cornering at low pressure (i.e. Cyclocross or mtbing).

No, the tyre is still tight to the rim, definitely not in the centre well, that would be flat, not a leak. But a small leak had developed at one point where there hadn't been for the last 1000kms. I could see the sealant coming out, but it wasn't sealing. If the tyre seals to the bed all the way around the rim, I don't see how it could move away from being sealed.

When I take the tyre off I will look for the sealing humps. I might try applying some rim tape. Or maybe look for different tyres. Of course the tighter the tyre is to the rim bed the harder it will be to fit.

Are there any "crusty" bits of congealed sealant anywhere near the rim bead on the wheel, or the tyre bead?   I've had that issue when refitting a tubeless tyre, it was a very small piece but let air out.

[PhilO]

When you say that this happens ~once per year, does that mean that the existing sealant has been in the tyre for 12 months?  If so, it might just be that the sealant has gone-off and the liquid in there is little more than water. I'd certainly expect sealant to seal any bead-seepage quickly if it was in good nick.

Also, are you sure it's coming between the bead and the rim?  Hitting a pothole hard enough to shift the bead will also pinch the tyre between the road and the rim. I've scrapped a few tubeless MTB tyres for snakebite punctures on the side wall, and the holes usually sit just below the line of the rim, so look like the bead's leaking. 

[Wycombewheeler]

Are there any "crusty" bits of congealed sealant anywhere near the rim bead on the wheel, or the tyre bead?   I've had that issue when refitting a tubeless tyre, it was a very small piece but let air out.

This is possible, but not something I can check and rectify beside the road. Once the tyre is removed to check there will be no means of refitting. I suppose it's possible that hitting the pothole temporary shifted the bead, and some bit of sealant gunk got in the temporary gap, preventing it reseating. I didn't inspect too thoroughly at 5am, removed tyre rinsed tyre and rim into gutter, checked for any old sharps (found none) fitted tube (luckily I hadn't missed a sharp)

When you say that this happens ~once per year, does that mean that the existing sealant has been in the tyre for 12 months?  If so, it might just be that the sealant has gone-off and the liquid in there is little more than water. I'd certainly expect sealant to seal any bead-seepage quickly if it was in good nick.

Also, are you sure it's coming between the bead and the rim?  Hitting a pothole hard enough to shift the bead will also pinch the tyre between the road and the rim. I've scrapped a few tubeless MTB tyres for snakebite punctures on the side wall, and the holes usually sit just below the line of the rim, so look like the bead's leaking. 

I'll check the tyre thoroughly for a hole before refitting with sealant. I do top sealant up occasionally through the valve with an injection nozzle, so it's not just year old sealant/mostly water.

[Dickyelsdon]

Hmm, my only experience of tubeless is mtb, cyclocross and now gravel and the only times i have seen issues like this (of a leak not sealing at the bead) was the tyre being too slack (as previously mentioned) or the pressure too high (such that the sealant doesnt have time to dry and clog the hole). There are many sealants available now and some are better than others, i dont have the experience to say one way or another, but there are some available with a higher level of solids in the liquid intended to clog holes and allow the sealant time to dry and seal the air leak.

Ive not gone to road tubeless yet myself, at 110kg I dont trust the sealants to quickly seal a small cut or thorn hole without leaking a ton of sealant at the pressures i need to ride, based on my experiences with gravel tubeless. Other people claiming reliability at high pressures doesnt align with my experiences unfortunately. I'd be interested if there was some sort of review of sealants that wasnst a crappy magazine review by a journalist that doesnt seem to understand the issues people are having in the real world.

[Dickyelsdon]

As a minor aside. You can buy tubeless injection and extraction kits ive found very handy for checking and topping up of sealant for times you dont want to remove the tyre.

This is a Giant one, others are available.  Note the plastic tube extends into the tyre and therefore doesnt work with some valves.

[Lightning Phil]

I’ve been pleased with the Stans race sealant.  It appears to have long life, lasting at least 6 months last year between top ups. Sealed all punctures I had in that period which was about 4 based on the odd mudguard spraying episodes.  I run my tyres at around 60 psi for 28mm but then I’m not a heavyweight.

I run hooked and not had an issue with bead coming off for a few years. Better rim and tyre compliance me thinks, compared to the tubeless setup I was running 10 years ago.

[Sergeant Pluck]

When I take the tyre off I will look for the sealing humps. I might try applying some rim tape. Or maybe look for different tyres. Of course the tighter the tyre is to the rim bed the harder it will be to fit.

My guess would be that another layer of rim tape + a very thorough clean of any dried sealant that will have accumulated due to those previous leaks will resolve the problem. If it doesn't, then there must be some kind of rim / tyre incompatibility there and choosing a different tyre known to be OK with 303s would be my next step.

Sealant is for fixing punctures. The tyre should stay inflated for quite a long time without sealant if there is no problem with the rim tape.

 

[Ian H]

When I take the tyre off I will look for the sealing humps. I might try applying some rim tape. Or maybe look for different tyres. Of course the tighter the tyre is to the rim bed the harder it will be to fit.

My guess would be that another layer of rim tape + a very thorough clean of any dried sealant that will have accumulated due to those previous leaks will resolve the problem. If it doesn't, then there must be some kind of rim / tyre incompatibility there and choosing a different tyre known to be OK with 303s would be my next step.

Sealant is for fixing punctures. The tyre should stay inflated for quite a long time without sealant if there is no problem with the rim tape.

'Tubeless compatible' will be more reliant on sealant than full 'tubeless'.

[pumpkin]

Slightly ot but whats the consensus on tubes with sealant in them, wether factory installed or put in by the owner? Or is it the same as tubeless, works sometimes but not always?

[robgul]

Slightly ot but whats the consensus on tubes with sealant in them, wether factory installed or put in by the owner? Or is it the same as tubeless, works sometimes but not always?

I have a customer who had lots of punctures - now uses Slime tubes and has yet to have a puncture (and he rides a lot of miles) - I've just put Slime tubes in one of my machines but not yet done that many miles on it to make a judgement.

On balance I think tubes with sealant are a good idea - but probably Slime ready-filled rather than squirting Stans or similar in through the valves.  BUT if you do get a puncture that the Slime doesn't fix there's no realistic way to repair the tube.

[vorsprung]

yes, had exactly this problem recently

It's only happened once in a few year of running tubeless

To mitigate on the road, fitted a tube.  Once I got back to base tried a few things but it was clear there was damage to the tire and it wasn't going to do tubeless anymore so I binned it and fitted a new one

I guess it is damage to the bead