View Full Version : TPMS Anyone?
Just wondered if anyone out there has looked into or heard of TPMS or Tire Pressure Monitoring Systems? I'm not talking about the those dinky little valve stem caps with different colors that you have to walk around the car and look at.
If you're not familar with the technology here is a good overview:
http://www-nrd.nhtsa.dot.gov/vrtc/ca/tpms.htm
If you don't care to wade through all the data, here is a brief summary:
- 2 Systems currently exist, one is WSB or wheel speed based and the other is PSB or pressure sensor based.
- WSB systems are less expensive and are currently used by some OEMs (Mini Cooper and previous generation Toyota Sienna are some examples). They use the existing ABS wheel sensors and operate based on the theory that a deflated tire will have a different circumference or diameter. The different rotation speed of an underinflated tire is picked up by the ABS wheel sensor. What this means is that it takes a while (too long) for the system to recognize that a tire is losing air pressure. Most systems don't respond until about 50% or more of the air is lost.
- PSB systems use individual wheel sensors and are also used by some OEMs but tend to be on more expensive models (Corvette has them) due to their higher cost.
- PSB systems are usually strapped around the wheel hub and located inside the tire. The sensors are sealed, RF transmitters that send signals to a receiver/display inside the vehicle. Most often they use lithium ion or similar batteries and have a life span of ~5-7 years.
- The downside to the PSB systems are usually cost, the need for retraining the system each time a wheel is rotated to a new location, replaced or tire pressure is readjusted, they also need special valve stems and have non standardized alert systems. Some do not have temperature alert systems and cause false alerts.
- Overall, the PSB systems appear to be superior especially if they have a temperature warning system as well as pressure indicator.
I just received a unit from a supplier I met at SEMA this year. This particular product has a backlite LCD display with car body icon showing each wheel, a digital readout for both temperature and air pressure, LCD will activate for 20 sec at first occurance, adjustable alert settings for both temp and pressure. A low/high pressure alert, initial low pressure alert, high temp alert, a 10 second audible alert for 1st occurance, tire icon that increases blinking speed, etc.
Anyway sounds good, as soon as I have a chance to evaluate it, I can post results/observations.
Just in case anyone thought I wasn't serious about doing this...
Here are some pix from the install, phase I is complete, tomorrow I go to have the wheel sensors installed.
How's this for irony, with only 4k miles on the car, I picked up a "screw" in the tire. I tried to back it out, but after about 1-1/2" came out, I started to hear air hissing and put it right back in.
Took it down to good old Discount Tire and found that the screw located itself between the sidewall and tread. They can't repair the flat in that location, end result, new tire at a courtesy price of $153 (ouch), retail is over $250 :(
Oh well, what you gonna do?
This first pix shows a piece of velcro that I attached to the headliner to the right and in front of the mirror. TPMS instructions call for the display to be mounted directly to the windshield. I thought this work better having it next to my V1 and block the sun coming in over the mirror.
This next pix, shows the "A" pillar and release button.
To route the cable I tucked it under the edge of the headliner along the top of the windshield. Here is how you need to remove the "A" pillar cover to run the cable down.
With a small flat blade screwdriver, you gently pry up the release button. Don't pull it all the way out, just pop it loose.
Once that's done, you need to remove the section of weather strip along the length of the pillar to allow it's removal.
Once you get it started it's easy to seperate it, just keep pulling.
After you've removed the weather seal, you need to pull off the cover. Gently pry it away near the top.
And pull it away slowly, there is one plastic button in the middle of the cover and it snaps out of the hole as you pull away.
You can see the center button here better, it's black.
You complete the removal by pulling the cover up and away from the windshield.
Here is how the cover looks from the underside, these are a lot heftier than they used to be but not any more difficult to remove.
Here is where you want to run the cable down along the existing one. A few wire ties to keep things tidy and you're about half done.
This is the new cable I'm running for the TPMS, the other photo has the cable I ran previously for my V1.
I used a long, soft piece of shrink tubing to snake the cable down below the dash.
Once I got below the dash, I used a volt meter to locate a hot lead and switched lead set of wires. The TPMS needs +12v always on and one that comes on with the ignition.
I used these crimp on connectors to make life a little easier.
Since I changed the mounting position from the windshield to the headliner, I had to modify the receiver/display by adding a strip of velcro along the top.
Here's a little tip I learned a long time ago. When you add self adhesive velcro to anything inside a car in Arizona, you can't rely on the glue to hold when interior temps exceed +140 F.
Add a few drops of instant glue on adhesive part first, then stick it on. Don't plan on removing it, as anything it sticks to will become damaged if you try. I guarantee it ain't coming off!
Here is where the cables come out near the mirror. I mounted my V1 to the left of the mirror and the TPMS to the right.
After plugging the cable in and switching on the ignition, the wiring is complete.
After putting it all back together again, here are the V1 and the TPMS side by side. After I install the wheel sensors and perform the setup tomorrow, I should be set to go. I'll let you all know how it well it works in a few days.
Because a few have asked me to post this, I'll add this too. The V1 remote is mounted to the underside of the door with... you guessed it, more velcro (I love this stuff).
