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#1003325 - 01/08/18 07:21 PM Re: 2017 R1200RT Stability [Re: dirtrider]  
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LIRider Offline
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LI, NY
Originally Posted by dirtrider
Originally Posted by LIRider
I'm not sure I follow dirtrider ... if you're tires were set to proper inflation pressure at the current ambient temperature (not your nice warm garage/shop), then why would there have been any issue with low pressure warning? In fact, had you set your tires in that nice warm shop, then indeed you were probably low once you got out on the road and the tires cooled to ambient temperature (before starting to warm up from riding, which should have brought the pressure up above the spec setting). Am I misinterpreting something?


Afternoon LIRider

BMW specified tire pressures (as well as most autos & motorcycles) are based on a nominal cold tire @ 68°f. Most manuals don't mention that as in most cases the ambient temps are not far enough off of 68°f (20°c) to make much difference so adding more confusion to tire checking procedures is not useful & can be confusing for most operators.

So lets assume I did the correct thing & (correctly) set my tire pressures in my shop to 32 psi at 68° (or 65°f in my case)-- I now ride the bike out into the -4°f cold. As the tires drop to ambient temps they could lose 7 psi, 32 psi minus 7 psi = 25 psi. 25 psi could be low enough to trip the low tire pressure warning. With the TPS temperature compensation system it all bases back to 68°f so the low tire warning threshold just drops to reflect that.

I am an all season rider (within reason) so usually run my tires a few pounds higher in the winter just so I don't bend a rim if I find a hidden square edged pot hole.



I have to say that's news to me and contrary to what I've been doing for the past 40 years. It's also contrary to anything I can find online too:

Air Pressure, Temperature Fluctuations

Winter vs. Summer Tire Pressure - What is the Proper Inflation?

Can you supply any information to back up that claim? I'm not being argumentative, just trying to establish the proper method based on facts (and yes, I know that not everything one reads online is in fact, "a fact").

The facts as I know them right now are:
The stated pressure is for the current ambient conditions and not some arbitrary "cold" setting.

#1003326 - 01/08/18 07:53 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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realshelby Offline
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realshelby  Offline
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I think part of your answer is in your owners manual......

#1003327 - 01/08/18 07:58 PM Re: 2017 R1200RT Stability [Re: dirtrider]  
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realshelby Offline
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Houston, Tx
Originally Posted by dirtrider


Actually my biggest problem is a fogging face shield & inability to turn my head very far due to head covering & a neck stuffer.



I have been about ready to do a "product evaluation" on this. I finally found something that keeps visors and glasses from fogging. So far I have tested in upper 40's to 90 degree rain with complete satisfaction. I won't likely get a chance to test in sub 20 degrees, maybe you could?

Clarity "DEFOG it" I bought the 5ml bottle and it goes with me on every trip.

Last edited by realshelby; 01/08/18 07:58 PM.
#1003332 - 01/08/18 09:12 PM Re: 2017 R1200RT Stability [Re: LIRider]  
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dirtrider Offline
The Oracle
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Ohio
Originally Posted by LIRider
Originally Posted by dirtrider
Originally Posted by LIRider
I'm not sure I follow dirtrider ... if you're tires were set to proper inflation pressure at the current ambient temperature (not your nice warm garage/shop), then why would there have been any issue with low pressure warning? In fact, had you set your tires in that nice warm shop, then indeed you were probably low once you got out on the road and the tires cooled to ambient temperature (before starting to warm up from riding, which should have brought the pressure up above the spec setting). Am I misinterpreting something?


Afternoon LIRider

BMW specified tire pressures (as well as most autos & motorcycles) are based on a nominal cold tire @ 68°f. Most manuals don't mention that as in most cases the ambient temps are not far enough off of 68°f (20°c) to make much difference so adding more confusion to tire checking procedures is not useful & can be confusing for most operators.

So lets assume I did the correct thing & (correctly) set my tire pressures in my shop to 32 psi at 68° (or 65°f in my case)-- I now ride the bike out into the -4°f cold. As the tires drop to ambient temps they could lose 7 psi, 32 psi minus 7 psi = 25 psi. 25 psi could be low enough to trip the low tire pressure warning. With the TPS temperature compensation system it all bases back to 68°f so the low tire warning threshold just drops to reflect that.

I am an all season rider (within reason) so usually run my tires a few pounds higher in the winter just so I don't bend a rim if I find a hidden square edged pot hole.



I have to say that's news to me and contrary to what I've been doing for the past 40 years. It's also contrary to anything I can find online too:



Can you supply any information to back up that claim? I'm not being argumentative, just trying to establish the proper method based on facts (and yes, I know that not everything one reads online is in fact, "a fact").

The facts as I know them right now are:
The stated pressure is for the current ambient conditions and not some arbitrary "cold" setting.





