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Cat 6 rider
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Discussion Starter #1
I was thumbing through the Specialized owner’s manual and found something interesting, “Patching a tube is an emergency repair… Replace a patched tube as soon as possible.” I thought once a tube was patched it was a permanent repair (if you’re using a real patch kit with rubber cement and fairly thick patches.) Assuming we’re talking about a thorn puncture and not rips or tears, there’s a massive amount of rubber welded around the damage, and the patch is held between the tube and the tire by the air pressure so even if the weld were to fail you’d be looking at nothing more than the same slow leak that caused you to patch it in the first place. Is this a serious warning, or are we seeing the result of Specialized’s lawyers attempting to head off litigation? (In point of fact I don’t make a habit of running patched tubes, but I do keep a patched tube in my bag in case I get a flat on the road. It’s not the five bucks for a new tube that concerns me so much, but it seems wasteful to landfill a tube that only has a pinhole hole in it.)


L33
 

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You will find that your Specialized dealer will sell you a bike with reflectors- and the shop where I lived made me sign a disclaimer that I would not sue them if i was in an accident.

A patched tube is fine. I have never had a tube fail where it was patched. I wouldn't use a glueless patch (a sticker, if you ask me) on a roadbike- but that is another matter.
 

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Ancient marketing tactic.

It’s not the five bucks for a new tube that concerns me so much, . . .
The concern is on part of the industry. They want your five bucks in the worst way. Creating fear increases their chance of getting them.

I've ridden patched tubes for decades - never a problem other than a rare slow leak because of a hurried repair.
 

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Cat 6 rider
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Discussion Starter #4
filtersweep said:
You will find that your Specialized dealer will sell you a bike with reflectors- and the shop where I lived made me sign a disclaimer that I would not sue them if i was in an accident.

A patched tube is fine. I have never had a tube fail where it was patched. I wouldn't use a glueless patch (a sticker, if you ask me) on a roadbike- but that is another matter.
Here in California you can't sell a bike unless it has front and rear reflectors, wheel reflectors, and pedal reflectors, so I'm sure that even our Trek, Cannondale, and Felt dealers will give us the full hookup. My mountain bike came with SPD pedals with cute little reflectors that clipped on to the pedal axles. I don't object to bikes with reflectors so much -can't imagine they add much drag- I just don't think they do that much good. I'm a fan of flashies, bright ones. (You can always tell the guy who's been hit by a car, can't you?)
Interestingly, here in the land of litigation, both bikes I bought in the last couple of years came with waivers to sign promising not sue, but neither dealer actually made me sign one. They just threw the blank in with all the other documentation. They probably figure it won't make any difference and they're going to get sued if a speed bump makes a rider fart at an embarrassing moment.

I tried a "glueless patch" once on a mountain bike tube. I won't say who made it. Let's just say it was green. The tube went flat about a week later. When I removed the tube I found that the patch had come unstuck and walked off the hole. Wait, where's my lawyer? I forgot to sue over that. The emotional distress has to be worth at least 50 grand, plus I got my hands dirty.
 

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maybe they put that in for liability reasons...after all given 50,000 patched tubes, one is bound to have problems. I've never had any problems....but this world seems to operate in a "what if" mode....
 

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If pached properly it's not a problem. I have paches on my BMX bike's tubes that have been there for years and still hold... However,,, I've heard of cases where the job was done half @$$, and the pach didn't hold.
 

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eminence grease
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I patch mine all the time and have had a very long run with no problems at all.

But, I did almost end up on my face, one time. Patched the tube, reinstalled and went off riding. Apparently, the vulcanization did not take all the way around the spot, because I had a slow leak. Didn't really notice it for quite a while and then discovered that the ride was feeling a bit squishy. Decided to pull over into an upcoming park to change it out, took a corner just a bit too fast the the tire tried hard to walk off the rim. Steering was compromised, I finally avoiding going down hard by unclipping and using my right leg as a tripod.

If they're done correctly - no problem. As I said, this one is the only one in hundreds. But it also only takes one. I learned my lesson, patch it and then pay some attention to it. If it goes soft - bag it. If not, ride on. I don't think they fail long term, it's more of an infant mortality issue.
 

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Cat 6 rider
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Discussion Starter #8
terry b said:
I patch mine all the time and have had a very long run with no problems at all.

But, I did almost end up on my face, one time. Patched the tube, reinstalled and went off riding. Apparently, the vulcanization did not take all the way around the spot, because I had a slow leak. Didn't really notice it for quite a while and then discovered that the ride was feeling a bit squishy. Decided to pull over into an upcoming park to change it out, took a corner just a bit too fast the the tire tried hard to walk off the rim. Steering was compromised, I finally avoiding going down hard by unclipping and using my right leg as a tripod.

