# Tire Pressure Monitor

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• 08-22-2019, 01:18 AM
Dann
[QUOTE=apbehnen;1176718]The charts are awesome. Thanks.

Dan's Chart does not match with Alan's Chart. Dan's chart indicates you should under inflate and Alan's chart indicates you should over inflate for temperatures above 68 degrees to get to the recommended cold inflation pressure, unless I am reading them wrong.[/QUOTE]

Air pressure increases with higher temp. This is why your tire pressure is higher when the tire is warm.
If the outside temp is higher, your tire pressure will be higher to start with. This why the pressure needs to be lowered at higher temp to compensate.
Otherwise it will rise even more when the tire warms up.
• 08-22-2019, 03:07 AM
PGlaves
[QUOTE=Dann;1176721] This why the pressure needs to be lowered at higher temp to compensate.
Otherwise it will rise even more when the tire warms up.[/QUOTE]

Nope. The specified "cold" temperature defined as at 20 degrees C is expected to go up. If it is correct at 20C = 68F, then it will still be correct as the temperature increases. In the old days we looked at a 10% pressure incease cold to hot. With modern radial tires an increase of 15% or a little more cold to hot is more typical due to more sidewall flex. I expect to see a warmed up rear tire to be about 35 degrees hotter than ambient air temperature. So on a 90 degree day I expect to see an internal tire temperature of about 125F, and expect to see a pressure 5 or 6 psi above the cold (68F) pressure. There is no need to bleed off that increased pressure. In fact, if you do you are running an under-inflated tire. Just say no and don't do it.
• 08-22-2019, 12:24 PM
gator
[QUOTE=Dann;1176706]When checking my air pressure I use an excel spreadsheet. (I'm not the one who set it up)
You enter the actual temperature and the pressure you want, and it will calculate which pressure you need to set your tire to in order to have your desired pressure at 68deg

YMMV[/QUOTE]

When I download this file Excel opens but there is no spreadsheet. Anybody else get this to work?
Gator
• 08-22-2019, 12:50 PM
Dann
[QUOTE=PGlaves;1176738]Nope. The specified "cold" temperature defined as at 20 degrees C is expected to go up. If it is correct at 20C = 68F, then it will still be correct as the temperature increases. In the old days we looked at a 10% pressure incease cold to hot. With modern radial tires an increase of 15% or a little more cold to hot is more typical due to more sidewall flex. I expect to see a warmed up rear tire to be about 35 degrees hotter than ambient air temperature. So on a 90 degree day I expect to see an internal tire temperature of about 125F, and expect to see a pressure 5 or 6 psi above the cold (68F) pressure. There is no need to bleed off that increased pressure. In fact, if you do you are running an under-inflated tire. Just say no and don't do it.[/QUOTE]

That's what I meant, I guess I cannot express myself correctly in english :dunno
• 08-22-2019, 12:53 PM
Dann
[QUOTE=gator;1176758]When I download this file Excel opens but there is no spreadsheet. Anybody else get this to work?
Gator[/QUOTE]

I just tried it and it works fine

Did you decompress the zip file first?

There is a file called :Tire Pressure Adjustment.xls inside.
That's the excel file
• 08-23-2019, 10:39 AM
lupinblue
Just be happy you don’t have a Canadian bike. Our pressures display in bars ( no, not the drinking kind). Try and find a pressure gauge on the road anywhere that shows bars!
The answer, of course, is to keep the engine running after you’ve ridden far enough for the display to work and top up the tires until the display shows the correct pressure: it takes a few seconds to stabilize.
• 08-23-2019, 11:49 AM
alstrickland55
This is a little off topic but maybe provides a little good info...

Yesterday the front TPM on my K1600GTL guilt working. The bike is several years old so I am pretty sure it is a dead battery. I had a spare. It's a Chinese knock-off but I have read on the K1600 forum that several people are using them. After I installed it I attempted activating it with the GS911. There are two methods. First is to use a special tool to set the sensor to transmit and then use the GS911 to but the bike computer in learn mode. The second method is to manually enter the serial number of the transmitter. Since I don't have the activation tool I used the manual method of putting in the serial number but I could not get the computer to return a confirmation. I read somewhere that the sensor can sometimes be put in transmit mode by inflating the tire to 50 psi and then letting all of the air out. I did this and then used the GS911 to put the bike computer in learn mode. Now neither the front or back monitor is working. My guess is the computer is still in learn mode waiting for a signal from the new sensor. I will take it to the dealership next week and see if they can set it. I will report back after that.

Sent from my XT1254 using Tapatalk
• 08-23-2019, 12:13 PM
gator
[QUOTE=Dann;1176762]I just tried it and it works fine

Did you decompress the zip file first?

There is a file called :Tire Pressure Adjustment.xls inside.
That's the excel file[/QUOTE]

I can't figure this out. With Excel 2010 on my pc I get a blank page. If I copy it to my ipad it works in excel, numbers and sheets. All three of the spreadsheet options available there.
everything in tried on the PC was blank
No idea why.
Gator
• 08-23-2019, 12:34 PM
strataj
[QUOTE=alstrickland55;1176827]This is a little off topic but maybe provides a little good info...

