Conti's failure
 

Attachment 153804Attachment 153805Attachment 153806Attachment 153807These are the pics of the tire

I've heard of that when tires are pryed on a tight fit with irons or the brake pad has rubbed the tire.
I've never had anything but great sevice and fortune with Conti's.
Same tire you are holding came with our Santana and got 2200 miles out of it on the rear with th front looking brand new.
Switched to GP-4000 in a 25c F and R and have 2000 miles on the rear and it is getting close to replacement time.

Thanks, DVS. As I mentioned in the other tread, these tires were always hand mounted. I have been using Continental Gatorskin's for many years and until now I had no unexplained failures. I am pretty sure there was no brake rubbing going on but since this is a traveling tandem it is possible that things got out of whack during transit. I will inspect the tire more closely for brake damage and will reassemble the tandem to inspect the brakes. I will report on that later.

We also had a front tire fail after a century ride in a manner that looked identical to pics. The front tire had only about 600 miles on it - there was no damage to the sidewalls, and the tire had been mounted by hand without tools. The rear tire, which was purchased at the same time (also had the same manufacturing date) had been rotated from front to rear and had over 1600 miles on it. Neither tire ever had a flat. As a precaution, i removed the rear tire and used it on my single - it lasted another 1500 miles before it was worn to the casing.

My conclusion is that our failure was probably caused by a manufacturing defect. Some additional thoughts:

• When Continental USA sent a replacement tire, they used a full sized box and did NOT fold the tire as seen at http://www.sheldonbrown.com/video/tire-folding.html The invoice that came with the tire indicated that you should NOT fold the gatorskin in this manner, and the bike shop where i bought the tires DID fold the tires to put in a bag at the time of purchase.

• Looking the tread design of the gatorskin in the picture, i'd say that's a pretty old tire ... could age be a factor?

I've always been leary of folding a wire beaded tire.
Seems the twisting doesn't make me feel good.
The only reason we had a wire bead Conti is because it came on the bike.
I haven't bought anything but foldables since they first came out in the mid 80's.

I checked the tire and there was no sign of damage anywhere except the busted area. The brake pads sit on the rim where they are supposed to. I do not know for sure when I purchased that tire but I could not be more than 2 years old.

The Gatorskins i've purchased over the past 5-6 years (including the one that failed) all had tread patterns that looked like this: http://www.biketiresdirect.com/pcoc3...700c%29/pp.htm

I think that all conti tires now have a date of manufacture stamp - it's a small circle with quarter quadrant marks followed by a number. The year is indicated by the number (0 to 10 = 2000 to 2010) and the month is indicated by counting little dots in the pie quadrants.

Thank you coloroadie! According to the stamp my tire was made in January 2005. I can not tell for sure where I bought that tire but since I usually check on line and then buy 4 to 6 tires at a time from the cheapest source, I must have gotten an aged batch. I checked the date on the rest of my stock and that was the oldest tire. The next oldest tire has a date of Nov. 2007.

Is five years to old for a tire to be used safely? I keep my bikes and tires in a garage/shop that has a thermostat/controlled attic fan... it gets hot in there but not extremely hot.

I don't know if there's a finite shelf life, but i believe that cool, dark, and dry are good places to store tires. Avoid places with heat, sunlight, solvents, combustion by-products, and ozone from electric motors.

I'm sure a real expert will correct me if I'm mistaken!

I think a five-year-old tire is aged very well. The aging (in a cool, dry place) allows the rubber to cure so that it is slightly harder than when new and less likely to pick up debris which could work its way thru. I always mark my tires wtih date of acquisition and weight in grams, and I use the tires in order of acquisition date.

With Contis, though, you need to make sure that the sidewalls haven't become "dried out" and brittle. I've found the sidewalls on Contis to be their big weakness.

Lots of people swear by Contis, but it occurs to me that most of them live in warm, sunny climates where it never rains, or they don't use the tires in the rain. Same with Phil Wood hubs; they last forever as long as you are not commuting daily in the Pacific Northwest. I've always had a deep distrust of bike components that have only been tested in Southern California. What kind of testing is that?

Luis

We have over 35,000 miles on our 2001 Santana, all on Contis. We live in Michigan and "if the roads are dry, we ride," no matter how cold it is. We have never had a sidewall failure.

Rick

Umm, probably not. Yes, diene containing rubbers used in tread compounds (typically NR, SBR, and blends thereof) crosslinked with sulfur can continue "curing" at room temp, albeit at a much, much slower rate. This in theory could result in higher modulus (stiffer) tires. However, some properties, such as tear strength are inversely related to crosslink density (modulus). So I wouldn't assume that a stiffer tread is necessarily more resistant to damage from debris. Keep in mind the manufacturer has likely designed the tire to function optimally as manufactured. Aging only increases the potential for other issues.

I would be more concerned that an older tire had a greater chance of exposure to and attack by ozone and UV. Diene containing rubbers are susceptible to attack even when properly compounded with protective ingredients. This attack results in a less elastic compound. If very severe, surface cracks can begin to appear (this used to be called "dry rot")

Storage in dark, cool, dry areas, away from sources of ozone (electrical motors, for instance) is good advice. If practical, I would store the tires unfolded. Speed of attack by ozone is increased and more severe on strained rubber. If not practical, store the folded tires in a sealed bag. Thats what I do.

CG

I've only had a sidewall failure on a Conti during a 0 mph fall-over. The bead tore from the rim and the sidewall ripped. Other than that, they've never failed.

We recently had a Conti Gatorskin rear tire with a slow leak and when we took the tire off to repair the leak we found two tears in the side wall at the bead. The tire was put on about a month ago and had about 800 miles on it. We have liked the Gatorskins and hope that it is an isolated problem. First time that we have been glad to have a slow leak.

I took my touring bike through a cactus patch the continental side walls were shreaded the serfas was undamaged.

Why?

Gads!!!

Would you care to comment on changes in stabilizers and plasticizers used in rubber over the years?

I have had two different Conti 26 by 1.95 tire versions show tread and sidewall cracks in as little as a year and a half of use on the bikes. I have had Bontrager mountain bike tires shed tread lugs in as little as 1 year of use of hot asphalt trails.

The reason I ask.

I put in over 30 years in a Firestone Tire & Rubber plant. In the Chem plant my specialty was BD gun dip for tire cord. QC from unloading of the BD to shipping the finished latex to several plants. Prior to the halt of tire production at the Pottstown plant I switched to the PVC Chem plant. Watched changes in stabilizers and plasticizers in that business.

In dealing with bicycle tires on our bikes it looks as if the rubber now being used is not as well stabilized or plasticized in terms of how long they will last. I have 15 year old tires in the basement off box store bikes that show no outward signs of aging.