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Permalink Reply by Michael Perz on February 14, 2011 at 5:01am

You should have taken them back to wherever you purchased them instead of patching. Splitting at the seam is a defect and unlikely attributed to weather or road debris. You probably just had the misfortune of coming across a bad batch.

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Permalink Reply by Far'arned Retrogrumpalunkus #63 on February 14, 2011 at 5:13am

I've had stick-on "scab" patches fail in cold weather.  Funny thing is one could just press down harder and they would seal back up inside my warm condo.  But they would eventually fail again after a heat/cold cycle or so.

 

My $.02

 

If you put your tire on with the label next to the valve stem it is easier to inspect the area better near a tube failure since you can find it and don't need to really inspect the entire rim/tire as closely and just concentrate on the failure area.  Most likely there is a teeny-tiny bit of rust or some other foreign material causing the puncture.  Tubes don't just puncture themselves.

 

Heating and cooling does cause things to expand and contract -and the tire/rim/tube all expand and contract different amounts since they are made of different materials with different thermal properties.  So when it experiences extreme temperature variations there is going to be a little more movement between the three.  If there is something pointy in there it'll be more likely to find a way home to puncture-town because of said increase in movement.  Also a tear at the seam might be caused by a hitherto unknown/unbeknownst pinch/fold that wasn't bad enough to tear until the tube started trying to move around more and couldn't without ripping something apart.   Baby powder/talc on the tube will allow it to move around without getting caught and tearing something.  But if you have garbage or slight imperfections inside the tire and rim this might actually increase the chances of them damaging things as the tube will be moving around more.  Inspecting it inside and curing issues before they have a chance to damage a tube is essential in tube-type clincher tire maintenance.

 

Disclaimer:  I'm not a professional "bike mechanic" but I do make a living turning a wrench and do all my own work on bikes/cars/motorcycles/machines and have for over 30 years.

 

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Permalink Reply by Melanie K on February 14, 2011 at 5:19am

Thanks for your responses- The tubes I have are well-used and have been patched before- I did find the leaks in the tubes themselves pretty quickly. I use the vulcanizing patches, and usually my patched tubes seem to last longer than the new ones.  

 

Thanks for the advice about talcum powder- I really think there is something crazy going on with my rims near the valve stem as this isn't the first time I have had problems with tubes getting punctured on the "rim" side of the tube near the valve.  

I appreciate the advice :)

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Permalink Reply by Liz on February 14, 2011 at 5:38am

P2(end pressure)=P1(start pressure)*T2(end temp in kelvan)/T1(start temp in kelvan)

 

Lets say you filled up your tires at 32 deg F that's 273K, and your apartment is 67 deg F so 292 K, if initial pressure is 120psi final pressure is 128psi so generally its not a big differential. 

 

If you fill up at 0 deg F its 255K and 100 psi becomes 114 psi or 120 psi becomes 137 psi

 

So what isn't a problem in 30 degree weather, could become an issue with the extreme cold of last week.

 

Combine this pressure differential with as James pointed the fatigue cycles, various levels of expansion between tire, tube and rim and stresses on the valve its probably just a part of winter cycling.

 

Baby powder your tubes, check for rust/salt around the stem area, and fill to lower psi than normal and maybe release some air when you get home if its extremely cold out and fill up before leaving.

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Permalink Reply by Melanie K on February 14, 2011 at 5:50am

Thanks, Liz- I am pretty sure that is what probably happened now. I filled up at most likely 35 degrees in an unheated basement, left the bike at the train station during the extreme cold (negative degrees), rode home, brought it upstairs in a 70 degree heated apartment (pretty extreme to go from negative deg F to 70. Never really thought about it until I heard the hissing later. The physics of it is interesting.

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Permalink Reply by Michael Perz on February 14, 2011 at 6:22am

Is the rim strip covering the valve hole completely?

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Permalink Reply by Melanie K on February 14, 2011 at 6:35am

The valve hole is fine, so is the rim strip- in fact it is pretty new since I replaced it last summer and it still looks fresh.  I am pretty sure it was the crazy temperatures of last week that did it, as Liz stated in her comment. This is only the 2nd year of biking in winter, and I don't remember last winter being as extreme as this one, especially as far as temperatures dipping into zero degrees.  I have to remember not to pump up my tires so hard during winter- I think that really contributed to this.

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Permalink Reply by travesty on February 14, 2011 at 6:35am

Fixing flats is something I've done for years, and yet I still find tricks and tips that I have not heard. One that is not specifically mentioned yet is rough spots on the rim. I've seen some rims that have rough rusty holes that are not easily covered by the rim strip.

I think the temperature can make it critical, but the splits may be induced by a rubbing or contact with a rough spot on the rim and one should always inspect for these when the hole is away from the road side, and use a file in there to take down rough edges and burrs. This includes the valve hole, it should be rounded and smooth to the touch on all sides. I have found rough spots under the rim strip that were penetrating even good rim strips, and that means the tough canvas strips, the rubber rim strips do not seem to perform as well.

I use baby (talcum) powder as well, especially if there is a strip to prevent punctures like a mr. tuffy.

 

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Permalink Reply by MagMileMarauder on February 14, 2011 at 7:13am

Interesting. Even riding in extreme climates (also going from 0 - 70F), that's nothing I've ever experienced. Let us know what you find out. Good luck resolving this!

 

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Permalink Reply by Liz on February 14, 2011 at 7:18am

Another failure mechanism could be the tube's rubber becoming brittle in extreme.  This might lead to easier tearing at the weak points or points of greatest stress.  The greatest stress occuring at the stem where the thermal friction due to metal expansion and conrtaction and increased pressure forces are at a "fixed" end. 

 

Failure machanisms are usually difficult to tie to one single condition, but rather a combination of many contributing factors. 

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