Cyclists - help with wheels please!

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kaned_ferret
kaned_ferret Posts: 618 Member
in Fitness and Exercise
Ok, I got a mountain bike frame, managed some great engineering and replaced the gears, and then bought some new tyres for it - put it all together and voila, awsome cheapo bike!

But my question is this: the recommended psi on the tyre says 40-65 psi. I inflated mine using my car tyre air compressor, and stopped at around the 30 mark, because the tyres felt firm when I pressed them (the way I'd always been taught to measure how well inflated my tyres were as a child :smile: ) I was too worried to just keep letting it pump them up for fear of over-inflating and bursting said new lovely tyres! So, what's my best course of action? Is it normal for them to feel firm and "done" at around 30 and you just keep on going with the air, or should I trust my instincts - which are based on possibly archaic information - and leave the bike as is?

Opinions please!

Replies

  • mamaclose
    mamaclose Posts: 219 Member
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    I would follow the recommended psi. Do you have a tire gauge you can use?
  • kaned_ferret
    kaned_ferret Posts: 618 Member
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    The air compressor I was using has a guage built into it (and I assume it's accurate) - if it was a hand pump job I think it would feel very hard to force more air in by hand, but of course battery powered compressors don't have that to worry about! I'm just scared that it'll be too much based on how the tyres already feel - I suppose really I should take it for a test spin and see how it feels underneath me :)
  • RickyRaj
    RickyRaj Posts: 25
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    They should be firm and only have a little give to absorb bumbs.
  • wellbert
    wellbert Posts: 3,924 Member
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    You should fill the tube in your t-i-res either based on carefully calculated values(why bother) or by the PSI markings on the side of the t-i-res. Your hand can't compress your t-i-re to the same degree that your entire body does. So squeezing isn't a good guide.


    (Sorry, the commonwealth spelling of tire drives me insane :P)
  • BrianSharpe
    BrianSharpe Posts: 9,248 Member
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    Go with the recommended inflation. If your tires/tyres are under-inflated you risk "pinch" flats when you hit bumps etc as the tire /tyre deforms more than it should pressing the inner tube against the rim.
  • kaned_ferret
    kaned_ferret Posts: 618 Member
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    You should fill the tube in your t-i-res either based on carefully calculated values(why bother) or by the PSI markings on the side of the t-i-res. Your hand can't compress your t-i-re to the same degree that your entire body does. So squeezing isn't a good guide.


    (Sorry, the commonwealth spelling of tire drives me insane :P)

    Yep, well being English I'm quite happy to differentiate between a rubber wheel, and to fatigue. No real need for the patronising spelling correction!

    However you made a very good point on squeezing not being a good guide for correct pressure, so thanks for that :flowerforyou:
  • wellbert
    wellbert Posts: 3,924 Member
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    You should fill the tube in your t-i-res either based on carefully calculated values(why bother) or by the PSI markings on the side of the t-i-res. Your hand can't compress your t-i-re to the same degree that your entire body does. So squeezing isn't a good guide.


    (Sorry, the commonwealth spelling of tire drives me insane :P)

    Yep, well being English I'm quite happy to differentiate between a rubber wheel, and to fatigue. No real need for the patronising spelling correction!

    However you made a very good point on squeezing not being a good guide for correct pressure, so thanks for that :flowerforyou:

    I'm just teasing. :)

    You can find calculators online that give you your "ideal" pressure based on bodyweight, but they are harder to find for mountain bike tires.
  • Dahamac
    Dahamac Posts: 213 Member
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    Go with the recommended inflation. If your tires/tyres are under-inflated you risk "pinch" flats when you hit bumps etc as the tire /tyre deforms more than it should pressing the inner tube against the rim.

    This is good advice. On my road bike with 700x25 I run 110-115psi in the back tire and 100psi in the front.

    This is an oversimplized explanation but maybe it will help. The heavier you are the closer to the maximum recommended pressure you need to run the tires. So if you are over 175 run the max if you are less that 175 then run the minimum plus 5 or 10 psi based on how soft you want to ride (lower psi = softer) or how fast you want to roll (higher psi = less rolling resistance).

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