Tubeless tyres- where is the 'seal'?

[Brian Reay]

I (think) basically understand the principle of how tubeless tyres
work/fit on the rims: there is a 'shoulder' behind the visible edge you
can see and the tyre sits on that. The 'shoulder' needs to be clean,
smooth, free of corrosion etc, and the inner edge of the tyre should sit
snuggly on it.

Is this correct, please?

Have I missed something?

Also, at one time, it was common to fit an inner tube if a seal couldn't
be made- this is now banned. Is this also true?

Reason for question: I've has a problem with a wheel on my trailer. I've
had the rim replaced. The 'shoulder' on the old rim doesn't look perfect
(the paint is bubbled due to rust under the paint) but so much so I'd
have expected it to be worse than I was seeing- pressure was slowing
being lost compared to the other tyres (the other working wheel and the
spare). Not wishing to risk a serious problem when towing, I opted to
change the rim as there was signs of rust.

[Fredxx]

Post by Brian Reay
I (think) basically understand the principle of how tubeless tyres
work/fit on the rims: there is a 'shoulder' behind the visible edge you
can see and the tyre sits on that. The 'shoulder' needs to be clean,
smooth, free of corrosion etc, and the inner edge of the tyre should sit
snuggly on it.
Is this correct, please?
Have I missed something?
Also, at one time, it was common to fit an inner tube if a seal couldn't
be made- this is now banned. Is this also true?
Reason for question: I've has a problem with a wheel on my trailer. I've
had the rim replaced. The 'shoulder' on the old rim doesn't look perfect
(the paint is bubbled due to rust under the paint) but so much so I'd
have expected it to be worse than I was seeing- pressure was slowing
being lost compared to the other tyres (the other working wheel and the
spare). Not wishing to risk a serious problem when towing, I opted to
change the rim as there was signs of rust.

You could have cleaned up the rim down to bare metal in the offending
part of the rim, applied primer and repainted for a good seal. Might be
worth doing to the old rim in readiness for the other side failing.

[Brian Reay]

Post by Fredxx

Post by Brian Reay
I (think) basically understand the principle of how tubeless tyres
work/fit on the rims: there is a 'shoulder' behind the visible edge
you can see and the tyre sits on that. The 'shoulder' needs to be
clean, smooth, free of corrosion etc, and the inner edge of the tyre
should sit snuggly on it.
Is this correct, please?
Have I missed something?
Also, at one time, it was common to fit an inner tube if a seal
couldn't be made- this is now banned. Is this also true?
Reason for question: I've has a problem with a wheel on my trailer.
I've had the rim replaced. The 'shoulder' on the old rim doesn't look
perfect (the paint is bubbled due to rust under the paint) but so much
so I'd have expected it to be worse than I was seeing- pressure was
slowing being lost compared to the other tyres (the other working
wheel and the spare). Not wishing to risk a serious problem when
towing, I opted to change the rim as there was signs of rust.

You could have cleaned up the rim down to bare metal in the offending
part of the rim, applied primer and repainted for a good seal. Might be
worth doing to the old rim in readiness for the other side failing.

I 'splashed out' and replaced all three, only to find the other two were
fine ;-( Having said that, for peace of mind, it was worth the money- I
don't want to be worrying about tyres etc when towing. (I don't mess
around with safety.)

[newshound]

Post by Brian Reay
I (think) basically understand the principle of how tubeless tyres
work/fit on the rims: there is a 'shoulder' behind the visible edge you
can see and the tyre sits on that. The 'shoulder' needs to be clean,
smooth, free of corrosion etc, and the inner edge of the tyre should sit
snuggly on it.
Is this correct, please?
Have I missed something?
Also, at one time, it was common to fit an inner tube if a seal couldn't
be made- this is now banned. Is this also true?
Reason for question: I've has a problem with a wheel on my trailer. I've
had the rim replaced. The 'shoulder' on the old rim doesn't look perfect
(the paint is bubbled due to rust under the paint) but so much so I'd
have expected it to be worse than I was seeing- pressure was slowing
being lost compared to the other tyres (the other working wheel and the
spare). Not wishing to risk a serious problem when towing, I opted to
change the rim as there was signs of rust.

