Repeated Flat tyres

Usjes

Hi,

My sister's front wheel was flat when she came out from work on Monday. I pumped it up a bit to be able to roll it home an was surprised that it did not go flat on again before getting home. So at home I pumped it up to 60psi (its a hybrid bike) with a tract pump and checked it after 20mins and it was still rock hard so I assumed someone must have let the air out rather than a puncture. So she cycled it to work again next day and again it was flat when she went to go home so this time I went in to her office and actually replaced the tube cheking the inside of the tyre in the process to make sure there was nothing sharp left stuck in it. She cycled it home and to work the following day with no problems but at time to go home it was flat again. I took it home and the tyre was punctured which I patched and checked the inside of the tyre inch-by-inch many times to be sure there was nothing sharp. That was yesterday evening. This morning when she went to go to work it was flat again. So that's two punctures in one tube and two (or potentially one very slow one) in another tube in four days. This seems highly improbable, so I'm wondering if there is anything else I should be looking out for (other than something sharp stuck in the tyre ? I've been fixing punctures for years and never had problems like this.
She's been cycling for over a year without a single puncture and now she's getting flats every day. The only other thing to add is that on Saturday she did a 60Km cycle for charity which is the longest she's ever cycled but I really cant see what you could do to a wheel on a long cycle that would cause repeated flats days later. I'm also wondering if the tract pump might have anything to do with it, I only got it recently so previously tyres I pumped up would have been much softer, but I am only going to 60 psi while the tyre specify max 75 so I assume that this shouldn't be a problem?

Anyone have any ideas?

Thanks

easygoing39

Check to see if a spoke end is coming through the rim tape.Although if this was the case the pncture would always be in the same place.Inflate the tyre to the max psi,75 as you said,higher pressure's resist punctures better.And lastly,is someone punctureing the tyre on the sly at work??

Khannie

This always happens in work? Is some muppet stabbing her tyres perchance?

07Lapierre

Check the Wheel rim for sharp edges. What about the valve?

Beasty

If it's always the front wheel it suggests some foreign object in the tyre, or something in the rim that's protruding into the tyre

One thing you could try is swapping over the tyres between wheels - that could rule out (or in!) the "foreign object in tyre" option

blorg

You generally shouldn't inflate to the max; the max is the max, not a target. Overinflation harshens the ride and actually makes the tyre slightly more vulnerable to punctures from sharp objects.

More important is that you inflate over the min, which you need to do to avoid pinch flats. Pinch flats generally occur soon after you hit something like a pothole and are readily identified by the two-holed "snakebite" pattern of the puncture. As pinches are not caused by a foreign object there is nothing left in the tyre or wheel to repuncture. Your situation does not sound like a pinch flat which is the only type of flat you get from inadequate pressure.

It depends on your sister's weight and the tyre width but 60 would sound closer to right than 75 on a hybrid: Sheldon suggests 60 on the back for 700x37c tyres, for a typical rider.

You likely have something stuck in the tyre you aren't finding, or it could be a rim problem. Concentrate looking where the hole in the tube is and always line up tyre graphics with the valve to make identification easier.

Usjes

Interesting, well at this point I have two different tubes, one of which must have a very slow puncture and the other which I patched yesterday and is flat again today. Yesterday the puncture (singular so not a snake bite) was on the external (tyre facing) surface of the tube. So it will be interesting to see where abouts it is today and where it was on the other tube. Its all very odd. As for someone manually interfering with the tyre, the first three times it was flat when she came out from work to go home but this morning it went flat just as she left to go to work, so unless she has a stalker, it seems unlikely. I suppose I could swap the front and back tubes as suggested but given that I've already used two different tubes I'm not sure this would give me any new information.

Beasty

Usjes wrote: »

I suppose I could swap the front and back tubes as suggested but given that I've already used two different tubes I'm not sure this would give me any new information.

I was suggesting swapping the front and back tyres, not tubes - it should help determine whether it's the tyre that's the problem (ie the back tyre then deflates) or the wheel/rim (ie the front one deflates)

Of course, if neither do, you may be none the wiser, but at least the problem is solved;)

blorg

Suggestion is to swap the tyres, not the tubes. If the puncture moves wheel with the tyre it is a tyre problem; if it stays on the same place, it's a rim problem. Although if the holes are on the outside, it is a tyre problem. You need to examine the tyre very very carefully just around the exact spot where the hole in the tube is- if it is not a pinch flat and you DON'T find the offending object it is virtually guaranteed you will repuncture.

Make sure you put the tyre back on in exactly the same position so you can see if repunctures are in the same location... I've also had situations with thorns where there have been multiple objects in the tyre and got multiple separate punctures from a single altercation with a thorn bush.

Usjes

Ah, yes good idea, I hadn't realised you were suggesting swapping the tyres. Anyway I've inspected the original tube and it does indeed have a very slow puncture (can only be detected under water). It is also on the tyre facing surface same as the one on the other tube I patched yesterday. Odd thing is that it looks to be about the same distance from the valve which would suggest that whatever is causing the problem is on the rim rather than the tyre yet the punctures are on the external surface of the tube furthest from the spokes. I won't have access to the bike until later tonight, but it'll be very interesting to see where the latest puncture is. I'll mark the tyre's orientation relative to the rim this time before removing the tube.

Paralympic Cyclist

Bit of a pain, but pump the tyre up and submerge the front wheel in the bath tub.

If there are bubbles - it might show where the problem is and you can narrow it down from there (if it's in the tyre, the rim, the valve, etc).