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2010RT Air Pressure Sensors

105258

Old Rider - OK Mechanic
The tire air pressure sensors on this bike have been perfect, until my latest trip through Glacier National Park. When I got to St Mary's I noticed the tire pressures were 5 psi low so I stoped to check. Theye were fine. Now that I am home on the Canadian praries they continue to read lower than they actually are bu some 5 psi. Any suggestions ?
 
What standard are you using to check the pressure? I have found almost all tire-pressure gages seem to drift out of calibration. The electronic ones included. Only one that has been really consistent is one attached to a tire inflater I have - from Harbor Freight. It agrees perfectly with my TPM system readout (which isn't a BMW system - it reads real pressures, not temperature compensated.)

My basic thought is - if you find a pressure that works for you - using one gage, then ALWAYS use the same gage to check your pressure. Oh - one other thing I've noticed.. I never need to add air to my tires as long as I don't check them with an external gage. It seems just hooking up, reading, disconnecting a tire pressure gage drops the pressure 1-2 PSI on a bike tire. Not so much on a car tire since it has a much greater volume of air.

Of course YMMV..
 
"...hooking up, reading, disconnecting..." It's tough to get the tire gauge to seal on the valve stem without losing a little, or a lot of air. The recent R12RTs at least have that clever spoke-mounted stem that sticks out the side which is a lot easier than the usual radial-mounted one in the rear.

Consumer Reports did a test a while back of various tire pressure guages and almost all were within a pound +/-, even some cheapies. I have three different types (round dial, electronic and pencil) and they agree exactly. The round dial has a straight chuck that is hard to get on the rear wheel stem; the electronic has a right-angle chuck that is hard to get on the front stem; the pencil gauge has a 45 degree chuck that works on both wheels.

I don't understand the point of BMW's temperature compensated TPMS. Shouldn't I know what the real pressures are. The change in pressure from cold to warm tire is a good indicator of correct pressure settings.

pete
 
I have checked with two guages, a mechanical and and electronic and both agree , but not with the pressure sensors ?
 
I have checked with two guages, a mechanical and and electronic and both agree , but not with the pressure sensors ?

Thing is - I can't imagine anything that would happen to change the calibration of both TPM's at the same time.. so the common factor ends up being the gages. You might try a 3rd.. :scratch
 
The problem could be with the TPMS receiver, since both tires show exactly the same symptoms.

The system is made for BMW by Schrader Electronics in Northern Ireland, UK. An Email to their customer service department might get some answers.
 
I've got a VW that allows me to reset the warning limits of the TPMS it has from its dash.
Its done simply by hitting reset after the tires are all properly inflated. So one good calibrated gauge allows an accurate reset of the car. But it doesn't read psi, thank goodness- it only shows a warning when it thinks you need air.
From my perspective I'm not happy with this uneeded crap in my vehicles- its just another unreliable and expensive electronic piece of junk put there to protect idiots and the oblivious from themselves by a nanny govt

Most every rental car I get that has a tpms has the warning light on. Can't wait to read about the first class action by all the folks allegedly injured in rentals with low air now that there is some visible evidence some lawyer can use to enrich himself...
 
Thanks

Thanks for your asstance. I have tried all your suggestions and I belive I have two gages that are accurate, but no change in the sensor readings. I will take the bike to the dealer next week.
 
No Resolution

As I suspected the actual air pressure, measured by four very accurate race guages, was four pounds higher than what was read by the TPS. The expensive guages read the same as a $6.00 Canadian Tire slide type guage by the way.

I took the bike to the dealer who confirmed the issue. BMW's response was the same as the fuel strips, the guage is not expected to be accurate, but is meant to be a warning for a tire going flat. They never did address the issue of the apparent sudden change in accuracy of the sensor.

For such an expensive bike you would think they would be better than that. Why would they put the readings in the computer and not just use an idiot light.

My GM van is very accurate and I purched a set of four sensors for less than $100.00 CDN for a set of snow tires a few years back. Wonder what the BMW ones cost ?
 
As I suspected the actual air pressure, measured by four very accurate race guages, was four pounds higher than what was read by the TPS. The expensive guages read the same as a $6.00 Canadian Tire slide type guage by the way.

