irclean

On impulse I called my LBS on Saturday; I was hoping they had a match for the water bottle cage I had purchased a few days before. They were in the midst of moving to a bigger unit in the strip plaza where they are located and when I made my purchase most of their stock was still in boxes. They had indeed uncovered one of the cages and had set it aside for me. He was getting ready to close up shop but said he would hang around for another 15 minutes if I wanted to head over. I quickly donned my helmet and grabbed my bike, but before I left I decided to top up the tires. I pumped them to their recommended max pressure and departed in a rush. I got about two blocks away and a strange noise started to come from the front end. I was just starting to wonder if I should pull over to investigate when BOOM... the tube exploded!

I've had this happen to me twice before, but only while inflating and stationary, never while in motion. I was doing about 20 kph at the time and the front end started to wobble back and forth as I attempted to slow the bike. I managed to get my right foot out of the toe clip and was dragging it along the ground while at the same time counter-steering the bike to avoid a wipe-out. For some reason I didn't apply the brakes (in retrospect I think that I was afraid it would make things worse) but I managed to coast to a stop. When I stopped I noticed that people on both sides of the street had taken an interest in the unfolding events and one guy even told me that he thought someone was shooting a gun. I was just happy to have escaped the incident unscathed.

I limped/carried my bike home, having to hoist the front end most of the way. Unfortunately I had a full pannier on one side of the bike making the trip rather difficult, and to top it all off it started to rain. When I finally got home I quickly put the bike in the garage, momentarily considered hopping on my Norco and trying again, but instead jumped in the car and raced to the LBS, knowing that time was a factor since it was a holiday weekend and I really wanted that bottle cage (and now, of course, a new tube). He was still there waiting; I love my LBS!

I got back in the saddle right away, but I can't help but have visions of a repeat performance while flying down a hill... or riding in heavy traffic... or toting my son in his child seat (like I did today for a 15 km trip). Anyway... I wanted to share this story in the hopes that others here would tell of their experiences with tire blowouts and the ensuing results. I'm hoping this incident was a rarity. BTW I am using fairly new, decent (Michelin Pilot City) tires on this particular bike and the tube split right along one of its seams. The tube had one patch on it but the split was nowhere near the old puncture.

mister

I've heard of blowouts before, but thankfully have never experienced one. I worked as a tire tech for a few years in college and saw the effects heat and low pressure have on auto tires and imagine it can't be fun on a bike.

Here's an interesting article on bike tire blowouts.

B. Carfree

I had a Schwalbe Marathon that just wouldn't stay seated on one of my rim. It turns out that they recommend different pressures for different rims and mine calls for pressure well below the maximum stated on the tire. I changed to a different type of tire and haven't had any problems since.

irclean

Hmmm... I wonder if you're onto something there; this bike has cheap aluminum rims. Maybe an email to Michelin is in order to inquire about some recommended tire pressures.

whitecat

Hm, I had a similar experience, but thought it was a fluke. My rear tire - Michelin City - blew out going at 35 mph down the hill. Got a nice rip in the sidewall, cords in the sidewall looked as like if they were cut, but the tire was new and undamaged - I checked it prior to that days ride, and I did not hit anything with it while riding. Two tires isn't really enough to say for sure, but there might be a trend developing here?
Anyway, I got a replacement under warranty, so far so good. These tires really do it for myself in a lot of ways, so it would be sad if I had to move on to other types of tires just because these have a design flaw. I can't be certain, maybe it's just a manufacturing fluke, but, I would sure like to hear of other's experiences with these tires - City and Pilot City.

tsl

Maximum pressure is just that--do not exceed. It does not mean "regularly inflate to this pressure" or "this is how much you should use". It means do not exceed.

Optimum pressure is generally much lower and is dependent on tire size and load. See PSI Rx:I've been using the article's guidelines for a while now. I adjust to my preference from the guidelines, but they're a pretty good start.

I weigh 170 lbs and have 28mm 700C Continental Grand Prix 4-Seasons tires on my commuter. The package states the maximum pressure is 115 PSI, with a recommended pressure of 80 PSI. I run 70 PSI in the rear and 60 PSI in the front.

