Continental GP 4000s sidewall blowout

Discuss light weight issues concerning road bikes & parts.
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by tommasini

prendrefeu wrote:Damn, that sucks.

Glad you're safe. Maybe Continental will send you a new one.

Conti's liability would likely max out at just replacing the tire.....shit too bad you couldn't get them to throw in a replacement Zipp wheel/rim....

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by wineguy

This is very troubling as these are usually very reliable tires. I've just taken a set off after a rather incredible 7000 k's with only one puncture.
BigCol & image12, these both appear to be relatively recent purchases, is this correct? I wonder if this could be a particular batch?

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by BigCol

Mine was purchased in may this year - the shop ordered them in for me.

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by wineguy

anyone know if there is a batch number printed on theses tires and where?

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by Toby

Wineguy, I was thinking while reading this that it feels like I'm starting to read a few more GP4000S failures than I'm used to. Can't remember where the other cases are, but it's bothering me (as I ride on the 25c version).

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by wineguy

Can't say I've seen the other failures but to suddenly see two incidents like this is troubling. I've been using them almost exclusively for the last 5 years due to the comfort, wear and grip of them (at least on the roads around Auckland). Hopefully if there have been more incidents like this they will come to light.

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by tinozee

I was wondering the same thing, if those have a batch number. One of the two I have has the label printed way off center (not that that is relevant at all). Mine were purchased in July and seem to be holding up fine.

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by equinox

Glad you're ok. What are those two small holes in the tread? Some type of wear indicator?

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by rijndael

equinox wrote:Some type of wear indicator?

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by petal666

Same happened to me 18 months ago on a front GP4000s that was 21.7kms old.

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by image12

11.4 wrote:
However, here are my two cents' worth. It looks to me like you had a brake block that slightly chafed one side of that tire right above the braking surface,

Here's a shot including the brake surface, zipp rims brake track are also wider than the tire. Brake pads are far from the tires.

I'll look for the batch number when I get the chance.

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by MarkMcM

Looking at the photos, it appears to me to be more likely a cut (albeit a large one) than a casing failure. I find it very odd that the cut/tear is at a relatively constant radius, and therefore diagonally across both casing plies. Tire casings consist of several plies (2 or more) at a 45 degree angle to the tangent (so the plies cross at 90 degrees). Most failured due to defective casings occur along the plies, so they would split along a diagonal line, rather than a circumferential line.

I think the casing tear is more likely due to being an external cut, from some external object. While I've seen circumferential cuts due to contact with brake blocks, as suggested by image12, the jagged edges of the cut suggest to me that instead it was due to some sharp object. Could you have picked up some sliver of metal or glass during the descent, that somehow wedged in the frame or brakes, and cut the tire casing as it rotated by? Maybe this seems an unlikelihood to an initial observer, but stranger things have happened.

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by 11.4

Mark seems to be looking at the same issue in somewhat the same way but with a slightly different cause in mind. However, the line that separated looks worn, not like a sharp cut, and it would be a weird cutting object that could lodge there and not move around at all while it's getting tugged at by the tire casing.

I've had some weird experiences with brakes rubbing on tire casings at the junction with the braking surface. Using 7900 brake calipers, I adjusted them so the blocks were a good 3 mm from the tire after one rubbing episode. However, with some hard braking, the brake block moved up and rubbed the tire again. I don't know whether the brake block was getting pulled up by the braking force (the force of braking is not purely tangential, plus the rim itself can potentially deform slightly, either circumferentially or more likely laterally), or whether the whole brake caliper was shifting. I do sense a lot of movement in the caliper assembly when I tighten up the brake block allen key bolt, and I've seen this on all kinds of brake calipers. Wish I had a betters solution. But bottom line, I don't see that the tire failed of its own accord. Something happened to it -- road hazard or adjustment or whatever.

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by wojchiech

I've had three separate blowouts with these tires.

One was the rear tire during a technical descent (Mt. Baldy), thankfully it was a slower section, although it was strewn with rocks. After an inspection it was a vertical cut in the sidewall.

The second blowout was during a race (criterium). The damage was very similar to the above Specialized with Zipps (torn sidewall along bead). It was a pretty violent blowout (tire exploded and deflated almost instantly). The blowout was mostly caused by the fairly rough roads that the course was on. The potholes and cracks in the road that were deep enough to damage the sidewalls enough to weaken the sidewall.

The third blowout was similar to the first one (vertical cut), although this time was on straight flat city roads. Must have been the plentiful debris of metal and glass that are strewn all over bay area roads. :lol:

Needless to say I don't plan on purchasing anymore of these tires. Sure they have decent grip and are fairly supple for clinchers, but something must be said about the sidewall strength of these tires. I'm sticking with Vittoria from now on. :thumbup:

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by wineguy

heres the code from the sidewall of a GP4000S I just purchased from PBK

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