Any Point Me Going Tubeless

General cycling advice ( NOT technical ! )
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andrew_s
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Joined: 7 Jan 2007, 9:29pm
Location: Gloucestershire

Re: Any Point Me Going Tubeless

Postby andrew_s » 26 Sep 2018, 2:27pm

Brucey wrote:Well you won't need to do this as often (if the tubeless system works as advertised, sealing small punctures which you might get from thorns or flints) but when you do (a significant fraction of punctures are bigger gashes that won't seal and need tube/booting for example), the chances are that the whole process will be somewhat worse than normal; tubeless tyres are designed to be a tight fit on the rims, and the rims have lips in the well to retain the tyre bead. When you do get the tyre off there is a mess of sealant to contend with.

In addition, if the sealant fails to seal and you need to fit a tube, you'll have to do something about all of the thorns and flints in the tyre that did seal - if you don't, your tube won't last very long.

It's often stated that tubeless tyres have a lower rolling resistance (i.e. are faster) than regular tubed tyres. This isn't the case - adding the necessary sealant adds resistance just like adding an inner tube does.

mattsccm
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Joined: 28 Nov 2009, 9:44pm

Re: Any Point Me Going Tubeless

Postby mattsccm » 26 Sep 2018, 10:02pm

Whilst I can't deny it happens, it may be worth considering the likely hood of a tyre carcase damaging puncture. Ignoring childhood, I can't remember ever having a tyre ripped. That's including touring on tubs as a skint teenager, MTB ing since 1985, cyclocross on and off since about then and more recently about 40,000 miles of gravel in the last dozen or so years almost entirely on either fragile cyclocross tyres or road tyres and even old tubs. It maybe different for others but I never even consider it. I may be bitten one day but that's a small risk I reckon. Just a thought.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Any Point Me Going Tubeless

Postby Brucey » 27 Sep 2018, 11:56am

larger holes/gashes happen sufficiently often that I carry booting fabric at all times these days.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

slowster
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Joined: 7 Jul 2017, 10:37am

Re: Any Point Me Going Tubeless

Postby slowster » 27 Sep 2018, 1:56pm

Last year while cycling off road I encountered a rider with a flat tubeless tyre who was pushing his bike. The tyre had a 1" gash in the sidewall, which obviously was far too large for the sealant to cope with. It turned out that it was his first ride after converting his bike to tubeless, and he had not thought to take a spare inner tube as a precaution. Unfortunately my spare tubes had schrader valves and so would not fit.

He had a 4 mile walk pushing the bike back to his car, which couldn't have been much fun given that it was a fairly heavy full suspension ebike.

I can see how the advantages of tubeless tyres in some circumstances for MTB riding might be significant depending upon the likelihood of the sort of punctures that the sealant copes well with and possibly also the weight saving* for a wide large volume tyre, as well as the ability to run such tyres at lower pressures without the same risk of pinch flats.

However, I cannot see how those advantages would similarly apply - certainly not enough to make tubeless worthwhile - to road tyre usage.

I can't help suspecting that this is a case of some MTBers finding that tubeless is a huge improvement for where they ride, and then believing based on that experience that the technology must be the best option for road riding as well.

* By which I mean saving rotating weight, not saving weight by not bothering to carry spare inner tubes like the rider I encountered.

busb
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Joined: 28 Sep 2017, 10:10am
Location: Berks, UK

Re: Any Point Me Going Tubeless

Postby busb » 28 Sep 2018, 7:00pm

slowster wrote:
busb wrote: One more point - remember to have the valves uppermost for adding or releasing air should you go with tubeless.

I thought that was only specifically recommended for CO2 use, i.e. to minimise any damage to the sealant from the very low temperature of the gas as it expands and comes into contact with sealant, i.e. most of the sealant will be at the bottom of the tyre, furthest away from the valve and the CO2 before it warms and is diluted by the air already in the tube.

I've read that it's advisable to store the bike with the valves in the lowest position, so that the valves are upright and any sealant in them will drain down into the tube. I don't know how much of a problem sealant in valves entering pump heads and pressure gauges is, but there is at least one (very expensive) pressure gauge with a removable filter to prevent it being damaged by sealant (https://singletrackworld.com/2018/08/pressure-gauge-group-test-the-evt-bleedin-gauge/).

If the valve has some sealant inside it, and the valve is released to let air out, would not the rapid movement of air being expelled from the tube be very similar to the escape of air through a puncture, and so result in the shear forces on the sealant which will cause it to solidify in the valve?

I just park my bike without any specific valve orientation - perhaps I'll store with the valves down-most to see if overcoming the initial lack of air entering the tyres changes or not. The reason for pumping up (or releasing) with the valves upmost is to not lose or get sprayed with latex.

slowster
Posts: 1141
Joined: 7 Jul 2017, 10:37am

Re: Any Point Me Going Tubeless

Postby slowster » 28 Sep 2018, 9:32pm

busb wrote:perhaps I'll store with the valves down-most to see if overcoming the initial lack of air entering the tyres changes or not.

That's the first time I've heard of an initial resistance to air being pumped into a tubeless tyre - is it something many tubeless users report?

If so, I wonder if that is a cause - possibly even the main cause - of the lumps of solidified sealant which many users report finding in the tyre when they take it off the rim after several months, i.e. if there is usually sealant inside the valve each time the tyre is pumped up and each time the air movement in the narrow space inside the valve creates similar conditions to those of a puncture, then some of that sealant will solidify. Presumably the numerous small solid pieces of sealant would combine inside the tyre over time into larger lumps.

busb
Posts: 180
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Location: Berks, UK

Re: Any Point Me Going Tubeless

Postby busb » 29 Sep 2018, 12:01am

slowster wrote:
busb wrote:perhaps I'll store with the valves down-most to see if overcoming the initial lack of air entering the tyres changes or not.

That's the first time I've heard of an initial resistance to air being pumped into a tubeless tyre - is it something many tubeless users report?

If so, I wonder if that is a cause - possibly even the main cause - of the lumps of solidified sealant which many users report finding in the tyre when they take it off the rim after several months, i.e. if there is usually sealant inside the valve each time the tyre is pumped up and each time the air movement in the narrow space inside the valve creates similar conditions to those of a puncture, then some of that sealant will solidify. Presumably the numerous small solid pieces of sealant would combine inside the tyre over time into larger lumps.

I remove the valve cap, unscrew the tip, press it in momentarily, attach the pump head then lock it, start pumping to find the pressure has climbed well over 100psi then suddenly drops then inflates as expected as happened this morning. I'm pretty sure I heard a hiss when I pressed in the unscrewed tip & if the case, would suggest no blockage. I’ll check more closely next time.
When I’ve sucked out sealant using a small-bore pipe attached to a syringe, the result has been very liquid, free of lumps with no blocking - perfectly clean, in other words. Bare in mind that I've only running been running tubeless for 18 months without any sudden deflations on 2 bikes.