Tire pressure monitor system

Stebe said:

Hmm. Good to know. I have a Battery Tender input wired directly to the battery, should the adapter not be able to adapt I will splice the output cable from one of my old Battery Tender's to the adapter and run it that way. Thanks for the info, I may not have thought about the canbus system not allowing it to work.

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You and me both Stebe. I purchased a Cycle Pump from Best Rest Products. It has alligator clips and a 2-prong SAE connector. I also have a fused SAE outlet to the battery for charging and it runs the pump fine. The pump draws 10amps, and my original intent to use the auxiliary power port was dashed when I discovered the 5-6 amp limit of the ports. Excellent pumps, by the way, for anyone shopping for one. At 10 amps, you don't have to wait all morning for it to fill a tire. Happy trails.

LFarling said:

I have ALWAYS seen a rise in my tire pressure during riding, and especially loaded or when I used to haul a passenger.

I really does not matter what temp something is calibrated to, if something gets hot, it expands, causes a pressure rise and should register.

I have seen 1 to 2 PSI on the front and 1-4 PSI on the rear loaded Depending on road and temp, how hard I am running and braking, and if I am loaded for a rally or trip. As a rule just me, no bags top case I see 1 in the front and 1-2 in the rear. And that is a cold check set 40/42 before the ride. It is a predictable and there is math to show you what % of rise one should see and not be concerned with if you want to look it up.

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I have never seen a rise on the dash. I have checked the pressure with my gauge cold and then on return after a long ride and the pressures do rise. Ah well.

Tire Pressure Gauge VS TPMS

How fortunate that this topic came up just when this happens. Recently I have noticed that my TPM always says both tires are 4-5 psi low. This morning I found my garage at 68F so I checked the inflation pressure with a very high quality gauge. I have verified the gauge accuracy with several other gauges and the TPM in my 18 Sierra. Front tire was 36.5 and rear was 42 on my brand new Roadmaster IIIs. The TPM on my 2014 RT says 31 and 37. Since this is corrected to 68F the readings should have been in agreement. Has anyone seen this problem before? Now I am questioning the accuracy of the BMW TPM system.

qbrodie said:

How fortunate that this topic came up just when this happens. Recently I have noticed that my TPM always says both tires are 4-5 psi low. This morning I found my garage at 68F so I checked the inflation pressure with a very high quality gauge. I have verified the gauge accuracy with several other gauges and the TPM in my 18 Sierra. Front tire was 36.5 and rear was 42 on my brand new Roadmaster IIIs. The TPM on my 2014 RT says 31 and 37. Since this is corrected to 68F the readings should have been in agreement. Has anyone seen this problem before? Now I am questioning the accuracy of the BMW TPM system.

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The TPC reads the tire pressure and temperature *inside the tire* at the time of reading. Should have taken it out just far/fast enough (19 mph) to get a TPC reading, and then re-checked.

r0ckrat said:

The TPC reads the tire pressure and temperature *inside the tire* at the time of reading. Should have taken it out just far/fast enough (19 mph) to get a TPC reading, and then re-checked.

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. Thanks for the advice but that’s exactly what I did.

If you have a jump starter battery you can bypass the whole thing and use one of these...

https://www.amazon.com/gp/product/B019IFDIIS/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

Based on the data I would venture that the TPMS is not accurate.

PGlaves said:

Based on the data I would venture that the TPMS is not accurate.

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I agree, to me, the value of the TPMS is the alert it provides when rapid deflation occurs. Everything else is relative.

PGlaves said:

Based on the data I would venture that the TPMS is not accurate.

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What data? I think if you compared ample size n data for BMW TPMS for accuracy versus *most all* hand held, person-interpreted and translated (temp corrrected, yeah sure) TP gauges I'd easily bet my money on BMW TPMS, and have for 6y now. After all, it's directly sensing pressure, there is no error for how the sensor (i.e., tip of your TP gauge) was applied by the human user, and what's more is perfectly temperature compensated. Hard to beat.

bigjohnsd said:

I agree, to me, the value of the TPMS is the alert it provides when rapid deflation occurs. Everything else is relative.

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Or, for that matter, slow deflation. It is a valuable safety device. The TPMS on my VW and my wife's Honda have each alerted us to nails in the tires. For four wheels it's a convenience to get the tire repaired before a failure on the road. For two wheels it's much more than that.

ncpbmw1953 said:

What data? I think if you compared ample size n data for BMW TPMS for accuracy versus *most all* hand held, person-interpreted and translated (temp corrrected, yeah sure) TP gauges I'd easily bet my money on BMW TPMS, and have for 6y now. After all, it's directly sensing pressure, there is no error for how the sensor (i.e., tip of your TP gauge) was applied by the human user, and what's more is perfectly temperature compensated. Hard to beat.

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We will just have to agree to disagree. If tested beside a known reliable accurate gauge and the TPMS reads materially different then I would conclude the TPMS is not accurate. And whether BMW put its name on the Chinese or Japanese or Indian made device matters not one whit.

Surface thermometer.

Recent world events have landed a touchless thermometer in my home. Last night I discovered it has a “human” setting and a “surface” setting. Last night I used the “surface” setting to measure the temp of my tyres in the garage. Initially 88* F after a couple of hours with the AC running I got it down to 77*F.

The owners manual indicates that the TPMS “adjusts” the temperature reading to a 68*F (20*C) compensated readout. By getting the cold tyre pressure as close to 68* that I can, my electronic tire gauge is used to get the desired pressures (38.5 front/42.5 rear).

By adjusting the cold tire pressure to match the 68* algorithm, I find the TPMS read out to be completely accurate all of the time.

(Except this morning, my 4 year old battery on my front TPMS died, throwing a red fault code. I need to get it replaced using my RPM One extended warranty) I new the battery was dying when I got new tires a month ago, and ordered a new one, we’ll see if my dealer followed through with the Munich order)