Tubeless Query

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peetee
Posts: 1031
Joined: 4 May 2010, 10:20pm

Tubeless Query

Postby peetee » 7 Feb 2019, 6:19pm

I have resided myself to the fact that this whole tubeless thing isn't going to pale away anytime soon so I guess I am going to have to, at least, try to understand the tech. So my first question is, just exactly what is it about these tyres that allow was them to be run at such low pressures?
Current status report:
Latter side of fifty and feeling less than nifty.
Too many bikes on pegs and too few miles in the legs.

mnichols
Posts: 1256
Joined: 22 Apr 2013, 4:29pm

Re: Tubeless Query

Postby mnichols » 7 Feb 2019, 6:59pm

peetee wrote:I have resided myself to the fact that this whole tubeless thing isn't going to pale away anytime soon so I guess I am going to have to, at least, try to understand the tech. So my first question is, just exactly what is it about these tyres that allow was them to be run at such low pressures?


There is no tube to pinch

Or put it another way, having a tube is what stops you being able to run tyres at low pressures

Not sure it is new tech. Can't ever remember having inner tubes in car tyres - and there doesn't seem to be any need to add them

Samuel D
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Location: Paris

Re: Tubeless Query

Postby Samuel D » 7 Feb 2019, 7:14pm

peetee wrote:So my first question is, just exactly what is it about these tyres that allow was them to be run at such low pressures?

Nothing! However, they have no tube to impact puncture. Of course the impact between road and rim with no air cushion happens anyway and may damage the rim or the tyre casing, so deliberately encouraging this risk is foolish.

Low pressures are currently in vogue, however. Look at the incredibly soft tyres of BikeRadar’s reviewer throughout this video (e.g. at 5:30 and 5:52). A decent pothole will have those rims on the ground.

A better way to run such pressures is to use wider-section tyres, tubes or no tubes.

Brucey
Posts: 32274
Joined: 4 Jan 2012, 6:25pm

Re: Tubeless Query

Postby Brucey » 8 Feb 2019, 7:01am

proper tubeless tyres and rims are constructed differently from standard ones. On a bicycle the prospect of rim/tyre damage may limit the lowest pressure. Or the stability of the tyre may affect the way the bike steers adversely at low pressures.

However in other vehicles the tyre may start to move around or come off the rim at low pressures and this possibility is mitigated by having rim lips and a specific fit quality between the tyre and the rim. There is a conflict here between ease of fitment, roiling resistance, and stability of the tyre if it should become deflated. Similar design features -and compromises- exist in bicycle tyres. Unfortunately there is more than one way to skin this particular cat and just as there are many different types of BB bearing there are different ways of implementing tubeless tyres and rims. Not all combinations of rims and tyres work equally well.

This illustration shows some of the differences;

Image

what it doesn't show is what happens if you fit standard tubed tyres on these rims. Some combinations are difficult to fit, others can blow off more easily than you might expect, and some (amazingly) can do both....

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

reohn2
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Joined: 26 Jun 2009, 8:21pm

Re: Tubeless Query

Postby reohn2 » 8 Feb 2019, 9:00am

As previous posters say,running too low TP's runs the risk of tyre carcass and or rim damage on say pothole edges or on large rocks etc off road,so logic tells me not to,with or without tubes in.

I ride three tyre sizes on solos all on 700C/29er rims I run 40mm( 37mm actual size) @40psi front 60rear.
50mm(47 actual)@ 20 to 25f, 40 to 45r depending on terrain.
2.4inch (60mm actual)@ 12 to15f,20 to 25r.
I've never experienced a pinch puncture and ride everything from UK crapmac to the roughest trails on those three tyre sizes,though off road more carefully on the 40mm tyres(which are slicks).All three bike are rigid framed with no suspension and have and all up weight load including the bike of 98 to 100kg.
The load per tyre is very important WRT tyre pressures,the lighter the load the less pressure needed in the tyre.
I can't see how tubeless would help me in regard to my present bikes and the way I ride.

