Duragrouch

(above) Makes sense. What I don't understand is, if sealant stays liquid in presence of oxygen inside tire or tube, how does it harden when going out leak hole? Unless it hardens in the presence of UV light, like composite dental fillings. I could think of stranger things, like Loctite (anaerobic thread locking adhesive) which hardens in the *absence* of oxygen.

SoSmellyAir

Silca's tire pressure calculator goes by measured width rather than nominal width, so if a 28 mm tire is installed on a wheel with a wider internal width (e.g., 21 mm), the tire may measure > 28 mm wide and allow one to ride it at < 80 psi.

VegasJen

OK, maybe I just don't understand it, which is completely possible. This is my Shiv (tri bike), running Reynolds AR80 wheels, which I believe are 21mm internal width, and a 25c tire.

Even so, I tend to run at least 90psi just to be safe. I don't necessarily run what the calculator recommends just because I do like a little softer ride, but I still maintain a minimum of 90psi to reduce the risk of pinch flats.

Part of the problem here is just the road conditions. Not so much the actual pavement, but the debris on the roads. There are very few dedicated bike lanes. What is marked as a bike lane is typically just a paved shoulder that often has whatever debris gets kicked up. I've had flats (mostly with tubes) due to auto tire steel belts and thorns from goat heads or mesquite trees most often. But I have had one or two impact flats from rocks. The rock they use before laying the pavement happens to be pretty much exactly like the rock that's IN the pavement, so it can be pretty difficult to distinguish at speed. And, of course, none of the rocks are flat or round. Oh no, they're perfectly tire flattening shaped, all big and jaggy sharp angles and s**t.

Duragrouch

I am by no means an authority, never used tubeless. For me, tubed, I am running higher pressure than recommended for my tire width, because a) a got a pinch flat including slightly bending rim side on a pothole, and b) my earlier skinside tires in same width, I could actually see the sidewall fibers and rubber being more stressed than on the front, due to greater flexing. So I aired up, solved both. My perception is that tubeless was first used on MTB for lower pressures while avoiding pinch flats, but that could be wrong. But I would ask yourself about your pothole or severe bump occurance (perhaps way better than my city, your greatest threats are only pokey), and how your rear tire sidewalls look running at lower pressure, both observed while on bike, and daily quick inspection of sidewalls; This may be more difficult if black tire sidewalls as more tires are going due to better UV resistance.

Whether tubeless will seal a poke at high pressure, may depend a lot on the diameter of the poke, and thickness of the tread (thicker I think better, longer sealant leak path), so lightweight race tires not as good in that respect. I haven't run lightweight in many decades, I go now for thick and flat-resistant. Any possibility of using heavier tires for training only (and on a second cheaper set of wheels, so easy swap), or would that throw off your training versus race expectations?

RCMoeur 

On this past weekend's Tour de Scottsdale, I helped a rider who was running 700x40C tubeless and suffered a hole in the tire that wouldn't seal. We ended up installing a tube so he could finish the ride, for which he was grateful (to the point of sending me a nice e-mail today).

Troul 

if it was available during the repair, would a plug worked?

Mtracer

I think there's two things going on. The tire plugs because of the way the sealant (liquid latex, I think) behaves under shear forces along with particle additives designed to plug up the hole. So, it doesn't need to harden or dry out due to chemical type reactions to stop the leak. As for generally drying, I think that is in fact it. It has a solvent that dries out. Not sure if that solvent is just water, though it clearly is water soluble. A tire is a sealed system, though the liquid sealant is only a small proportion of the tire volume. But once the volume inside the tire becomes saturated with the solvent vapors, the sealant would not continue to dry out. Rather like your milk doesn't dry out inside a partial filled carton. Or more to my liking, my whisky doesn't dry out even when there's just a small amount left in the bottle.

In the end, I don't think the sealant is relying on a chemical reaction at all. Though, no doubt over long periods of time the sealant likely does oxidize, as do many things. And it probably does react to UV light. And I bet it could be burned too. But none of that has to do with it's intended use.

Of course, over some weeks and months, the sealant does in fact dry out inside the tire, simply because the tire is not 100% gas tight.

Anyway, this is my understanding, but I'm no expert on this, so take it all with a grain of salt.

RCMoeur 

He said he'd tried a plug, but it didn't fully seal the tire. The tire was rated for 50 psi, but I'm not sure it had all that when he installed the plug.

VegasJen

I do have a bike with heavier tube tires on it, but it's just not as nice a ride as the Shiv. I should ride it more, if for no other reason than being able to set it up for the durability. But I just really, really like riding the Shiv.

