Bicycle Mechanics - Rim tape issue.... I think
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01-02-12, 11:17 PM
So I bought my wife a new bike for Mother's day in 2011 and we've been riding some, but less than we want. We were about to head out 2 days ago and she had a completely flat front. I fixed it, replaced with a brand new tube and then today as we're heading out, flat again.
When I inspected the tube, it appears that the tube is deformed, like pimples or something, into the "divots" at the top of each spoke well. The rim tape appears to have been sucked into the spoke well, if that's a good term for it. It's still intact and in place, but there are big concave depressions in the thing. On my bike, the rim tape is slightly depressed into that cavity but nowhere near as bad, and my tubes don't show the same sort of dimpling.
So aside from replacing the rim tape (it looks like one of those presized plastic strips you just squeeze onto the rim) is there anything I should watch out for? Repairing flats on my own bike is one of my least favorite activities and there are 4 bikes in my house I have to keep running. :)
I'm assuming fresh rim tape will fix it but I've never had this problem before.
Well the rim tape on my wheels have dimples into the spoke wells as well, and I haven't gotten a flat in a while. Are you sure you are properly installing the tire and tube? (Not trying to patronize or anything).
You can inflate the tube and immerse it in a shallow pan of water to locate the leak.
Once you locate the leak, you can do detective work to find the cause. It could be a thorn embedded in the tire, or a burr on the rim, or...
To help, it's best to note the location of the tube's valve stem in relation to the tire. If you find a hole in the tube, say at 90 degrees from the tube's valve stem, you'll be able to narrow your search in the tire to the general area. Note, when you mount a tire, it's often helpful to align the tire's label with the tube's valve stem.
01-03-12, 12:31 AM
No patronizing read into it... I have never ever thought about rim tape before. I should take a picture, but the tube I removed first had a small leak two spokes away from the valve. It was obvioue where the leak was and it was in the little dimple formed by inflating the tire into the spoke well (and the rim tape is properly installed... but maybe not, It's on and centered though.)
The new tube i put on yesterday had never been ridden on but had been inflated to 100 psi and had the same dimple pattern and had a leak in a different spot. Again, the leak was obvious and coincided with the spoke well (different spoke)
I'll probably take the wheel into a shop and solicit opinions and some new rim tape at the same time. Kind of weird.
01-03-12, 02:21 AM
Definetly bad rim strip. Seen the exact same problem with a lot of relatively new bikes that come thru the shop.
The issue is the plastic/rubber type rim strips being used on double walled rims.
They simply are not strong enough to keep the inner tube from sinking into the spoke holes at 100psi. The dimples are bad, sure they look smooth and the spokes heads are not visible, but under high pressure the inner tube has to stretch and conform to them; stretching in a highly localized area leads to holes in the inner tube - even though there were no sharp spoke nipples etc exposed.
They work OK on a single wall rim where there are no deep holes to sink into, but for a double wall, you really do need a cloth velox type rim strip. Cloth tapes have fibers in them so they don't stretch and dimple over time as a rubber strip will.
Thing is, that the plastic/rubbery strips are cheaper than the cloth velox ones; so many manufactuerers put them into bikes by default; they'll survive long enough to sell the bike, last a month or so till they finally stretch too far, and then its you who gets to buy the real stuff cause your warranty is up. Saved a few pennies in manufacturing though. -alternate case, the buyer doesn't know about propor inflation so he leaves the tires squishing around at 40psi and the pressure is so low the rim strip never stretches out, common on dept. store hybrids.... also see a lot of Marins with the issue (shouldnt they at least know better?)
01-03-12, 06:14 AM
When I inspected the tube, it appears that the tube is deformed, like pimples or something, into the "divots" at the top of each spoke well. The rim tape appears to have been sucked into the spoke well, if that's a good term for it. It's still intact and in place, but there are big concave depressions in the thing.
If you can see the tinyest little arc of exposed metal spoke well, that's it. When you pump up the tire air pressure forces the inner tube against the metal edge and cuts it. Better rim strips will fix it. Ideally the rim strip should completely cover the rim from flange to flange but sometimes you can't do that.
Back when I owned my shop we had so many of those issues with Raleigh bikes that we routinely removed the rim strips, replaced them with Velox, and got Raleigh to give us a rebate. Nothing worse than a happy customer riding off with a new bike only to return unhappy in an hour or so with a flat tire.