My other bikes, with the 25mm version of the same tire (package says 120 max, 95 rec) get 80 in the rear and 70 in the front.

Perhaps that guy who works for Schwalbe will chime in here too.

Wanderer

If this has happend before - you should, take more care to insure that you aren't pinching the tube during installation, inspect the tire for a bad bead, inspect the rim for a defect. MHO

irclean

Thanks for the link tsl; I bookmarked that page. BTW I weigh close to 300 lbs and I have always used max pressure because I read somewhere that it would help me to avoid pinch flats.

I should have qualified my earlier statement - my two previous blowouts were on two different bikes. The first was as a kid with my BMX. The second was with my Raleigh MTB shortly after I bought it from an online classified ad; I tried to pump the old, cracked tire up to the max psi with disastrous results. It now sports some nice, new 1.5" slicks and I've had no repeat performances of blowouts.

The bike that I had the latest blowout with is my Big Box Store Schwinn. It has some cheap aluminum rims (I assume they're single-walled) but I didn't detect any noticeable imperfections after the blowout. Ditto the tire; and it seems to be holding the new tube just fine so far... even at max pressure.

Good point about the installation - the patch that I mentioned in the original post was due to a self-inflicted puncture with a tire lever. These Pilot City tires are a b*tch to install; the sidewalls are very stiff... which added to my surprise when the tube blew out.

Oh... I should also mention that I recently bought a new floor pump and I was wondering if maybe the gauge was off and I was over-inflating the tires. I checked the readings against a digital gauge that I have and it is spot-on, so unless they're both off I seem to be getting accurate pressures.

irclean

Further to tsl's link, here's a nifty (although application-limited) calculator: https://www.dorkypantsr.us/bike-tire-...alculator.html

d2create

sounds like a pinch flat to me.

irclean

I don't believe an immediate loss of pressure like I experienced can happen without the tube escaping the confines of the tire. So... unless a pinch flat included tearing a hole in the sidewall through which the tube could escape, the tire would take some time (at least a few seconds) to go flat. My tube came out of the tire and blew it right off of the rim; the sidewalls are still intact and the tire is holding air within its new tube as I type this reply. Besides, I had no indication that I was experiencing a flat tire (and I've had my share) before this happened. There was just a strange, momentary noise and then BLAMMO!

d2create

I've had tubes "blow" on me before and it's usually user error.
Either the edge of the tire is pinching the tube when installed, or you need new rim tape or something.
And don't run at max pressure.

whitecat

Um, anybody seen or noticed my post at all? Why is it being ignored? I will repeat - I have had THE SAME experience on the same type of tire, mine resulting in a ripped sidewall all from itself while riding downhill.Only difference is that my tire got a hole innthe sidewall, your's did not, otherwise mode of the failure is the same. What width of the rim are you using?

whitecat

Why? I always run max pressure because on a 1.4" slick with my weight(260), it needs max pressure to ride properly, and not to have the tire sag to much. Anyway, never had a problem that way, aside from once, but that was a poor quality tire. And the real blow off pressure is most likely at least 50% higher then stated pressure. Recently I've been running pressures about 10% higher then max stated pressure because some tires need that to support my weight properly, no problems there. Everything has a safety margin built in, and if you push it slightly, it will probably be safe. But if you push it real hard, it might blow off, so use common sense. But the bottom line is that it is real hard to blow a tire off the rim only due to over inflation. When a tire blows, there is usually another cause at work - a tire defect, rim defect or improper mounting.

prathmann

It's being ignored by most in this thread because the mechanism for the failure was completely different. In your case the tire sidewall failed - that indicates either than something cut the tire (and that's a possibility even if you didn't notice it at the time) or the tire was defective and had weak cords in the sidewall that failed under the stress of the tube's pressure. But the OP's tire remained intact. In his case, the tire bead first started to separate from the rim (which is when he noticed an unusual sound prior to the blowout) and that allowed a portion of the tube to escape from under the tire bead and then suffer the blowout. The most common cause of this type of failure is improper installation with a bit of the tube being trapped between the rim and the tire bead. That pushes the bead up and off the rim and eventually lets part of the tube escape. But it could also be a rim and tire combination that's incompatible or a defect in either the rim or the tire.