I took the bike to the dealer who confirmed the issue. BMW's response was the same as the fuel strips, the guage is not expected to be accurate, but is meant to be a warning for a tire going flat. They never did address the issue of the apparent sudden change in accuracy of the sensor.

For such an expensive bike you would think they would be better than that. Why would they put the readings in the computer and not just use an idiot light.

My GM van is very accurate and I purched a set of four sensors for less than $100.00 CDN for a set of snow tires a few years back. Wonder what the BMW ones cost ?
YOu do understand the temperature compensated nature of the BMW system. Your gauge and your TPMSnly match at 68 Degrees F.

You send set your tires with to the pressures you desire on the TPMS. and then take a reading with your gauge to determine the diffeentail between your gauge and the TPMS, and then adjust accordingly This is explained in the Owner's manual. See attachment
 

Attachments

  • RT TPMS0001.pdf
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Their Back !!

Just last week on my way to Toronto, they began to work again. Now they read exactly what the tire qage reads. Go figure .
 
YOu do understand the temperature compensated nature of the BMW system. Your gauge and your TPMSnly match at 68 Degrees F.

You send set your tires with to the pressures you desire on the TPMS. and then take a reading with your gauge to determine the diffeentail between your gauge and the TPMS, and then adjust accordingly This is explained in the Owner's manual. See attachment

The example in the Owner's Manual essentially states to inflate your tires so the TPMS shows the desired values. Since the TPMS shows what the pressure would be if the temperature were 68 F, the result is an under-inflated tire on cold days and an over-inflated tire on hot days. For bikes without TPMS, BMW does not provide a table of desired cold pressures versus ambient temperature. They provide only a single desired pressure. The whole temperature compensation scheme conflicts with the information provided by tire manufacturers, who are the real experts.
 
Tire pressure

Seems to me that the pressure monitor on the bike is more of a fancy warning light than a accurate reading of the "tire pressure" as we have all come to understand. I was always taught to check the tire pressure when the tires were "cold" meaning before you began to ride. And the TPMS on the bike gives a warning signal only if it reads a figure plus or minus 5 psi I think.

I don't use the TPMS to determine accuracy of the tire pressure. I use a gauge before I ride.
 
I took the bike to the dealer who confirmed the issue. BMW's response was the same as the fuel strips, the guage is not expected to be accurate, but is meant to be a warning for a tire going flat. They never did address the issue of the apparent sudden change in accuracy of the sensor.

For such an expensive bike you would think they would be better than that. Why would they put the readings in the computer and not just use an idiot light.

Many cars do that, but then you know motorcyclists ... .

Yes, the point of the system is to advise you of a significant change from the pressure YOU intitially set (within reason). Rather than testing against a guage, you should test whether the change creates the notification properly.

And, it's not an expensive bike ... it's a German bike.
 
BMW's assertion that the TPMS readings are not designed to be accurate sounds like typical BMW BS. The US DOT test procedure for TPMS on automobiles requires that the warning light illuminate when any tire pressure is 1 psi below the threshold. The same procedure specifies confirmation of pressures with an accuracy of 0.5 psi. Therefore, the systems need to be fairly accurate.

While the test procedure in not applicable to motorcycle TPMS, the BMW TPMS manufacturer, Schrader, is the largest manufacturer of automobile systems, so I would expect the same accuracy. Also, the tire pressure setting procedures in the BMW Owners Manuals reads like the TPMS display is spot on. If all BMW intends is a warning for low presures, why didn't they simply install an idiot light like most automobile manufacturers do?
 
Ride with confidence.
Use a pressure gauge.
Regularly.
And invest in a small 12 volt inflator.
It makes adjustments effortless.
Like the fuel strip, don't rely on the pressure indicator for an accurate reading.
 
Here is my take on TPM: I always rely on a manual gauge. The one I use is the one that will be less troublesome fitting on both the front and the rear wheels of my RT. There aren't many, and it's the pencil kind. I chek my cold tires, inflate if necessary, and ride on. I take note of the pressures indicated by the TPMs on my OBC, ant that will be my reference fron then on, even if they differ from the gauge to start with. If the indicated pressures change by more than a couple of psi down, I will check the pressure again. Other than that, I don't bother, knowing the TPMs will warn me in time. That's their only useful purpose, not to give exact pressures.
 
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