Yesterday the front TPM on my K1600GTL guilt working. The bike is several years old so I am pretty sure it is a dead battery. I had a spare. It's a Chinese knock-off but I have read on the K1600 forum that several people are using them. After I installed it I attempted activating it with the GS911. There are two methods. First is to use a special tool to set the sensor to transmit and then use the GS911 to but the bike computer in learn mode. The second method is to manually enter the serial number of the transmitter. Since I don't have the activation tool I used the manual method of putting in the serial number but I could not get the computer to return a confirmation. I read somewhere that the sensor can sometimes be put in transmit mode by inflating the tire to 50 psi and then letting all of the air out. I did this and then used the GS911 to put the bike computer in learn mode. Now neither the front or back monitor is working. My guess is the computer is still in learn mode waiting for a signal from the new sensor. I will take it to the dealership next week and see if they can set it. I will report back after that.

Sent from my XT1254 using Tapatalk[/QUOTE]

I'm not aware of the transmit mode you mention, the other two methods work. Your Chinese senors may not have the numbers you need so you need a wake up tool. This one should work fine [url]https://www.amazon.com/VXDAS-EL-50448-Pressure-Monitor-Activation/dp/B072BK693N[/url] or find alike.

Jay
• 08-23-2019, 07:23 PM
AlanColes
[QUOTE=apbehnen;1176718]... chart indicates you should over inflate for temperatures above 68 degrees to get to the recommended cold inflation pressure, unless I am reading them wrong.[/QUOTE]What you are meaning to say is correct (increase the cold-tire PSI), but the wording is problematic (overinflate).

All that the chart or Dann's spreadsheet do is identify the adjustment in cold-tire pressure required for different ambient temperatures, as Paul pointed out.

Where a lot of people go completely wrong is thinking that they should put less air in a tire on extremely hot days or when riding with heavy loads. This is wrong. Not only is it wrong, but it is the opposite of what should be done and can easily lead to tire failure. Sometimes catastrophic failure.

Too little air in the tire will increase tire flex which generates more heat on a moving bike than ambient temperature. Too much air (cold-inflation) doesn't allow for sufficient tire flex and therefore generates less heat. The tire will have trouble (in medium ambient temp days) getting up to its optimal operating temperature. In either situation, traction is sacrificed.

Therefore, if one is going to err, it is better to err on the high side of inflation. I've always found that I prefer my tires inflated 1-2 PSI over the manual on newer bikes and 2-4 PSI on the older ones (I suspect that new tire technology is part of that). YMMV
• 08-24-2019, 02:29 PM
Dann
[QUOTE=gator;1176828]I can't figure this out. With Excel 2010 on my pc I get a blank page. If I copy it to my ipad it works in excel, numbers and sheets. All three of the spreadsheet options available there.
everything in tried on the PC was blank
No idea why.
Gator[/QUOTE]

Your 2010 version of excel is probably too old
• 08-25-2019, 09:14 PM
ajaxthegreater
Crap system
How sad that the computer on this \$25K motorcycle which knows air pressure, temperature, and internal tire pressure can’t figure out something that you can do with a spreadsheet. Mine’s off consistently by 5-6 lbs low on both wheels and the dealer told me there is nothing that can be done about that. I seem to recall that the TPMS on my 2010 K1300GT was spot on. If the RT readout was just meant to be a “low pressure” sensor it should have been an idiot light and not some display of bogus numbers. How BMW can say this is OK is beyond me, that's bull\$hit.
• 08-25-2019, 11:29 PM
ncpbmw1953
[QUOTE=ajaxthegreater;1177102]How sad that the computer on this \$25K motorcycle which knows air pressure, temperature, and internal tire pressure can’t figure out something that you can do with a spreadsheet. Mine’s off consistently by 5-6 lbs low on both wheels and the dealer told me there is nothing that can be done about that. I seem to recall that the TPMS on my 2010 K1300GT was spot on. If the RT readout was just meant to be a “low pressure” sensor it should have been an idiot light and not some display of bogus numbers. How BMW can say this is OK is beyond me, that's bull\$hit.[/QUOTE]

My '16's TPMS is completely reliable and correlates well after the tires are road-warmed. Moreover, its temperature-correction appears perfect. Sounds like either something is wrong w/ your specific implementation of TPMS, or your manual gauge is off, or they're both off in opposite directions.
• 08-26-2019, 12:10 AM
apbehnen
Same problem as Bill
Bill, I have the same problem with my 2019 R1250GS, which was the subject of my original post in this thread. I inflate the tires with my "Motion Pro Professional" digital tire pressure gage to spec, and the tire pressure monitor on my bike consistently reads the pressure about one pound lower. Not sure which to trust, the gage or the bike, but I think I will trust the motion pro tire pressure gage and use the pressure monitor on the bike as just a guide. I had the same problem with my 2014 GS.
P.S. I use to live in Highlands Ranch. I retired and moved to Tennessee because the cost of living here is lower. I miss the riding in Colorado, however.
• 08-26-2019, 12:14 AM
PGlaves
[QUOTE=apbehnen;1177122]Bill, I have the same problem with my 2019 R1250GS, which was the subject of my original post in this thread. I inflate the tires with my "Motion Pro Professional" digital tire pressure gage to spec, and the tire pressure monitor on my bike consistently reads the pressure about one pound lower. Not sure which to trust, the gage or the bike, but I think I will trust the motion pro tire pressure gage and use the pressure monitor on the bike as just a guide. I had the same problem with my 2014 GS.[/QUOTE]

I think 1 psi lies within the noise level. After all, when BMW says the recommended pressure one-up is X, they have no idea if the rider weighs 160 or 250.
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