*p word* leak on tubes x 8!

[Majorbloodnok]

Mate of mine is suffering from P issues, always on the same point of tube...see below pic.  He's been through 8 Conti tubed,.  Thought it was a problem batch so switched to another brand and same issue.  He has rotated tyre to ensure he isn't missing something embedded in tyre wall but still suffering.  He's running at 110 psi.  Gets the ride done, but always finds the tyre proper flat the next day.... anyone seen this before?

https://flic.kr/p/28yy92j

Many thanks

Stu

[Brucey]

it looks to me as if (for some reason) the inner tube is perhaps creased near the valve, and that the folds in the tube are deformed/rubbed enough during the ride that the tube springs a leak.

 An analogy is that (say) paper is flexible but if it is folded repeatedly at the same point it will fail.


The reason I think this may be happening is that there are signs of a polished area either side of the valve (although this might be where an attempt has been made to fit a patch...?); anyway, if these parts have been rubbing against one another (as seems likely, they have the same shape) then there is probably a crease nearby.

A possible reason for this is that the tubes are not the right ones for the tyre/rim being used. For example if a (cheaper) 700C tube is used in a 650B tyre, or a wider/narrower tube is fitted than is ideal, I can see this sort of thing being quite likely to happen. It may work as a 'get you home' but for regular use it isn't such  a great idea.

If the tube is too narrow, it will most likely fail where it is least stretchy, and this is often near the valve; the valve region can't move and of course the remaining part of the tube is strained to bursting point.

Another possibility is that the tube is the right size but is routinely being installed without any talc, and in a weird way that creases it somehow.

Anyway, not a bad idea to read the tyre size designation carefully and compare it with the tubes, and to make sure that the tube is being installed in a sensible way.

cheers

[Feanor]

Have you watched him fitting the tube?
One thing that's common to all the failures is the person doing the fitting.

For example, I always pump them up with a couple of pump-strokes to give them some shape before installing them. If you attempt to install them totally flat as-bought, they can sit not-quite-right.

[Torslanda]

Especially if he is using a tyre lever for the last bit...

[Majorbloodnok]

Thanks all...some good points.  Most I think we have covered...I agree that I think it's him though!  I haven't witnessed him fitting but he talked through and all sounds fine. 

He putting two pumps in for a little shape before fitting.

The tubes a Conti (8 of!!) So good tube.  He has also tried Micheline with same results.  All on rear drive side... actually I think one was front but a one off.

All new tubes with nothing patched.

He has rotated the tyre to ensure he hasn't missed a foreign body - my general view is that this is the cause...but he says can't be that unlucky.. which is true if he has genuinely repositioned tyre.

I wondered if he could be doing something wrong ref valve....like unscrewing too much or over tightening.

But it's always on the reinforced patch opposite the valve.

Weird

[Majorbloodnok]

Sorry about some of that spelling and grammar ^^^

[hatler]

Daft question. Is the hole on the outside, inside, or side of the tube ?

[Majorbloodnok]

Outside, but right on the seam where the reinforcement is, opposite side of the valve.  See the arrow on his picture.

[Brucey]

what about the sizes marked on the tube and the tyre?

cheers

[Majorbloodnok]

what about the sizes marked on the tube and the tyre?

cheers

I think this is one to double check to be honest.... I'm sure they're compatible as he has Conti 4000s. And tubes are in the correct size range I think but definitely worth checking.

[Phil W]

Do he push the vallve up, and go round the entire rim to ensure no trapped inner tube before inflating? Is the failure always on the side where he fits the second tyre bead last?

[rogerzilla]

Oil in track pump?  Some oils eat butyl tubes fast.  This is why I don't use Velox rim tape on SA hubbed wheels - oil that runs down the spokes soaks into the Velox and the tube gets perforated.  Impermeable rim tape solves the problem.

Oil in the air would naturally collect opposite the valve.

[Majorbloodnok]

Definitely worth a look.

Thanks for taking the time to reply

 

[mzjo]

How deep is the rim? If the rim is relatively deep and the tube is slightly off to one side it could be pulling the valve against the tube ( the valve will be pulled straight by the rim but the rest of the tube won't necessarily follow, giving the creasing talked about by Brucey). It wouldn't need to be a colossal aero rim for this to happen. Solutions would be talc on the tube, rotating the tyre slightly to align the valve correctly with the valve hole before fitting the second bead and taking care generally.

I have had repeated punctures due to a rim joint that was too open but they all happen on the inside of the tube, not the case here.

[Brucey]

FWIW if the valve reinforcement is trapped beneath the tyre beads (because the valve wasn't prodded upwards before the tyre was inflated) the tube can be pinched local to the valve.

 This often/usually results in things that look a bit like pinch flats in the trapped region.

 However it occurs to me that if the tyre is not a super-tight fit on the rim, the tube could be trapped but not be pinched badly enough to puncture just there. Also, it will still be way too stretched just above the valve, and this could cause the punctures that are seen, even if the tube is nominally the correct size.

Could this be a solution to the mystery?


cheers

[Majorbloodnok]

FWIW if the valve reinforcement is trapped beneath the tyre beads (because the valve wasn't prodded upwards before the tyre was inflated) the tube can be pinched local to the valve.

 This often/usually results in things that look a bit like pinch flats in the trapped region.

 However it occurs to me that if the tyre is not a super-tight fit on the rim, the tube could be trapped but not be pinched badly enough to puncture just there. Also, it will still be way too stretched just above the valve, and this could cause the punctures that are seen, even if the tube is nominally the correct size.

Could this be a solution to the mystery?


cheers

Now then! This sounds very feasible.  I haven't had chance to inspect myself, but hopefully will later in the week.

Thanks everyone

Stu