Tyre pressures

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Comments

  • My old vredesteins were rated to 140 psi but I got a lot of punctures.

    Now I use contis at about 95 and (touch wood) can't remember the last time I had a p*ncture. Amazing tyres.
  • I use Conti GP4000s's or Gatorskins and they're always pumped up to 120psi

  • Pixie,

    650 wheels are smaller than 700s. If you tried to fit 700s they wouldn't fit - so don't do it. We are talking distance from axle to edge not tyre width here.

    115-120 for Conti GPs for me as I am lardy. Training tyres a little less and also tend to do a about 5PSI less on the front.

    Please remember that the the valve is non-return on the tyre so unless you knock the valve you won't lose any. What will rush out is all the air in the pump also at 110 PSI.

    M.eface

  • I normally pump my clinchers (Continental Gatorskins) to 110 (sometimes up to 120) on the back, slightly less on the front, in the winter maybe 10 less.  Its worth checking pressures every week as they'll bleed air, maybe loosing 10 PSI in a week.

  • Thanks meface, that makes sense about the air in the pump rushing out, i think I will increase the pressure in mine a bit before next ride as I'm lardy too,
  • IronCat5 in the Hat wrote (see)

    If their 650s then 80psi may be all that is needed. There is alot less volume in a 650 than a 700.

    What does it say on the side of the tyre for pressure range?

    cat - you are an engineer, no??  then you should know that volume does not equate to pressure.  so tyre size has no meaning here - you need the same pressure irrespective of size.

  • Thanks FB - I was having a thick day. image

    I'll now say that as 650 has a smaller volume they'll need a higher pressure. Volume is related to area. image

    Pressure = Force / Area.

    Force (rider + bike weight) is a constant here, so as the internal Area of the tyre increases (say from 700x23C to 700x25C) the Pressure required to support the Force reduces.

    By the same token as you reduce the area of the tyre (650x23C) then the pressure must increase for a given force.

    Your MTB tyres support your weight the same your road bike tyres, but at a lower pressure. The volume of the tyre is bigger. Perhaps my explanation/understanding is amiss, but the theory is sound.

     

     

  • you run MTB tyres at lower pressure for grip off-road - it has little to do with support.  there's nothing to stop you running them much higher but a) it's bloody hard work pumping that volume up, and b) they would be skipping and jumping all over the place on the knobbies.   

  • 100 normal, 110 race, 120 smooth race, 90 if my arse is sore or in winter.

    Don't they make a loud bang if one goes off! Especially indoors in front of the telly when the wife is asleep on the sofa. Though it was very funny!

  • I think it is because of width of tyre and relative footprint/ area in contact with the road. A thin racing tyre needs higher pressure than a mtb tyre because of the area supporting the rider. (Something like comparing a stiletto heel with a trainer heel, the first needs to be harder because of a smaller area carrying the weight). Follow what is on the side of the tyre and you can't really go wrong.

    On the bit about unscrewing valves and running the wrong pressure I did both of these, but then gained a couple of free mph when I worked out what I was doing wrong!

  • 100 on 25mm tyres and 110 on my 23mm tyres.

    Bought a track pump for it after spending an entire day with my Dad and Hubby saying you could get them to that pressure with hand pump or electric pump.

    Once disproved a late dash to Halfords and my point was proven.

    Men image

    Next is to convince them as to how the electric circuits in my house work.

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