You need to drill a small hole throught the back of the red lined box and feed the wire through and that's basically it. The V1 junction box (power connections) are under the dash and except for the hard wiring up the "A" pillar along the top of the windshield it's almost the same process I just outlined above.
Well, it's finished and so far here are my impressions;
Just had the tire shop install the individual wheel sensors which are small and mount to special valve stems that include hollow screws. Very easy install for tire shop and all the parts are included.
Once the sensors are installed and tires mounted, all that's left is programming the display.
There are about 6 modes you can enter to customize the display.
Rotation mode let's you choose to have the system continuously scan all the tires (rotating through each), while it reports the pressure and temp for each (about 5 seconds/tire). In Normal Mode, it displays the tire with the lowest pressure. Either way if any tire has an issue (pressure too low or high or temp too high) the system alerts you.
Programming Threshold settings offers two choices, factory or user. The factory settings can't be changed and are set to 120 kpa (17.4 PSI) for low pressure, high pressure is 300 kpa (44 psi) and high temp is 80 degrees C (178 degrees F). Otherwise in User Mode you can pretty much override these.
Sensor Exchange is for whenever you rotate the tires. They asked me at the tire shop how I will deal with tire rotations as it could get expensive breaking down the tires to relocate the senseor every 6k miles and I was nervous about that. Then I read in the manual how to overcome this problem. In this mode you basically are reprogramming the sensors to correspond with the tire position icons in the display, so there is no real issue or need to relocate sensors during tire rotations.
Learning mode allows you to program a new receiver or display should you need to replace the original unit.
Backlight display let's you have the backlight on always on or auto which turns it on for the first 20 seconds at startup or whenever an alert is received.
The last mode offers you an optional setting (on or off) if you choose to buy an extra sensor for the spare tire. It provides another icon (shown in the trunk) to provide the same readouts for the spare.
As for how it works, so far I'm impressed. I left it in the rotate mode and it continuously scans each tire for about 7 seconds displaying the data. I rechecked the air pressure in each tire with an accurate air gauge and the display is dead on.
I plan to drive to LA at the end of this week so when I return I can give an update on the overall performance.
The best thing about it so far is the how much more aware you become of the tires condition. Of course the air pressure is importatnt and usually overlooked, but it's interesting to note the temperature differences in the tires as well.
At the very least, it will definitely help prolong the life of the tires or alert you to a slow leak. At the very most, it could prevent a disasterous blowout by driving on underinflated tires. :eek:
Very Cool.. Too much work though for a lazy guy like me.. Hehe :D
I stick'ed the thread because I think many people will show intrest in this.
schalliol
01-31-2004, 09:13 PM
I'm very impressed! It's a lot of work for tire pressure monitoring which realistically doesn't make that much difference in safety, but it is cool and ensures that you'll get maximum gas mileage and can get the best performance. Great work!!
BTW, generally the tint at the top of windshields reduces performance of radar detectors (and V1 "locators" as Valentine says). I kept my V1 down in the middle for this reason (at least on my old Camry this was the case).
Originally posted by schalliol
I'm very impressed! It's a lot of work for tire pressure monitoring which realistically doesn't make that much difference in safety, but it is cool and ensures that you'll get maximum gas mileage and can get the best performance. Great work!!
BTW, generally the tint at the top of windshields reduces performance of radar detectors (and V1 "locators" as Valentine says). I kept my V1 down in the middle for this reason (at least on my old Camry this was the case).
I disagree, it definitely adds to your awareness of the tires condition because it always available. Always seeing the pressure and having visual and audible alerts to warn you of potential tire destruction due to low pressure or overheating are not frivilous (IMO). When you realize how many blowouts and loss of control occur because of people forgetting to check air pressure, it makes perfect sense.
Actually the system is very simple and only requires three wires to connect. It's only when you choose to install it the way I did that it becomes a little more challenging. Overall, it's not that hard, it probably took about 3 hours to do and I had fun doing it.
I suppose it's all relative, on my Ody, I installed inflatable lumbar supports that required complete dismantling of the seat and a rear sensing obstacle system that required removal of the rear bumper skin and lots of wiring from back to front so really by comparison, this wasn't that difficult.
As for the tint, your're right about some possible reduction in performance, but I haven't seen it. Even when you add in all my other windows have film the V1 detects radar way before I ever can see it.
The best part is I no longer feel compelled to remove the detector each time I leave the car as it is virtually invisible behind the tint band from the outside.
schalliol
01-31-2004, 09:40 PM
It does sound great! I should have said, vs. checking pressure more often or the hokey color bands, etc.
johnej
01-31-2004, 09:43 PM
The only thing I would ask is how would you hide the wires so they are not in the middle of the windshield....
Originally posted by johnej
The only thing I would ask is how would you hide the wires so they are not in the middle of the windshield....
Next time your in your car, run you fingers along the headliner where it meets the windshield. You should feel a gap under the headliner where you can tuck in the wires.
Just as a followup, here is the TPMS display showing a readout for one of the tires. It scans every tire for about 5-7 seconds and displays its stats. You can also push a button that let's you scroll through each tire instead of waiting for the scan to occur.
Considering the number of flats I've had recently this thing has really proven itself. :cool:
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