Tire pressure PSA, something I just learned

Discussion in 'Equipment' started by AZQKR, Aug 30, 2018.

  1. Jmunk

    Jmunk Adventurer

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    In regards to tire cupping I think that there are multiple factors to consider and not air pressure alone to include air pressure, balance, load/weight, tread design, etc.

    I ride my bike on and offroad usually on the same ride. I set my tires at a pressure which it is a compromise for both. Due to my compromise a few pounds one way or the other isn’t a factor. I accept that my tires may cup and wear uneven but that’s all part of the game with a dual sport.

    I set my tires to a certain PSI which I know works for me given the ride conditions just before pulling out of the garage. I set it at the current air temperature. To myself 2-3 pounds isn’t a worry.

    I can see both sides of the discussion, however I leave my mind free to consider important things like oil brands....
    #41
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  2. RoundTrip

    RoundTrip Unintentional deerslayer Supporter

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    Scientific = pressure adjusted for temperature/altitude at start. Useful on track for the first pit setup. After that it is all tire/track temp and outside density altitude is unimportant. It is also very OCD on street.

    Practical = check your tire pressures before the ride. Pick ones that work for you. Forget about it unless large variation shows on TPMS which will require repair.

    In AZ, we get 30-40* temp swings in a day or in a couple of hours if we head to the mountains. Checking tire pressures at evey temp and altitude is not riding, it is lab work. It is also unnecessary for any reasonable street safety considerations.
    #42
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  3. MarkM

    MarkM Been here awhile Supporter

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    To the folks who claim you should adjust inflation pressure up or down to compensate for temperature (such as 1 psi per 10 degrees difference from 68°F): Can you provide a published reference for this claim that isn't part of instructions on using TPMS? Something like a tire mfr website link, photo of your manual, recommended pressure label on your bike, etc. Not a forum discussion or other non-professional reference. All I'm seeing is hearsay.
    #43
  4. Tor

    Tor Imported Norwegian

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    Anyone with a TPMS on their bike will have to calculate in their head what the actual tire pressure is, compared to what is showing on the TPMS, unless the ambient temperature you're riding in is 68 degrees F, and basically renders the TPMS absolutely useless :imaposerwhile riding.

    Leaves
    [​IMG]
    as the only option....
    #44
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  5. RoundTrip

    RoundTrip Unintentional deerslayer Supporter

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    TPMS isn't useless. I top off with a tire gauge to my satisfaction and whatever the TPMS reads is now baseline. From there all I do is monitor for changes on the ride. Noticing a slow leak between gas stops can save a lot of effort rather than waiting until your butt-o-meter tells you there is a problem in the middle of nowhere.
    #45
  6. AZQKR

    AZQKR Long timer

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    It wasn't an instruction on TPMS, it was distinguishing how TPMS functions and reads, how the system will show different values and why vs actual pressures.
    #46
  7. AZQKR

    AZQKR Long timer

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    You have it correct sir. Actual vs what TPMS reads is a baseline for the TPMS on THAT bike. Not all TPMS reading are equally accurate.

    TPMS isn't designed to be used to set air pressure. It's designed to work with the computer to inform the rider of a rapid loss of air pressure.
    #47
  8. MarkM

    MarkM Been here awhile Supporter

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    I'm not sure what you are referring to. Do you mean that post from the MOA forum you posted?
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  9. Plawa

    Plawa ¿ʞO ǝʞᴉq ʎɯ sI

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    Next time I ride with a group of 10+ people I'll make sure to ask them to wait for me while I adjust my PSI with every 10 degrees or 1000ft of altitude difference...
    #49
  10. flei

    flei cycletherapist

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    The group just might be ok with that. In my group of elderly male riders, we have to stop like every 15" so someone whose Flowmax stopped working can stop to take a leak. Everyone is very empathetic. :-)
    #50
  11. AZQKR

    AZQKR Long timer

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    Yes,
    #51
  12. AZQKR

    AZQKR Long timer

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    That's not to be expected nor has it been suggested. It's suggested on adjust their initial cold air pressure based on ambient temperature at the time.
    #52
  13. Plawa

    Plawa ¿ʞO ǝʞᴉq ʎɯ sI

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    I wasn't being completely serious but since we're in the same hell hole I'm sure you realize how quickly your initial settings become "wrong" once you get going...
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  14. AZQKR

    AZQKR Long timer

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    Just like initial setting whether set based on adjusting for temp or just the recommended pressures, right?
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  15. motoinmoab

    motoinmoab Questioning Reality Supporter

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    The manufacturer's recommended tire pressures are for what load on the bike? Can't you also adjust tire pressure based on a heavy load or light load? I'm fairly light weight and alone on my bike all the time- shouldn't I run less pressure than a bike with 2 heavy riders or loaded bags? Temp and altitude and total load matter???
    #55
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  16. AZQKR

    AZQKR Long timer

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    BMW recommends, for my GS, two different pressures based on one rider; one rider with luggage and/or two up. They same pressures are recommended whether it's one up or two up for the 07 GT.

    When I called Heidenau and gave them weight of bike, my weight and weight of panniers and gear for the trip to Ak. the rep recommended I start each morning airing the tires to 38/41. Weight was taken into consideration by the tire makers rep.
    #56
  17. Bungholio

    Bungholio Long timer

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    OMFG!! 56 POSTS ABOUT THIS!
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  18. worwig

    worwig Long timer

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    I use synthetic air. It is less affected by temperature.

    :photog
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  19. AZQKR

    AZQKR Long timer

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    56 posts about something as important as tires isn't that much actually. Hell, there's people that will discuss what tire to begin with for dozens of pages. Tires seem important enough as to which tire, pressures should be at least as important where discussion is concerned, don't ya think?
    #59
  20. brianbrannon

    brianbrannon They'll ride up with wear

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    You have it backwards. The pressure in the tire is what counts. If you use the same gauge to check the same tire at sea level and at 10,000 feet the gauge will read a 5 psi difference but the pressure in the tire is the same. The goal is to have the same pressure in the tire when the tire is hot. Hot pressure is going to depend on the temperature of the tire and the number of air molecules in the tire. Assuming constant hot tire temperature:; in order to get the same number of air molecules in the tire on an unridden tire you will have a lower reading on the gauge when it's colder outside and a higher reading on the gauge when it's hotter outside because the number of molecules in the air is higher per psi when the temperature is lower. Therefore adjusting the cold pressure to compensate for temperature not only makes the TPMS sensors read the proper number it also puts the proper number of molecules of air in the tire.

    If the BMW sensor read out is adjusted for temperature then if the read out is the right number then you have the right number of molecules in the tire. So, having the sensor read the right number means you have the right pressure in the hot tire regardless of outside temperature or pressure
    #60