Flat tyre and not sure why

Alibran

This is a bit of a long story, so please bear with me ....

A week or so ago, I pumped up my bike's tyres before going for an easy ride. Two days later, I came to ride it and the front tyre was completely flat. I wasn't all that surprised because I knew the valve on it was dodgy, and I figured it had finally given up. I didn't ride it that day because I was in a hurry to get out before it got hot, so went running instead.

I'd been meaning to put new tyres on the bike anyway, so I ordered a couple of Rubino Pros and some more tubes, and waited until they came to do anything about it.

On Friday, I replaced both tyres and tubes, pumped them up nice and hard and left the bike overnight. Yesterday, I got the bike out, pressed my thumbs against the tyres as I usually do, to make sure I can't feel any give, then rode about 15 miles.

I noticed the same intermittent squeak that I hadn't been able to pinpoint on my previous ride, and kept stopping to try and figure it out. About half way, I got it. One of the fixings on the front mudguard (where the "spokes" that attach it to the end of the fork join the mudguard itself) was scuffing the tyre slightly on and off. It was most noticeable on bumpy roads. I couldn't stop it out on the road, but figured it wasn't doing any harm - after all, I'd just put puncture resistant tyres on the bike - and finished my ride.

This morning, I went to the bike and found the brand new front tyre (with brand new tube) was completely flat - and I really do mean flat as a pancake, no air came out at all when I opened the valve. I took the wheel off the bike and examined the tyre carefully, but it just looks like a brand new tyre with a bit of dirt on it. I put it back on and pumped it up again - right up to 100 psi with no sound of escaping air. It's now sat in the garage, and I'm very puzzled.

Could the scuffing mudguard cause this? Any other suggestions? I suppose there could be something between the wheel and the tube that I haven't noticed, but I examined the old tube that I took out on Friday, and couldn't find any damage (the old tyre was all cut up, but I knew that, and that was why I was replacing it, but I'd never had a puncture using that tyre).

What I'm finding odd is that it waits until after I've finished riding it and it's sat in the garage to go flat, but it doesn't go flat if I haven't ridden it and it's sat in the garage!

loveaduck

Long time ago (many bikes ago) I had problem flats when ever i rode this BSO ( made from pure evil), it turned out that i had really cheap rim tape and dodgey rim walls.

Headhuunter

If the "scuffing" sound and the point at which the mudguard is touch the tyre hasn't produced noticeable wear or poked a hole through then it must be down to the rim tape or the rims, or some bit of grit or something that has got lodged somewhere under the tape or rim... It's the only thing left that it could be. I would the tyres and tubes off and carefully check the rim tape and rims, if you want to be really certain, replace the rim tape altogether....

Alibran

OK, thanks. That's what I was leaning towards, since the scuffing mudguard doesn't seem to have caused any damage at all.

A couple of questions ....

If it turns out to be a problem with the rims themselves (presumably the sides where they're not covered by tape), is new wheels my best/only option?

Bearing in mind that I don't have a local bike shop nearby, and it will take a few days for new rim tape to come from Wiggle, if I do find the rim tape is damaged and something's poking through, is a plaster a viable temporary measure so I can ride it?

(I'm a real amateur as far as bike maintenance is concerned. I know how to change tyres myself, but anything beyond that it always used to go to the bike shop to be done, so please excuse the stupid questions.)

desweller

Firstly, you need to locate the source of the leak. Obviously, if it's on the outside of the tube it's not going to be rim tape. Take the tube out, put some air in it and run it through a bowl of water to see where the air's coming out.

It's also a good idea to, when refitting the tyre, to line the manufacturer logo up with the valve so you can match the position of any leak you find in the tube up with the tyre.

black20vt

As I read it you are getting flat tire in your garage, you can pump it up and ride, but when you put it back in the garage it goes flat.

Has anyone else got access to the garage?
Are they letting the tire down when you are not around?

Alibran

I did think about that, but my partner has assured me she hasn't touched my bike (which I didn't expect her to have done), we don't have kids, and I don't think the cats have that skill!

