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Tubeless tyre pressures.
Sorry for the naive, dumb question:
I have just got some tubeless rims with Motoz Tractionator tyres for my Yamaha T700. I've never run tubeless tyres before: do the factory recommended tubed tyre pressures still apply to tubeless? Should they be run at a higher or lower pressure than tubed tyres? Cheers. |
Same pressure.
Andy |
On a mountain bike, one of the key reasons to switch from tubes to tubeless is the ability to run lower pressures (because no danger of snakebite flats), thereby increasing the contact patch. I'd wonder why this is not true for motorbike tires, at least when running off-pavement. Lower pressure is also claimed to improve pedaling efficiency due to the tire's greater ability to conform to surface irregularities, which might be relevant or not.
Top speed on a mountain bike is probably around 20mph/33kph, so that's one obvious variable. With me riding, maximum weight would run around 230 lbs./105kg, so that's another. On motorbikes I've typically lowered air pressure for long runs on dirt, gravel or mud whether tubed or tubeless, which also might be relevant or not. Mark |
Longer answer.
A tyre is a spring. The spring rate is set by the pressure and combination of steel wire, rubber and goodness knows what else the rubber is adulterated with. Air is air. Going tubeless barely changes the construction of the tyre (chances are its the same tyre) and air is air. The starting point is therefore the same pressure. The advantage of an air spring is that it is naturally a variable rate. Compress the gas by adding load and the spring gets stiffer as the volume drops. With a tyre a volume change almost always involves a change of contact patch area and hence grip. A low pressure though also means the sidewall is flexing more and getting hotter. This heat comes from the power source so those cyclists are wrong regardless of how, it feels. The sidewall flexing also means more forces off centre so a tendency to wobble. The bigger, more conforming contact patch is more likely to find grip on an uneven or loose surface. The tubeless tyre must have a safety bead to get the seal. At low pressures this mechanical retention of tyre to rim still works where pneumatic no longer does. A traditional tube type doesn't have this so needs a given amount of air in it. However, unless you want a go on my CL350 I doubt many rims are traditional. The tyre will be marked TL and the rim will have the bead, so the fact fashion dictates spokes and spokes done on the cheap need tubes doesn't make a difference. Run at 8 PSI and the near empty tube might creep and snap the stem off, but the tyre will still be on the rim. Personally I won't have tubes on anything made this century and will only run two pressures, road as defined by the vehicle manufacturer and serious off road at 8-10 psi (not that I've done this for years with my own bikes). Messing about in piddling steps between the two is personal choice but the engineer data (and I've been through the hell that involves central tyre inflation system salesman and the MOD) says you can create heat, wear, odd steering etc. much more easily than you gain traction. Andy |
Sounds like you know a lot about how things work with motorbike tires--far more than me. I'd still suggest leaving room for what you don't yet know, and for other preferences. Me, I air down somewhat off the pavement and I like what it does for me, though I'm no expert.
I'd leave some room as well for the likelihood it works differently again for mountain bikes. For example, I've never noticed significant heating of tire sidewalls at low pressure, no matter how hard I ride (although that's not very hard, as a rule). Things are different on a heavy, powered motorbike. 'Course, this is not a mountain bike forum. Mark |
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My tubeless racing bike tyres at 28mm need less pressure than a tube tyre in same size. I think the construction of the tubeless tyres walls is different. The footprint of tubeless racing bike tyre gets smaller - shorter in length while being wider which results to less rolling resistance and in more comfort on wavy/bumpy streets. That was explained to me by a Schwalbe product manager on bike faire about the new tubeless tyre line. I clearly feel that there is more comfort because my pain after riding in cervical spine area is far less so I can ride longer distances now. Isn`t there a difference existing in the construction of the walls of motorcycle tyres regarding tubeless/tube? Think they must be much stiffer to stay in place at the safety bead? Because I am not used to psi as a european and I don`t fully get that part of your answer, I would like to ask you for the pressure difference road/offroad in percentage? (I have no experience with tubeless on motorbikes but I am thinking off installing rims and tubeless.) |
When you let air out of your tyres, the surface area of rubber contacting the ground increases. It gets slightly wider, and a lot longer.
