icemilkcoffee 

The OP didn't blow anything. The OP was following SOP in using overpressure to seat the bead on a tubeless tire. Everyone does this. If these Hunt rims assplode before you can even get the bead to seat, then this is entirely a problem with Hunt.

My guess is that Hunt has to make the shelf area tighter than normal, because there is no bead to keep the tire from lifting off. That bead has to be tight against the rim shelf to prevent air pressure from prying underneath the tire bead. This tight construction, in turn means you need much higher pressure to seat the bead. But the weak hookless sidewall cannot stand the higher pressure. So now you have a death spiral.

BlazingPedals

Yep, hoop stresses. I spread a double-walled aluminum rim that way once.

Alan K

No CF rims thus far, and no hospital - not that carelessness couldn’t land me in a hospital with Al rims. I guess I became cautious through learning other people’s mishaps.

Some people have a tendency to go to extremes in their hope to substantiate their argument but end up comparing proverbial oranges and apples. Use of CF in jets produced for our war department was thrown in by someone as the proof of material’s reliability - I’m not sure that the level of testing and quality control applied by bicycle companies will approach that of leading aerospace and war industry, such as Lockheed Martin etc. Of course, this is just a guess, may be bicycle industry perfected the technology and Lockheed Martin copied it. 😉

I have good quality frames made from steel, titanium, aluminum, and yes CF. They all work satisfactorily and admirably well for the purpose they were made and built up.

rsbob 

A quick defense of Hunt carbon rims since they all don’t explode. Have had a pair of 60 mms for two years and have put on three sets of tires - using a compressor to seat the them. Don’t know the pressure used, but enough to get them in place, and never an issue.

Sy Reene

Got any pics of their factory floor or location?

wolfchild

Improper spoke tension is the main cause of metal fatigue on alloy rims...A properly built wheel especially if it's a disc wheel where brake track wear isn't an issue will last forever, unless it is crashed badly or seriously abused.

terrymorse 

Everything we know about material science says that is untrue. Use an aluminum rim long enough, it will eventually fail from fatigue.

rosefarts

Stan’s rims are frequently rated at lower PSI than their counterparts. I like their wheels and have several of them. They are noticeably thinner (and lighter) than typical aluminum rims. You absolutely can blow the sidewall out.

So there is that.

79pmooney

Brake wear or inconsistent spoke tension? Which is this?

sweeks

Brake tracks were at least 1.0mm thick, and spoke tensions were all within 20% of the mean tension (at the time of building). I initially thought this was brake track wear that spread inward, but the rims weren't very worn and Bill Mould knows more about rims than I do, so I'm willing to accept that interpretation. In any case, the problem is licked.

79pmooney

This was directed at wolfchild who stated explicitly that only brake track wear and uneven spoke tensions can cause aluminum rim failure, not you. You posted evidence against. Thank you.

Alan K

Well, folks - it’s really not rocket-surgery (=rocket science + neurosurgery). All materials yield to pressure/force. The thinner the material, greater likelihood of failure, all else being equal.
The only reason my Al wheels seem indestructible is because I start with a slightly heavier rim of high quality, build it myself quite well using a sturdy set of hubs, 32H laced 2-cross with double butted SS spokes - and most importantly, even (very close to equal) tension on all spokes. One can easily true a wheel without equal tension on spokes but they will not stay true for very long.

I’m sure that if I have someone weighing twice as much as I do, the bike and the wheels will survive… for a while, but wouldn’t prove indestructible in the long-run.

Im sure very similar principles apply to CF rims/wheels.

Given enough time, everything gets weaker and eventually fails. Things that built well will last a life-time of a person but it doesn’t mean they will never fail.

Shimagnolo

Some years back I learned the hard way that a larger cross-section on a tire increases stress on the rim,
when I cracked the sidewall of an aluminum rim...twice.
I broke the first rim, moved the hub & spokes to a new rim, then that one broke a couple months later.
Failure was where the bead of the rim met the inner rim wall, pressure was at max rating of a 1.9" tire.

So I did some digging. (PDF)
Understanding the Influence of Pressure and Radial Loads on Stress and Displacement Response of a Rotating Body: The Automobile Wheel

See page 3, Section "2.2. Influence of tire air pressure".

sweeks

My pleasure. I just thought the extra information would help.

rosefarts

So I find this thread enlightening.

