Tire pressure new wheel sizes 21/18 to 19/17

Discussion in 'The Garage' started by Chillis, Sep 5, 2019.

  1. Chillis

    Chillis Long timer Supporter

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    Stock CRF450L tires are 80/100-21 front and 120/90-18 rear. Honda says 22 psi f/r.

    Just mounted up these beasts:
    IMG_20190905_111905.jpg

    110/80-19 and 150/70-17.

    Any rec's on tire pressure?

    For mountain biking you lower the pressure for the more voluminous tires.

    I have it at 22 f/25 r.
    #1
  2. Yinzer Moto

    Yinzer Moto aka: trailer Rails Supporter

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    Considering the weight/size of the bike, I’d be shooting for closer to 10 than 20. You might want to apply chalk to the tread and see what kind of contact patch you get at different pressures.
    I ride a bike that is a similar weight and on traditional 18/21 tires, I run 15 for all around riding. 20 if it is going to be an all day highway blast. 10 if it is going to be totally in the dirt. I’ll drop to 5 if it is really muddy.
    Do some volume calculations and that should lead you to a percentage of difference, then you can apply that number to your pressures. You might be looking at close to 10 f/r.
    #2
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  3. CDN Rick

    CDN Rick Canoodia Eh?

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    Obviously a spreadsheet is in order here....
    I hope the OP posts it when it's done so I can print it out and hang it on my shop wall for future reference.....
    #3
  4. Bultaco206

    Bultaco206 Back-to-back motos suck Supporter

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    They’re radials and don’t like the lower pressures, even off-road. They get very sketchy and vague. I’d not really want them below 20 on a super-light bike like an Elle. My CB500X didn’t like them below 30 on any surface.
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  5. Yinzer Moto

    Yinzer Moto aka: trailer Rails Supporter

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    Radial tires on a dirtbike? :hung
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  6. Yinzer Moto

    Yinzer Moto aka: trailer Rails Supporter

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    So, radial tires are not really intended to conform to the terrain. I am so pigeon holed into the world of small dual sports, I forgot about radial tires. I remember from back in my rock crawler Jeep days, the bias ply tires were better.
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  7. foxtrapper

    foxtrapper Long timer

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    @Chillis,

    Start at stock pressure, then go up 5 psi, and down 5 psi. You don't have to ride far to get a pretty good idea which direction worked right, and which direction didn't. If it wasn't clear enough, do it 10 up and 10 down.

    From there, go another 5 psi in the right direction. Then another 5 psi.

    You'll quickly reach a point where there doesn't seem to be any appreciable change from a 5 psi change. You're in the range of "right" at that point. You can further dial in, but it becomes difficult to optimize because most of us aren't sensitive enough.

    Use a notebook.
    #7
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  8. Chillis

    Chillis Long timer Supporter

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    Running 22f/25r seems good but I was bouncing like crazy on washboard. Traction was decent though.

    Rear at 25 psi, no problems anywhere. Bike is very neutral handling as well.

    I won't truly be able to dial it in until the lowering links are on and sag is set. Right now there is too much weight up front.
    #8
  9. shinyribs

    shinyribs Thumpers for life

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    Smaller diameter tires will do that. You'll just have to adapt.
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  10. Chillis

    Chillis Long timer Supporter

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    Still waiting on lowering links, speedo healer, and smaller rear sprocket before I tackle tire pressure testing.



    Good news is they arrive today.
    #10
  11. ohgood

    ohgood Just givver tha berries !!!

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    nice looking street tires.

    air pressure is changed for the terrain. if you're riding street, set street pressure, if you're riding dirt lower it.
    #11