Atlanta is a giant construction zone. It's been that way for more than a decade. That means there are plenty of tire-hungry nails, screws, and metal bits on the roads. Even though I check my tire pressures every couple of weeks, my daily-driven 328i has suffered four tire punctures in three years, two of them in the past three months. To make matters worse, my 45-series tires don't provide much visual evidence that they're low on air until they're nearly flat.
Flat-tire monitors are becoming more common as original equipment on new cars. They're mandatory equipment for cars that come from the factory with run-flat tires. The National Highway Traffic Safety Administration (NHTSA) recently declared that all new vehicles weighing less than 10,000 pounds shall have tire pressure monitor systems by the 2008 model year.
Most of the current BMWs and MINIs use the DSC system to detect unequal wheel rotation rates rather than a drop in air pressure. Many high-end luxury cars use pressure transmitters that attach to the valve inside the wheel. The aftermarket system made by SmarTire Systems Inc. (http://www.smartire.com/) uses transmitters that strap to the drop center well of the wheel like in this picture:
http://www.smartire.com/pix/mediacenter/PF.0103z.jpg
The transmitters start working when the car starts moving. They send pressure and temperature information to a receiver located inside the car. The receiver is normally powered via a 12-volt adapter that plugs into your cigarette lighter socket.
The basic kit consists of the receiver, power adapter, four pressure transmitters, and worm gear straps for the transmitters. The kit also includes a bracket, suction cups, and Velcro strips that you can use to mount the receiver to your dash or windshield like a radar detector. The receiver offers no numeric readouts at all; it simply beeps and flashes LEDs to alert you when a tire's pressure drops below 22 PSI. By matching the LED on the receiver to its corresponding color-coded transmitter, you determine which tire it is. The pressure measurement is accurate to +/- 1.5 PSI, and the temperature measurement is accurate to within +/- 5 degrees F.
The accessory full function display, on the other hand, includes a backlit LCD that gives numeric readouts of tire pressure and temperature. You can scroll through each tire's pressure and temperature by pressing buttons on the display. Furthermore, you can program the pressure drop and temperature rise that cause the alarm to sound. If a tire's pressure deviates from the programmed limit or its temperature rises above the limit, the display flashes a red warning light and shows you which tire is the bad one.
You can choose from two types of full function displays: one that clips directly to the front of the receiver, and one that connects to the receiver via a six-foot-long cable. The latter option greatly expands your mounting options. Either full function display costs an extra $50 on top of the cost of the basic kit.
Picture 1 - Basic Receiver and Full Function Display
I bought the second-generation system and full function remote display from The Tire Rack (http://www.tirerack.com/accessories/...artire_all.jsp). I decided to hardwire the receiver and display into the car so I wouldn't have to worry about plugging in and unplugging the power adapter every time I stepped into the car.
Here's how I hardwired the receiver and mounted the display in my 1997 328i. There are many possible ways to mount these things and tap into power sources, so as Ron Stygar would say, feel free to do it your own way.
Parts I used:
SmarTire second-generation system (basic receiver, tire pressure transmitters, etc.)
SmarTire full function remote display
BMW/AMP eight-position connector (BMW part number 61 13 1 378 116; list price $2.50)
Two BMW 2.5mm male pins pre-crimped to 16-gauge wires (BMW part number 61 13 0 007 452; list price $1.25 each). You can also purchase the pins loose and crimp them to whatever kind of wire you want to use.
Crimp-on inline Mini fuse holder (Littelfuse part number 153002) and 2A Mini fuse
DC power plug to match the SmarTire power adapter (3.5mm OD x 1.3mm ID)
Other tools and materials:
Multimeter
Wire stripper/cutter
Crimping tool
Soldering iron & solder
Screwdrivers
Coping saw
Small files
Sandpaper
Zip ties
Adhesive-backed Velcro
Two-part epoxy
ABS sheet plastic
Black satin spray paint
Nuts, bolts, lock washers
Candle (heat source for bending ABS plastic)
Bentley manual
Disclaimer:
I am not an automotive professional, nor am I affiliated with BMW. The procedure posted here is based solely on my experience with my 9/1996 production 328i. Wiring and connectors can vary widely between models and years, so verify what you have before you purchase any parts or make any connections. I am not responsible for any damage or injury you cause while performing or utilizing this modification.