Ive been on bikes in a semi serious to way too serious capacity since the early 90’s.

In that time, this simply has never come up for me. To be fair, my super serious years were spent on 20 and 23c tires, often glued on. So a totally different story.

Still, I’ve got a load of gravel and mountain bikes now. All tubeless. I would have never thought that the lower of either the rim max pressure or tire max pressure could destroy a rim, based on tire size. Seems like a more detailed rim sticker would be an easy fix.

I think I’m probably like most of us, it’s never happened to me before only because my tires feel pretty firm around 40-45psi. Not because I knew any better.

indyfabz

He trolls by intentionally posting inaccurate information.

Either that, or he’s clueless.

tomato coupe

It doesn't have to be an either / or situation.

bampilot06

Damn, I mounted my hunt wheels the other day. I have never set up tubeless before and watched a bunch of youtube videos on it. The one thing I never saw was how to install the valve stem correctly. The videos just showed inserting and hand tight the little nut. So that’s what I did. 6 co2 cartridges later I couldn’t get the bead to set fully. Gave up and took it to the shop to install.

Something that took me hours, took my buddy 5 mins.

bampilot06

Should clarify, I did not push the valve stem in place while tightening the nut. I got 70 percent the tire to set but couldn’t get the rest of it.

icemilkcoffee 

was the air leaking out? Or did the air stay inside the tire, but the bead refused to pop?
the valve stem should definitely be pushed down firmly while you tighten the ring nut.

bampilot06

Air leaked out of the drain hole and the valve stem.

indyfabz

True.

Russ Roth

I find this conversation to be very informative as I'd always assumed that 100psi is a 100psi and if that's what a rim is rated for than why would the tire matter. Still not fully getting it as the amount of material in contact with the rim would seem to be the same regardless of the tire size, either way its the same amount of tire contact at the bead as well as the same amount of pressure contained within the system, So is it ultimately a leverage situation? The way the tire expands pushes out on the rim differently effecting how the stress of holding the tire is placed on the rim? Cause I read the amount of area being an issue but I don't see how a larger tire has any more area in contact with the rim. The larger tire has a larger cross section obviously but it would seem to me that there can't be any additional amount air in contact with the rim as the bigger tire does nothing to change the amount of surface area of the rim the tire/tube/air can act upon. How can any size tire with a 100psi apply more pressure than 100psi onto the rim other than by increasing the load on the tire?

I've seen aluminum rims in cross races shattered, a lady walked off the course with her rim cracked into 4 separate pieces and rims split width wise from trick riding, so there's plenty of ways an alloy rim could fail.

SoSmellyAir

Ideal gas law: P V = n R T [Pressure x Volume = number of moles of gas x R (ideal gas constant) x Pressure]

What is the ideal gas law? (article) | Khan Academy

A wider tire has greater Volume (than a narrower tire). Thus, at the same Pressure and Temperature, the wider tire also contains a greater number of moles (i.e., amount) of air than a narrower tire.

All of the air within the tire exerts a force against the sidewalls of the wheel via the tire, not just the air at the boundary of the tire and wheel. If you don't believe me, you can do this experiment: Mount a 700x25c tire and a 700x32c tire to the same wheel and inflate each to the same pressure, and see which tire feels firmer?

This is confirmed by the Hoop Stress formula: Pressure Vessel, Thin Wall Hoop and Longitudinal Stresses Equation and Calculator (engineersedge.com)

... which shows that at the same Pressure, Hoop Stress increases with the cross-sectional diameter of the tire, which is proportional to Volume.

Shimagnolo

See post 88;
All explained on page 3 of that document.
Look at Figure 4 and Equation 5.
"a" is the overall radius of the tread of the inflated tire.
"rf" is the radius of the rim at the inner surface of the bead.
Assuming the tire has a round cross-section when inflated: a - rf = <width of tire>
Now think about varying "a" by changing tire width;
As "a" becomes closer to "rf" (narrower tire), the lateral force on the rim decreases.
As "a" becomes further from "rf" (wider tire), the lateral force on the rim increases.