DiabloScott

I've been getting punctures on my commuter bike tubes that look like spoke pokes.
-I've got good rim tape on there - not Velox but similar.
-The rim tape looks intact and not deformed or shifted out of position
-There is no spoke poking through the rim tape
-The tube where the poke is, has a bulge deformation that looks like it did poke down into the spoke hole - one of them has two deformations for the same spoke area - like it shifted at some point; only one puncture though.
-The deformations and punctures are near the valve hole.
-The rims are really narrow and I've got 28mm tires on them.
-As my commuter, I do ride it over curbs and such, so an impact could be involved.
-It's happened to the front wheel twice and the rear once in the last few weeks.
-It's never interrupted a ride, it's always been that I notice the flats before starting a new ride.

So I guess the question is, can rim tape actually move and cause this kind of puncture and then move back so it looks like it's OK?
Or is there some other explanation?

noglider 

This has happened to me, and I can't explain it.

DiabloScott

Once it was both wheels at the same time - fine one evening on the ride home and flat the next morning. I thought my wife was pranking me and just let the air out because 1) she MIGHT have been mad about something and 2) two garage flats at the same time just never happens.

fietsbob

Single wall Rear of my Brompton did this, It had a fused loop plastic rim strip,
so I cut a section of narrow rubber rim strip , joined around the valve hole with duct tape,
put the plastic rim strip back on over it and it was fine after that..

90 psi 349-35 tires..

ThermionicScott 

Like this? Weinmann LP18 Geometry Causes Flats?

We never did figure that one out.

79pmooney

Do the spokes protrude above the nipples? I'd eliminate that first (bolt cutters then a file, PIA I know) then consider going to Velox tape.

It's been decades since I used non-box rims but they were always with Velox and flush spokes and I don't recall ever seeing your issues.

Ben

DiabloScott

YES exactly!!! Thanks. Weinmann DP18s vs LP18s

Very much like the photos in that thread; what the heck is that? Seems like the most likely fix is to put on a second layer of rim tape.

CliffordK

I had about 72 of them happen on Mom's bike.

MomsTape1.jpg
MomsTape2.jpg

It actually makes some sense that you'd get hit by two hitting at once. You probably recently re-inflated both tires to a fairly high pressure.

I've heard that the rubber rim tape is bad for double walled rims as it tends to sink into the holes. I have some non-reinforced plastic tape that did that too, but it was permanently deformed.

I've moved away from the velox cloth tape, too thick. One bike, I put in veloplugs, then covered them with plain electrical tape (covered edges with off-center rims). So far, so good.

Papa Tom

I've always assumed a wheel flexes when you hit a bump or jump a curb. If this is true, then that would partially explain why your spoke heads are pushing into your tubes. Why this isn't a more common problem is a big question, though.

CliffordK

The spokes should stop flush with the top of the nipples more or less.

With single walled rims, one can file off the ends of long spokes.

With double walled rims, the spokes should be recessed a bit.

Any bump strong enough to bend a rim, say 1/4" likely is enough to do permanent damage to the rim. Keep in mind, the tire should take up most of the transient flex of the rim beyond simply the rider's static weight.

Tape should be strong enough to take some nipple/spoke bumps from below.

I've seen pocks like @DiabloScott posted. One of the issues is that the rim wall holds part of the tube, and a very small area of the tube expands to the point where it is at risk of splitting without actually having anything puncture it.

Michelin is now intentionally making bumpy tubes with the idea that the bumps actually add compression to the tube rubber, and tend to hold holes closed.



I can't say if they'd help in @DiabloScott's situation, unless a bump happens to be close to the spoke pocket.

DiabloScott

Are you saying the tube kind of sticks to the rim and inflates unevenly? If that's the case, more rim tape won't help. I usually use baby powder in my tires, maybe I didn't on this more recent install... that should help I think. I'm going to try that.

Except there definitely IS a puncture, right in the middle of one of the pimples.

BTW, those weren't my photos, but the look is identical.

CliffordK

No, well, in part.

One has dimples in the rim tape.

I presume that as the tube inflates, it inflates up to flat against the rim tape, which then will hold the tube more or less in a fixed position.

Then the tube continues to expand into the dimples, and thus, only a small portion of the tube is expanding at that point, and eventually gets thin enough to split.

However, the rim tape either has to have dimples in it, or perhaps is flexible enough to allow that to happen.

Somewhere I have some rim tape with about 3/16" dimples/pockets at each spoke hole, and a tube that has popped because of that. It was kind of nice. The dimples held the rim tape in place quite well, but the popped tube wasn't good, and it is very hard to patch.

I have some errands to do this afternoon, then I'll browse around this evening and see what I can find.

HillRider

I expect it's not enough like Velox. I recommend you get the real thing. I've used Velox exclusively and never has the problem you describe.

79pmooney

Hmmm, those bulges are 1) outward and 2) in pairs an inch apart. This says to me that there is a set of holes somewhere on your wheel or tires that match. I'd blow up one of those tubes slightly, put in in the tire and see if there is anything suspicious at the bulges in either the tire or rim. (Or the same distance from the valve in the other direction.) Front and rear doing the same thing? Weird.

Kontact

They aren't an inch apart. They appear to be pretty much the same distance as the diameter of one spoke hole.

Looking at the other thread, I wonder if the grooves the run in the bottom center of the Weineman rims act in concert with the holes to make small punctures in the cloth rim tape. After those spots of weakened sufficiently the tube is going to force them open until they allow the tubes down into those spots where they burst. This would explain why the tube bulges are oriented in the same direction as those grooves.

Once it starts happening, you'd have to replace your rim tape or at least off set it by half a spoke hole. You should be able to find these weak spots in the tape with a dull pencil.

cny-bikeman

That is a stumper as far as spacing of the dimples. The distortions are greater than the width of the hole in the rim above the spoke ends, but much smaller than the distance between holes. They are not right next to the valve stem, and presumably not at the seam. Although I can't explain the spacing I do know that it is a common problem to get such dimple failures when one combines a very narrow rim with a wide tire, and that the use of thicker/double rim tape, in order to minimize stretching of the tube into the narrow inner section of the rim, can help. However it can also make mounting more difficult. It's simply poor practice to combine a narrow rim with wide tires, especially as there is no advantage to doing so.

Kontact

Since when has it ever been a problem to use narrow rims with wide tires? The first lightweight MTB rims were narrow road rims rolled down, and we're only talking 28c.

As far as the spacing goes, the tubes in the picture are over an inch wide - those punctures are less than half the width of the tire. Spoke rim holes are around 3/8" - why are you saying the holes are spaced wider than the diameter of the spoke holes?

dsbrantjr

Continental has an HP series of rim strips which are rated to 220psi that you could try: https://blobs.continental-tires.com/...ip-en-data.pdf