justinzane

Thanks! And, though I have no data to support the idea, I have an intuitive idea that higher pressures/skinny tires may actually limit thorn penetration. Consider that the width of the contact patch increases as pressure decreases for a given tire at different pressures:
(Formula from Boeing: https://www.boeing.com/assets/pdf/com...ontactarea.pdf) This means that lower pressures expose the tire to more road surface and therefore more potential thorns.

Also, it is easier to indent a low pressure tire. Since thorns are "focused" normal to the tread and tube by indentation, this should mean that low pressures again increase the likelyhood that thorns will penetrate a tube.

Now, given that wider low pressure tires are usually thicker than narrow tires, changing to a wide commuter tire may benefit overall. But, with a given tire that can run between say 90 and 135 PSI I'm guessing that the higher pressures will no only prevent pinches but also thorns to some degree.

Be curious to know if this thought stands up to scrutiny and testing.

chaadster

Yeah, a wider tire at lower pressure has a bigger footprint than a skinny, hi-PSI one, but the real question is whether the odds of hitting a thorn are statistically impacted by the variance. It seems unlikely to be meaningful, to me, but even if it is, it also seems like there are more significantly effective measures you could deploy.

intransit1217

Cool. By simple physics, a skinnier tire has less chance of finding and therefore being penetrated by sharp objects. Makes sense. I still say: schraders, tuffys, slime. Because sitting on a bunch of thorns while changing out a tube or patching it....comes with alot of expletives!

JohnJ80

One step further - go tubules tubular. I switched to tubular tires 5 years ago and I have gotten two flats since I switched. I used to get 6-8 a year.

I run Tufo Tubulars in a 25mm tire with sealant. I change them just before the cords show through.

I do ride clinchers on my cross/adventure bike using a 28c tire (Vredelstein Senso Extreme). They are fantastic tires, very light and seem to hold up well.

J.

JohnJ80

Why schraders? They're just harder to pump up due to the spring valve.

J.

TrekNerd

When I was 210lbs I used 25mm tires and ran the rear at 110psi and the front slightly lower at 95-100. When I was over 210lbs I found the 25mm tires were better for comfort than the 23mm.

meanwhile

And they go to 28s on less manicured road surfaces - a lot of teams have cross bikes or custom frames for this purpose. And again, we're talking about 150lb guys who are racing and optimizing tyre width for reductions in aero.

intransit1217

A) The whole world runs schraders except road bikes. It's easier to just un-cap and put the airline to it versus having to constantly carry a stupid adaptor.
B) Bike pumps are for minimal pressure to get you to a station/ bike shop.
C) I'm totally presta-ist and proud of it !

But you probably already knew this

JohnJ80

I've never had the need to just pump up to minimum pressure and then find an air hose especially since the advent of CO2 inflators. I haven't carried a pump for at least a decade.

j.

intransit1217

How to use CO2 for cycling ? a beginners guide | DC Rainmaker

Fine. But you still can't make me like prestas.

chaadster

I don't use shraeder, I don't use CO2, I don't carry/keep/use a presta/schraeder and have never wanted for one that I can recall; my floor pump works fine, my on-bike pumps work fine, and I can't imagine a scenario where my presta tube would need inflating and I'm without a suitable pump...unless it's some weird scenario like I'm riding cross country, get mugged by a gang of thugs with a pickup who steal all my stuff, but decide to leave me naked, with my bike and two flat tires, at a remote, desert gas station, where it just so happens they have clothes and the stuff I need to continue my ride, in which case, yeah, I'd wish I had schraeder.

ThermionicScott 

Being incompetent with presta valves isn't a great way to sell schraders to the rest of us. It's totally irrelevant to this discussion.

justinzane

How long are your rides typically? I find that the "road feel"/vibration transmission from very firm tires is not uncomfortable in my typical 1-2 hour rides, either. I'm wondering though, if an significantly longer ride might change my understanding of the issue?

txags92

I typically ride 2-3 hours when I am out on the road, but depending on time of year and what I am training for, 4-5 hours isn't terribly uncommon. I know I am going to be sore after a 4-5 hour ride no matter what I do, but I just really don't seem to have an intolerance for how the ride feels that would make me feel the need to go with lower tire pressure.

justinzane

I don't know, but my thinking is this... Goatheads are natural caltrops which have one active spike supported by three others. So, consider that a caltrop or goathead is an effective point on the road plane, not an area. And consider that the thorn/caltrop is damaging at footprint_width * 1.10 (5% added low sidewall hits). Since the modified footprint describes a long skinny rectangle on the plane of the road and that the thorns points have a random distribution on the road plane, the likely hood of thorn point intersection with tire rectangle is a simple linear function of footprint width for a given ride distance.

And, I am assuming that this only is really accurate for a given tire-rim combo, for example an ISO25x622 Foo-3 Wire tire on a 19.5x622 Bar SuperV, at pressures between its usable minimum and maximum. Because the sidewall shape changes with rim width and tire width this is not likely to be super significant in comparing 23mm tires on 19.5mm rims with 32mm tires on a 23mm rim.

I'm pretty sure that this would be easy enough to test with a few buckets of goatheads, a boatload of tubes, a few 23, 25, and 32mm tires and a treadmill or belttop dyno. Of course, the only thing I've got is a huge natural supply the the terrible tribulus terrestris. Anyone who wants to donate the other bits in the name of science, feel free. )

justinzane

I just switched to Prestas after having two different Schrader valves blow out on me. 105PSI and as soon as I remove the pump head: pop, hiss the air floods back out the valve. Both on a "Specialized" branded tube costing $9.99!!!! at the LBS and a generic tube tube costing about $4.00 from Amazon. I agree that at least in the US, Schraders make life easier, though.

justinzane

Thanks.

justinzane

Interesting. Seems that some of the conventional wisdom of road cycling has started to bend to empirical data generated by well funded pro or national teams.

As far as aero goes, probably the single biggest improvement I could make in reducing drag is by losing the "love handles". Excess waist fat: unattractive and a serious vortex generator.

justinzane

To all the gentlepeople who have suggested tubeless... It seems that it is currently a less available and more expensive option. If I ever move closer to civilization and decent LBSs, I might go there. Right now, I have to either wait for Amazon or scrounge for something decent at WalMart. (My LBS has been dark and locked during posted business hours the last two times I stopped by!) So I am trying to stick with high availability in parts if I can while I live in the middle of nowhere.

I also wonder about the value proposition of tubeless clinchers. While repairing a thorn-flat now involves simply replacing the tube and cleaning the tire; roadside repair of tubeless seems less manageable, especially if one runs sealant. That, I presume is the subject of another thread, though.

JohnJ80

Fixing a tubeless clincher on the road is relatively easy, you just put in a tube and pump it up. When you get back, you go to tubeless again.

Tubulars will fix the problem especially if you use tubeless tubulars and sealant. You will need new wheels, but rim for rim, they'll be considerably lighter and the ride will be better.

J.

chaadster

I don't see how you're assessing the fact that tubeless reduces flat in your value calculation.

intransit1217

oh no. they're on to me.

JohnJ80

Avoidance of pinch flats.

J.

Joe Minton

justinzane:


LOL, LOL ---- ;o)


Joe

justinzane

I'm not. I'm being, possibly excessively, conservative in the rubber-meets road department for the above mentioned reasons. I'm not at all discounting any of the likely thoroughly valid reasons you and others have put forward. Just explaining my personal choice (not recommendation) at the moment. Perhaps when I upgrade my rear wheel, derailer and shifter I will do a rethink.