Anyway, I've just taken the tyre off, examined the rim and tape carefully, and couldn't find anything except for a few slightly catchy bits right round the edge of the rim, but I'm sure the tyre will be between those and the tube.

I still couldn't hear any hissing from the tube, so put it in water, and immediately found the leak. It's very, very slow, and coming from the outside of the tube, right on the seam. This is a bit of a weird coincidence, but I'm now assuming this is a faulty tube that was strong enough to hold together at 100psi, but couldn't take the extra weight of me getting on the bike, and this caused a very small split, and the air leaked out over the next few hours. (The tyre did go soft eventually after I pumped it up this morning, but didn't ride it.)

Is this a reasonable assumption to make?

(For anyone who hasn't read the whole first post, I put a brand new tyre on with this tube, so it wasn't something stuck in the tyre from a previous puncture.)

desweller

The puncture will be due to road debris poking through the tyre, e.g. glass or a sharp stone.

As the tube is pressed against the tyre with a lot of force, you can sometimes find that that tube seals against the tyre well enough to defeat slow punctures, but once you start riding, the tube slides against the tyre and the seal is broken, causing your slow leak.

Patch the hole and it should be fine. Don't forget to check the tyre carefully for anything that might have caused the puncture. Remember that sometimes things get lodged in the tyre, but only penetrate through to the tube under load, so you should carefully examine both sides of the tyre.

Alibran

DesWeller, it's a brand new, puncture resistant tyre without a mark on it that I can see under the bright fluorescent light in the garage, and a brand new tube, which has a small leak right on the seam. Doesn't that sound more like a faulty tube than a puncture?

Edited to add: I decided to check the tube from the original flat, and the air came hissing out of the valve as soon as I took the pump off, so that wasn't caused by a puncture. The valve must have just failed while it was sitting there in the garage.

Alibran

cadseen wrote:

Hopefuly you did not pinch the innertube when fitting it to give it a slow puncture.
Try not to use tyre levers to fit tyres.

I don't think so, but anything's possible. I'm very careful to make sure it isn't trapped before I pump up the tyre after an experience with one that burst and nearly gave me a heart attack, and nearly put my neighbour's pregnant cat into premature labour!

There's no way I could have managed these tyres without levers, although I do most of it with my fingers, until it gets too tight to get my fingers under. I just try to be careful, and use what should be decent quality tubes.

desweller

<shrug> I think a faulty tube is the less likely of the two scenarios, based on how often I encounter a badly extruded tube (extremely infrequently, in fact I can't remember it happening) versus how often I get punctures on new tyres (enough for it not to be a surprise). Although you've bought a so-called puncture resistant tyre, that doesn't mean you're immune to them. You might easily get one early doors and then not get another for 3000 miles.

It's your bike, however, so replace the tube if it makes you feel comfortable! I'd patch it, check the tyre and stick it back in, myself.

Alibran

I did examine the tyre carefully, as I said, and couldn't find anything that might have punctured the tube. I'm not sure what I can do more than that, other than put a new tube in and hope it happened because the old tube was faulty.

sungod

tbh i think desweller is spot on

what "puncture resistant" means is, it'll puncture

the tube won't split inside the tyre, it's punctured, punctures along the seam are common as this is in line with the contact point with the road where highest force is applied to any sharp bits

also sounds like your tyre has a removable valve core, if it isn't tight and you use a screw on pump, or sometimes even just a push-on that wiggles as you pump, it can come loose and whoosh no air, tyres fresh from the factory do not usually have the cores tight enough, always tighten them as much as possible

andrewjoseph

Yes, but this is a brand new, unused tyre, and new inner tube.

My best guess is the use of tyre lever may have pinched the new inner tube on fitting.

Alibran

Well, I guess we'll never know what actually caused it.

The tyre is back on with another new tube. I scooted across the garage on it with all my weight over the offending wheel and, four hours later, the tyre is still nice and hard, so I'm keeping my fingers crossed. If it's still up in the morning, I'll take it out for a ride and see how I go.

What's a removable valve core, by the way? The new tubes are the standard conti road tubes. The original one was a nasty, cheap thing that I bought in an emergency, and was never meant to be used long term (funny how these temporary things become semi-permanent!)