Typre pressures....again

bigharj
bigharj Posts: 78
edited May 2013 in MTB beginners
I've got a feeling I've been running my MTB (Decathalon Rock Rider 29er) tyres like my road bike tyres. Is 90 PSI too much?

I am a heavy rider (20st) and always feel that the tyres look like their under inflated and have been keeping them topped up above 90 PSI. Anything lower would feel like running a flat tyre, am I being to cautious? Also I am also worried about pinch flats.

Any good advice appreciated as I am going out to Cannock Chase later for the first time.

Harj

Comments

  • Chunkers1980
    Chunkers1980 Posts: 8,035
    Way too much, over double.
  • Petenat
    Petenat Posts: 2
    General rule 40psi off road 60psi on road
  • warpcow
    warpcow Posts: 1,448
    Anywhere between 20-40psi, depending on surface and conditions (and your weight, to a slightly lesser extent imo). 90psi would be like riding blocks of wood, with less grip.
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  • Thewaylander
    Thewaylander Posts: 8,593
    i ride 20psi up front, 24 or so on rear to just help against pinches when i ride like an idiot.
  • lostboysaint
    lostboysaint Posts: 4,250
    Petenat wrote:
    General rule 40psi off road 60psi on road

    That, maybe fractionally more given your weight. But not a lot. Those are good starting figures. (I used to be 115kg)
    Trail fun - Transition Bandit
    Road - Wilier Izoard Centaur/Cube Agree C62 Disc
    Allround - Cotic Solaris
  • Thewaylander
    Thewaylander Posts: 8,593
    See I have never encountered a single person who runs at 40Psi off road on a tyre. but there you go.
  • RyanMelvinKinch
    RyanMelvinKinch Posts: 16
    lostboysaint wrote:
    Petenat wrote:
    General rule 40psi off road 60psi on road

    That, maybe fractionally more given your weight. But not a lot. Those are good starting figures. (I used to be 115kg)
    Maybe thats why there are cracks in the roads
  • danlikesbikes
    danlikesbikes Posts: 3,898
    Tend to ride 30-35psi, but does depend as can go lower if I want.
    Pain hurts much less if its topped off with beating your mates to top of a climb.
  • Yacoby
    Yacoby Posts: 211
    IMHO just keep lowering the pressure until you start getting pinch flats or feeling your rims (or you h ave enough grip and it feels smooth enough...). Having my tire much over 30psi just feels really harsh to me.

    To some extent numbers are a bit meaningless as it depends as well as how and where you ride (My tires get pumped up for the peak district due to the high speed square edged hits that just cause pinchflat after pinchflat. On smoother stuff they can be run a lot lower)
  • lostboysaint
    lostboysaint Posts: 4,250
    RyanMelvinKinch wrote:
    lostboysaint wrote:
    Petenat wrote:
    General rule 40psi off road 60psi on road

    That, maybe fractionally more given your weight. But not a lot. Those are good starting figures. (I used to be 115kg)
    Maybe thats why there are cracks in the roads

    The ones that don't exist? Make up your mind!
    Trail fun - Transition Bandit
    Road - Wilier Izoard Centaur/Cube Agree C62 Disc
    Allround - Cotic Solaris
  • gavstorie
    gavstorie Posts: 11
    Use your weight in pounds divided by 7 for the front and add between 2 & 5 for the rear..

    168/7 = 24psi in the front

    24+3 = 27 psi in the rear..
    This is what I normally run.. and its pretty good..
    You may need to tweek it up or down slightly depending on the tyres you are using and your riding style but it will give you a good place to start..
  • bigharj
    bigharj Posts: 78
    Went out at Midday running 50 PSI, seemed OK to me, will try to experiment with lower pressures.

    Still got a puncture, damn thorns again!
  • felix.london
    felix.london Posts: 4,067
    Thewaylander wrote:
    i ride 20psi up front, 24 or so on rear to just help against pinches when i ride like an idiot.

    yep. 22 + 26 (ish) front and rear
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  • paulbox
    paulbox Posts: 1,203
    For your weight I'd say that 40psi would be about right, I'm a little lighter than you and tend to run about 38.
    XC: Giant Anthem X
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    Trainer: Bianchi via Nirone
    Hack: GT hardtail with Schwalbe City Jets
  • swod1
    swod1 Posts: 1,639
    Thewaylander wrote:
    See I have never encountered a single person who runs at 40Psi off road on a tyre. but there you go.

    I do run about this in my tires as the places, i ride at the minute are dry dusty gravel tracks around local nature reserve so i can blast a long.

    my front tyre nobby nic i had to put over 30 in it otherwise the ride didn't feel too great due to thin sidewalls on it compared with the bontrager xr4 team issue i was running before.
  • MrM
    MrM Posts: 60
    I go by feel not psi
  • bigharj
    bigharj Posts: 78
    Took the advice here a few weeks ago and lowered the pressure to 40 and not a single puncture, the ride has been a lot better too..thanks
  • The Rookie
    The Rookie Posts: 27,812
    Just as a general point, it would be worth looking at the max and min pressures on the tyre sidewall, also consider the stresses placed on the wheel rim with the inward force of 90pounds for every square inch of rim interal surface (compare a 12mm internal rim width road wheel with a 21mm internal rim width MTB rim!)
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.

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