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Discussion in 'Bicycle Mechanics and Repairs' started by hongkonguk, 23 Aug 2007.

  1. hongkonguk

    hongkonguk Well-Known Member

    Hi. I have just taken delivery of a new bike,after a few years of being bike-less. After assembling it,I went to pump up the tyres and read on the sidewall that it requires 75psi pressure. I thought that sounded a lot so pumped it up to 70 until I could check that would be ok.

    After half an hour the the tube went bang! So I wondered if maybe I even overdid it with 70psi. Does anyone know what the correct pressure would be? The size is 28X1 5/8.

    Thanks in advance. :biggrin:
  2. John Ponting

    John Ponting Über Member

    what brand and model of tyre have you got?

    My road bike sidewalls state max 110psi and my hybrid max 85psi.
  3. hongkonguk

    hongkonguk Well-Known Member

    Just the ones that came with the bike. Raleigh branded ones,can't see a model on the sidewall.
  4. Elmer Fudd

    Elmer Fudd Miserable Old Bar Steward

    Probably a dirt cheap inner tube. Don't forget that (some) bike companies, as in any other company, are out to make a profit, so some corners will be cut.
    have you got a wheel liner ? (the banding that fits on your rim) Which side was the puncture ? Towards the inside or outside ? I had an unexplained puncture directly in line with a spoke hole, nowt wrong with the liner but on the off chance I put a patch over the offending area. Then bought some new tubes from LBS, never had a problem since.

    (Now I've said that, guess what will happen..................................)
  5. Chuffy

    Chuffy Veteran

    Hmmmm. A few questions if I may. Forgive me if they seem obvious.

    1) Was it the tube or the tyre that blew? If it was the tube, then take the tyre off and check inside for intrusions (bits of wire, glass etc) the problem may be a sharp foreign body inside the tyre casing. If it was the tyre, you have a problem. See below. Also check what Elmer said above. Poorly finished spoke holes in the rim can easily blow a tube. Rim tape is your friend.
    2) Do you have a track pump, or one with a pressure gauge? 70psi isn't especially high pressure.
    3) 'After half an hour' of pumping (!) or after inflation?

    If it was the inner tube that blew then replace it (and the other one) with one from a local bike shop. The supplied tubes may be poor quality or even old and perished. If it was the tyre that blew then I'd go back to the supplier and ask for a replacement. Or go to a bike shop and source a replacement yourself.
    I hope this helps.

    Welcome to the forum btw!:biggrin:
  6. hongkonguk

    hongkonguk Well-Known Member

    It was the tube. I have checked the rim and the tyre and both seem fine.

    I have just bought one today with a gauge. 70 just seemed a lot more than I was used to (my last bike was a MTB)

    LOL!! Not after half an hour of pumping. After I pumped it up I nipped out in the car and it went bang while I was out (wife heard it from inside the house). Looks like I will be replacing 2 tubes tomorrow! :biggrin:

    Thanks very much. And thanks to all for the advice. xx(
  7. Chuffy

    Chuffy Veteran

    Sounds like a duff tube then. But do get some rim tape, the pressure forces the tube into the spoke holes and a small blemish can be enough to bang your tubes. Rim tape will prevent that.
  8. hubgearfreak

    hubgearfreak Über Member

    could it be that the tyres and tubes are all OK, but you had a badly seated tyre?
    if the wire beads aren't sat in the rim hooks ok, then the tube will pop.
  9. hongkonguk

    hongkonguk Well-Known Member

    That could well be it. The first attempt at inflating it made it pop over the rim and I deflated it to reseat it. I then inflated it using a frame pump. Couldn't get a lot of pressure so went to buy the track pump. After that it popped.
  10. rustychisel

    rustychisel Well-Known Member

    Yep, that sounds a lot more like it. Cheap tyre or poorly seated tyre on rim, or combination of both. I've had some which is a factor of both those things. Usually you'll see the tyre unhooked at the site of 'explosion' and the tube will be completely shagged and unrepairable by star shaped burst or long jagged rip. About all you can do is replace the tube, be very careful in replacing it and make sure the tyre is seated as well as you can get it, and carefully reinflate. I've heard of people taking new bikes back and demanding replacement tyres "fit for purpose" after numerous failures.
  11. Elmer Fudd

    Elmer Fudd Miserable Old Bar Steward

    As an aside, I had problems after a puncture I'd repaired where I 'bumped' down the road. The tyre was not sitting correctly on the rim round the valve area. I've now learned that I have to push the valve well into the tyre before pushing tyre back on to rim and pumping a bit of pressure in before tightening the lock ring. In fact, this has made me check that the tyre looks 'correctly' fitted all round before pumping up to correct pressure (85p.s.i.) and re-fitting the wheel.
    (Teaching Granny to suck eggs moment I know !!)
  12. hongkonguk

    hongkonguk Well-Known Member

    Bought a couple of replacement tubes this morning. Also noticed a rough looking join on the rim that I sanded down just in case that was a factor. Made sure it had rim tape evenly all the way round too.

    It was a pig to seat evenly all the way round. Just used a bit of washing up liquid around the bead (both sides) and took my time to make sure I got it right. As a ex tyre fitter (car tyres mind) I could tell it had been a while since I gave up that game! And it reminded me why I don't miss it! :biggrin:

    I just hope it stays all right now. Thanks again to all of you for your advice. xx(
  13. Chuffy

    Chuffy Veteran

    <flips HKUK a lazy salute>
    'sno problem, happy to oblige. :biggrin: