Tube punctures on inside - what's the problem?

[ignatius986]

Hi all,

I'm getting pretty exasperated by a recurring problem on the back wheel/tyre of my road bike.

I am not much of an expert on technical stuff, but this problem has not been solved in two bike shop visits.

The problem is I keep getting blowouts on my back tyre after inflation to a high - but not unreasonable - pressure. I am going for 90-100psi on a tyre that has a range of 85 to 120psi.

These blowouts seem to occur when the bike is stationary. Most recently, I'd pumped up the back tyre after going for a 20mile ride the day before. I had moved on to the front tyre (which, touch wood, is fine) when the back suddenly started hissing and rapidly lost pressure. [This is basically a repeat of what has happened twice before.]

I should add that I have had new rim tape fitted and a new tube fitted two days ago (because of an earlier 'blowout'). I rode without any problem after this, until I pumped the tyre today (should have just left it alone at 60psi!).

I patched the tyre and pumped it up again this evening, however I got to about 60psi and then the tube burst - this time in another place but again on the inside of the tube.

My tape seems to be pretty good.

The tyre has problems in its seating - i.e. it is difficult to get it sitting on the rim properly, although I can make it sit fairly well. I am thinking that a new tyre may be the simplest solution.

Does anyone know if blowouts are consistent with a tyre sitting slightly out of the rim?

Also, why would this mean that the tube always ruptures on the rim side?

Maybe this is all obvious, but it'd be nice if anyone fancies offering some advice.

Sorry if this is in the wrong forum - I think it is the correct one though, right?

My tyre is a 700 x 23 Schwalbe Lugano , and the tube is the correct fit (18-25).

My rim is (I think) an Alexrims RP15F (at least, that's what the sticker says)

I don't mind buying a new tyre (I've already spent a small fortune on tubes that last five minutes), but am worried that it won't actually resolve the issue.


Thanks in advance for any help anyone can offer - and apologies for my first post being a 'help me' one, maybe other people will be facing a similar problem though, and replies will be useful to many!

PS. I was going to add pictures to this post, but then I thought that, with the crap resolution on my camera phone, it wouldn't actually add much info. I can add one, or give any other info that I have missed out though - just ask!

Cheers,

[Vorpal]

If the tyre isn't seating correctly, it could be pinching the tube. You may also have something stuck inside the tyre that is causing the problem. When you remove the tube, what does the puncture look like? Where is it? Is it a small slit or cut? A pin hole? Hve you checked the tyre for small protusions, foreign objects, etc. (don't cut yourself on a piece of stuck glass, though!). If there is something wrong with the tyre, or something stuck in it, a new tyre will fix the problem.

I'd say it can't hurt to spend the money on a new tyre. If it does work, problem solved, if it doesn't, you have a spare tyre. However, if you aren't certain, try a different bike shop. If the bike shop couldn't sort it, I wouldn't have much confidence in them. Say approximately where you'd like to find a new shop, and maybe someone on here can recommend one?

[nez]

Say approximately where you'd like to find a new shop, and maybe someone on here can recommend one?

I'd like one at the end of our road.

(sorry - only excuse is I fell off my bike today and have addled my head)

[cycleruk]

Swap the tires from front to back and visa-versa.
Put the tyre "logo" next to the valve so that you can locate where the puncture matches the tire section. This helps if it's there in something in the tire.
If the tire is too big then perhaps the tube is squeezing the bead off and trapping itself between rim and bead.?

[ILikesToCycle]

I would have suggested rim tape if you didn't mention you already had some. I'd save yourself some time and pain and go with cycleruk's suggestion. It will be one of the two things he's suggested and my money would normally be on some tiny sharp object that's very hard to see inside the tyre, however given its happening to you when you're stationary it sounds more like its something to do with the tyre not seating on the rim. Sat in one place you're probably emphasizing the moment off the bead.

In the long run a tyre will be more cost-effective too

[Tasker]

I had the same problem too. In my case it was simply too high a pressure.

Please don't think I'm calling you stupid if this has not occurred to you already but I was relying on the pressure gauge of the rather expensive foot pump I was using - it was way out. Naturally, this didn't matter to the front tyre which never blew.

Just suggesting that if this possible cause hasn't occurred to you it might be worth checking out the pressure with another pressure gauge.

[ILikesToCycle]

A few little interesting posts on here. I found another one where a chap had a small tear in his tyre and was getting blow outs as well. I'm guessing yours aren't that old though?

http://www.totalinnertubes.com/blog/a-n ... every-week

[ignatius986]

Thanks for all your replies, most helpful!

I think I will swap over the tyres as cycleruk suggested - didn't think of that! I might get a new tyre too anyway, especially since I'm supposed to be going on a night ride this weekend.

Tasker, I didn't consider that the pump's gauge is incorrect. Since it worked on the front tyre though (i.e. it hasn't exploded on me despite being around the same psi as the back) I thought it must be okay. Maybe I will try a track pump in a shop though just to be sure.

I have just got a hand pump. Is it bad for the tube to be using this?

FYI, Vorpal - the puncture is a small rip - I wouldn't exactly call it as small as a pin prick though. I have checked the tyre though many times - inside and out - and not found anything.