01-03-12, 08:22 AM
A number of years ago while on a long distance sustained tour I started getting flats after the first couple of hundred km. It turned out that the Sun Rhynolite rim had some really tiny burrs that worked their way thru the black electrical tape used as a rim tape. As I was in outback Australia I took one of the multi-punctured and multi-patched tubes and made a "rim tape" with scissors and the rubber glue that I was quickly using up.
End of problem! The holes causing the flats appeared in various places as the burrs from the 48 spoke holes (this was a double-walled rim) worked their way thru the tape. The "eureka moment" occurred as I looked at the rim in reflected sunlight and saw the tiny burrs. Th problem was over and I completed the rest of the 2100 km tour with no more flats. This year with the same rim I had flats from road debris and goat-head thorns, but not from the rim burrs.
I also used sand paper to try to remove the burrs, but I don't think I got them all.
Tim tape will develop normally recesses at the spoke wells as the pressure in the tube presses down pretty firmly. The issue is how deep those recesses are. A decent rim tape will only make shallow pans and not actually blow down into the well.
Since tour tube shows dimples, I suspect the tape is not resisting the pressure effectively ant might be bad, or simply not designed for this application - some are made for rims that don't have recessed spoke wells.
A quick test will tell you if it's the rim tape or if you should look elsewhere. Press a pencil eraser down onto the tape at a well and see how well it resists the force. It shouldn't press into the well more than about 1/16" or so even with considerable force on the pencil. If it does, replace it with a new rim strip of the right type, or cloth surgical tape, or 2 turns of filament tape (what I use).
01-03-12, 08:41 AM
I was on a 50 mile wine tasting run with a friend this fall and she got a flat about 10 miles in. I carry a spare tube along with a patch kit and just changed the tube as a quick fix didn’t inspect the rim but checked the tire closely for a hole or nail or something and didn’t find anything threw it back on and 20 miles more another flat. Exact same problem and had to patch the tube alongside the road. This time I looked at the rim and the pressure had blown a perfect hole in the rim tape at the spoke hole (double wall rim) I ended up patching the tube and using another patch as a boot over the rim tape and we finished the ride. After seeing all the dents in the rim tape though I deemed it a safety issue and we began to worry about fast downhill’s that made for long grinding uphill’s on the rolling terrain. I would recommend people take a close look at this problem on newer bikes and higher pressures. If they are throwing a cheap rim tape on these bikes to save a few cents, get them changed.
I haven’t tried it yet but was thinking of trying a wrap or two of gorilla tape as an experiment on a high pressure tube. That stuff is the strongest tape I have seen yet. Wondered if anyone had tried it?
01-03-12, 08:48 AM
Velox rim tape is the best you can use.
01-03-12, 09:28 AM
.....I havenít tried it yet but was thinking of trying a wrap or two of gorilla tape as an experiment on a high pressure tube. That stuff is the strongest tape I have seen yet. Wondered if anyone had tried it?
When I made the new tape from an old tube I also used duct tape. Now it is 6 years later and it is still there. It will probably be a bear to remove, but as the saying goes "if it ain't broke, don't fix it" :p
01-04-12, 11:10 PM
xenologer nailed it - that was exactly the problem.
I replaced the rim tape with velox, put the tube in for the 11ty billionth time in 3 days and all is well. Now to do the rear wheel before it's an issue on a ride. Sigh.
Thanks for the various tips, I really haven't ever had problems with rim tape before!
01-05-12, 10:02 PM
Velox rim tape is the best you can use.
I have a few bikes with 20+ year old velox rim tape in them. They're discolored to a golden brown, but still doing the job...,,,,BD
01-06-12, 07:06 AM
Velox rim tape is the best you can use.
+100. There are cheaper alternatives and "make-dos" like strapping tape and duct tape but Velox trumps them all. It's very strong, easy to apply, doesn't shift or slip and lasts the life of the rim.
01-06-12, 12:00 PM
When ever I lace up a new rim, I take a bit of emory cloth and go around the rim once smoothing out any burrs or sharp edges at each spoke hole. After I am done lacing, use a good rim tape like velox or strapping tape with the fibers in a pinch.
01-06-12, 12:24 PM
The inspection and learning Why, is an important part of puncture repair.
align the label on the sidewall with the valve stem, so you can do forensics to find the object in the tire
when you find the hole in the tube.
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