irclean

My experience was not the same... my sidewall did not fail. My tire came off the rim, allowing the tube to escape and the resulting pressure differential caused it to fail. I don't know if the problem was with the tire or the rim itself; when I installed the tires I noticed the sidewalls were very stiff, but it seemed to seat in the rim just fine. I also don't know the rim width, but the OE tires were 38s while the Michelins are 35s. BTW the Pilot City is different than the City in that it has a "Protek" reinforced sidewall as well as 5 mm under the tread vs. the City's non-reinforced sidewall and 1 mm under the tread. It's designed to be more resistant to sidewall tears and pinch flats.

I have been riding with these tires at max pressure since their purchase and they have an estimated 2000 km on them. Since I top up the pressure on a weekly or bi-weekly basis one would assume this problem would have presented itself earlier if these tires were prone to failure. I'm quite confident that the problem lies with the rims and not the tires. In any case I have lowered the front tire to ~77 psi but am keeping the rear at max as per Jan Heine's tire drop formula (thanks again for the link, tsl).

whitecat

I must disagree with you. In my case, the tire blew off the rim while going downhill at 35 mph (about 55 kph). I rode on for quite a distance getting the bike under control, with no pressure in the tire. Since there was no apparent damage to the tire before, I came to the conclusion that the cut in the sidewall is due to the sidewall being cut by the rim. Mode of failure: Riding along when BOOM, tire goes off the rims suddenly. Then a series of correcting maneuvers, zig zagging all over the road while I got it under control, all while braking gently not to throw off the balance. I concur with you that something cut the sidewall - but judging from the situation, it was most likely the rim itself after sudden deflation of the tire, making the rim ride on sidewall. Gash location supports such conclusion, as it fits perfectly where the rim would be if the tire was completely deflated. And in my case, the bead also snapped out from the rim first. Or the deflation wouldn't be so sudden, with a bang.

So it looks to me that Michelin might have quality control issues with these tires, much to my dismay. Since they were expensive, and I find them outstanding for my use, it is a pity that I must always have that doubt in back of my head - will the next one blow off again, for no apparent reason? And yes, they are pretty tight fitting on the rim. Ironically, I've never had anything like this happen with much cheaper tires that fit quite loosely on that same rim. Punctures, yes. But a sudden spontaneous blow off, no. And those cheap tires were overinflated by about 20%, while, get this, Michelin was under inflated by about the same amount when it blew. Enough about quality, if we can call it that.

OP's tire probably remained in one piece because it has reinforced sidewalls, it was a front tire and as such it carries quite a bit lower load then the rear tire in my case, and OP was not going so fast at the time of the blow off. All of those factors considered, I can see how a tire can remain intact. Well that might be a useful advertising tactic for Michelin; our protection is so good that the tire will remain intact even in a case of blow off during riding. As for the rest of the bike and the rider combined, that won't be mentioned here

Tires are from the same family of tires, only difference is in the reinforcement level. Casing is the same, rubber compounds and chord configuration is the same. So two tire of almost practically the same construction blow off the rim instantly without warning, for no good reason; am I the only one here who sees something fishy about those tires quality?

sudo bike

FWIW, I have CiTY's and never had an issue. I run 35's at around 6 bars. I did notice the tires felt... very odd when turning sharply when they were still new. Something about the design, I guess. Felt kind of oddly "grabby". After riding with them for this long, they feel a lot more natural now but still with some of the same attributes. It's only really noticeable when slaloming.

whitecat

I listed the reason why I believe my sidewall failed, add the fact that I have about 260 lbs, full laden weight of me, my bike and gear is about 320 to 330 lbs, and you get the picture. Also, the tires are of the same basic construction, in the same size, a difference in the protection level might have contributed to your tire not ending up being cut, as I noted before, along with other factors.

