Has anyone done an RPA Retrofit in X5?
 

Hi guys! Just wondering whether anyone has done an RPA retrofit in an '03 4.4i? I believe the RPA is better to go in for rather than the RDC, as the RPA entails the use of a module and uses wheel rotational signals to trigger a fault. Whereas the RDC requires sensors in each wheel well,etc. Do most X5s come with this already installed to detect a "Tire Defect" or does one have to add it? I have not seen a MOD item on x5world and hence was wondering...... Can someone elaborate on this, or provide installation directions/insight on this? Thx in advance!

Hope to hear from you soon.

Regards,

Kris

There may be some confusion around the acronyms in different parts of the world. In North America, the tire pressure monitoring system uses wheel speed sensors, and is commonly referred to as TPM. That is the one you are referring to as RDC. It should be a fairly simple retrofit, assuming your vehicle had it as an option originally. Search on TPM to see related posts, or if anyone on the board has done it. The sensors are the standard DSC/ABS sensors. There is a button to reset it, and likely a module to add the logic to the vehicle.

In North America, RPA can stand for Remote Parking Assist, also known as PDC or Park Distance Control. What you are referring to as RPA is a system that has pressure sensors in each wheel, whatever it is called by BMW. It is not available in North America, as I understand it. It is also available from the aftermarket (Tirerack.com sells one, so do other tire stores) as well as BMW, outside of North America (for certain models). The advantage of this system is that if your tires slowly lose pressure over time, the wheel speed sensors won't pick it up, because they measure the rotational speed difference between each tire. The pressure sensor will pick up a slow pressure drop, if it crosses the threshold pressure setting. Having said that, I am not sure that it is really necessary in a road vehicle. I have some experience with this type of system in off-road heavy equipment tires, but in that case the price of a low pressure or flat tire is much higher because tire repair costs are insignificant compared to the costs of machine downtime.

I would invest in a good manual tire pressure gauge, and make it part of your regular vehicle check. If the wheel speed sensor system was an easy upgrade, that would be the only one I would consider. I have that system on my Z4, but it has provided no value to me yet. The slow and relatively equal pressure drop over time isn't caught by that system (see note above) and it is really just there as a safety net for the run-flat tires, to let you know that you are 'running flat' as it were.

Jeff

Hi Jeff! Thanks for the promopt reply. No, I am not talking about PDC. You see, BWM used two different types of tire pressure monitoring systems the Tire Pressure Control (RDC) system, and the Tire Defect Indicator (RPA) system (formerly know as the “DWS” system). The RDC system uses pressure and temperature sensors installed in each wheel as part of the valve stem. The sensors transmit their individual tire data to antennas mounted in each wheel well that feed to the RDC controller. This system is technologically superior, because it can alert you to absolute pressure changes (like when all four wheels decrease pressure over time), it is more sensitive to slight changes, and it can react faster. The disadvantage to the RDC system is that it puts a few ounces of extra weight in each wheel, and the system is more expensive and labor-intensive to retrofit. The RPA system uses the speed pulses from the ABS controller to calculate their relative rolling diameters. The advantage of this system is that it is passive (does not add “stuff” to your wheels and lots of extra wiring) and less expensive and easier to retrofit. It’s down side is that it is not as sensitive to pressure changes.BMW introduced the RDC system in the E38, and they may have used it in the E65/E66. However, the RPA system is clearly BMW’s preference, because they switched to the RPA system for all other models. Most much prefer the RPA system too, since they do not want the weight and complexity of a sensor spinning mindlessly in each wheel. The RPA is better suited to a high performance vehicle, and I suspect that BMW has similar priorities, since they dropped their absolute pressure system for the ABS wheel speed version. According to the BMW WDS, the RDC system will detect about 5 PSI pressure change. The RPA system will detect pressure drops of about 30% (roughly 10 PSI, depending on tire pressure).
In my opinion, Jeff- RDC will be a tough MOD, as it entails rotational and temperature sensors in each wheel. The RPA however, is what I am referring to, as it will be much easier to connect the module to the sensors. I just wanted to know if anyone had done it, and how was it done? Aparently, the installation is very straightforward, almost as if BMW has intended for us to retrofit a system like this. Hence, I thought that if the mod is simple and cheap, then why not?!?! Anyways, thanks for replying, and hope to get more knowledge on this as well as other things.

Thanks!

Kris

FYI Stay away from the Intellavalve aftermarket system. I had it fitted with new tires and it never worked correctly. I had to wait 6 months for the company (PDK Wheels) to replace it and it also proved defective. They were supposed to refund price plus 2 X refitting costs. Took a year to get price less 15%. Both company and product are crap IMHO!

I'm considering doing the RPA retrofit in my '04 4.4i as well.
The only info I could find on it is this install (uses parts from an E39): http://www.bimmerboard.com/forums/posts/179456

Is there any wiring diagram of the X5 posted somewhere so I can try to find where the wires I need to tap into are? And/or if anyone has already done this install in an X5, any info would be much appreciated!!

X5 & X3 Wiring Diagrams are listed at the top of the screen... 'Online WDS'

Good Luck. I have an 04 as well. Keep us posted on the mod.

My M5 most certainly does not have RDC (as it is defined) but it does have Tire Defect via tire revolution monitoring. As far as I was aware, BMW never used tire pressure monitoring, just Flat tire monitors on the IBus cars. My X5 did not come with RDC or any form of tire monitor.