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Spokes or Nipples Causing Flats?

Old 03-03-18, 10:35 AM
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408mopar
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Spokes or Nipples Causing Flats?

My 77 Motobecane Super Mirage has Gatorskin tires (27 x 1 1/4) that can be inflated to 102#. If I inflate them that high, after a few days, I get a hole in the tube right at one of the spoke and nipples. If I keep them at 85#, they seem to be okay. I have 2 rim strips on the rear, and 3 on the front to try and prevent the problem. There is never any obvious damage to the rim strip(s).

The front rim has Weinmann 2115 on it., and the rear has just Weinmann on it. Neither is original to the bike, and are different rims with the same problem.

It's frustrating because I commute with this bike and bought Gatorskins to avoid flats while I'm going to work, only to have a different problem causing flats. I didn't ride the bike much before the tire change, and didn't have the problem with whatever tires I've had on it.

Other than the obvious solution of keeping them at 85#, what do I look for? Maybe 85 is the max for this set-up?
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Old 03-03-18, 11:08 AM
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Are the rims single walled or double walled?

Are the rims hooked to hold the tires in place?

Do the spokes stick up past the nipples?
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Old 03-03-18, 11:16 AM
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That 102# rating is the max inflation for the tire only. I personally never feel the need to go over 70# on that size tire. And I have had flats exactly as described and they have been directly attributed to rim strip and spoke nipple issues.
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Old 03-03-18, 11:20 AM
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I have a single wall rear rim on my folding bike ..when I had that sort of issue

I doubled the rim tape , rubber under a fused loop plastic tape that was already there..

Velox cotton tap over rubber would do nicely,

there were no protruding spokes .. if there are, file or dremel off the excess..





..
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Old 03-03-18, 03:55 PM
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Are you sure it is a puncture from the rim side, or is it possible the tubes are splitting at the seam?
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Old 03-03-18, 08:24 PM
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Originally Posted by CliffordK View Post
Are the rims single walled or double walled?

Are the rims hooked to hold the tires in place?

Do the spokes stick up past the nipples?
I think they are single walled. (I'd have to look, I have double, but I'm pretty sure they're on another bike.)
Not hooked. If I understand what you mean.
No, nipples are smooth, spokes don't stick up.
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Old 03-03-18, 08:26 PM
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Originally Posted by dh024 View Post
Are you sure it is a puncture from the rim side, or is it possible the tubes are splitting at the seam?
I'm sure. The nipple leaves an impression, and the hole is always in the center of it.
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Old 03-03-18, 10:06 PM
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The nipple leaves an impression through two or three layers of rim tape? wow
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Old 03-03-18, 10:13 PM
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Have you pulled off all the rim tape and looked at the nipples? Are there any threads sticking out past the tops of the nipples? If so, there is you problem. Those sharp threads will go through a lot of fabric. Take a file and file all the protruding spokes down to the tops of the nipples. With one good rim strip, you shouldn'[t have issues.

(A '77 Motobecane is highly unlikely to have a double walled rim. That was the dark ages for clincher rims.)

Edit: I didn't read as far as your post #6. Is your pressure gauge right?

Ben
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Old 03-04-18, 01:10 AM
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Originally Posted by 408mopar View Post
I'm sure. The nipple leaves an impression, and the hole is always in the center of it.
I had failures looking like that too on a batch of Geax tubes.
A tube autopsy revealed a thin streak in the rubber, causing local overstretch and a dimpled appearence. But dimple spacing didnít really match nipple spacing, which what set me wondering in the first place.
Thereís another theory that deep/narrow rims together with rapid inflation also can cause local overstretch and subsequent flats.
Talc, and a slow/paused inflation - to allow the tube to creep and equalize the stretch - is supposed to help too.
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Old 03-04-18, 12:59 PM
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If you think you have spokes protruding through your rim tape and into your tubes, something like this might help prevent the punctures, perhaps even installed under the rim tape:

https://www.spokeservice.ca/shop/pro...gs#description

The other option might be to add a thin layer of window foam inside the rim and secured with gorilla tape, which is how a lot of ghetto tubeless setups are installed on mountain bikes (lots of Google hits if you search on: window foam tubeless). I might try this if I were desperate, especially if I didn't want to file down protruding spokes.
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Old 03-04-18, 01:37 PM
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Originally Posted by dh024 View Post
If you think you have spokes protruding through your rim tape and into your tubes, something like this might help prevent the punctures...
Veloplugs don't work for single-walled rims. There's no hole to stick the plugs into.

@408mopar : What kind of rim tape/strips are you using? Is it wide enough, or put another way, does it sufficiently cover each spoke & nipple (and then some) so that if it squirms a little bit, you don't have an exposed edge? Do any of your spokes protrude past the nipple, indicating that the spoke may be too long?
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Old 03-04-18, 05:32 PM
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Do the dimples look like this? If so, visit this thread. It wasn't the spokes/nipples that were causing the punctures.

Weinmann LP18 Geometry Causes Flats?

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Old 03-04-18, 07:02 PM
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Originally Posted by dh024 View Post
The nipple leaves an impression through two or three layers of rim tape? wow
Two, anyhow. I just added a 3rd to the front wheel.
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Old 03-04-18, 07:05 PM
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Originally Posted by 79pmooney View Post
Have you pulled off all the rim tape and looked at the nipples? Are there any threads sticking out past the tops of the nipples? If so, there is you problem. Those sharp threads will go through a lot of fabric. Take a file and file all the protruding spokes down to the tops of the nipples. With one good rim strip, you shouldn'[t have issues.

(A '77 Motobecane is highly unlikely to have a double walled rim. That was the dark ages for clincher rims.)

Edit: I didn't read as far as your post #6. Is your pressure gauge right?

Ben
I've used different gauges.
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Old 03-04-18, 07:17 PM
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Originally Posted by 79pmooney View Post
Have you pulled off all the rim tape and looked at the nipples? Are there any threads sticking out past the tops of the nipples? If so, there is you problem. Those sharp threads will go through a lot of fabric. Take a file and file all the protruding spokes down to the tops of the nipples. With one good rim strip, you shouldn't have issues.
+1 to this.
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Old 03-04-18, 07:21 PM
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Originally Posted by SquidPuppet View Post
Do the dimples look like this? If so, visit this thread. It wasn't the spokes/nipples that were causing the punctures.
yes, except there is only one "pimple", not two.

Seems my best bet is to keep the pressure lower.

I appreciate all of the advice.
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Old 03-05-18, 09:53 AM
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Originally Posted by 408mopar View Post
yes, except there is only one "pimple", not two.

Seems my best bet is to keep the pressure lower.

I appreciate all of the advice.
If you have "pimples" like the ones in SquidPuppet's pictures, that a classic rim strip problem. It's also a classic double walled rim problem. Your rim strip is too weak to hold the pressure and is allowing the tube to push through the rim strip and expand into the chamber of the second wall. There's sharp edges on the rim that will cut the tube or the tube can't expand that far and the tube pops.

Change your rim strip to a cloth strip. Velox is about the best around in my opinion. Even if you have single wall rims, Velox would help with any chafing that might cause flats too.
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Old 03-05-18, 10:04 AM
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Originally Posted by cyccommute View Post
If you have "pimples" like the ones in SquidPuppet's pictures, that a classic rim strip problem.
Nope. Visit that thread that I posted. It's a weird stretching phenomenon. The suspected culprit is a very narrow rim with an odd shaped channel. Those pimples do NOT line up with any spoke holes in the rim.
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