OnAFriday

Per the tread title, I had a front tire blow off the rim at 30mph, on a flat, with a tailwind. Very, very fortunately, I was able to bring the bike to a stop without crashing. I was not making a descent, the tire and rim were not hot, it was not a warm day.

Upon inspection of the tire, I was clearly able to identify the location where the tire blew off the rim. The tire shows significant damage to the bead at this location. I always line up my logos to the value stem, so I am positive of the tire's location when it blew off.

There is a very small irregularity on the rim hook where the tire blew off, on the same side, on the same circumference of the wheel. However, the wheel was sent back to Trek, and Trek concluded that it was a bad rim strip that allowed the tire to blow off.

The Aeolus 5 TLR are sold with both a tubeless rim strip, and one for tubes. The tires were mounted to the wheels by the shop, who incorrectly used the tubeless rim strip to mount the tires with tubes. Trek has replaced the tubless rim strip with one appropriate for tubes.

My question is: from the photos, does it seem reasonable that the rim strip in fact caused the issue?

Update - Failure was due to rim strip:

To answer myself: The irregularity in photo 3 is in the rim strip, not the carbon rim itself. And these wheels have a very particular rim strip which alters the rim hook, and and then the bead failed at its weakest connection point to the rim. It all makes sense.

Rowan

If you are asking a question about the rim, it's a bit pointless posting pictures of the tyre (for a start, I can't even see what the issue is with the tyre). Post pictures of the rim instead.

And this probably would have been better posted in the Mechanics forum.

andr0id

I don't know about the rest of your problem, but this sounds like utter horse carp to me. A lot of us run clinchers with tubes using tubeless tape rather than an old fashion rim strip. It works just fine as long as you make sure the tape is clear of the bead hook.

OnAFriday

Rowan, I DID post pictures of the rim. The tire picture, the 1 of the 4, is to show the damage to the tire bead where the tire blew off the rim.

edit: wrong rim strip type was installed, and additionally rim strip was likely defective. Double whammy.

rpenmanparker 

Pressure?

Robius

Sorry to hear that glad you are OK. I've read so many sidewall blowouts recently and most of them was Continental.

OnAFriday

Pressure was pretty normal, 105 psi on 25s (on the front). I realize that's more than many run, but I am a clyde (6'4", 205lbs). That's well under the max listed by Continental of 120psi.

Rowan

Yes, I see now. Poorly composed pictures.

The rim wouldn't have anything to do with it. I wouldn't fuss it any more. Go with what the Trek people said.

Darth Lefty 

The TLR rim strips are not just tape but are molded to match the Bontrager rim, and they run up the sides of the bead hook to make rubber-to-rubber contact with the tire.

Now whether this could cause the failure, I dunno.

rm -rf

"Upon inspection of the tire, I was clearly able to identify the location where the tire blew off the rim. The tire shows significant damage to the bead at this location. I always line up my logos to the value stem, so I am positive of the tire's location when it blew off."

Is the tire bead broken or scuffed or what?

How hard is it to mount the tires on these rims? Do they just slip over the edge, or do need a tire lever to get the last bit over?

Is this part, circled in blue, the damage on the rim? And is that the bead hook where it's circled?



I'm guessing the tire was defective or damaged during installation.

rm -rf

Hmm, that's interesting. So the tubeless rim strip runs up the sides to where the bead is seated? I've never heard of that before. I could see it might affect the non-tubeless bead.

Darth Lefty 

Here's a cross section of the TLR tubeless setup. The strip essentially converts the rim from a regular clincher-style to a tubeless-style interior shape. Imagine a tube in it, that's what the OP accidentally had.

1989Pre 

How many miles had you ridden on the tire before the blowout?
I had this happen to me in very similar conditions, but I was the one who had mounted the tire, maybe 2 days prior, so only 10 miles ridden before blowout. I can only conclude that it was some fault in seating the bead or I damaged the bead, like RM suggested. My tire was an IRC Redstorm Street, and an 8" section of the bead was shredded.
My only advice is to stay away from that model of tire. If you like TREK, maybe go with R3's.

OnAFriday

The tire bead is scuffed, look at the last photo. You can see some of the fibers of the tire bead exposed.

That part that's circled in blue by rm -rf is exactly what I was wondering about. Yes, that part is the bead hook. Yes, that is exactly where the tire came off the rim. It's not "damage" to the rim per se, it's simply the way the bead hook is shaped. It's in the carbon structure.

