tubeless tire pressures

General cycling advice ( NOT technical ! )
ndwgolf
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tubeless tire pressures

Postby ndwgolf » 5 Jan 2019, 12:25am

I watched a GCN Youtube yesterday about running tubeless tires on a road bike.........there was one section where the guy went from say 100 psi to 70 psi and said that the ride was more comfortable at the lower pressure and because he was using the tubeless tires the lower pressure won't cause a puncher as in if you were using non tubeless tires at low pressures it would provoke a puncher..............dos all that sound about right??

Neil

Samuel D
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Re: tubeless tire pressures

Postby Samuel D » 5 Jan 2019, 1:38am

If the tyre pressure is so low that impact punctures must be expected if a tube isn’t used, what prevents the rim from being wrecked?

Rims should have an air cushion between them and the sharp edges of potholes. Any scheme that involves deliberately running the risk of that not being present is optimistic.

For that matter, just because a tubeless tyre does not puncture does not mean that squishing it with great force between rim edge and road does it no harm. Such abuse risks damage to the casing threads, and will you notice that if no puncture alerts you to check the tyre?

I treat pinch punctures as a warning that the set-up is marginal and should be improved.

A safer route to lower pressures is larger-section tyres with or without tubes. They’ll have lower rolling resistance than small-section tyres run at a greater drop, too.

But yes, tubeless tyres eliminate the possibility of a pinched tube causing a puncture.

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Cugel
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Re: tubeless tire pressures

Postby Cugel » 5 Jan 2019, 11:59am

Samuel D wrote:If the tyre pressure is so low that impact punctures must be expected if a tube isn’t used, what prevents the rim from being wrecked?

Rims should have an air cushion between them and the sharp edges of potholes. Any scheme that involves deliberately running the risk of that not being present is optimistic.

For that matter, just because a tubeless tyre does not puncture does not mean that squishing it with great force between rim edge and road does it no harm. Such abuse risks damage to the casing threads, and will you notice that if no puncture alerts you to check the tyre?

I treat pinch punctures as a warning that the set-up is marginal and should be improved.

A safer route to lower pressures is larger-section tyres with or without tubes. They’ll have lower rolling resistance than small-section tyres run at a greater drop, too.

But yes, tubeless tyres eliminate the possibility of a pinched tube causing a puncture.


When a tubed tyre gets snakebite, there is no air cushion between the rim and the road - only some squished rubber. In fact, a bad snakebite will often see rim damage too.

The same can happen with a tubeless tyre, as you mention, except there's no snakebite puncture as there's no tube. You could imagine an impact so hard that both the rim and the tyre wall get damaged though.

As Brucey has often pointed out elsewhere, a soft tubeless tyre that can have it's walls flexed too much will eventually crack or otherwise degrade. In addition, cornering on a tyre that's too soft (any tyre) may cause the tyre to distort so much it causes a poor cornering or even a fall.

In practice many people have mistakenly over-inflated their tyres, no matter what the type of tyre technology, in the belief that harder tyres roll faster. They don't in the real world and much lesser pressures than is traditional often see the tyre rolling much better. There are more hysteresis losses but these are small compared to the gain from losing much less energy to suspension losses (bouncing the bike and rider up and down, perhaps off the road surface momentarily).

There are lots of articles these days about tyre pressures for both tubed and tubeless road tyres. Here's the latest from that Jan Heine. which is well-argued but must still be absorbed with the knowledge that he also sells his own brand of tyres....

https://janheine.wordpress.com/2019/01/ ... is-faster/

Cugel

althebike
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Re: tubeless tire pressures

Postby althebike » 5 Jan 2019, 12:09pm

The tire pressure indicated on the sidewalls of my tires are as high as standard tires with inner tubes, and so I try and keep them at around that pressure, they do leak pressure faster than tires with inner tubes, during a multi day tour in the summer the tires ran down to around 50, the ride was less bumpy but I still felt safe, a high impact over a sharp edge of a pothole may have taught me otherwise , and so I would not recommend trying this, but it can be done .

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The utility cyclist
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Re: tubeless tire pressures

Postby The utility cyclist » 5 Jan 2019, 3:53pm

althebike wrote:The tire pressure indicated on the sidewalls of my tires are as high as standard tires with inner tubes, and so I try and keep them at around that pressure, they do leak pressure faster than tires with inner tubes, during a multi day tour in the summer the tires ran down to around 50, the ride was less bumpy but I still felt safe, a high impact over a sharp edge of a pothole may have taught me otherwise , and so I would not recommend trying this, but it can be done .


The max or minimum tyre pressure on the sidewall is no guide whatsoever as to appropriate pressures for any given individual. Rarely would you need or want to pump them up to the max and similarly at the lower end unless you were on really fat tyres and didn't weigh much.

reohn2
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Re: tubeless tire pressures

Postby reohn2 » 5 Jan 2019, 5:43pm

althebike wrote:The tire pressure indicated on the sidewalls of my tires are as high as standard tires with inner tubes, and so I try and keep them at around that pressure, they do leak pressure faster than tires with inner tubes, during a multi day tour in the summer the tires ran down to around 50, the ride was less bumpy but I still felt safe, a high impact over a sharp edge of a pothole may have taught me otherwise , and so I would not recommend trying this, but it can be done .

Tyres should be run at pressure for load,this is a good guide to tyre pressures:- https://www.google.co.uk/search?num=10& ... NwExjl-QBM:
The pressures indicated are per tyre load so if your weight distribution on the bike is say 60% rear,40% front(which it is more often than not for most riding positions and is easily checked with bathroom scales)the tyre pressures should reflect that distrubution tubless or not.
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althebike
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Re: tubeless tire pressures

Postby althebike » 6 Jan 2019, 7:48pm

I think getting technical about it would not make any difference for my type of usage .If it drops below 85 , I pump it up to 100 and wait for the pressure to drop to 85 before I repeat the process. I read a review that tested some tubeless tires, and the IRC ones I have apparently are only really responsive at higher pressures (100+ I think the review said) but on the road I do not notice any difference so I do not worry about it.When I did jogle last year I started with the pressures around 110 but by the time I finished they were certainly a lot softer, so I guess I used them throughout and beyond the lower recommended pressure range.