How can you be confident that the problem lies with the rim, and not the tire? If every other tire worked fine on that rim of yours, and only this one blew off, please explain me how did you get to the conclusion that the rim is defective? I had that blow off problem only with this Michelin tire, not with any other of more then a few dozen tires I used on that same rim - to me, that points in the direction of the tire as being responsible for the fault, not the rim. I will probably be exchanging them for some cheap CST tires that I used to run before - minus the puncture protection and a bit less grip, but no thinking about will it ever blow off again on it's own accord.

whitecat

It's good to hear that they do work for some people. But to be honest, I'm getting a bit too paranoid - I ride a lot of rush hour traffic at speeds of up to 28 mph, and really would not want to have a repeat performance in that setting as that might get ugly. Me and the OP had a lot of luck not to bite the dust when tires blew, so I'm probably going to the safe side - riding another tire. And yes, city tire feels quite abrupt and twitchy when pushed to the limit when cornering and especially leaning into the turn. So I'm not the only one who felt that. Thanks for your input.

sudo bike

I wouldn't blame you. Can't say that I wouldn't do the same if it happened to me.

Also, for me, that feeling didn't so much feel "twitchy". For me, it felt more like how a low-air tire grips the asphalt. When I think I have a low tire in the back, I usually do some light slaloming to determine if it actually is - I generally know right away if it's low by how it grabs when I slalom. The CiTY's give that sort of feeling when they're full (that's how I first noticed it, actually). It's really pretty bizarre. Took forever to get used to. I kept thinking I was low all the time, then would discover when I got home that it was fine.

whitecat

Yeah, they feel like they are going to wash out under you when riding hard in corners. Takes a bit of time to get used to it. I'm thinking, considering and reconsidering... for now it's Michelin City in 35 mm up front, and CST slick in 35 mm rear. Might just leave it that way for some time, and see how that setup fares. I have more City tires in stock, but am really reluctant to try them again. Front did not blow off (at least not yet), so I kept it on. Time will tell how it behaves. Maybe it was only a fluke, but then this report of other riders having similar problems doesn't quite inspire confidence in that tire.

irclean

My conclusion is purely speculative and not in any way based on scientific data. I came to this conclusion based on the fact that the bike in question is from a Big Box Store and has cheap aluminum rims. Ironically enough, when I went to grab the bike from the garage this morning I discovered that the tire had been blown off the rear wheel! This got me thinking that maybe whitecat was on to something and the tires are indeed defective. Maybe, maybe not, but I have to take a couple of other variables into consideration:

First, my rims: After removing the rear wheel today I carefully inspected the rim. Although I could see no obvious defects I also noticed that there were no markings on the rim at all: no brand name, no sizes, no manufacturer's stamp, nothing. I double checked with a magnet to make sure they were at least aluminum and yes, they are. Based on the images I have seen of double-walled rims mine seem to be single-walled. There is a few mm of material which seems to double over upon itself creating a bead around the circumference of the rim. This strip of material also appears to have been knurled, which I assume is meant to grab the tire bead more securely.

Second, my new pump: I recently purchased this pump because my new bike has Presta valves and my old pump only handles Schrader (BTW the bike in question has Schrader valves). The pump is well-reviewed by MEC members and "feels" quality in my hands. As I mentioned earlier, I double-checked the pressure against a digital gauge that I have and it was spot-on. This leads me to believe that maybe my previous pump (also cheap, and also purchased at said BBS) was displaying too high a pressure, and therefore I was unknowingly running my tires at lower pressures than I assumed. Perhaps when I later topped them up with my new pump the resulting pressure overcame the seal between the tire bead and the rim.

In any case, I am going to try to find a happy medium; a lower pressure that is high enough to prevent pinch flats, but low enough to avoid blowouts. Other than that I will be riding on faith (and at slower speeds - just in case). Wish me luck!

p.s. I'm just waiting on a rack for my new bike so I can use it as my primary commuter, and then the "blowout bike" can wait for better rims (and maybe tires).

cab chaser

I had a front tire blow out on me once while braking to a stop from a good clip at a stop light. Got some nasty road rash that day.

will be was

https://www.youtube.com/watch?v=M9RzJAWvOMQ