On this latest tube the two punctures have both been to the left and right of the valve, although I have had punctures occurring all around the tyre in the past.

I got my latest repair at cyclopaedia on the fulham road (before that I was at a shop in Kent). The mechanic there was pretty helpful - and sorted my bike out on Saturday so that I could ride on Sunday. He did emphasise though that he couldn't guarantee that the tyre would be fine now - and that the tyre not seating properly meant that it had to be inflated in stages (20 - 40 - 60 - 80 - 100 psi) and then checked that it was not coming off the rim (I did follow his advice today).

So, I wouldn't say that it was any fault on their part - more likely my own mechanical dilettantism!

I will post back with what happens tomorrow, thanks again everyone...

[Alex L]

What tubes are you using?

I have those tyres (on different rims) and they go on a breeze. Can get them on without tyre leavers and pump them to 100psi.

I wouldn't say the hand pump is causing that problem but be careful. Too much force pushing and pulling the valve can damage/break it.

[ignatius986]

What tubes are you using?

I have those tyres (on different rims) and they go on a breeze. Can get them on without tyre leavers and pump them to 100psi.

I wouldn't say the hand pump is causing that problem but be careful. Too much force pushing and pulling the valve can damage/break it.

Well, the most recent tubes to puncture are Continental 18/25, they have 'Race 28' printed on them.

Previously though (also punctured) I have had Specialized 700x20/28, and some other make which I forget the name of..

I have some Giant 18-23c tubes spare, but I am reluctant to use them in case they just get punctured straight off.

I have the same tyre on the front, and I have no problems with that.

[wirral_cyclist]

I replaced a tube a while ago that was badly abraded, apparently by an over-wide sharp edged rim tape that was riding up the well edge, it hadn't let go due to the abrasion but I'm sure it would have done if it hadn't died early from a snakebite puncture. I'd repaired one hole and still had no pressure (not realising it was a pinch flat) and upon examination I found the second hole and also the abrading. If I'd thought I'd have taken a photo of the tube but it really didn't look much but had a very matt finish in places that matched the wavy edge of the rim tape.

It seems unlikely you'd have two lots of iffy rim tape but perhaps worth thinking about?

[JohnW]

This is a nightmare.

Have I got this right Ignatious? When you've pumped up to a certain pressure, which is less than the maximum pressure quoted on the tyre, the tyre lifts from the rim, the tube is forced through the gap thus formed between the rim and the tyre, and punctures at that point?

Does the tube actually come though the gap and puncture?

Have you noticed whether the tyre lifts each time at the same place on the rim? - or is it the same place on the tyre that lifts? Have you noticed these?

From what you're saying, and subject to your answer to my questions above, quite a lot of common puncture causes seem to be eliminated and my guess without seeing it actually happen is that either - (1) the rim is slightly undersized - (2) the tyre is slightly oversized - (3) the tyre is deformed or malformed (the wire kinked?) - (4) the rim has a flat section (which isn't visually obvious), possibly due to hitting a pothole or something in the road or possibly even faulty manufacture.

When did this start? Is everything new? Have you had other tyres on the same rear wheel, which have performed faultlessly?

As for your question of whether this is the right forum for your question - yes it is, and as you can see, there are a lot of us trying to help.

It's very difficult though, if we can't actually see it happening.

I don't think you have a puncture problem - I don't think your tube is a problem, I think, from what you say, it's deeper seated that that. Come back to us.

I'd give some credence to Vorpal's doubts about your bikeshop.

[7_lives_left]

This is a nightmare.
[snip]
From what you're saying, and subject to your answer to my questions above, quite a lot of common puncture causes seem to be eliminated and my guess without seeing it actually happen is that either - (1) the rim is slightly undersized - (2) the tyre is slightly oversized - (3) the tyre is deformed or malformed (the wire kinked?) - (4) the rim has a flat section (which isn't visually obvious), possibly due to hitting a pothole or something in the road or possibly even faulty manufacture.
[snip].

A couple of years ago I had a tyre where the wire bead had poked through the inside of the tyre, lying flat along the inner surface. This cause a couple of mystery punctures because I didn't spot the problem. I did eventually track it down but too late. A few miles further on that day, the tyre bead failed completely with the trye literally falling off the rim and the inner tube poking out. I had to resort to using about 2 dozen tiewraps to hold the tyre to the rim while I limped home. I posted a picture of it somewhere on the boards here.

Edit: here is the thread, viewtopic.php?f=24&t=34369

It's a slim chance, but it might be worth checking if the wire bead is intact and not poking through somewhere on the inside. If it is, you want to ditch the tyre immediately as a health hazard.

[JohnW]

'Seven-lives-left' (that's quite a mouthful) has a good point, worth checking. The only tyre that I've had a problem with the wire parting company with the tyre was also a Schwalbe - about three years ago but not the same model as yours.

Better to spot this now than half way down a long hill 20 miles from a hospital.

I've risen from my bed and come back on-line because it did occur to me, not being familiar with the rims that you refer to - is the front rim identical with the errant rear one?

[Vorpal]

I'd gues that a punture that looks like a cut (rather than a pin hole) is more likely to be caused by pinching between the tyre and rim. You can also try marking rim and tyre where the valve is, so you locate the puncture and see if it's in the same place each time.