Continental GP 4000s sidewall blowout

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by thisisatest

could you take a close-up pic of the blown out section of tire? i'd like to see the bead breaker strip and what may have happened to it.

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by WMW

11.4 wrote: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.

The brake pad hitting the sidewall is the most likely culprit. When the brakes are applied and they will bend and rotate counterclockwise, so the top-front of the pad would be the most likely to make contact. Or it could happen when just riding if the pads are high and the wheel flexes enough to make contact.

Or maybe the rip in the tire occurred right after the blowout, while the tire was sliding on the ground. In which case there should be some other damage that was the original cause.

Not seeing how an opening like that could appear on a sidewall spontaneously... cutting across the cords...

BTW... there isn't a chance in hell that tube "stayed inflated"... unless he commonly rides with 1psi. It just has twisted and trapped some air. There has to be a big hole in it somewhere.
formerly rruff...

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by MarkMcM

WMW wrote:The brake pad hitting the sidewall is the most likely culprit. When the brakes are applied and they will bend and rotate counterclockwise, so the top-front of the pad would be the most likely to make contact.

That could happen if it were a front brake, but rear brakes arms, being behind and below the mouting bolt, tend to bend downward as they bend forward.

But maybe there is another brake actuation dynamic at work here. On dual pivot brakes, the right arm on the rear brake rotates on a offset pivot. Because the pivot is offset further form the center than the pad/rim contact point, when the brake is actuated the right pad will move in an arc inward and upward. As the pad wears, the arm moves even further in the inward/upward arc, and if the pad worn down too much the shoe may actually arc upward far enough contact the tire.

So, I guess the questions are: Are the pads worn down on the brakes? When the brake is actuated, does the brake shoes arc upward enough to contact the tire?

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by goodboyr

It looks like the FD cable has a huge amount of excess on it, and it's got a sharp bend in it. Could it be the culprit, if it lost the cable end and got caught?

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by smike

I had a similar blow out. In my case the brake pad was too loose and had rotated slightly upwards causing the edge of the brake pad to cut into the side wall. Like others have mentioned, this might be your case.

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by DGcyclist

:idea: The most common cause for sidewall damage is from cornering. Leaning the bike over in
a corner places the paper-thin sidewall dangerously close to the road surface allowing small stones
or other sharp bits to make contact with the tire's wall nicking a few threads. Miles later, maybe many,
the compromised sidewall bursts open without warning like a defective zipper. It would be very
good if tire manufacturers "locked" their threads so they can't run like cheap pantyhose when threads get cut.

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by image12

*Update: Brought the bike to the dealer and inspect to see the cause. They concluded that the tire failed, no brake pads or cables caused an external cut on the tire. Again the tube still has air, no hole/tear. The shop contacted continental and told me they were very concerned and currently reviewing the pictures taken by the shop.

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by gabriel959

It will be interesting to hear if they are prepared to pay for the new Zipp rim you are going to need.

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by onyourlefty

On July 4th I was on Glendora Ridge Road in San Gabriel Mountains near L.A., traveling about 25 mph. While rounding a corner, 4 inches of the sidewall on my front Continental 4000S split open and 6-8 inches of both beads of the tire came off the rim and jammed in my front brakes. I don't remember anything after the pop, but was told by friends I endo'd and hit pavement hard. I was medivacked out, unconscious, by helicopter to L.A. County Medical Center, where I came to a few hours later. Severe concussion kept me in the hospital for a few days, residual double vision starting to clear up now. Could have been a lot worse.

Sons of bitches at Continental don't respond to any requests for information - just keep selling their goddamn defective tires.

A friend on 4000s had the front blow up in what seemed like a repeat of my situation. She went down went down hard and broke her hip last week - something's gotta change here. I'm riding again, and discovered Michelin Pro 4s are are very similar in feel - even roll a bit better. Oh yeah - they don't seem to blow up unexpectedly.

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by fogman

I had a Conti GP4000S from PBK blowout at the bead about 3 years ago. Isolated incident. No problems with the newer GP4000SII so far. I have been ordering from Bike Tires Direct more recently.

I have been transitioning to Vredestein Fortezza Senso All Weather as my Continentals wear out.
It's all downhill from here, except for the uphills.

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by joepac

I have lost 4 gp4000s II tires to sidewall cuts where the tube actually sticks out of the tire and it gets cut as soon as I lean the bike during a turn. This was happening in the middle of last summer and early fall as well as this spring and summer. For me, the original 4000s was a bit finicky, but for some reason the sII has been much worse. Sounds like I just got lucky with the 4000s. My dad actually had the casing under the tread split on a 4000s resulting a in bump on the tire. We were riding and he stopped to look. He saw the bump and it actually exploded in my face when I came over to look at it. I had to ride back 15 miles to car the and come back and pick him up. Needless to say, I don't trust the 4000s or sII and have switched to Schwalbe One clinchers, which have been fantastic. I actually e-mailed conti about how many S IIs I lost and they offered to send me a replacement. I was so fed up I never even took them up on the offer.

I still use conti 4seasons in the winter, hopefully that doesn't bite me in the butt. No problems so far with them.

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by Nejmann

Same here.. New tires new bike, first time on it.. So *f##k* close to go down.. Happend in a corner.. Never ridden Them since.. Mine was the II

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Just saw this thread, Ive also had 4 sidewall blowouts one resulting in a bad crash and destroyed Zipp 202 front wheel
Curt Brown

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by spdntrxi

My wife a 4000s blow out 2/3 years ago .. Lucky it was on a MUP at low speed. I have thousands of miles on 4000sii with no issues.

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by mimason


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