[dcgriz]

There's been a significant amount of discussions lately on several forums about tires blowing off rims.

When it happens during or immediately after a tubed tire change, potential reasons are usually linked to a pinched or faulty inner tube. No surprises here as it has been, is and will be happening for as long as tubes are used.

What is surprising and problematic however are the blow-offs reported to mysteriously happen after the tire/tube have seen lengthy use, the bike is parked and found with the tire blown off. Operator error still is a possibility, specially when latex tubes are used, but considering that some of the people reporting are either seasoned cyclists or in the bicycle business, it makes me wonder what really is going on.

When these type of blow-offs happen the typical reaction is to blame the tire. Blame poor QC, poor bead construction or whatever else and move on to another tire. When tire manufacturers are confronted, the finger tends to point to the direction of the rim manufacturer not manufacturing rims in accordance to standards.

Going over several threads reporting the "inexplicable" blow-offs I notice a pattern developing. A lot of them, if not most, are with the super wide tubeless/tubeless ready rims (inner rim width of 19mm+) when fitted with tires of width that is outside the ETRTO standards.

Meeting ETRTO has caused a lot of controversy in the past as these standards have been regarded as unnecessarily too conservative even from authorities in the bicycle world as renowned as the late Mr. Brown. This is true and countless trouble free miles have been put on 17mm rims with 23mm tires.

What is happening now with the newer developments in rim design, however, I think has really stretched the envelope and pushed us into a new territory. It seems to me that the super wide tubeless/tubeless ready inner rims have exhausted the compliance safety margins between tire and rim and when narrower tires (specially ones with supple walls like the Challenge or Veloflex) are used the potential for the tire blowing off the rim is exaggerated. Maybe its time to start looking at the ETRTO stds more seriously than before when using these setups.

Incidentally, I never had any issue with non-tubeless ready rims up to 17mm inner width and any size tire I used; even below the ETRTO standrds. Anything from 23mm Contis on HED C2 to 32mm Strada Bianca on 23mm Archetype. However I do not feel as comfortable with the newer stuff.

What say you?

 

[ziscwg]

I've never had a tire blow off using 15mm and 19mm (tubeless) rims (internal width)

I only use 25 or 27 mm tires. The 23 mm tires are just too harsh for me. I'm a knuckle draggin' mtb biker who is used to 140mm of squish.

Running 23 mm tires on 24-25 mm rims (external width) is supposed to be the most aero. However, it's not all that aero if you flat.

I can see going too wide for a certain tire could be an issue if the bead does not seat correctly.

I actually feel more comfortable with the new stuff. Maybe because I run 25 mm tires all the time. Or, I like to hear that bead snap when I inflate the tires on the tubeless compatible.

 

[dcgriz]

The other thing that is happening to further confuse us all is tire sizing inconsistencies. A 25mm tire may actually measure 28mm on the rim while a 27mm may measure 25mm.

The mishaps I hear, seem to concentrate more on the "plus" rims. Rims like the Ardennes + at an inner width of 20.6mm outfitted with tires way below the ETRTO listed widths.

 

[jfaas]

This is a little concerning as I have outfitted my wife's bike with SL23 V1 rims and Conti GP4000s II 23 mm tires. Have you heard any blow off with this combination? I'm relatively new to the wide rims and have not experienced any blow off events.

 

[tednugent]

I had a blowoff of conti gp 4-season on Stan's alpha 400 after install

Reinstall. No issues

 

[Marc]

The other thing that is happening to further confuse us all is tire sizing inconsistencies. A 25mm tire may actually measure 28mm on the rim while a 27mm may measure 25mm.

The mishaps I hear, seem to concentrate more on the "plus" rims. Rims like the Ardennes + at an inner width of 20.6mm outfitted with tires way below the ETRTO listed widths.

23s-28s (sidewall rating) on Belgium+ rims. No blowouts here, either tubed or tubeless.

 

[November Dave]

Funny, I was just thinking about this very issue last night. The ERTRO chart is basically useless. What "is" a 23mm or 25mm tire? One that measures that width on some standard rim? Is there some "flatten the tire out and x distance between the beads makes it a y-sized tire" thing?