Procedure:
0. Have an experienced shop mount the tire pressure transmitters on your wheels. It's easy to wreck the transmitters if the guy who mounts your tires isn’t careful. Be certain that the tire shop pays close attention to the mounting instructions, particularly the torque setting for the straps, the recommended location of the transmitter on each wheel, and the color-coded rings for the valve stems. Matching the transmitters to their respective color-coded rings allows you to set up the system to recognize which transmitter is at which corner of the car.
Picture 2 - Color Coded Valve Stem Ring
It would be convenient to have the transmitters installed at the same time you're getting new tires. The Tire Rack or another SmarTire vendor might even be able to install the transmitters for you if you are buying a complete wheel and tire package from them.
1. Briefly insert the SmarTire power adapter into the cigarette lighter socket. Verify that the center of the coaxial plug is 12V and that the outer sheath of the plug is ground. Confirm that the fuse in the power adapter is a 2A fuse.
2. Remove the center console per old skool's instructions. If you have a center armrest, you do not need to remove it.
http://forums.bimmerforums.com/forum...d.php?t=328939
Somewhere under the center console should be a black rectangular, eight-position connector with five wires running to it. The connector in my car was wrapped in foam weatherstripping material and stuffed into a recess in the armrest base. This is the X400 connector for the dealer-installed BMW cell phone, and it is also present in some Z3 roadsters and Z3/M Coupes.
Picture 3 - BMW X400 Connector
Make a note of the positions of the female pins for the violet/white (12V switched) and brown (ground) wires. Confirm that the violet/white wire is hot with the key in the accessory position. I don't know whether this connector is common to all E36 models, so if you do not have it, or if it is being used for your car phone, use the Bentley manual wiring diagrams to find 12V switched power and ground somewhere else in the center console.
3. Make a simple wire harness. Solder the wires to the DC power plug, making sure to note which wire is ground and which is power. Crimp the fuse holder into the power wire and insert the 2A fuse. Lastly, insert the male pins into the X400 connector you bought. Double-check the pin positions before inserting the pins.
Picture 4 - Wire Harness
I chose to construct the wire harness pictured above because it makes the modification completely reversible. If you don't want to use the BMW X400 connector, you can cut or remove the 12V switched and ground wires from the car’s cell phone connector and make the connection using AMP or Molex two-position connectors, tap-in connectors, or whatever method you prefer. The inline fuse is just a bit of cheap insurance that duplicates the function of the SmarTire power adapter and takes only a couple of extra steps to insert.
Connect your wire harness to the car's cell phone connector and turn the key to the accessory position. Verify with the multimeter that, like the SmarTire power adapter, you are getting 12V power at the center of the plug, and the outer sheath is ground. If not, check your work.
If you inserted the pins in the wrong positions in the X400 connector, you can unlock the connector and reposition them. Click this link for the procedure.
http://www.leatherz.com/install_ugdo.htm
You can also use the cell phone connector to get switched power for almost any automotive accessory. The connector includes a red/white 12V power wire that's hot at all times.
4. Plug the receiver into the wire harness and place the receiver in a location where you would like to mount it permanently. If you opted for the basic kit without the full function display, you should mount the receiver where you can see the LEDs; if you purchased the remote display, mount the display where you can see it and hide the receiver wherever you choose. In either case, position the receiver so that it receives the signals from all four pressure transmitters. Go for a test drive to see if your chosen location works. If not, relocate the receiver until it does. Page through the tire pressures and temperatures on the display to be sure that it does not display any error messages.
5. After you return from your test drive, secure the receiver. I used Velcro to stick the receiver to the carpet in the small space at the rear of the center console. There is a hole in the armrest base that allows you to feed wires to the back; follow the wires for the rear ashtray light and the parking brake light. There is sufficient room under the rear ashtray for the receiver. In my car, mounted under the rear ashtray, the receiver successfully picked up the signals from all four pressure transmitters. I used zip-ties to keep the slack in the wire harness and display cable away from the parking brake handle and shift lever.
Note: I have installed an E46 armrest in my car and modified the center console, so what you see in this picture will differ slightly from what you have in your E36.
Picture 5 - Receiver in Center Console
6. If you bought the remote display, mount it. With six feet of cable between the display and the receiver, you can put the display just about anywhere. You could put it in the sunglasses holder or the center console ashtray, as VietSB did in his E39. See the link below.
http://www.bmwdiy.info/smartire/index.html
I first made a simple bracket out of gray ABS hobby plastic and attached it with adhesive-backed Velcro to the dashboard. The next day, the bracket and the Velcro fell off the dashboard. So, I made another bracket, spray painted it black, and attached it to the upper steering column cover with nuts, bolts, and lock washers. This method works much better. It's cheaper and easier to replace a $10 plastic cover than to have to deal with messy adhesives or holes you’ve drilled into the dashboard.
