Phantom flat tyre

insomnium75

Hello,

I recently had a slow puncture on the rear tyre of my Boardman CX Team. Nothing strange there I guess, but when I came to repair the puncture I couldn't find a cause for the flat.

I checked the inner tube in a sink full of water - no holes found or bubbles anywhere on the tube or from the valve.

I turned the tyre inside out (a few months old Schwalbe Marathon Plus 28mm) and checked for embedded debris several times around the tyre.
Again the inside of the tyre looks brand new with no visible debris or scarring, and there was no embedded debris in the tread of the outer shell either.
Next I checked the rim - again no spokes sticking though or potential problems I could see here either.

I replaced the inner tube with a new one and put it down to being "one of those things" and thought nothing more of it.

A couple of weeks of commuting later, and the tyre was still inflated fully.

I put the bike away on Friday evening, and came back to it today (no commuting so far this week because of the snow) and the tyre was completely flat again.

I haven't stripped the wheel yet and investigated, but given the infrequency in which I have encountered punctures on Marathon Plus' in the past, I'm not expecting to find any issues with the hardware again.

Can anyone assist in trying to identify what the issue might be here, or suggest any other steps I haven't tried to try and find a cause for the flat tyre?

Many Thanks

crankycrank

Take a bright torch and check inner and outer of the tyre again. Occasionally you get tiny little wires, thorns etc. that are very hard to spot and can take awhile to work their way through a tube.

homers_double

Is the inner part of the valve in properly? I went through two brand new tubes before realizing they were all loose, must have been the same batch as the third one revealed itself and I just nipped it up.

milemuncher1

homers double wrote:

Is the inner part of the valve in properly? I went through two brand new tubes before realizing they were all loose, must have been the same batch as the third one revealed itself and I just nipped it up.

This is a good shout. I try to use one piece valves wherever possible, but I have found loose cores to be an issue in the past. A small sized spoke key is useful for tightening up the cores on 2 piece valves. If it isn’t a loose core, check the rim tape carefully, as well as all of the wheel, and look for any issues with the spokes, and the holes.

insomnium75

Thanks for the suggestions folks.

homers double wrote:
Is the inner part of the valve in properly? I went through two brand new tubes before realizing they were all loose, must have been the same batch as the third one revealed itself and I just nipped it up.

I did check the inner part of the of the valve a few times when I discovered the initial flat a few weeks ago. It was screwed in tight.

What I did notice prior to the initial flat occurring with that tube, was that when I took the dust cap off sometimes to put air in the tyre, sometimes the inner part of the valve would come away with the cap, deflating the tyre immediately.
The tubes I use are Conti Race 28's. I bought a pack of 5 a while ago online - maybe there is a fault with the batch I bought as the tube I have in currently is also from this batch.

cooldad

Tighten up the valve core. There's a little tool to do it, or gently with some long nose pliers.

insomnium75

OK,

I'll need to have a look at getting one of the valve tools then I guess moving forward.

I haven't checked the valve yet to see how tight or indeed loose it is, but I'm guessing that it would make sense that
there could potentially have been a gradual leak of air if the valve core wasn't super tight, given that the tyre had 80 - 95 psi of air in it.

keef66

I only use the dust caps on spare tubes in my saddlebag to stop the valve wearing a hole on the tube. Once on the bike the cap goes in the bin. Valve core can't have been very tight if it came out with the valve cap.

I now tighten up any removable cores with a tiny adjustable spanner before use, having had these issues before with Conti tubes. One core shot past my ear when I took the pump off it. Another started leaking during a winter ride. I'd just reached the stage of losing the feeling in my fingers and it was starting to snow. I didn't have anything with which I could tighten it properly, so I just pumped it up between sprints back home.

When you were looking for bubbles in the sink did you include the valve without the pump attached??

insomnium75

When you were looking for bubbles in the sink did you include the valve without the pump attached??

I put a small amount of air in the tube, detached the pump an put the tube in the water - checking all the way around tube including the valve, yes.

The Rookie

With slow (very slow) punctures you can need more than a little bit of air for it to leek (visibly).....

I also had a tube where the tube had started to pull away from the valve, no leak at all at lower pressures unless I pulled at it.

svetty

The Rookie wrote:

I also had a tube where the tube had started to pull away from the valve, no leak at all at lower pressures unless I pulled at it.

^ this. The valve/tube interface can be subjected to traction during pumping leading to leaks over time which can be a bit 'ball valve' in character resulting in intermittent air loss.

Another other issue might be migrating rim tape leading to the tube getting small holes from the spoke holes - although these are usually apparent when using water testing.

bbrap

Insomnium75 wrote:

OK,

I'll need to have a look at getting one of the valve tools then I guess moving forward.

I haven't checked the valve yet to see how tight or indeed loose it is, but I'm guessing that it would make sense that
there could potentially have been a gradual leak of air if the valve core wasn't super tight, given that the tyre had 80 - 95 psi of air in it.

If you drive a car and have one of the old style pencil tyre pressure gauges they often have the tool screwed into the end of the bit that moves in and out to indicate pressure.

battaglin

Insomnium75 wrote:

Thanks for the suggestions folks.

homers double wrote:
Is the inner part of the valve in properly? I went through two brand new tubes before realizing they were all loose, must have been the same batch as the third one revealed itself and I just nipped it up.

I did check the inner part of the of the valve a few times when I discovered the initial flat a few weeks ago. It was screwed in tight.

What I did notice prior to the initial flat occurring with that tube, was that when I took the dust cap off sometimes to put air in the tyre, sometimes the inner part of the valve would come away with the cap, deflating the tyre immediately.
The tubes I use are Conti Race 28's. I bought a pack of 5 a while ago online - maybe there is a fault with the batch I bought as the tube I have in currently is also from this batch.

Conti tubes have removable valve cores. I discovered this to my cost once on a very cold Winter ride when trying to unscrew my race rocket pump after pumping up a fixed puncture. The pump just kept removing the core and I was left stranded. Of course, the same thing doesn't happen with the lever attachment on the track pump at home, so I hadn't even realised the valves were removable until it was too late.

For this reason, and because I've no intention of replacing my race rocket pump...I now never ever buy Conti tubes. I'd suggest giving away the five tubes you have and buying some decent tubes instead ;-)

trivial_poursuivant

Continental inner tubes are a swine for having loose valve cores on them from new. Not sure if it’s so they are easier to put an extended valve in or something but I’ve never had issues with other brands like Conti. Especially annoying if you get a puncture and when you go to pump up the new tube with a pump that threads on it unscrews the valve when your done!!! Schwalbe and Vittoria never give me issues.