Author [NL] [FR] [ES] [DE] [SE] [IT] Topic: Recommended tyre pressures and their relevance.  (Read 6674 times)

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  • Offline Robwebb

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    Offline Robwebb

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    Recommended tyre pressures and their relevance.
    on: Feb 03, 2017, 01.57 pm
    Feb 03, 2017, 01.57 pm
    On a previous post I spoke of pinholes and cupping. This got me to thinking about tyre pressures.

    What relevance does 36 and 42 really have when it comes to actually riding the bike? I do not believe it has any. The only logical explanation for ensuring we start at these pressures is that they are the lowest recommended for our wonderful machines, nothing more.

    If there was a poll asking members what pressures their tyres had in then 10 minutes into a ride (I would start it if I knew how) you would get a variance of 8 to 10 psi.

    Tyre pressures change with the air and surface temperatures, road conditions , riding styles and much more. Some members would say they were within a couple of PSI whilst others would say considerably more. Last summer my wife and I rode to Albury NSW. 8 hrs in 38c temps. Rear tyre went from 42 to 53 psi.

    Surely there is an upper maximum pressure? just as surely as there would be an optimum RIDING pressure.  I am told that many professional GP riders do a couple of hot laps to heat their tyres, check the track surface with a thermometer, then adjust pressures to suit. Not suggesting we do that, but why are we so obsessed with pressures that are only relevant whilst the bike is safely tucked up in the garage, then appear to give absolutely no thought to what happens to them on a ride, just as long as they do not fall below 36 / 42?

    There has to be a point where we say that there is too much pressure - time to let some out.
    Can anyone tell me what it is, and what is the optimum riding pressure?

  • Offline duckman

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    Offline duckman

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    Re: Recommended tyre pressures and their relevance.
    Reply #1 on: Feb 03, 2017, 04.27 pm
    Feb 03, 2017, 04.27 pm
    I have only a little information on this subject because I had some of the same concerns.  Last year I spoke with the regional Avon Tyre rep.  He was insistent that the pressure had to be what the manufacture specified.  His reason made sense.  Once on the road the tire heated up 'X' degrees and if cold is set properly that when hot it was performing at the designed operating temp for optimal performance and longevity.  If it is too high or too low the tire could/would prematurely wear on the side walls and treads and could/would be an issue especially when riding 2 up and loaded. 

    He went further to say, to verify you are running at the correct pressure. After riding and tires are hot, when you stop, measure the tire pressure immediately to insure they are 'X" pounds over your cold temp.  If they are within 5% you are good.  If they are 5-10% out better make adjustment when you get to a place, if its over 10% diff then you are harming your tires so correct the pressure ASAP.

    Of course this will require a precision gauge and a lot of diligence keeping up with it every time one rides.  Most of us don't, we check it at the house if at all. Plus now we have the monitors which makes us check even less. So - How precise are the tire monitors??  I cannot answer that but probably not as good as a precision hand gauge we left at the house.

    Waitin' for my ride!
    Currently: 99 Nomad, 05 C10, 03 Voyager XII

  • Offline AZBob   us

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    Offline AZBob

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    Re: Recommended tyre pressures and their relevance.
    Reply #2 on: Feb 03, 2017, 05.31 pm
    Feb 03, 2017, 05.31 pm
    If the tire pressure is too low, the tire carcass will heat up much faster and get to a much higher temperature (due to flex), significantly reducing tire life, and possibly causing a spontaneous catastrophic failure. It will also, obviously, reduce the specified load rating.

    If the tire pressure is too high, handling will degrade as less tire will be in contact with the road. It will also cause the tire to bounce more and you may see cupping/scalloping. If it's _way_ too high, the tire will spontaneously explode, but that is a very high pressure.

    It's a game of balance for a particular tire on a particular bike with a particular load. The engineers take into account the weight of the bike and the expected average load and come up with cold pressures that will allow the tire to operate within the design envelope the tire manufacturer has specified. The tire is designed with the knowledge that it will heat up, and the amount it heats up is not random, it's math and physics -- the engineers specify the pressures with the idea that if the bike is ridden at its the max loading and max performance, will still be within the design envelope of the tire. This is why it is super important to follow the direction of the VEHICLE MANUFACTURER on tire pressures and NOT the tire manufacturer.
    2014 Triumph Trophy 1200 SE
    2013 Honda CB1100

  • Offline Oransay

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    Offline Oransay

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    Re: Recommended tyre pressures and their relevance.
    Reply #3 on: Feb 24, 2017, 11.00 am
    Feb 24, 2017, 11.00 am
    Interesting thread. Bob you state to follow the bike manufacturer guidance over the tire manufacturer and I agree with that, because those design parameters are engineered with a specific tire, but most of us like to try different tires throughout ownership. Once you change from the "factory" tire the pressure dynamics change too. It's enough to make your head hurt.  :084:

