Bike chewing through inner tubes
July 7, 2009 5:48 AM Subscribe
Bike gurus: What's causing these weird grooves on my inner tubes?
I bought a new bike a few months ago and for the first few months it was fine, but in the last few weeks I keep getting punctures, and they're being caused by the tube wearing through rather than by sharp objects.
The tube is covered in these diagonal grooves (photo) that possibly match the weave pattern on the inside of the tyre. In a few places they're deep enough to let air out. After repairing a couple of punctures, I bought a new tube, and it lasted only a few days, incurring the same type of damage.
It's a cheapo folding bike with 20 inch knobbly mountain bike style tyres. Only the back wheel is affected - I've never had a puncture in the front one.
Anyone seen anything like this before? Any suggestions what to do about it?
I bought a new bike a few months ago and for the first few months it was fine, but in the last few weeks I keep getting punctures, and they're being caused by the tube wearing through rather than by sharp objects.
The tube is covered in these diagonal grooves (photo) that possibly match the weave pattern on the inside of the tyre. In a few places they're deep enough to let air out. After repairing a couple of punctures, I bought a new tube, and it lasted only a few days, incurring the same type of damage.
It's a cheapo folding bike with 20 inch knobbly mountain bike style tyres. Only the back wheel is affected - I've never had a puncture in the front one.
Anyone seen anything like this before? Any suggestions what to do about it?
This is a sign that the tube is too small in diameter -- it's being streched too thin. It's also a sign that the inside of the tire is too abrasive.
You need a new tube. You probably want a new tire.
posted by eriko at 6:26 AM on July 7, 2009
You need a new tube. You probably want a new tire.
posted by eriko at 6:26 AM on July 7, 2009
Seconding not enough pressure. The cheapo tires probably don't help. Most of your weight probalby sits on the back tire thus, more tire deformation, thus more wear. Pump it up!
posted by notsnot at 6:27 AM on July 7, 2009
posted by notsnot at 6:27 AM on July 7, 2009
Exactly where on the inner tube were the punctures? Are they on the inside facing the wheel, or outside facing the tire? The heads of the spokes need to be covered with rim tape to prevent them from causing a puncture on the inside of the tube. Cheap bikes often come with bad rim tape. Your local bike shop can sell you quality rim tape if that is your issue. Velox is the only brand I trust. I find it hard to believe that the inside roughness of the tire would cause a puncture, although it is theoretically possible. Sometimes you get a small stone inside or there can be a small bit of glass in the tire that keeps flatting your tubes but can be fiendishly difficult to find as it only pops out under a big stress such as going over a bump. Are all the punctures in the same place on the tube? Then it might be a hidden glass shard. Turning your tire completely inside out and giving a careful examination, including gently running your fingers over the surface, is the best way to find the glass. Also, if you are careful in removing the tire and wheel you can match up the location of the puncture with the location on the tire.
posted by caddis at 7:26 AM on July 7, 2009
posted by caddis at 7:26 AM on July 7, 2009
Best answer: Go to the bike shop and have them tell you the size of the tire. Then buy proper tubes of that size. Get a tire gauge and a stand-alone pump to make sure that you are getting it to the proper inflation. Hand pumps are emergency items, so if you're using that, you are likely not getting it up to where you want it to be. Make sure that you clean out the tire too.
posted by Ironmouth at 7:26 AM on July 7, 2009
posted by Ironmouth at 7:26 AM on July 7, 2009
i recently bought an old bike and the back tire deflated three times in two months. replacing the rim tape did the trick for me, and it only cost me 50 cents, then another couple of bucks for an inner tube patch kit. try that before replacing the tire.
posted by molecicco at 7:35 AM on July 7, 2009
posted by molecicco at 7:35 AM on July 7, 2009
Just seconding everyone else:
Check for:
Proper inflation.
Proper sizing on the tube.
I've actually seen that type of wear before, though I don't think it resulted in a flat. I think it may have been related to a situation where the tube was too big for the tire.
posted by wfrgms at 7:36 AM on July 7, 2009
Check for:
Proper inflation.
Proper sizing on the tube.