Correct. This seal is in fact remarkably tolerant of dirt, debris,
corrosion, etc, especially when the tyre is fitted with the lubricating
grease used by garages.

Don't know about legality of inner tubes but AFAIK they are still
required for wheels with wire spokes.

If it is an alloy wheel, another failure process can be minor cracking
and/or tracking of a crack through the inevitable regions of porosity in
a casting.

In my experience rusted steel rims can often be recovered by
sufficiently vigourous wire brushing. Repainting with a sufficiently
thick paint may also solve the problem. Perhaps forever, with two part
epoxy, or for a few years with hammerite.

[Dave Plowman (News)]

Post by newshound
Correct. This seal is in fact remarkably tolerant of dirt, debris,
corrosion, etc, especially when the tyre is fitted with the lubricating
grease used by garages.

Think they use something more akin to a contact glue these days.

When having new tyres fitted to my old car, the fitter got a phone call in
the middle of doing them. He'd already applied the gunge to one wheel. And
it was some time afterwards before he fitted that tyre. And it leaked. ;-)
None of the other three did.

[newshound]

Post by Dave Plowman (News)

Post by newshound
Correct. This seal is in fact remarkably tolerant of dirt, debris,
corrosion, etc, especially when the tyre is fitted with the lubricating
grease used by garages.

Think they use something more akin to a contact glue these days.
When having new tyres fitted to my old car, the fitter got a phone call in
the middle of doing them. He'd already applied the gunge to one wheel. And
it was some time afterwards before he fitted that tyre. And it leaked. ;-)
None of the other three did.

Or perhaps it had just "dried out" a bit? Don't know whether they are
solvent or water-based.

This one is described as "quick drying" (seems to be a soap)

https://www.ebay.co.uk/itm/TYRE-LUBRICANT-TYRE-MOUNTING-PASTE-TYRE-SOAP-WATER-BASED-5KG-WITH-BRUSH-/161737927458

[Kevin]

Post by Brian Reay
Also, at one time, it was common to fit an inner tube if a seal couldn't
be made- this is now banned. Is this also true?

Two reasons not to use inner tubes: if you get a nail in the tyre - or,
more likely these days - one of those viciously sharp modern woodscrews,
a tubed tyre will deflate very much faster, losing air through the valve
hole in the rim; and some tyres, unless marked "TT", have moulding lines
on their inside surface which can wear holes in tubes. I've had this on
a Range Rover.

If your rims aren't designed for tubeless, they may not have the shallow
humps on their bead seat area which are claimed to reduce the chance of
a tyre becoming dislodged under extreme conditions. I made some effort
a few years ago to find any recorded incident where this had happened,
and failed. My judgement was that rapid deflation posed a bigger risk
to me than bead separation, so I fitted tubeless tyres to my classics.
YMMV.

Alloy wheels were invented by the devil, for use on his chariots, so if
you can't get them to seal properly, it serves you right.

Kevin

[Brian Reay]

Post by Kevin

Post by Brian Reay
Also, at one time, it was common to fit an inner tube if a seal couldn't
be made- this is now banned. Is this also true?

Two reasons not to use inner tubes: if you get a nail in the tyre - or,
more likely these days - one of those viciously sharp modern woodscrews,
a tubed tyre will deflate very much faster, losing air through the valve
hole in the rim; and some tyres, unless marked "TT", have moulding lines
on their inside surface which can wear holes in tubes. I've had this on
a Range Rover.
If your rims aren't designed for tubeless, they may not have the shallow
humps on their bead seat area which are claimed to reduce the chance of
a tyre becoming dislodged under extreme conditions. I made some effort
a few years ago to find any recorded incident where this had happened,
and failed. My judgement was that rapid deflation posed a bigger risk
to me than bead separation, so I fitted tubeless tyres to my classics.
YMMV.

Thank you.

I wasn’t thinking of fitting tubes I was just curious if my memory that
fitting then to tubeless tyres was banned.

Post by Kevin
Alloy wheels were invented by the devil, for use on his chariots, so if
you can't get them to seal properly, it serves you right.

The rims on the trailer are steel.

We’ve alloys on a couple of cars, they are normally fine. Motorhome has
steel rims.