In order to remove and reinstall the steering column cover, I had to disconnect the battery and remove the airbag and steering wheel. Here's a link to a write-up that shows how to remove the steering wheel and airbag:
http://home.earthlink.net/~frankie66...ringwheel.html
My bracket places the display at the bottom right side of the instrument cluster and angles it slightly upward for maximum visibility while driving. The instrument cluster warning lights are still visible with the display mounted, and the display does not hinder the operation of the windshield wiper stalk. A couple of layers of weatherstripping foam on the back of the bracket prevent it from rattling against the dashboard. A co-worker and fellow car nut who looked at the display said the bracket looked almost like it had come from the factory, so I guess I did something right.
Here are some pictures of the display and bracket, as well as the backlit display at night:
Picture 6 - Display Side View
Picture 7 - Display Front View
Picture 8 - Display at Night
The display backlight comes on when it powers up. It's just bright enough to let you read the numbers in the dark, but it isn't so bright as to be distracting. The numeric readout goes blank after about five minutes if you don't press any of the buttons. The backlight turns off after another five minutes of inactivity. The lighting for the buttons stays on. It all comes back to life when you press a button or when an alarm sounds. I programmed the unit to alert me when a tire drops to 30 PSI; the 22 PSI standard alert level seemed a little too low for my liking.
It would be nice if the backlighting for the buttons and the display matched the amber instrument cluster lighting, but that's a minor quibble for something you shouldn't have to look at too often.
After driving around town with it for the last three days, I'm very pleased with the system. It's very useful, yet unobtrusive. My husband is now interested in getting one for his MINI Cooper.
One caveat: If you have to have a shop dismount a tire from a wheel that has a transmitter installed, be sure to tell the guys that you have the pressure transmitters installed, or else they'll mangle the transmitter. The standard mounting location for the transmitter is near the valve.
Special thanks to: My husband, Bimmerforums member Doctor Wha, for soldering assistance and for chauffeuring me to and from the tire shop; my new favorite tire shop for installing the new tires and pressure transmitters; VietSB for wire harness ideas; Ron Stygar for posting the BMW part number for the X400 connector; and Bremsen for sharing his thoughts on the SmarTire system.
Added 10/7/05: Links to SmarTire instruction manuals in PDF format. Right-click and save as:
User's Manual - Gen II System for Light Vehicles
User's Manual - Full Function Display
User's Manual - SmarTire for Motorcycles
Last edited by G. P. Burdell; 02-26-2008 at 10:13 PM.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
Very nice writeup. I recently got a nail in my tire and have been thinking of how practical it would be to wire this into the cubby below the OBC.
I have had my smart tire set up for a while and I have been thinking about the hard wire install. I was going to mount it in conjunction with hard wiring my Valentine 1, but I am 6'4" and I need all the unobstructed windshield space I can get. Now I see the shining path! Thanks for the great write up! I will get on it this weekend if I can find time between chores.
I like girls with a couple stab wounds, bullet holes, been knocked up a few times. I like girls who'll be able to drive me and look over and be like 'you know my driver's license is suspended.' I like girls who you know have bad credit when they're 21."
So are there any reported incidents of those things flying off at high speed?
Thanks for the compliments. I didn't realize the utility of this system until two of my tires got nailed this summer. I swear, my old set of tires must have been magnetic.
Actually, it's "ma'am," and you're welcome!Originally Posted by Mistermotorist
If you're referring to the pressure transmitters coming off the wheels, I haven't read or heard of any problems with them. The instructions say to torque the steel straps to 30 in-lb.Originally Posted by M52 POWER!
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
dont they throw the wheels out of balance or are they just really light?
Balancing the wheel/tire with the transmitter installed takes care of potential balance issues. The second-generation transmitters are light enough that they can be balanced out with the usual lead balancing weights.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
G. P. will you marry me? woman with taste and know how's
There's no USB interface, but I'm sure someone with the right know-how could send the receiver output to another device.Originally Posted by Daved
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
I'm happily married to another Bimmerforums member, thank you.Originally Posted by SecretAznMan4u
Originally Posted by G. P. Burdell
Last edited by G. P. Burdell; 10-09-2005 at 08:50 PM.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
A couple of observations after driving around for two weeks with the system:
--Paging through the tire information can be distracting, so I don't allow myself to touch the buttons when the car is in motion.
