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Discussion Starter · #1 ·
I had a scary blowout happen to me on a descent this afternoon and wanted to know if this has occurred to anybody else out there running Ksyrium SL's wheels.

A little bit about me would help:

6'9"
223 lbs
Conti GP 4K 700x23 tires
Air pressure = 120 psi

The roads were wet enough that it wasn't too safe to let it all hang out on the descent. Thus, I was on/off the brakes most of the time and enjoying the view. I could feel that the brake pads were heating up because I was losing some stopping power and the brake fade was coming on.

After descending about 800 feet I came upon a stretch of road that flattened out. I let my speed run out and soon thereafter I heard a loud BANG! The rear tire had blown out and was about to start the death wobble. Luckily I got it under control and stopped.

Here's what I found: the tube had a 2" blowout that was perfectly straight along the tube (i.e. the tear was parallel to the wheel). I've had snakebite flats w/ this combo before, but this was something completely new to me.

I'm interested to know if this has happened to anybody else and to learn what changes (700x25?) might work best going forward.

-Thanks, Todd
 

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Are you 6 feet '9" tall...or 69 inches [email protected] 223 lbs. with the second height you will be considered obese. Wether that has a bearing on your blowout may not be a factor. The tire pressure @ 120 psi sounds reasonable for most quality clinchers. Did the brake pads overheated your rear rim and consequently cause the unexpected blowout...who knows! Maybe it was just a case of simp[le "bad luck"! What can anyone do? I choose to pray to my Lord Jesus before riding my bike, and take X2 extra tubes, X2 air cartridges, and stay away from bad roads!
 

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Discussion Starter · #3 ·
ru1-2cycle said:
Are you 6 feet '9" tall...or 69 inches [email protected] 223 lbs. with the second height you will be considered obese. Wether that has a bearing on your blowout may not be a factor. The tire pressure @ 120 psi sounds reasonable for most quality clinchers. Did the brake pads overheated your rear rim and consequently cause the unexpected blowout...who knows! Maybe it was just a case of simp[le "bad luck"! What can anyone do? I choose to pray to my Lord Jesus before riding my bike, and take X2 extra tubes, X2 air cartridges, and stay away from bad roads!
6 feet, 9 inches :)

One thing I forgot to mention in my original post was that the rear wheel was extremely hot to the touch. I wonder if the heat caused the problem?

I'm running Mavic SSC brakes w/ the brake pads that came standard with these...should I try some different pads?
 

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Details?

If there was no damage to the tire sidewall, then it is a mystery how you had this failure. Most common cause of tires blowing off the rim is a poor mounting job, where the tube is pinched under the bead of the tire, but usually that happens within a few hours or days of mounting the tire. However, there appear to be times when it happens inexplicably. I have NEVER had this happen in over 100K miles of riding clinchers (between my wife and me). 120 psi should not be too high for a 23 mm tire. Wider tires are not likely a specific solution to this, but at your weight you probably should be on 25 mm or 28 mm tires in the rear at least.
 

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Discussion Starter · #5 ·
thud

Kerry Irons said:
If there was no damage to the tire sidewall, then it is a mystery how you had this failure. Most common cause of tires blowing off the rim is a poor mounting job, where the tube is pinched under the bead of the tire, but usually that happens within a few hours or days of mounting the tire. However, there appear to be times when it happens inexplicably. I have NEVER had this happen in over 100K miles of riding clinchers (between my wife and me). 120 psi should not be too high for a 23 mm tire. Wider tires are not likely a specific solution to this, but at your weight you probably should be on 25 mm or 28 mm tires in the rear at least.
I gave a close inspection to the tire before I remounted it, and there was no visible damage to the sidewall.

However, over the past 200 miles of riding I did notice a slight 'thud' feeling from the rear tire so I wouldn't be surprise that the tube was pinched under the bead.
 

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it´s possible the blowout happened because the tube was pinched between tyre and rim, but as kerry said that would probably have happened very soon after putting the tyre on. do you check your tyres and tubes regularly? were they new or old? older tyres and tubes develop weak spots and if you get a bit of glass stuck on the tyre next to a weak spot on the tube... most blowouts happen because either the tyre and tube are not installed correctly, or they have a weak spot, due either to age or a cut, etc.
also, when you say the rear wheel was extremely hot to the touch, i guess you mean the braking surfaces of the rim? rims do get hot with heavy braking, but i don´t think i´ve ever had one get that hot (not that i check them after each descent!). maybe you need to work on your braking technique to reduce heat build up.

foz
 

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Had something similar last weekend on my Felt F55 (Amercian Classic CR420 wheels with Vittorio Rubino Pro Slicks with less than 300 miles on them at 115psi) - I am 6' and 175lbs

Going 18mph 4 miles into the ride...BANG about a 3-4" gash in the side wall parallel to the rim.No over heating... no pinching of the tube....

Unfortunately the tube blew out as the tire came off the rim. The tube got caught in the rear wheel cogs and jammed the wheel before I could stop so I ended up skidding on the wheel rim - leaving a 15 foot aluminum skid mark on the pavement. Unfortunately the skid ground off a 4" long section of the clincher RIM effectively ruining the wheel...I was not a happy camper...American Classic does not sell rims the only option is to send the wheel to them and pay 240$ and they will replace the spokes and rim (basically build a new wheel on the old hub)

luckily we were close to the start of the ride and a buddy rode back for the truck to pick me up...we headed home to pick up my second bike and finished the ride on that...so no idea if it was a tire defect or what (tube was ruptured in a couple of places and torn ishreds but the cogs may have done a lot of that.) an expensive 4 miles :mad:
 

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foz said:
it´s possible the blowout happened because the tube was pinched between tyre and rim, but as kerry said that would probably have happened very soon after putting the tyre on.
I think this is exactly what happened. You can get away with a pinched inner tube for a long time (I've had it happend before) until repeated rim heating from braking finally weakens it enough to blow. The "thud" is good evidence that this is what happened.
 

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I agree, next time maybe blow the tire up to 60 or so, then let it back out and work the tire sideways and inspect it. Sounds like you did this and that you know what you are doing, so maybe it was just pinched a little and you did not notice, your mention of the bumping feeling tends to support that. I have ridden with a pinched tires for quite some time before it blew. You may want to try some talc with those tires, maybe they are just giving you a hard tire on mounting up.
 

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Actually..

jroden said:
I agree, next time maybe blow the tire up to 60 or so, then let it back out and work the tire sideways and inspect it. Sounds like you did this and that you know what you are doing, so maybe it was just pinched a little and you did not notice, your mention of the bumping feeling tends to support that. I have ridden with a pinched tires for quite some time before it blew. You may want to try some talc with those tires, maybe they are just giving you a hard tire on mounting up.
I think the original OP said that he felt a "thud" after installing the tire and a new tube and all? If so, it could be that the tire has been kind of tweaked a bit. This has happened to me before when I've felt a slight "thud" or a small bump in the tire from bad threads in the tire that have "moved" when I've sprinted or something of that nature. After awhile when the tire keeps "thudding" or bumping, it blows the tube out. Chances are good it has nothing to do with the wheel, but it could just be a defective tire.
 
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