brokenknee1980

A shop installed tubeless Panaracer Gravelking 700 x 38c tires on my Ultegra 622 x15c rims. I didn't know anything about tire or wheel sizes, other than I wanted something better-suited for gravel than the skinny tires I was running before, so I left it up entirely to the bike shop to install a tire compatible with my rims. On my first ride with the new tires, I had a blowout that caused me to crash and seriously injure my knee. There was no sign of puncture on the tire and nothing in the road which would have caused a puncture. Based on some charts I found online, it seems like the tire was too wide for the rim. Does anyone on here have an opinion on whether the tire was too wide for the rim? If so, could that have contributed to the blowout? I checked the tire pressure before the ride and it was nominal, and the blowout happened in the last mile of a 17-mile that covered an equal mix of pavement and gravel. Any feedback at all is appreciated. If the shop was in error, I'd like to let them know to prevent anyone else from getting hurt like I did.

I should add that I noticed the rear tire was low on air prior to the ride, and I pumped it up and monitored it over the course of the ride. I thought this was odd because I'd gotten the bike back from the shop only a couple days before and hadn't ridden it yet. Both tires were at about 50 PSI at the start of the ride.

Andrew R Stewart 

I think someone who knows this stuff needs to examine the tire, tube and rim. There are tell tale signs of a bead blow off that might be present.

Tire pressure is not an absolute. What's right for a "perfect" width rim could well be too much for a seriously under width rim. How long between the bike pick up at the shop and the incident?

I hope you are OK. Andy

ThermionicScott 

Wide tires have been installed on narrow rims successfully for years. I think the shop pinched the tube or something.

brokenknee1980

Thanks, Andy. This was my first ride on the bike after getting it back from the shop a couple of days prior. I added in my original post that I noticed the back tire was very low on air prior to the ride, but I pumped it up and monitored it over the course of the ride and it seemed OK. Strange that the tire was so low so soon after getting it back from the shop.

Andrew R Stewart 

The problem with trying to figure this type of incident out is often the lack of real data. Do you know the pressure the shop set the tires at? Do you know who much might have bled off before you topped off the pressure and went for the ride? Do you know what pressure you had increased them to?

Even the "proper" match of tire and rim widths can suffer blow offs from a few reasons. Already mentioned is trapping the tube under the tire bead and it's acting like a little jack to push the bead further up the rim's inside. There are rims that are slightly under sized and tires that can be on the larger end of bead diameter range. A rim production batch can be different enough from the last batch to not be prone to loose tire fits.

So making any blanket statements can be hard when you're trying to be always right. Having said that this problem, tire blowing off, has been an issue since I entered the trade (1973) and still is today. That might suggest something. Andy

DrIsotope

Gravelkings set up tubeless have to be run pretty low-- I had a 700x35 blow out on me @ 55psi, 5psi below it's tubeless rated max of 60psi. I think the GK SK is really only happy up to around 50psi-- and this is tough for me, as my bike + rider weight is looking for something more like 60-65psi for mixed use.

So I'm definitely curious as to what pressures were run.

ThermionicScott 

I saw 622x15c in the OP and it didn't even occur to me that it might have been set up tubeless! So used to tubeless rims also being wide.

If the tire was low, perhaps it never sealed up properly...

OneIsAllYouNeed

Let’s do a fact check...
blowout: tire rips suddenly and tube protrudes through hole in tire; the tire cannot be salvaged.
blowoff: tire separates from rim; tube protrudes through gap between tire and rim; the tire appears to be intact.
In both cases, there’s a loud “bang” right before the tube gets a long slit in it.
Was it a blowout or blowoff?
What pressures were you running? What’s the tire’s rated pressure?
You mentioned that the rear tire needed air before the ride. Which tire failed?

To your question... I put lots of miles on 40mm tires and i15 or i17 rims. It was fine. I prefer i23 to i31 rims for my ~40mm tires now because the handling is superior. I wouldn’t recommend 38mm tires on your narrow rims, but it doesn’t increase risk of tire failure.

Eggman84

Jan Heine over at Rene Herse Cycles has done a fair amount testing of tubeless setups and has published some clear intelligent pointers at https://janheine.wordpress.com/2017/...road-tubeless/. It seems that there are still problems with road tubeless and unfortunately you seem to have experienced what appears to be just another unwanted tubeless tire blowing off the rim (while riding the bike and not on a stand). Was it pressure, rim width, tire/rim incompatibility, or just an event that happens (until they don't happen anymore)? Hope you heal soon if not already.

DrIsotope

The OP didn't blow the tire off of the rim, the tire failed.

But please, for the love of all things, let that Jan Heine article rest. It's woefully outdated (I'm running Pirelli tubeless on one of my bikes right now,) and written from the perspective of a pure luddite, begrudgingly talking about that new-fangled tubeless. I have over 10k miles on tubeless 700x25, and +20k on 700x32 and larger. I have recorded one spontaneous failure (mentioned in my previous post) which Panaracer replaced without issue, and that replacement tire served me well it's whole life. I've also hit a pothole so hard the rim bent without unseating the tire-- with an Ultegra rim and a 700x25, btw.

Kapusta

Until the OP explains what exactly “blowout” means (did the tire bead blow off the rim or was the tire just flat?) and indicates if this was an actual tubeless setup (and if so, what rim does he have), any speculation as to what happened here is an utter waste of time.

Andrew R Stewart 

Exactly! But I do note that the OP said there was no casing puncture or cut found. To me this suggests the bead separated from the rim. We have no data on whether the tire was still fully mounted when the OP stopped, whether there was a tube or much else. Andy

TimothyH

For the sake of discussion, Shimano officially supports up to 32 mm wide on current generation Ultegra wheels (RS500-TL and RS700-TL).

