Repeat punctures, possible rim-tape problem

[OnYourRight]

Hello all.

I recently bought a pair of Continental Supersonic lightweight tubes and installed them in a new pair of 23 mm Michelin PRO4 Grip tyres. (This is the first time I’ve run 23 mm tyres in quite a while. They’re predictably too narrow, but these ones certainly have impressive grip and they roll tolerably well.)

However, I’ve now suffered three punctures in maybe 300 km, all on the rear wheel. In each case, the puncture has been a pinhole on the rim side of the tube, and always aligning with a spoke. The latest hole had a 1.5 mm abrasion leading to the pinprick proper.

The rims are the originals on my Dawes Clubman. The spokes don’t appear to be poking through the rim tape, but perhaps the edges of the holes are a little sharp to the touch despite the tape. (Though I wouldn’t have worried if I hadn’t got these punctures.)

I never had a problem with these wheels before, but that might be because I’ve never used them with 23 mm tyres (and accordingly higher pressures) and super-light tubes.

Since I can’t afford not to use the tyres, is the solution a thicker tube, an additional layer of rim tape, or something else entirely?

Thanks.

[axel_knutt]

My rim tapes are made from rubber similar to inner tube material. At 85psi they stretch enough for the tube to split without even touching the spokes.

[JimL]

Are you running your tyres at sufficient pressure (120 psi is normal for 23 mm tyres) assuming the rim tape is in good condition and suitable for high pressure.

[Valbrona]

...assuming the rim tape is .......... suitable for high pressure.

I think there's your problem: rim tape you are using is not rated for high pressures.

[OnYourRight]

Axel_knutt: could you clarify if you’re saying it’s a good or bad thing to use tube rubber? Splitting due to stretching doesn’t sound any better than punctures from hitting the spokes.

My punctures seem to be caused by the edges of the holes in the rim, not the spoke itself. (Is that possible?)

JimL: I’ve been running the rear at about 100 PSI (the front much lower, around 70 PSI). However, I am light, at around 65 kg (145 lb or 10 ¼ stone), and ride lightly over obstacles. All three punctures have been at the rear. They’re not conventional pinch flats.

Valbrona: now you know the pressure I use (around 100 PSI), would you still say that? Seems odd that Dawes would ship a bike with rim tape unsuitable for heavy guys on the original 25 mm tyres.

Any specific rim tape recommendations?

[PT1029]

A photo of the rim tape in the rim might be useful.
Sometimes correctly fitted rim tapes gets moved off centre when fitting the tyre. If the tape is only just wide enough to cover the spoke hole, then you get a gap at the edge of the spoke hole when the tape is nudged off centre. Cure would be a better fitting (width wise) rim tape. Often some insulating tape wrapped round (or bits periodically) can hold the tape in position, but a better tape would be the best cure.
It wouldn't be the fist time a good new bike was let down (along with its tubes) by bad rim tapes. About 18 years ago, the only way we could get Dawes tyres to seat correctly was by replacing the (too wide) rim tapes on all the hybrids that got delivered.
In the late 1990s' 2 customers made it to the south of France on their new Orbit tourers before their tubes punctured due to no rim tapes at all!

[Brucey]

My punctures seem to be caused by the edges of the holes in the rim, not the spoke itself. (Is that possible?)

yes, very much so.

Any specific rim tape recommendations?

Velox is good, and so are some (but not all) hard plastic rim tapes.

cheers

[OnYourRight]

Thanks for all the advice.

I removed the rim tape and discovered that most of the spoke holes in the rim have terrible burrs, with the holes aligned with my three punctures being especially poorly finished. No wonder they felt a bit sharp through the rim tape.

I intend to file off these burrs and apply known good rim tape. If anyone thinks this is a bad idea for any conceivable reason, please chip in!

By the way, I tried the Continental Supersonic tubes not because they were light, but because I thought their thinness might reduce rolling resistance. Probably not worth the hassle, in retrospect.

[OnYourRight]

A photo of the rim tape in the rim might be useful.
Sometimes correctly fitted rim tapes gets moved off centre when fitting the tyre. If the tape is only just wide enough to cover the spoke hole, then you get a gap at the edge of the spoke hole when the tape is nudged off centre.