RCMoeur 

That's intentional, both for traction improvement and pavement durability. An asphalt concrete or chip seal pavement with all rounded rocks tends to wear poorly and can develop rutting, shoving, and stripping (and not the typical type of stripping found in your area). There is even a "fractured faces" test that is performed on pavement aggregate to make sure it's jaggedy enough.

In my experience, I had a piece of seal coat aggregate flatten a tire on my racing bike - the sharp edge went right through the tread, cord, protective layer, and underlying SpinSkin. Wasn't all that happy, but it was OK after the tube was swapped.

RCMoeur 

Knowing southern Nevada (which is much like where I live in Arizona), that would mean not riding at all.

Troul 

lmao

squirtdad

try the rene herse...it will give you a range, (me at total bike and me weight of 260 and 23 mm tires range is 82 to 67 change it to 28mm and it is 85 to 105....and 25mm I blow up the calculator) but bottom line is you need enough air to support the load https://www.renehersecycles.com/tire...re-calculator/

also to remember one of the original motivations was for large MTB tires running low pressure to avoid pinch flats in tubes

VegasJen

Thanks. According to that, I can run them down to 79psi. I probably won't go that low but I might try it in the 85-90psi range just to see how that feels.

VegasJen

Indeed. And just as an aside, I know much of my problem revolves around the specific location. Living in a rural area, there is far less routine maintenance of the roadway, i.e. sweeping. I have noticed I rarely get flats, even with my skinny 23c tires and lightweight tubes, when I ride in Vegas. Those same tires would barely make it to the end of my street here.

PeteHski

This misconception came from mountain biking where minimum pressure with tubes was dictated by pinch flats. Running tubeless allowed riders to run lower pressures on the same width of tyre without risk of pinch flats.

With road tyres the optimum pressure for rolling resistance is pretty much the same with or without tubes, as confirmed by the Silca calculator. To run lower pressure you need to be running wider tyres and rims, which you probably don't have adequate clearance for on your bike. Ideally you would want to be running 28 or 30 mm wide tyres at around 60 psi to get the most flat protection from tubeless sealant.

alcjphil

Tubeless tires are much more resistant to pinch flats than tube type tires. Years ago, while riding with a fast group on a slight downhill at about 70 kph i hit a pothole with enough force to eject my water bottle and ding my rear rim. The tire did not go flat
I had to have the rear rim replaced. The tire was fine

Duragrouch

Hmm... I wonder if I could take my tubies and seal them tubeless style, so if the tube did get a pinch flat, the air would just leak into the same void? Of course, like run-flat tires, you need an indication of a flat; Early with run-flats, it was with a wireless pressure sensor on the inside of the rim. Now, they just use the same sensors as for the ABS brakes; When a tire goes flat, even run-flats, it changes its rolling circumference quickly, which is detected by the car computer and you get a warning light. After fixing the tire or putting on a spare, there's a procedure to reset the system and clear the warning.

hidetaka

You'd still need tubeless ready rims, taped and running with sealant. Adding a tube inside instead of just switching to TLR tire sounds like a lot of work (and mess) for dubious benefits. Not even considering a need for the sensor (which exist, eg. Quarq TyreWiz).

rekmeyata

Nah, I use to live in the Mojave Desert of S Calif back when the only good tire against goatheads was the Specialized Armadillo Pro, and I never got a flat using those tires. In today's world they have even better tires than that one. I never had to use a liner, or slime, or a thorn tube with those Armadillos.

I got those tires from a bike shop in Bakersfield California back around 1996 for the first set and 98 for the second where I use to lived which the team captain owned the bike shop who won, and they still hold the 4 person RAAM race record since 2004, used those same Armadillo tires to win the race on, and to train on, and they didn't have a single flat in the entire race or while training.

So you would be fine without tubeless tires in Nevada, or Arizona, or anywhere else.

Duragrouch

Yes, that's what I meant by "seal them tubeless style".

I had to look up Quarq TyreWiz. I'll be damned. But not surprising these days, due to both the micro tech available, and the prices people are willing to spend on bikes and parts. Most road motorcycles these days have ABS, I wonder if they sense for low tire pressure and by which method?

VegasJen

This is why I feel pretty confident that the only flat I've had with my tubeless setup was because of a through-and-through puncture. Two holes but I don't recall any impact that could have caused it. Since I replaced that tire, I've probably put 200-300 miles on the bike again with zero problems. And that's pretty much unheard of for me.

MilhouseJ

I've had pretty good luck with Muc-Off tube sealant for my tubed bikes, LOTS of glass in the bike gutters in Portland.. Tubeless has treated me well otherwise.

Jayup

I think im going back to tubes with all my rims. so much money dumped in having to put new celent in every season and flat repairs are a lot faster. I know tubeless is better but im happy with going back to tubes for a bit

Duragrouch

Trivia, from wiki: