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[Larry_Legend]

I have a 135 with just 3000 miles on it. I don't drive it that often and live in NJ. I typically leave the car in the garage and just drive it on weekends. We had a cold snap back in early November (I think) and the sensor went off. I freaked out, not having had RFT's before, and went to the gas station, put air in the tires, reset the TPM, and had no issues.... until tonight!

This time I didn't panic and read the monitor. Front Driver Side tire was low. Yellow light went off. I think it was this tire last time based on my own tire pressure measurements I took before I refilled the tires, but they were all kinda low.

At any rate, I got some air at the service station and drove 25 miles with no sensor issues. The temp did drop a lot from this afternoon to this evening, and the car was in my girlfriends driveway for the day, so it is quite possible that this was the issue. In fact, I think it happened the same way the first time the sensor went off.

Okay, I'm rambling.

First, I have no idea how this sensor works. Does it go off only for the low tire? multiple tires?

Second, how hard do you have to hit a rim to bend it? I baby the hell out of my 135 and haven't hit any curbs/pot holes/rocks yet (knock on wood) and even drive 10 mph going over railroad tracks. Could this be an issue? I did go months before the sensor went off again (and the temp did drop a lot over a few hours).

Third, since the first sensor issue, I've noticed a drop in gas mileage. Was getting about 23 mpg, now down about 40 miles per tank. Friend with a mechanic dad said the winter gas could do that. Thoughts? I worry it could be related to the tire.

All in all, I think I'm going to call BMW and make them earn the free maintenance package we all paid for. Any advice would be GREATLY appreciated.

[MerlinMc]

Originally Posted by Larry_Legend

I have a 135 with just 3000 miles on it. I don't drive it that often and live in NJ. I typically leave the car in the garage and just drive it on weekends. We had a cold snap back in early November (I think) and the sensor went off. I freaked out, not having had RFT's before, and went to the gas station, put air in the tires, reset the TPM, and had no issues.... until tonight!

This time I didn't panic and read the monitor. Front Driver Side tire was low. Yellow light went off. I think it was this tire last time based on my own tire pressure measurements I took before I refilled the tires, but they were all kinda low.

At any rate, I got some air at the service station and drove 25 miles with no sensor issues. The temp did drop a lot from this afternoon to this evening, and the car was in my girlfriends driveway for the day, so it is quite possible that this was the issue. In fact, I think it happened the same way the first time the sensor went off.

Okay, I'm rambling.

First, I have no idea how this sensor works. Does it go off only for the low tire? multiple tires?

Second, how hard do you have to hit a rim to bend it? I baby the hell out of my 135 and haven't hit any curbs/pot holes/rocks yet (knock on wood) and even drive 10 mph going over railroad tracks. Could this be an issue? I did go months before the sensor went off again (and the temp did drop a lot over a few hours).

Third, since the first sensor issue, I've noticed a drop in gas mileage. Was getting about 23 mpg, now down about 40 miles per tank. Friend with a mechanic dad said the winter gas could do that. Thoughts? I worry it could be related to the tire.

All in all, I think I'm going to call BMW and make them earn the free maintenance package we all paid for. Any advice would be GREATLY appreciated.

We have two BMWs with the RFTs and when it got cold here in Seattle they both went off and needed to be reset. The RFTs ride harshly in both of these vehicles compared to previous BMWs and other vehicles without RFTs.

[jkp1187]

I'm curious, too. Does the TPMS sound the alarm if pressure goes below a pre-set PSI, or just if one tire is significantly lower than the others? If it's the former, can I specify what PSI the alarm should go off at?

[FOXYCaymanS]

Originally Posted by Larry_Legend

.

First, I have no idea how this sensor works. Does it go off only for the low tire? multiple tires?

Second, how hard do you have to hit a rim to bend it? I baby the hell out of my 135 and haven't hit any curbs/pot holes/rocks yet (knock on wood) and even drive 10 mph going over railroad tracks. Could this be an issue? I did go months before the sensor went off again (and the temp did drop a lot over a few hours).

Third, since the first sensor issue, I've noticed a drop in gas mileage. Was getting about 23 mpg, now down about 40 miles per tank. Friend with a mechanic dad said the winter gas could do that. Thoughts? I worry it could be related to the tire.

All in all, I think I'm going to call BMW and make them earn the free maintenance package we all paid for. Any advice would be GREATLY appreciated.

I suggest reading this:
http://www.edmunds.com/ownership/tir...8/article.html

But I've also had issues with my runflat tire pressure; unfortunately the best way to ensure you have the proper pressure is to check them yourself. Weather here in Atlanta changes too much to rely on the TPMS. TPMS which doesn't actually check the pressure, it just detects the difference in rotation among the tires. This system can pick up low pressure in a single tire, but not seasonal pressure changes (due to temperature drops in the fall and winter) that affect all 4 tires- which is exactly what continues to happen to me. Don't forget this either... TPMS had to be "initialized" right after the tires are inflated to the correct pressures, because that's the reference point used by the computer to compare the tire rotation later. If the system is not initialized properly, e.g., not reset after tire rotation or a flat repair, that would also end up running the tires at the wrong pressure.

Basically, carry a pressure gauge and check your tire pressure on RFT more diligently than with non-RFT tires since we can't "visibly" see that there is low pressure in the tire because RFT's have stiff sidewalls that make a flat tire stay more round- and since BMW's tires are more low profile it makes it even THAT MORE difficult to tell.

I personally check my tire pressure every two-three weeks... but I live in a climate where it's 80's one week and 60's the next.

Good Luck. Darn RFT's!!!!