I didn’t take a photo of the rear, and didn’t even check all 32 holes closely before removing the tape, but looking at the indentations on the old tape I can tell a couple of holes were perilously close to being exposed. Combined with the fairly harsh burrs on some of them and my sensitive Continental Supersonic tubes, this probably caused my punctures.

Although the front didn’t suffer punctures (yet?), I gave it the same treatment. I noticed two things:

• the rim tape was as you described: too narrow and off-centre. The photo below shows the worst example, but three or four holes were slightly exposed
• the spoke holes were better finished than those at the rear, with no significant burrs. Maybe this rim came off a different line

I got some plastic rim tape (or a rim strip, really) from a nearby bike shop, not being able to find Velox locally. It is wider, thicker, and fits the rim bed tightly.

Although thicker and initially sitting a little higher in the bed, the new rim strip didn’t seem to make the tyres significantly harder to fit (though I’ve been getting a lot of practice at fitting them lately, and I’m a little quicker every time!).

[CREPELLO]

Very poor show for a leading bike brand to be fitting rim tapes that are obviously too narrow. They could easily lead to a blowout IMO. Or a rapid deflation at least, as the inner tube expands into the eyelet well. More so with higher pressures.

[OnYourRight]

I agree it’s disappointing.

In partial defence of Dawes, the original heavy-duty Kenda inner tubes withstood this abuse, albeit at slightly lower pressures in 25 mm tyres.

And although the rim tape was too narrow and thus able to move around, I cannot guarantee I didn’t move it myself when replacing tyres. (Though it must also be said the large indentations in the tape at the spoke holes may have located it firmly where it was when it left the factory.)

I did a 30 km spin today with the new rim strips and the thrice-patched Continental not-so-Supersonic tube without issue. Perhaps all’s well that ends well.

[wearwell]

I just had this problem too with new wheels. Thin stick-on rim tape with punctures in both wheels both over a spoke socket. A split where the tube has burst. I thought the first one was chance but the second one, exactly the same, means a fault in the wheels/tape.
Waiting to see what the supplier has to say.

[Brucey]

that looks like schwalbe rim tape you had there. This is about half as thick as Velox. IIRC if the spokes protrude out of the nipples, the nipple/socket edges are sharp, and/or the sockets are shallow, these tapes can split.

It ought to be simple to specify a decent rim tape, but it is a very common failing. On production bikes I think it is viewed as a good place to save money, and it if doesn't work it is the dealer's problem.

cheers

[wearwell]

that looks like schwalbe rim tape you had there. This is about half as thick as Velox. IIRC if the spokes protrude out of the nipples, the nipple/socket edges are sharp, and/or the sockets are shallow, these tapes can split.

It ought to be simple to specify a decent rim tape, but it is a very common failing. On production bikes I think it is viewed as a good place to save money, and it if doesn't work it is the dealer's problem.

cheers

Spokes OK, socket edges sharp and some exposed due to tape not being applied dead central. This seems to be the cause. The tape only overlaps the socket by a mm or so - so I think would fail in time anyway. The glue will go with time/heat/pressure.
yers it's the dealers prob and they are sending me Schwalbe plastic tapes and two new tubes
PS The tapes didn't split but I think the tube caught on the rim of the exposed spoke socket. Lot of pressure there at 100psi or more, plus working loads over bumps.

[wearwell]

Spa said they'd send me replacement tape and tubes but they haven't. They seem to think it's not their fault. But they are wrong. It's the wrong tape and badly applied.

Sharp spoke socket edges exposed:



Tape well over on the other side:



More ditto



Tape right on edge




Even when it's central there is only a tiny glue area holding the tape from the hole. You can see from the wrinkles how it's been stretched into the hole



Result, 2 tubes punctured, 2 spoiled rides, 1 roadside puncture repair (seems years since I last did this but still carry the kit), 1 car rescue, 1 trip to LBS for the proper tape (Veloc) and 2 new tubes.



This thin tape is rubbish. Never had this problem with the rigid plastic type.

C'mon Spa cycles pull your finger out!

PS and the glue is a crap idea - it will fail - soon if there is any water or temperature involved. The velox tape has the advantage of stiffness - the glue just locates it - it is not glue dependent.