--During a highway drive in 80-degree ambient temperatures, my rear tires can get as hot as 115 degrees F. Tire pressure rises from 35 PSI cold to 39-40 PSI. The rears seem to get a few degrees hotter than the fronts.
--The system occasionally fails to "see" one or more of the transmitters when I start the car and drive off. It seems to happen if I start the car, drive a short distance (so that the system only picks up one or two transmitters), stop for a few seconds, and start off again. The receiver picks up the remaining transmitters within a few minutes. I don't know if this is a defect in my receiver, but it doesn't bother me. It doesn't happen every time I start the car. One of these days I'll send an e-mail to SmarTire asking them about it.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
Update...
Exactly one month since I had brand new S-03s mounted and the SmarTire pressure transmitters installed, the system has proven its worth.
During my commute home this evening, the pressure in the right rear tire consistently read about 2 PSI lower than the other three tires. Although the pressure difference was within the transmitters' specified margin of error, I made a mental note to look at the tire when I got home. Sure enough, when I looked near the center of the tread, the head of a wood screw stared back at me. I must have picked it up sometime during the morning drive to work.
These tires don't even have 2,000 miles on them and I've already managed to get a puncture.
I'm glad I had the SmarTire system to tell me there was something wrong.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
ouch, that sucks. how are you liking the S-03's? I'm running some on my M contours, I really like them.
--DrDubHold on let me get my laptop and read this on the toilet.
This is my fourth set of S-03s. They're great in the dry and wet. I've managed to squeeze 29,000 and 25,000 miles out of the last two sets!
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
thanks for the writeup!
sweet
Another update:
When I had the right rear tire patched, the shop accidentally broke off the pressure transmitter. There's always a risk that this will happen, even when you know the transmitter is mounted on the wheel near the valve. Stiff tire sidewalls appear to increase the likelihood of transmitter destruction. Fortunately, Geordie, aka BimmerDawg, went the extra mile to get a new transmitter for me.
Unfortunately, the Tire Rack sent us the wrong type of transmitter twice; the first one Geordie received was a unit that attaches directly to the valve stem, and the second was a Generation I high-pressure transmitter for commercial vehicles. On the third try, we got the right transmitter, mounted it on the wheel, and re-balanced the wheel and tire. Thanks, Geordie!
The SmarTire system doesn't automatically recognize the new transmitter. You have to tell the system to forget the old transmitter and introduce it to the new one by activating the full function display's Learn mode. After clearing the old transmitter out of the system's memory, you have to shake the new transmitter vigorously or inflate/deflate the tire by at least 3 PSI to force a transmission. The receiver "listens" for a signal and beeps in agreement when it receives one from the transmitter. If you were to add transmitters for, say, the wheels on a trailer, this is how you would incorporate them into the system.
The broken transmitter had a blue dot on the label, but the new transmitter did not. Still, the system recognized its signal when I let 3 PSI out of the tire. The learning operation was very easy and required just a few minutes, including the time it took to drag out the compressor and put air back in the tire afterward.
You can read more about the Learn mode in the full function display instruction manual linked at the end of my first post. I'm not sure how you would train the system to recognize the new transmitter if you had only the basic system without the display. The basic system instructions make no mention of how to replace a sensor if one is broken or lost.
Even though the transmitters seem a little fragile, I'm still quite satisfied with the system. My commute is too long, and the risk of a tire puncture too great, for me not to have a tire pressure monitor system installed.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
Update.
While rotating my wheels and tires a week or two ago, I noticed...yep...another puncture! This time, it was an industrial staple that had entered one of the left rear tire's tread blocks at about a 30-degree angle. About 3/8" of this staple penetrated the tread block and nicked the belts just enough to cause a very, very slow leak. I spread some soapy water over the hole and it blew a tiny bubble.
Back to Butler Tire we went to have the tire repaired. The pressure transmitter broke off when they dismounted the tire. Butler Tire employs some of the best guys in town when it comes to finessing tires off of expensive wheels, so I'm certain it's not their technique. Day in and day out, they handle wheel/tire sets that are probably worth more than my car and Doctor Wha's car combined.
Doctor Wha and I discussed the SmarTire transmitters with Geordie. We theorized that the rather tall profile of the transmitters, combined with the stiff sidewalls of my S-03s and the weakness of the plastic transmitter bodies, may be to blame for the two breakages we've had so far.