The Ultegra "Acceleration Concept" wheels are 17 mm inside width and support up to 38 mm tires.

https://bike.shimano.com/en-US/produ...gra-r8000.html

I'm sure people do it but to me, 15 mm sounds awfully narrow for a 38 mm wide tire.

It would be interesting to know if this was a blowoff. There have been issues with rim and tire manufacturers splitting the difference between BST and UST tubless standards to try and fit as many rim/tire combinations as possible. The differences in the standards are small but enough that some, such as myself, have had wider tires blow off rims. Wider versions of the Shwalbe G-One in particular don't play well with Stans based rims including American Classic. This is just an example


-Tim-

TiHabanero

I have experience with this rim width/tire width combination. The rim is Velocity Deep V, 14mm internal width. Tire is Continental 37mm city tire. Not tubeless, running at 80psi. Been running them for 5 years without a flat or any other issue. Commuting and light weekend getaway excursions. It is possible the installation was faulty, or a brake pad rubbing the tire, or something else such as tire pressure too high.

brokenknee1980

Thanks for all the replies. Sorry if "blowout" was confusing, I wasn't sure what else to call it. I heard a "POP" when I landed off the curb, and suddenly my bike and I were tumbling down the hill. I was riding straight, not turning. The tire was completely dismounted from the rim when after the crash. The only damage I could find on the tire was a small tear on the bead, and I'm not sure if that was from the blowout (sorry) or from the resulting crash.

Kapusta

OK, you have clearly answered the first question I brought up.

What about the second: was it SET UP tubeless? You mentioned that you had a tubeless tire, but not if it was set up tubeless (I am guessing it was, but have not actually said so). And what rim do you have? Is it tubeless ready?

Uhhhhh.....

brokenknee1980

The shop did the tubeless setup; I had only ridden tires with tubes before. The rims are Shimano Ultegra, and it says on the rims they're tubeless-ready.

I get that accidents happen but it's weird that the tire failed on the first ride after I got it back from the shop...

Kapusta

Hmm, I guess I would wonder about setting 15mm rims up tubeless with 38mm tires. Not sure either way on that. Would not give it a second thought with tubes, though.

I am a bit curious about the "landing off the curb" part, though... is this a normal occurrence for you? If you are regularly doing stuff like riding off curbs, you might be riding the wrong rims to start with, and going with a large tire like that may have just exacerbated the problem. Tubeless run at low pressure can get burped off the rim with some hard sideways deflection. It is rare nowadays on mtb setups but it does happen, not sure about road setups. You say you went straight off the curb, but what did you land on?

Regarding the tire being a little low a few days after the tubeless setup.....Was this a sealant-based setup? If so, it is not unusual that it might not have been completely sealed after the initial setup and lost some air after a few days. But it should have sealed as soon as you started riding it.

TimothyH

That a 38 mm Gravelking on a 15 mm inside width rim would burp and deflate when dropping off a curb doesn't surprise me at all.

Blowouts aside, an Ultegra wheel isn't designed for curb dropping. A heavier wheel is needed.


-Tim-

delbiker1 

In my opinion, this is the likely cause. Tires and wheels need to be capable of handling the stress that the type of ride is going to produce. Sometimes these things happen with no obvious cause. In this case, to me, there are numerous factors that point to what Tim has stated.

Eggman84

I am so glad tubeless works well for you (and many others that are technically astute). But what I am reading from reputable sources (maybe you don't consider Leonard Zinn or Jan Heine reputable - whatever) but road tubeless is not fail proof. As to "The OP didn't blow the tire off the rim, the tire failed". What makes you say that? The OP said "....I had a blowout that caused me to crash and seriously injure my knee. There was no sign of puncture on the tire and nothing in the road which would have caused a puncture. Based on some charts I found online, it seems like the tire was too wide for the rim..."


"The tire failed" how? The OP say no signs of puncture, so I assumed that means there was no hole including a gapping hole. So if no hole, did the tire burp and loose all the air? That seems to be a safety hazard if that happens, and what I am reading burping is not an isolated event but whatever, who needs air in their tires on a downhill at speed.


Believe me, calling me a luddite doesn't bother me. Not everything new is better. Case in point, for years we were told narrower is better. And now, the reverse.

cyccommute 

A "heavier " wheel would do little to prevent the pressure spike that could be caused by a curb drop. The more likely culprit is a poorly executed curb drop or a bad tire or both. If you hit the ground with all the rider weight, the pressure will go up significantly. And it sounds like the curb drop was made with significant speed. I drop curbs all the time on road bikes, mountain bikes and even loaded touring bikes but I never have enough speed to crash.

ksryder

Jan Heine doesn't understand gravel.

Also, I will continue tilting at this windmill: 700c x 38mm

ThermionicScott 

I don't know how any of the Jan Heine bashing follows in this thread. He's skeptical of *road* tubeless involving ~25mm tires, but he's pretty content to run larger tires tubeless on gravel. Retro-grouches sometimes come around on new technology, they're just not early adopters.

WizardOfBoz

Are you referring to the fact that 700 x 38c should be written 700c x38mm? Specifically, the "C" refers to the French 700 C rim system, which is 622 mm BSD per ISO? And that the tire width is in mm? Don ksryder, consider the Wizard your Sancho Panza in this matter.


As a counterargument, I had an argument via email with the Philly Inquirer's excellent food writer, Craig Laban. He used the work decadent to describe a meal, meaning indulgently and overly rich. I consider the root of that word to relate to decay. So a decadent meal is a disgustingly decaying meal. He argued that words mean what the populace has come to understand them to mean. Bah. You might as well use "gender" when you mean "sex". Wait.. hmmm.

Anyway, numbers, units, and specifications mean something. So it IS 700c x 38mm.