Is there any evident reported correlation between tire pressure and this happening?

 

[Marc]

Funny, I was just thinking about this very issue last night. The ERTRO chart is basically useless. What "is" a 23mm or 25mm tire? One that measures that width on some standard rim? Is there some "flatten the tire out and x distance between the beads makes it a y-sized tire" thing?

Is there any evident reported correlation between tire pressure and this happening?

I'd figure if there was there'd be a CPSC or some such advisory out on it, given the risks to life/limb from a blowout at speed.

 

[dcgriz]

Funny, I was just thinking about this very issue last night. The ERTRO chart is basically useless. What "is" a 23mm or 25mm tire? One that measures that width on some standard rim? Is there some "flatten the tire out and x distance between the beads makes it a y-sized tire" thing?

Is there any evident reported correlation between tire pressure and this happening?

I dont think we should be in a hurry to dismiss the value of ETRTO, if for nothing else just for the need of having some traces of a common base to limit experimentation from the public. The inconsistencies in declared tire sizing vs. actual size dont help either.

In a recent interview of Mavic's Brunand with BikeRadar he said:

"We have not gone crazy wide for a reason, because there are compatibility and safety issues," Brunand said. A 19mm rim, for instance, should not be used with a tyre any narrower than 28mm, and a 17mm rim should not be used with anything smaller than 25mm, according to ETRTO (European Tyre and Rim Technical Organisation), which sets the international ISO standards. As its name implies, ETRTO is comprised of European tyre and rim manufacturers. As the wide-rim trend began, Michelin hosted other ETRTO companies at its facility, Brunand said, "to demonstrate that when you get outside these specifications there is a danger of the tyre blowing off the rim".

 

[dgaddis1]

I had a blowoff of conti gp 4-season on Stan's alpha 400 after install

Reinstall. No issues

Re-using a tire after it blows off is risky, the tire bead is often damaged during the blow off. Stan's Alpha rims have had some reports of blowoffs, I think it's the short sidewall to blame, not rim or tire width.

The one tire I've had blow off was a Challenge Strada Bianca (30mm) on a Pacenti SL23 v1 rim (18mm inner width), which is all good as far as the ETRTO chart is concerned. Wide rim, wide tire, all is bueno. I was using a Challenge latex tube, which apparently have a reputation for sucking.

The tire was STUPID hard to mount. The 2nd tire I mounted I actually pre-stretched by hand, and the bead is stretchy enough that it went on pretty easily. 1,000 times easier than the first tire. I did a ride or two on the tires without problems. Then one I rode to work one day (my morning commute has a 40mph downhill in traffic!!) and when it was time to go home I went out to the bike rack and found this:



Rode home gingerly, and pulled the tires off. A friend is turning one of them into a belt for me.

 

[dcgriz]

Your tire/rim combo meets Challenge's recommendations. Challenge tubes have been problematic though. What happened to you may be more on the tube side rather than the rim/tire side. What pressures were you using?

From the Challenge website: http://www.challengetech.it/public/...min/Mounting_Instructions_for_Challenge_Clincher_and_Foldable_Tires_low_res.pdf

Matching tire sizes and rims

When choosing tires you are restricted to certain tire sizes by
the size of your rims. You will find the tire size marked on the
tire's sidewall. There are two designations for the tire size, with
the more precise one being the standardized millimeter sizing
system. The combination 50 – 559 corresponds, for example,
to a tire width of 50 mm in its inflated state and an (inside) diameter
of 559 mm. The other one is an inch-based designation
for the same tire which, in our example, would be 26 x 1.90.
For new tire fitments, observe rim width matches to DIN 7800:
N

The DIN 7800 table looks similar to the ETRTO table.

 

[dgaddis1]

I don't remember the pressure, but it was low. The whole idea of using those tires was the make the bike more gravel capable than the tubeless 28's. The Challenge tires measured around 32mm on those rims, and juuuuust fit the bike. I want to say the pressure was somewhere around 50-60psi.

