1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

"never use the max. PSI pressure from the sidewall"

Discussion in 'Bicycle Mechanics and Repairs' started by swee'pea99, 1 Feb 2008.

  1. swee'pea99

    swee'pea99 Legendary Member

    Following my third visit from the p*nct*re fairy in a week, I was googling
    around on 'flat-proof tyres' and came across a discussion
    http://www.bikeforums.net/archive/index.php/t-218157.html
    featuring the quote in the subject line.

    I've got used to standardising on 100psi with my Grand Prix 2000s, which is
    well within their supposed max (and I'm about 11 stone, so not a massive
    load). And I checked the Sheldon link provided, which seemed to suggest
    c.100 would be about right for me. I guess 'try it see' is an obvious
    answer, but should I take them down to 80 or something? Any thoughts? What do other people do? (I'd always previously thought that problems came when you didn't inflate *enough*.)
     
  2. rustychisel

    rustychisel Well-Known Member

    All things being equal, a well inflated tyre is much less likely to puncture, due to an ability to deflect some objects sideways where they might otherwise pierce the tyre. Unfortunately all things are rarely equal. I'd check very carefully where and how the punctures are occurring: pinch flats from bad tubes or installation; repetitive flats from flints or thorns embedded in the tyre; or silly bastard flats from spoke ends or rim tape not doing its job.

    Pull tube out (when punctured) and have a good look at the site. Is it on the outside or inside curve of the tube. Measure the approximate spot on the tyre where the puncture might have occurred, then [carefully] run your fingers inside the tyre feeling for the 'little prick' of a foreign object. Remove tyre completely and examine rim tape for any sign of rucking, folding, or spoke poking through. A obvious depression (or series thereof) in the tape at the spoke holes may indicate the tube is expanding into spoke holes then blowing. That should be apparent from where on the tube the repetitive punctures occur. etc etc. It's often a matter of being thorough and thoughtful in examining the evidence.
     
  3. Steve Austin

    Steve Austin The Marmalade Kid

    Location:
    Mlehworld
    Tyres are supposed to be at the right pressure for grip and rolling resistance imo. Avoiding p*******s has very little to do with the pressure i put in my tyres.
     
  4. Dave5N

    Dave5N Über Member

    Puzzled by this, certainly the received wisdom is the harder they are the fewer punctures.

    Personally I try and cram as much air in as possible on the road bike - might run slightly softer if it's a bit slippy.
     
  5. Tynan

    Tynan Veteran

    Location:
    e4
    sure I read somewhere (Sheldon?) that the tyre is perfectly good to go a fair bit past the 'max' pressure, there's a decent margin of error

    my experience is that a hard tyre is a good tyre as long as you're happy with the ride
     
  6. OP
    OP
    swee'pea99

    swee'pea99 Legendary Member

    Thanks. Also hmmm

    Thanks for your responses. Yes, I'd always understood that under-inflation was what made you vulnerable, and have always tended toward teak. These are all classic p*nctu*es by the way - thin shards of glass coming straight thru' the tread (and the kevlar). There seems to be a consensus that other things being equal, hard is better, so I guess I'll just grit me teeth and stay with it and hope for the best. Thanks again.
     
  7. Tynan

    Tynan Veteran

    Location:
    e4
    if there's a persistent glass problem some more resistant tyres are called for surely? assuming you can't avoid the glass natch

    something like those Schwalb Marathon Pluses? Heavier but supposedly proof to penetration and supposedly push out anything that doesn't get through
     
  8. andygates

    andygates New Member

    "never use the max" is tosh. You've got delicate little tyres, a nasty bit of road and some bad luck, that's all.

    Punctures are so random that people get weirdly superstitious about them. On which note, I must make an offering of tea and tip-top glue to the fairy...
     
  9. yello

    yello Guru

    I've not heard that before either, and I don't go for it. I'll still inflate to the max as I prefer the ride it gives. Though I must admit, I was a tad surprised by the 125psi stated on the (std) Kenda's I have on my pompino.
     
  10. col

    col Veteran

    Not wanting to spanner and works,but isnt not rock hard a little better for less punctures,as the tyre gives slightly,so not helping something peirce.?just a thought?
     
  11. mr_hippo

    mr_hippo Living Legend & Old Fart

    Have you ever had an injection? You are asked to "Relax" - easy to say but sometimes difficult to do! If you tense your muscle, it is very hard to get the needle in but if you relax then it is easy. So if your tyres are pumped up hard (tense), it is more difficult to get a p*nct*re than in a 'relaxed' tyres.
    Anyway, injections are painless; I must given thousands in mu nursing career and never felt one!
     
  12. hubgearfreak

    hubgearfreak Über Member


    for the tyre to deflect due to its softness around an object (let's say thorn) it would have to be extremely soft....indeed the p***t*** would normally occur at the point of the tyre contacting the road so to get a tyre so soft to move around the object, the tyre wouldn't support the weight of the rider.

    what you say is true, to a point, i.e. if you were to wish to take your wheel for a walk like you might a dog, using front forks instead of a lead
     
  13. col

    col Veteran

    I know what you saying,but its a different thing,there is no muscle inside a tyre:smile:I just wondered,there might have been something in it?
     
  14. Stick on a Giant

    Stick on a Giant New Member

    I think there might be something in what col has to say. It probably won't help against something as sharp and pointy as a thorn, but it might stop a flint or piece of glass from cutting the tyre, if it can deform around the lump, it should spread the pressure across more of the tyre and and hence not put enough pressure on it to cut/pierce it.
     
  15. Jacomus-rides-Gen

    Jacomus-rides-Gen New Member

    Location:
    Guildford / London
    Pressure makes almost no difference to pierce flats, however it does reduce the chanses of snakebite flats.