I've actually seen that type of wear before, though I don't think it resulted in a flat. I think it may have been related to a situation where the tube was too big for the tire.
posted by wfrgms at 7:36 AM on July 7, 2009
I think there are a few things in play here (already mentioned), but that the straw that is finally breaking the back and resulting in flats is low air pressure:
When you ride over a bump or the edge of a pothole, the pressure is low enough to let the tire compress at that point, which drives the rim into the outer tire, folding the edge of the tire - with the inner tube sandwiched in-between. This momentary crushing of the inner tube pushes through and creates the holes.
The solution is to
1. Make sure the tires are pumped to correct pressure (note: this can mean a less comfortable ride - on some bikes this will mean that the tires are rock hard)
2. Before riding, pinch the tire to check no air has leaked through the valve (ie check it's rock solid). Valves leak very slowly, so good pressure on Tuesday can be mostly-good pressure on Sunday, so it's very easy to not notice it happening.
3. Air valves start to slow-leak because dust gets in them. So keep them capped when not pumping them. I also suspect that chalk dust lining the inside of the tube often gets into the valve when you deflate a tire through the value for a patch repair.
Until I clued on to really making a strong habit of #2, I got a lot of flat tires from riding without realizing that my once-correctly inflated tires had lost a bit of pressure, and were then increasingly vulnerable to crush damage during riding.
As per #3, a brand new tube, once inflated, will usually not slow-leak. If anyone knows a way to clean a valve that has a slow leak from chalk dust, let me know :-)
posted by -harlequin- at 10:49 AM on July 7, 2009
When you ride over a bump or the edge of a pothole, the pressure is low enough to let the tire compress at that point, which drives the rim into the outer tire, folding the edge of the tire - with the inner tube sandwiched in-between. This momentary crushing of the inner tube pushes through and creates the holes.
The solution is to
1. Make sure the tires are pumped to correct pressure (note: this can mean a less comfortable ride - on some bikes this will mean that the tires are rock hard)
2. Before riding, pinch the tire to check no air has leaked through the valve (ie check it's rock solid). Valves leak very slowly, so good pressure on Tuesday can be mostly-good pressure on Sunday, so it's very easy to not notice it happening.
3. Air valves start to slow-leak because dust gets in them. So keep them capped when not pumping them. I also suspect that chalk dust lining the inside of the tube often gets into the valve when you deflate a tire through the value for a patch repair.
Until I clued on to really making a strong habit of #2, I got a lot of flat tires from riding without realizing that my once-correctly inflated tires had lost a bit of pressure, and were then increasingly vulnerable to crush damage during riding.
As per #3, a brand new tube, once inflated, will usually not slow-leak. If anyone knows a way to clean a valve that has a slow leak from chalk dust, let me know :-)
posted by -harlequin- at 10:49 AM on July 7, 2009
Yeah, even tho the tire "feels firm" - it probably isn't at the proper pressure unless you checked with an air-gauge. (Car gauges sometimes don't go high enough... go get a cheap bike-specific gauge from the local hardware store, X-Mart, bike shop, etc.) I used to have problems with pinch flats all the time, until I started checking the pressure instead of "going by feel."
posted by Slap*Happy at 12:44 PM on July 7, 2009
posted by Slap*Happy at 12:44 PM on July 7, 2009
Response by poster: Thanks everyone - this all makes sense. I got a normal pointy-metal-screw-in-tyre puncture just before this all started, and I must have not pumped it up properly afterwards. That's definitely something I'll try harder at in future.
The tyre is labelled "20x2.125" and I think original inner tube said something like "20x1.75-1.95" (it's back on the bike, so I can't check right now) and the new one I bought ("Specialized" brand) was "20x1.5-2.125" (on the box) and "20x1.5-2.125 THIN" (on the tube), which I was a bit suspicious of when I saw it. I'll make sure the next tube I buy is designed for larger tyres.
Thanks again.
posted by cillit bang at 12:47 PM on July 7, 2009
The tyre is labelled "20x2.125" and I think original inner tube said something like "20x1.75-1.95" (it's back on the bike, so I can't check right now) and the new one I bought ("Specialized" brand) was "20x1.5-2.125" (on the box) and "20x1.5-2.125 THIN" (on the tube), which I was a bit suspicious of when I saw it. I'll make sure the next tube I buy is designed for larger tyres.
Thanks again.
posted by cillit bang at 12:47 PM on July 7, 2009
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You might try inflating the tire to a higher pressure to keep the tube from moving around as much, that might work.
posted by fore at 5:54 AM on July 7, 2009