It was WAY less than the 90-130psi recommendation printed right there on the tire sidewall! Which really makes you think "WTF?!" doesn't it?

 

[dcgriz]

I am not sure what this 90-130 psi stamp really means. The Challenge instructions say "Never exceed the recommended pressure range during use.". The max pressure limitation is obvious, the low end is not.

I have been using the Strada Bianca on Archetype for my Rando rig for thousands of miles . I run mine at 85/70. So I have a horse in the race, lets say. No problems so far but I do have to say that the more the miles on the tire the much easier becomes to take the tire off the rim as the beads seem to stretch a lot.

 

[dgaddis1]

They were fun and rode well. But, I lost faith. Maybe it was the tubes. I can't wait to see the belt my buddy is making me though!

 

[dcgriz]

I love these tires and with the Vittoria tubes I find them to be the closest thing to a tubular.

I'm in the process putting a new rig together and was thinking of using 21mm rims and change tire sizes to suit the task at hand- but then got cold feet with all of these things happening. Non-tubeless rims are getting scarce to find and I'm sure the trend will continue and worsen as the road tubeless technology further develops.

Trying to derive to a common denominator from people's bad experiences I find that to be:
super wide rims tubeless ready (eg 21mm), supple wall tires way off the ETRTO chart and low pressures.

The accuracy of this determination is debatable because of the difficulty to decipher true cause from people's experiences as described but enough to cause me concern.

For the time being I decided to stay with what I have found to work for me so far

 

[November Dave]

The value of the concept of a range of tire widths being appropriate for a range of rim widths is absolute. The current execution of that chart, where there is no definition of what any particular tire size actually is (I feel like Bill Clinton - it depends on what your definition of "is" is...), makes application of ERTRO standards nearly impossible.

Let's say tire "a" measures 23mm on a 14mm inside Mavic. That's not within ERTRO guidelines. If you put it on a 17mm Kinlin and it measures 25mm, it's all of a sudden within ERTRO guidelines? Makes no sense at all.

 

[dcgriz]

I have not. I have used and still use the Conti on Belgium C2, Archetype, Deep V, factory Mavic, factory Fulcrum, Enve, DT Swiss 585, CXP33, CXP22 and a few others without any issues.

I dont think your combo presents concern.

 

[Marc]

I dont think we should be in a hurry to dismiss the value of ETRTO, if for nothing else just for the need of having some traces of a common base to limit experimentation from the public. The inconsistencies in declared tire sizing vs. actual size dont help either.

In a recent interview of Mavic's Brunand with BikeRadar he said:

"We have not gone crazy wide for a reason, because there are compatibility and safety issues," Brunand said. A 19mm rim, for instance, should not be used with a tyre any narrower than 28mm, and a 17mm rim should not be used with anything smaller than 25mm, according to ETRTO (European Tyre and Rim Technical Organisation), which sets the international ISO standards. As its name implies, ETRTO is comprised of European tyre and rim manufacturers. As the wide-rim trend began, Michelin hosted other ETRTO companies at its facility, Brunand said, "to demonstrate that when you get outside these specifications there is a danger of the tyre blowing off the rim".

Personally...it sounds to me like Mavic is just making BS excuses to keep making 1980s narrow width rims in spite of what everyone other than them are doing. Mavic, the latest in 1980s rim design.

He really does nothing to back his stances. Especially given that most of the newer 23-25mm width rims are designed with tubeless in mind and therefore have stronger/better clincher beads than Mavic.

 

[tvad]

In 30 years, I have never had a tire blow off a clincher road rim; over a dozen different rims and tires ranging from 19mm to 25mm.

 

[Mike T.]

In 30 years, I have never had a tire blow off a clincher road rim; over a dozen different rims and tires ranging from 19mm to 25mm.

Me neither in 30 yrs too (it was tubulars before that) even with old tires on Open Pro rims where fingers alone (no thumb or heel of hand struggle) can roll the whole tire and tube assembly off the rim in one motion.