The third picture is a close up of this area of the rim bead hook.

The tires are not hard to mount, just a regular amount of pressure with the hands, you have to give a good tug but it's not hard to do. No levers required.

The tire actually had quite a few miles before the blow out. Hundreds. Actually, two weeks before, I was going over 45 mph downhill on that same tire and wheel...scary.

Carbonfiberboy 

I've had tubed tires blow off the rim from a slightly too wide rim strip, though I thought the tires I was using could have had a better bead. More than once, until I figured it out. Changed rim strips, tossed the tires, never had that exact problem again. My poor choice in rim strip wasn't nearly as close to the bead as what is in the drawing. Mine blew off under braking, though the rims weren't hot. I once had someone on my wheel blow their front off on a very slight descent at high speed. No obvious reason. No one hurt but scared me pretty good. We'd just done a long, fast technical descent through trees. Whew.

It happens. As above, change strips and tire model and don't worry about modifying more than one variable at a time.

exmechanic89

You were really lucky to bring the bike to safe stop, OP. 30mph could be catastrophic..

smarkinson

Going by Darth Lefty's picture I'd say that the rim tape was most likely the problem. The rim tape in that picture sure does go a long way up the sides of the rim (much further than I've ever seen before). I could see the extra rim tape for the tubeless tape under the bead of the tyre making it difficult for the tyre to get sufficient purchase on the rim edge.

This review goes into quite a bit of detail about the rim tape and it seem like you must use the TLR tyres with that particular tubeless rim tape.
Bontrager TLR 2013 Review - Slowtwitch.com

Here's a picture from that review showing the differences between normal tyres and the TLR and to me it looks the tubeless rim tape would be a real problem with standard tyres.

CliffordK

Have you checked that the brake pads aren't rubbing on the tire?

OnAFriday

Thanks to everyone who was helpful in the thread, especially Darth Lefty and smarkinson with those diagrams.

I can now definitely see what's going on. The little imperfection IS in the rim strip. I didn't realize until I looked closely at the back wheel that the strip does wrap around that far, all the way to the edge of the rim hook.

I removed the rim strip from the rear wheel (which btw is nearly impossible to do, it's VERY hard to get that strip out). Now it makes sense both why the rim strip would cause the failure AND why the failure would occur at that particular point: it was simply the weakest connection point on the rim.

Unfortunately, it looks like removing the rim strip destroys it, so I suppose in the future when I go tubeless (which I intend to do) I'll need a new one.

StanSeven

Great post and explanation!

CliffordK

Here is a BikeRadar review of the Aeolus 5 TLR D3.
Bontrager Aeolus 5 TLR D3 carbon clinchers review - BikeRadar



And from the Slowtwitch article above.



Note the very crisp looking hook on both the BikeRadar photo and the Slowtwitch photo.

To me, it doesn't look like there should be any problem running a tube tire with properly installed tubeless tape, although installation might be a bit more of a pain than normal.

HOWEVER,

The TLR Tubless tape appears to be tapered, thick in the middle, thin at the edge, and should taper to a point BELOW the hook.

The OP's tape appears to go up and over the hook, and is all ruffled on the edge. This might put a fat section under the hook, absolutely a problem.

So, I'm wondering if the fault isn't the existence of tubeless tape, but rather that it was either not properly installed, or was too wide. It might have even been installed over the hook, then trimmed giving the rough edge look.

OnAFriday

In the end, the tires should have been installed with the cloth rim strips that come with the wheels. While the tubeless strips might work with tubes, why take the chance? That's clearly why Bontrager ships the wheels with both rim strip types. Sure, the tubeless strip might have been bad on top of that, but it really shouldn't have been there to begin with.

Basically, shop made a mistake, and it could have really cost me. Fortunately, everything worked out in the end. It's a shame to have this negative mark on the wheels because otherwise, they are fantastic! The 19mm internal width really makes for a very comfortable ride, they brake great with the Black Princes, they spin up quickly and hold speed well.

StanSeven

That's it exactly. It's a mistake anyone could make but a shop that sells these wheels should absolutely know better.

Looigi

The method I use it to use a small bladed flat screw driver which I poke under the strip at the valve hole then use it to lift the strip so I can insert a plastic rod crosswise under the strip to lever it off.

Jiggle

Interesting post.

I did have a tire blow off a rim recently but I determined it was a bad bead. The tire would blow off if you let it sit in the sun and warm up.