If they're done correctly - no problem. As I said, this one is the only one in hundreds. But it also only takes one. I learned my lesson, patch it and then pay some attention to it. If it goes soft - bag it. If not, ride on. I don't think they fail long term, it's more of an infant mortality issue.
Actually, I found out my tire was going low when I tried to take a sharp turn after a long bumpy straight. I had't noticed it going down. I'm actually extremely new to clipless pedals, but to my surprise I was out of them and tripoding before I could have been out of the old fashioned pedal clips I was using before- amazing what panic adrenilin will do for you- goes to show that it's not the patch that's the problem, it's the loss of air, regardless of whether it's a bad repair, or thorn in the road.
 

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Nah.

More likely to fail? Maybe - but that doesn't make it more dangerous. Might even be safer in some circumstances.

We have to look at the source of damage. A second puncture would be no different than a first puncture in an intact tube, so no difference there.

The only time there would be a safety difference between an intact tube and a patched tube would be in a spontaneous blowout situation, such as can occur from overheating by dragging the brakes on a long descent.

But while the patched tube might be more likely to fail in such a place, its failure is more likely to be slower and gentler, allowing for a chance to get to a safe place/speed before going completely flat. The intact tube will be less likely to fail, but if it does go, it's gone all at once, with chances of a safe pullover much diminished.

Sometimes I replace them right away, sometimes I let it slide. I honestly can't tell you if I'm currently riding patched tubes or not.
 

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Cat 6 rider
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Discussion Starter #12
danl1 said:
More likely to fail? Maybe - but that doesn't make it more dangerous. Might even be safer in some circumstances.

We have to look at the source of damage. A second puncture would be no different than a first puncture in an intact tube, so no difference there.

The only time there would be a safety difference between an intact tube and a patched tube would be in a spontaneous blowout situation, such as can occur from overheating by dragging the brakes on a long descent.

But while the patched tube might be more likely to fail in such a place, its failure is more likely to be slower and gentler, allowing for a chance to get to a safe place/speed before going completely flat. The intact tube will be less likely to fail, but if it does go, it's gone all at once, with chances of a safe pullover much diminished.

Sometimes I replace them right away, sometimes I let it slide. I honestly can't tell you if I'm currently riding patched tubes or not.
So, in the case of a blowout, are you saying the vulcanization where the patch is applied weakens the tube at that point and that's where it fails? (They call it vulcanizing liquid, but I thought it was a cement.)

On a side topic, has anyone every had a blowout during a decent? Is it recommended to lower tire pressure before a technical decent? Is it better to alternate one brake then the other to give a rim time to cool, or use both brakes equally to lessen the heat build-up on one rim? Or perhaps it's better to favor the rear brake, as I'd think it better to have a rear than front blowout.
 

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blowoffs and brake dissapation

California L33 said:
On a side topic, has anyone every had a blowout during a decent? Is it recommended to lower tire pressure before a technical decent? Is it better to alternate one brake then the other to give a rim time to cool, or use both brakes equally to lessen the heat build-up on one rim? Or perhaps it's better to favor the rear brake, as I'd think it better to have a rear than front blowout.
I think the term "blowout" is sometimes misused to describe a failed tube. A true "blowout" only occurs when the tire integrity fails, as when the casing rips. A tube failing, or even a tire puncture that doesn't cause a gross casing failure, is merely a flat tire, not a "blowout"

Brake overheating is more likely to cause a "blowoff", which is when the tire unseats from the rim - often without actually damaging tire or rim.

In any case, the best way to prevent a blowoff when descending is to use your brakes for as short a time as possible. That means that instead of constantly dragging your brakes all the way down, coast on the straight aways and then brake hard before the corners. This minimizes energy dissapation from the brakes, by increasing the disapation from air drag. Air drag power is proportional to the cube of speed, so energy dissaption by air drag at 40 mph is more than double what it is at 30 mph.
 

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You're right about the blowout term, and spot-on with the technique. Maybe disk brakes on road bikes aren't a completely silly notion after all!

It can happen that a tube will get hot enough to let go without a blow-out or blow-off. Far more likely with pre-existing damage, I've seen stems blow free "from the heat" with no apparent reason. Yep, they were probably damaged from lots of unkind chucking, and the fellow in question habitually ran above listed pressures (they're only some lawyer's guidelines, after all :rolleyes: ). I dare say he would have been better off with a badly glued patch to work as a safety valve.

A good patch is as good as a new tube. A weak patch is an annoyance, but not a danger.
 

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I carry a couple patched tubes when I ride and I'm using one now. No worries on my part. If I puncture I replace the tube on the side of the road and take the punctured tube home and repair it there. I mount it on a rim and inflate. If it holds overnight after the repair. It's good to go.

Somtimes I've had trouble patching a tube when the hole was very close to a seam. It wouldn't hold overnight. The only time I've had a patch go bad, I could hear it hissing as I rode, also that particular one was the last one I ever patched on the side of the road.

It's almost not worth it to patch a tube, since you can get deals on them for under $2 each. But I patch any tube I can. I'm cheap, and Proud of it :).
 