Afternoon LIRider

Most if not all tire pressures that I work with daily in engineering (some days many) are based off of a 68°f cold factor. Due to the ideal gas law you just can't (with accuracy anyhow) call any temperature a cold temperature. It needs to be defined (especially when setting safe operating pressures).

While the BMW manual says a cold tire they don't define what a cold tire is that could be anywhere form a -25°f or a +112°f & still be an overnight cold soak. They also don't expect a rider to stop & allow their tires to cool to a cold tire the get re-air'd to the ambient as they ride from a desert area to a very cold high mountain area.

Nothing wrong with using the overnight cold ambient temps for base tire setting as long as that temperature is reasonably close to 68°f (48°f to 88°f will get you within 2 lbs so usually close enough for most riders & most conditions.

You need to look in the riders manual as under the general tire pressures area, there they just call out cold tire (no temperature definition or fudge factor). Seeing as EVERY 10°f in cold-tire-temperature-change changes the tire pressures about 1 pound you would thing think that if BMW was really concerned that they would specify a nominal cold tire temperature range or give a conversion chart. They don't for the same reason that the company that I work for is very hesitant to use different front & rear tire pressures on general consumer vehicles as most regular drivers get very confused by the split numbers (we do use split pressures on some now but it is a big fight to get that to be written in the owners manuals)

Most riders that ride hard (not just think they ride hard) have a good idea of the tire pressures that work for their tire type, bike, & riding style as well as temperature ranges so they usually use their own cold tire temperature offsets.

BMW if very contradictory in their riders manual as in the general tire pressure section they just say COLD TIRES. (non defined)

But later in the same manual they have a very specific tire pressure & tire filling chart with an explanation on how to use the RDS system to obtain corrected tire pressures (the RDC system IS corrected back to 68°f (20°c).

If you use the riders manual & a pressure gauge to fill to 34 psi at 90°f cold tire (think desert areas), or use 45°f cold tire (think upper Midwest in late fall) then your pressures will be way off per the RDC system & RDC procedures.

One of the nice things about using the RDC system to (at least check/verify the pressures) is that it IS corrected back to 68°f (20°c). It might not be totally accurate to tenths of a pound but at least it is ALWAYS apples to apples so no matter the temperatures the tires will be well within safe & correct pressure ranges. (without temperature compensation if a rider fills a tire at 0°f to suggested cold pressure then gets on the freeway at 90mph for a couple of hours his tires will be well above max safe operating pressures).

[Linked Image]


D.R. ___
Sent from my rotory dial wall phone!
#1003337 - 01/08/18 11:05 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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That’s very clear DR.

So here in FL I set my tires to 36.3 in the garage at 68F, go out on a 98F day, ride at 80 and heat the tires another 50 degrees (my car tire pressures go up about 5 psi at that speed) and my actual tire pressure will be 44.3 psi but the display will still indicate 36.

#1003339 - 01/08/18 11:57 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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terryofperry Offline
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"One of the nice things about using the RDC system to (at least check/verify the pressures) is that it IS corrected back to 68°f (20°c). It might not be totally accurate to tenths of a pound but at least it is ALWAYS apples to apples so no matter the temperatures the tires will be well within safe & correct pressure ranges. (without temperature compensation if a rider fills a tire at 0°f to suggested cold pressure then gets on the freeway at 90mph for a couple of hours his tires will be well above max safe operating pressures)."

What is the max safe operating pressure?

Thanks.

Terry

Last edited by terryofperry; 01/08/18 11:57 PM.

Terry

Perry, GA
#1003352 - 01/09/18 11:51 AM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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Naples FL & Cape Cod
Hey Terry,
When I saw your question, I thought “that’s easy, I’ll go read the sidewall.” All I can find on either front or back is a max load spec at a certain pressure. That pressure is 42 psi COLD on each tire. The front load is 520# and the rear is 805#.

Last edited by roger 04 rt; 01/09/18 11:55 AM.
#1003873 - 01/18/18 05:05 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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TJRL Offline
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England
Originally Posted by roger 04 rt
That’s very clear DR.

So here in FL I set my tires to 36.3 in the garage at 68F, go out on a 98F day, ride at 80 and heat the tires another 50 degrees (my car tire pressures go up about 5 psi at that speed) and my actual tire pressure will be 44.3 psi but the display will still indicate 36.


No, I do not think that is how it works. If I fill my tyres up (after an overnight rest in the garage) to the pressures indicated in the manual or perhaps a few PSI above, when I start my ride the display shows the pressures exactly as I filled them. Then as the ride progresses both tyre pressures are shown to increase a few PSI. The next day the display shows the pressures as they were filled the day before.


1999 Harley Davison MT350 (with 604e engine)
2014 F800GT
2015 R1200RT LE
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