  • Offline Donk

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    Offline Donk

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    Re: Recommended tyre pressures and their relevance.
    Reply #4 on: Feb 25, 2017, 12.08 pm
    Feb 25, 2017, 12.08 pm
    And to add to the conundrum, if you do not have your tires set at 36 and 42 cold the TPS takes exception and you find yourself looking at a red light on the dash.  I ride solo, no luggage and my bike is currently in Florida as in not many curves.  There is no reason I should be running 42lbs in my rear tire the bike isn't carrying any weight 38-40 would be more appropriate.  I am running the middle out of my rear tire every 5000 miles because it is slightly over inflated for the load.  I also ride the bike a bit aggressively when there are corners and think 42lbs is a bit over inflated for that type of riding with an unloaded bike.  Both tire and bike manufacture guidelines should be adhered to but they are guidelines not absolutes.  A couple of pounds variation should be acceptable but the TPS won't let you do it.     

  • Offline Phil   gb

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    Offline Phil

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    Re: Recommended tyre pressures and their relevance.
    Reply #5 on: Feb 26, 2017, 10.23 pm
    Feb 26, 2017, 10.23 pm
    Incorrectly infated tyres wear quicker and don't do fuel consumption any good.   
    More importantly, if by chance you are unfortunate enough to be involved in an "life changing" accident and the police may check your tyres.  If your insurance company then get hold of the information and find that the tyres were not inflated correctly, you have even more agro. on your plate. 

    Apart from anything else I find the handle differs when the tyres ain't right.

    kper

  • Offline Oransay

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    Offline Oransay

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    Re: Recommended tyre pressures and their relevance.
    Reply #6 on: Feb 27, 2017, 12.50 am
    Feb 27, 2017, 12.50 am
    *Originally Posted by Phil [+]
    Incorrectly infated tyres wear quicker and don't do fuel consumption any good.   
    More importantly, if by chance you are unfortunate enough to be involved in an "life changing" accident and the police may check your tyres.  If your insurance company then get hold of the information and find that the tyres were not inflated correctly, you have even more agro. on your plate. 

    Apart from anything else I find the handle differs when the tyres ain't right.

    kper

    Aye, apart from anything else on a motor bike tires make all the difference.  :700:

    I've been riding for a long time and I'm constantly amazed by how far tires have come over the years. I remember low siding my KZ1000 on the Mull of Kintyre damn near 40 years ago, warm sunny day (yes, they have sunny warm days), low speed and no gravel... wtf...

    Now leaned over on my Ape, wet Macadam underneath, gravel be damned, nae problem! tires have come a long way indeed! :046:

    Dunlop RoadSmart III's now rate for over 20K, with no performance loss. I'm a Ludite so  :440:

  • Offline Shemogolee

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    Offline Shemogolee

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    Re: Recommended tyre pressures and their relevance.
    Reply #7 on: Mar 01, 2017, 06.45 am
    Mar 01, 2017, 06.45 am
    *Originally Posted by Donk [+]
    I ride solo, no luggage and my bike is currently in Florida as in not many curves.  There is no reason I should be running 42lbs in my rear tire the bike isn't carrying any weight 38-40 would be more appropriate.  I am running the middle out of my rear tire every 5000 miles because it is slightly over inflated for the load.  I also ride the bike a bit aggressively when there are corners and think 42lbs is a bit over inflated for that type of riding with an unloaded bike.  Both tire and bike manufacture guidelines should be adhered to but they are guidelines not absolutes.

    Hi All,

    There are always a variety of opinions about what tire pressure to run in our tires. Here are my comments about the Triumph recommended pressures of 36 and 42. The pressures on the tire sidewall are not recommended tire pressures. They indicate the maximum pressure for the max load that the tire is rated for (also shown on the sidewall. The only recommended pressures come from the Owners Manual.
     
    On my two previous motorcycles, both of which weighed about 900 pounds before any load was added, there was a range of pressures that were recommended by the manufacturer of the motorcycle that were weight dependent. The 36/42 recommended pressures recommended by Triumph for our TTSEs cater to all riding and load conditions. The Triumph engineers have determined that there is no need to vary the tire pressures as the motorcycle weight changes.

    As mentioned previously in this thread too low a tire pressure will cause more tire flex which will lead to abnormal tire wear patterns, increased tire wear and increased heat in the tire, all of which may lead to an  increased chance of a blow out. Too high a tire pressure will lead to abnormal tire wear and the increased chance of a blowout. It will also make the tire too rigid which will change the way the tire grips the road and therefore reduce the amount of traction available.

    Following the procedure of checking my tire pressure every day, setting 36/42 cold pressure and not letting the hooligan in me out too much  :002: (well, maybe in the corners) has allowed me to ride about 19,500 kilometers on my stock tires. I am not down to the wear bars and there is no abnormal wear showing on the tires. By the time I get the tires replaced next week I will have over 20,000 kilometers and still not be at the wear bars.

    best regards,
    Shemogolee
    If you're not disciplined enough to apply your knowledge and skills you're an accident looking for a place to happen