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Cat 6 rider
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Discussion Starter #16
Mark McM said:
I think the term "blowout" is sometimes misused to describe a failed tube. A true "blowout" only occurs when the tire integrity fails, as when the casing rips. A tube failing, or even a tire puncture that doesn't cause a gross casing failure, is merely a flat tire, not a "blowout"

Brake overheating is more likely to cause a "blowoff", which is when the tire unseats from the rim - often without actually damaging tire or rim.

In any case, the best way to prevent a blowoff when descending is to use your brakes for as short a time as possible. That means that instead of constantly dragging your brakes all the way down, coast on the straight aways and then brake hard before the corners. This minimizes energy dissapation from the brakes, by increasing the disapation from air drag. Air drag power is proportional to the cube of speed, so energy dissaption by air drag at 40 mph is more than double what it is at 30 mph.
I had a stem blow off my old road bike. Luckily, I wasn't riding it at the time. I inflated the tires on a cool Summer morning, went for a ride, came home and parked it in the shade. At about 3:00PM I heard one heck of a bang. The temperature had gone way up, the sun had moved and the tire was in the sun. The interesting thing is that the stem blew off- not the tire, and that bike doesn't have hook bead rims.

One other question about tire heating. Is it just from brakes? Does tire friction at speed play an important roll in the heating?

Your description of using air drag with brief hard braking makes a lot of sense. I've actually used air drag a couple of times. Just sit up and you can feel the drag. Throw your knees and elbows out and feel it more. Does anyone know if there's a better position to get drag?
 

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Tire heating/expansion

California L33 said:
I had a stem blow off my old road bike. Luckily, I wasn't riding it at the time. I inflated the tires on a cool Summer morning, went for a ride, came home and parked it in the shade. At about 3:00PM I heard one heck of a bang. The temperature had gone way up, the sun had moved and the tire was in the sun. The interesting thing is that the stem blew off- not the tire, and that bike doesn't have hook bead rims.
Of course, temperature increases increase pressure. But heating up from the sun may not increase pressure as much as you might expect. The gas laws say that pressure (at constant volume, as for a bicycle tire) is proportional to temperature - but it is absolute temperature, not relative temperature. So if you leave a wheel wit 100 psi in a car on a sunny summer day, and the temperature increases from 80 deg. F (=27 deg. Celsius = 300 deg. Kelvin) to 180 deg. F ( =82 deg. Celsius = 355 deg. Kelvin), the pressure only increases by 355/300, from 100 psi to 118 psi.

California L33 said:
One other question about tire heating. Is it just from brakes? Does tire friction at speed play an important roll in the heating?
Sure, there is some heating from rolliing resistance, but it is very small. Road tyres typically have coefficients of rolling resistance of 0.004 - 0.006, so if 100 kg of bicycle plus rider is rolling down the road at 25 mph ( = 40.2 kph = 11.2 m/sec.), the power dissipated as heat in the tires is only 44 - 66 Watts. Barely enough to raise the temperature of the tires more than few degrees. Motor vehicles tires support higher loads and roll at faster speeds, so heat build-up in motor vehicle tires is much greater than it would be on bicycles.
 

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Patched=Good As New (Usually)

IMHE, Patches on the more common small punctures or slow leaks are usually permanent. The more difficult ones are the 'snake bites' resulting from the rim edges, or pinch flats. These require a longer patch that encompasses more area on the tube. Your'e more likely to see improper adhesion due the odd contact surface - or, when the patch moves before it bonds, which is why it is best to not use so much cement that it doesn't tack up but remains fluid when you put the patch on. (Here I'm attempting to revive the 'art of tube patching')
I no longer attempt roadside tube repairs but wait to accumulate a bunch of failed tubes and then repair them at home. I use a Dremel tool to rough up the surface. It literally takes less than a minute to do and you can tell that the bond is tight. Surface prep is the key.
Bulk Patches and rubber cement are cheap if bought from an auto supply shop.

Mersault said:
It's almost not worth it to patch a tube, since you can get deals on them for under $2 each
BTW, I'd be interested in knowing where those deals are to be found.
OTOH, Maybe there's an 'anti-patcher' who'd be willing to mail me their old tubes. I'll patch them and send back half the batch and keep the remainder as payment. Any takers?
 

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When I was younger, and therefore more foolish, I was curious about this very thing. So I took a tube that had been patched and pumped it up until it exploded... in a closed garage. When the vertigo left and I could hear again, I inspected the frayed ends of the tube and it didn't blow where the patch was, but in a spot that had no visible defects. I say that the patch, if done correctly with vulcanizing fluid, is just at strong as the rest of tube.

-James
 

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Does it matter?
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Deals on Tubes

I've gotten those deals at pricepoint.com and performance.com. and the local performancebike store. It was ten tubes for under 20 bucks. Of course I piggy backed the tubes onto the order while I was ordering something else. Those are their house brand. Once I got a bunch of Michelin tubes for less than 2 bucks each, but half of those Michelin got "pin holes" in them without me puncturing them. So that wasn't such a good deal. But the house brand ones have been ok.

Even at those prices, I still patch any tube I think is fixable.
 
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