Which leaves puncture protection,weight saving,and possibly ride quality.
Weight saving can be a plus as the weight of a tube can be as much as 200g on a large one but it doesn't worry me too much,ride quality could also be a plus though with the supple tyres I ride I think it'd be minimal.
Puncture protection is a definite plus and if I suffered a lot of punctures it could tip the balance toward tubless but then I'd be forced to renew the sealant every three months or so,but as I only puncture approx twice a year it isn't worth the trouble and if the sealant fails to seal I'd have to fit a tube anyway.

In short,the mither of going tubeless is for me,outweighed by the convenience of tubes and the lack of any major gains that I'm aware of.

My tubeless 2d's worth,though I'm willing to listen to the contrary and be educated.
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Cugel
Posts: 1083
Joined: 13 Nov 2017, 11:14am

Re: Tubeless Query

Postby Cugel » 8 Feb 2019, 10:01am

reohn2 wrote:As previous posters say,running too low TP's runs the risk of tyre carcass and or rim damage on say pothole edges or on large rocks etc off road,so logic tells me not to,with or without tubes in.

I ride three tyre sizes on solos all on 700C/29er rims I run 40mm( 37mm actual size) @40psi front 60rear.
50mm(47 actual)@ 20 to 25f, 40 to 45r depending on terrain.
2.4inch (60mm actual)@ 12 to15f,20 to 25r.
I've never experienced a pinch puncture and ride everything from UK crapmac to the roughest trails on those three tyre sizes,though off road more carefully on the 40mm tyres(which are slicks).All three bike are rigid framed with no suspension and have and all up weight load including the bike of 98 to 100kg.
The load per tyre is very important WRT tyre pressures,the lighter the load the less pressure needed in the tyre.
I can't see how tubeless would help me in regard to my present bikes and the way I ride.

Which leaves puncture protection,weight saving,and possibly ride quality.
Weight saving can be a plus as the weight of a tube can be as much as 200g on a large one but it doesn't worry me too much,ride quality could also be a plus though with the supple tyres I ride I think it'd be minimal.
Puncture protection is a definite plus and if I suffered a lot of punctures it could tip the balance toward tubless but then I'd be forced to renew the sealant every three months or so,but as I only puncture approx twice a year it isn't worth the trouble and if the sealant fails to seal I'd have to fit a tube anyway.

In short,the mither of going tubeless is for me,outweighed by the convenience of tubes and the lack of any major gains that I'm aware of.

My tubeless 2d's worth,though I'm willing to listen to the contrary and be educated.


Experience is the best teacher - one's own and that observed in others with similar cycling habits. Web and magazine articles may or may not contain pertinent and accurate information - there is a lot of commercial influence, a lot of ideological (rather then experience-based) stuff and postings that are by people with very different cycling habits & mechanical abilities to one's own.

I've used tubeless on the winter bike for two winters now and never knowingly had a puncture. I've got them on & off (just for practice) topped them up with "milk" but never had to fix a puncture. Whilst riding with the club, I've seen two tubeless punctures that didn't seal themselves....

One was a significant rip that required a boot and a tube. It sprayed the unlucky cyclist with latex (which is hard to get out of a jersey once dried-in) and took some 10 minute to deal with. That's not to bad, since a conventional tyre with a boot-rneeding rip would probably take as long. He had no trouble getting the tyre off the rim and on again after booting/tubing it. It also inflated with an ordinary mini-pump. He might have been lucky there.

A second lad had a puncture that spit latex to a noticeable extent, with a softening tyre. The hole was a big one but he fixed it with a rubber grommet, which is still in there as far as I know. It took him about ten minutes too - largely because it was the first time he's applied such a grommet so he went carefully.

Those are probably the extreme circumstances where a puncture doesn't fix itself. Neither event put me off from the tubeless - although I suspect that a poor tyre fit on the rim or a cack-handed cyclist would both greatly increase the potential difficulties of that first booting/tubing event.

Cugel