popeye

https://road.cc/content/forum/tubele...houghts-282787

So that's the reason.

Sy Reene

Who is the author and what's his/her weight? Article says he had the 25mm tires at 75psi

Roval recommended inflation chart

colnago62

He mentioned his weight in the article.

sfrider 

You mean they went back to tubes. What would have happened if a tubed tire exploded? I suspect not much difference in outcome - the tire will roll off the rim just the same.

In other words: look where you put your wheels and avoid crap.

Sy Reene

Ahh.. buried in the comments. So he is 160lbs. And Silca pressure calculator, in addition to the Roval chart, indicates seem to both put recommended PSI in the mid to upper 80s. Could be a contributing factor, especially on 4500 mile (or km?) tires?

Edit: and the author seems to have a history of tire problems (his 3 previous tires all had "total tyre failures due to punctures within about 1000km"

ericcox

This is interesting. I cut a sidewall yesterday on a long ride including some terrible pavement. The cut was big enough that it wouldn't seal - but the tire stayed seated and the rim was protected. Slowed down easily, popped in a tube, went another 60 miles.

popeye

That chart recomends about 20 more lbs than I run with tubes. I thought the advantage of tubeless was running lower pressure?

smashndash

Yeah if TL isn't safe unless you run really high pressures (which might be true), what the heck are we doing out here? We may as well use latex tubes and sealant, which is just as fast (if not faster) and seals pretty well.

I've run very, very low pressure in tubes. 40 psi in 25mm tires at 135lbs. No issues ever.

That being said, those pressure recommendations seem inline with what I find to be the optimal balance between speed and comfort, if you use measured tire size, not marked. Those pressures are absurd if you go by marked width. Zipp doesn't even let you go past 72psi.

WhyFi

That's for wide hookless and it's not just Zipp - it's the as-of-yet-unannounced ETRTO standard. Regardless, it's plenty for most riders - I'm 185ish and run +/- 60psi.

Zaskar

25mm or 28mm?

I have clearly been running too much pressure. I'm 175ish and run 90psi and 85psi - R/F - with 25s

Sy Reene

That actually sounds about right (to me at least) for an ~200lb overall load.

WhyFi

28mm, but this is on 23mm int width rims.

DaveSSS 

The zipp pressure calculator includes bike and rider weight, plus internal rim width. I've been using their recommendations with my fulcrum racing 3 wheels. Must yesterday I hit a big piece of flagstone rock about an inch thick and 3-4 inches in diameter at over 30 mph on a winding descent. I was paying too much attention to the cars ahead and caught it on the left side of the tire. It hit hard enough to bend the bead area in one spot, but no air was lost and the tire was had only a minor scuff. When I got home, I removed the tire and straightened the ding with a pair of wide jaw electrician's pliers, with a popsicle stick on both sides to protect the rim. All is good now. A carbon rim might have a chunk broken out of it, with a hit that extreme.

asgelle

Or would have been totally unaffected. And another aluminum rim might have crumpled and failed completely just like a different one might not even have had a dent.

Sy Reene

So would damage have occurred with more pressure than Zipp recommended? Do we know that Zipp isn't just recommending what their rims can handle, vs. what's actually a good pressure?

And how did this become an alloy vs CF discussion?

DaveSSS 

My problem had nothing to do with what the rims can handle. It's what's recommended for a reasonably low rolling resistance and most likely adequate rim protection under normal circumstances, for my 138 lb weight with a 19mm internal width rim. I've never damaged a rim in 35 years of riding, so this is a first for me. I've also never hit a big pothole or pavement mismatch large enough to damage a rim. Descending Colorado mountains is always risky with all of the rocks that flake off the walls of a canyon.

I should be able to speculate on what might have happened with a carbon rim. My wheel hit so hard that I heard the rock to metal contact. If I'd been using 80-90 psi, the rim might not have been damaged. At least it was easily repaired.

Sy Reene

Recommended by who? What was your actual 'recommended' pressure for what size (as measured) tire width?

spdntrxi

CL/CLX series dont hold a tire bead all that well. Having CLX32,50 and 64's I decided to off them last year. As for why spesh has gone back to clinchers well the new rapides are not tubeless approved .. so what do you expect ?

WhyFi

Hit a big chunk of rock through your own error and then question the validity of a pressure calculator and cast aspersions upon carbon rims that you weren't riding. Makes sense.

Seattle Forrest

I hit a pothole so hard I was sure I must have damaged the wheel and it was still true. An alloy rim would have never been perfectly straight again.

Seattle Forrest

Moral of the story: don't choose a bad line.

bruce19

I was running 120 psi (rear) with clinchers and now run 80 psi with tubeless. The chart suggest I could go to approx. 75 psi.

tomato coupe

I hit a curb at 20 mph one day and dented my alloy rim. If it had been a carbon rim, it would have exploded and probably killed everyone within a 100 ft. radius.

Atlas Shrugged

You forgot to mention the Hazardous Waste cleanup. This would have closed the road and taken a week to decontaminate the area.

DaveSSS 

As already mentioned, zipp.com.