I'm planning to call SmarTire sometime this week to discuss this matter with one of their engineers. I'd especially like to know if they have anything in the works (perhaps a new Gen III system?) that would eliminate the problem of transmitter breakage. A smaller, lower-profile transmitter or one that attaches to the valve stem would be a step in the right direction. SmarTire makes a valve stem transmitter for OE applications (e.g., for the Aston Martin DB9), but I wonder if it can be readily adapted to a "universal" application where the wheel profile can vary widely. We'll see what they say.
Last edited by G. P. Burdell; 01-11-2006 at 09:18 AM.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
Update:
I didn't get the chance to talk to the SmarTire people, because a week after my last post, my SmarTire-equipped 328i suffered the dreaded "rear end delete mod" at the hands of a negligent SUV driver. I eventually sold the car and drove a MINI for a year before finding my new ride last month.
There are a lot more aftermarket TPMS kits on the market now. Hella has brought out a kit called the TC-400. The Tire Rack has just started stocking them, and as of today, the kits are not shown on their e-commerce Web site. If you want one now, you'll have to call them up and talk to a real live human being.
Going over the components of the Hella kit, I notice several things that set it apart from the SmarTire kit:
1. The Hella pressure transmitters are the valve stem mounted type, not the strap-mounted type like the SmarTire system. This means the transmitters are far less likely to be broken when a tire is dismounted. You can just deflate the tire, loosen the mounting nut, gently push the transmitter back into the tire, and collect transmitter after dismounting the tire. With a strap-mounted transmitter, your tire either clears it during mounting/dismounting, or it doesn't.
2. The Hella kit includes a full-function display. The SmarTire system requires you to purchase one separate from their Gen II kit. The Hella display puts one button on each side of the LCD, so it is a bit wider than the SmarTire display. The Hella LCD also has a chrome trim ring around it. (I may be seized by the urge to paint the trim ring black.)
3. You can choose one of seven colors for the Hella display; blue, red, green, orange, light orange, white, and light blue are the available colors. We'll have to see how well orange or light orange matches the BMW interior lighting. The SmarTire full function display color cannot be changed.
4. The Hella control unit is slightly larger than the SmarTire unit, and it also includes a plug-in accessory antenna to pick up the signals from the pressure transmitters. The SmarTire system doesn't require an accessory antenna.
5. The Hella control unit requires not only switched power, but also constant power (i.e., hot at all times). I can only assume that the control unit needs constant power to keep your custom settings (display color, cold tire pressures, warning thresholds) in memory. It makes me wonder how the SmarTire control unit memorizes your settings.
6. The Hella kit includes everything you need to hardwire the system into your car. It even includes a fuse holder and a 5A fuse for the power wire. The SmarTire kit provides only a cigarette lighter adapter. I had to source the parts to hardwire the SmarTire kit into my E36. If you like working with wiring or prefer a seamless installation, the Hella kit is a good choice; if you want the easiest possible installation and don't mind seeing exposed wires, something like the SmarTire kit would fit the bill.
7. The Hella kit includes a metal bracket for mounting the display to a hard surface. (The instruction manual shows the bracket mounted to the dashboard of an E46.) The SmarTire full function display doesn't include one.
The Hella and SmarTire systems are comparably priced. On the surface, I'd have to say that the Hella kit is a smartly-engineered, more complete system compared to the SmarTire Gen II kit. Having installed Hella's superb CELIS Xenon headlamp kit into my old E36, I'm hardly surprised by the quality of their TPMS kit.
I intend to hardwire this system into my E46 sometime in the next couple of months. I'll probably use the E46's cell phone harness for power. I haven't decided on a display location yet - I may make another custom bracket to mount it on the steering column cover, or I may put it in the ashtray that's just forward of the shifter.
Last edited by G. P. Burdell; 02-28-2007 at 08:37 AM.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
It was really interesting to read these posts and see how the system performed over time.
I look forward to seeing how it all goes with the E46.
Thanks!
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
Further update. The Tire Rack has just listed the Hella TC-400 kit on their Web site.
http://www.tirerack.com/accessories/hella/tc400.jsp
Last edited by G. P. Burdell; 05-07-2007 at 11:32 AM. Reason: Corrected URL.
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
I've posted my writeup on the TC-400 to the E46 subforum.
Click here!
E36 DIYs: Air Pump | Vent Gauge | E46 Armrest | SmarTire TPMS
E46 DIYs: Hella TPMS | Aftermarket Horns | Window Regulator Notes | Trunk Wire Harness | Trunk 12V Socket
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