From full tyre pressure down to around 15PSI your surface area nearly doubles which is terrific in sand on bikes and 4x4s'. If that is your environment, then fitting rimlocks (on bike rim) is a good idea to avert the risk of the tyres slipping on their rims, which could result in deflation or a tyre coming off altogether. In mud I tend to go to 28psi and if if it seems like a bog (what am I doing in there anyway????doh) it happened by accident (read stupid!) I got down to 22 and got filthy in the process. In sand I've been down to 15 psi Remember that as you lower tire pressure, the tire becomes more vulnerable to damage by stoking the sidewall or rolling the tire off the rim. I's a balancing act of what is needed at the time to get you going. I bought a Via air pump compressor from an advertiser on this forum (apologies amigo, your name has slipped my old brain) and it has served me very well - get a reliable one as you may need to deflate and pump up many a time on just a few hundred meters! In 4x4 the Via air compressor On the moto the Best Rest cycle pump compressor Both tested for years and years and have proved to be very reliable. Keep them clean and off the deck helps. IMHO, buying a cheapie compressor can be a big mistake! (a lesson learned the hard way:innocent:) Look at the tyre pressure guide to give you an idea on how your tyre footprint increases as you decrease the pressure. And if you can't be bothered with tyre pressures then.....see 3rd picture below...:Beach: |
A few factoids / opinions that may help:
14.7 PSI = 1 BAR HARDER stiffer tires = less rolling resistance. Tubeless tires have a "tube" as part of their inner construction - very thin, but does the same job of sealing the tire. Are tubeless stiffer to stay on the rim - not necessarily, it's more of a mechanical retention. Note: Running Tubeless tires on a TUBE rim that does NOT have the "safety bead" is a BAD BAD idea. INSTANT deflation is possible. HIGH pressures are pretty safe, but not perfect, low pressures really bad. Hope that helps! |
There may also be confusion about "tube" and "tubeless"?
A tyre marked TL is the same tyre run tubeless on an alloy or spoked rim with a tube. A tyre marked TT is a different construction and will always be run tubed. Andy |
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A bit off topic: How low can you go on a bike with tubles tires, like my XT1200Z, before it makes pfffffffffff? sushi |
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I agree with most of what has been said here, this is my take on it. You can run tubes in a "tubeless" construction tyre but personally I'd only do that as a "get me home" - such as a major hole that can't be plugged. Tubes add weight and do little to improve protection against deflation.
The manufacturers' recommended pressures are designed to give you the optimum size and shape contact patch for best life and grip. Reducing pressures off road allows the tread blocks to flex more, but only if you have a very knobbly tyre in the first place. Reducing pressures also brings the risks of unseating the bead or bending the rim on rough ground. The desired increase in contact patch area may not be achieved either, since a tyre running well below its design pressure can take on a concave shape at the contact area, reducing surface area. Finally, running tyres at low pressure on the road increases hysteresis heating of the carcass and risks delamination and chunking. I wouldn't recommend reducing tyre pressures by more than 5 psi from the recommended settings. |
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Go buy a new Triumph or Honda or..... All the tyres are marked Tubeless and all the lower end spoked rims require a tube. Cowboys? A tube increases the running temperature, so you drop the speed rating by one or two. Most tyres are rated at 168 mph , so if you drop two to 130 mph there might be bits of autobahn you might need to slow down on. There is a legal trap. A Heidenau K60 is a T rating, so dropped to R is a 106 mph tyre. Your Bavarian Behemoth lists a top speed of 130 mph. A trained vehicle inspector in a bad mood might add to your admin box, especially if they are investigating why you had a blow out. Chances of this happening? Slim enough not to worry, there enough to make it worth getting the rim straightend when you can. Choice in say a 19-inch TT marked tyre explains why even a new Bonneville comes with ****y Brazilian Dunaplops marked TL and fitted with tubes. TT just aren't made for road use anymore. Andy |
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The second part though is close to the exact problem with an old car I have. The car came out of the factory gate 50+ yrs ago fitted with 155 section tyres good for 130mph (H rated). These days 155 section tyres are only one step up from wheelbarrow size and the best you can get (and then after some searching) is T rated (118mph). Even wheelbarrows are using tubeless these days but the car's wheels were designed to take tubes. So now I (and every other Elan owner still running stock wheels) are stuck with tubes in a lower rated tubeless tyre. If the tubes knock the speed rating down another two notches that becomes R rated - 106mph. The pedants answer to this is take the car off the road and don't use it again until you can get the correct tyres (I've had that 'advice' in the last week) but meanwhile in the real world people are using whatever they can get. Is heat buildup the core issue with tubes or is there another problem? For many years tubes were the only option and all wheels were fitted with them. When the magazine testers back in the day were hitting close to 130mph on the autobahn in the car I mentioned they were doing it on tyres fitted with tubes. Was that kamikaze level irresponsible or within the manufacturers design parameters? A lot of my bikes - including ones I do substantial distances on - have to use tubes, and a right royal pain in the ar*e they are when you get a puncture. But it's when I'm riding along puncture free that I'm wondering about. If I could omnipotently look inside the tyre as I cruise along what would I see happening - a tyre and tube rubbing along in perfect harmony or a mismatched couple scratching each other's eyes out just before an explosive divorce? How much of this down to tubes being looked upon as yesterdays technology - along with carbide lamps, trembler coils and, increasingly, carburettors. If you don't have to use them (as most bikes don't) it's easy to dismiss them as outmoded or even dangerous using social arguments rather than scientific / engineering ones. It's a bit like dismissing film cameras as dangerous because of all the chemicals that went into film production. |
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