official TPMS info from Toyota tech training class

If the sensors are hard to find in Toyota dealers (few models have direct sensors as of now), why don't you try Lexus? Lexus have many models with direct systems for a couple years now. Their parts department should have them at counters. I know the 2005 Lexus LS430 have them as standard. So do most 2006 models.

 

Ceric,

The problem is that owning a 2nd set of sensors has little to no value in the Prius. According to the best data that we have right now... every time you change tires, you need to reprogram the ECU with the individual serial number of the 4 sensors. This requires a trip to your Toyota dealer unless your tire company has the equipment to program the numbers into the ECU... and alas... having Toyota do this will be more expensive than just moving the sensors between your summer and winter wheels each season.

My tire dealer is shocked at how the Prius operates... but they said they will just move the sensors from rim to rim for me at no charge every time. I am not too upset... I save $848 in sensors (8 X $106) for my two Prii... and for sure they will re-spinbalance the tires each time I change wheels. No chance of them taking a shortcut and assuming the balance is "still OK".

/Jim

 

Well, it's not always so simple as moving the sensors from wheel to wheel. Differnet wheels may need different sensors. Here's why.

The sensor is basically a little box that sits agisnt the rim near the valve. Out of this box sticks the valve stem. Now, the problem is when the wheels don't have valve holes at the same angle. THe sensors onthe Prius wheel have the valve at about a 45 degree ange from the box. THe tC and Tundra have it at about a 20 degree angle. It's a mechanical thing, not electronic. So, if someone gets a set of aftermarket wheels, the valve may not sit flat against the rim. That could spell trouble when driving.

So the issue is not jsut switching them but making sure that they are the right design for the wheel. As the Prius and tC use a different setup, I doubt I'll be able tojust move them over. That is why I'm going to wait and buy a set ot tC sensors once they are available. Then I'll have then install the sensors and see if they are compatible with the Prius TPMS ECU. IF not, it's back to square one. Maybe the Tundra sensors will work. Or, as ceric said, maybe Lexus sensors are compatible. At least hey are available, since they've been using them before 2006. Then again, maybe if they ARE compatible, evne Lexus is running on short supply to make up for the greater demand.

For now I'm just waiting for them to arrive at my local parts dept.

 

Evidently, the TPMS sensors work with our winter rims... because they have already been mounted and are working

I have no idea what the valve stem angle is on the new rims.

/Jim

 

Yeah, you're lucky. I wish that were the case for the tC rims, but alas...

 

This is great information. I have a 2006 Prius and plan to increase the tire pressure to 42/40. Do I need to reset the TPMS, and if so, where is the reset tire pressure option? I've looked through all the menus on the MFD and can't find it anywhere.

 

It's a button under the steering coumn. One diasbles the SKS system, the other resets the TPMS.

 

Your momma so fat, she set off my TPMS!

 

LOL! My point exactly

 

Hello, Everyone!

I only just found this thread, but was instantly caught up by it. I've been interested in TPMS for a couple of years. I recently completed a 2 year long tire experiment on my 2003 Prius to establish the best pressures to use. My goal was to maximise both treadwear and MPG, if possible, at the expense of ride comfort and noise, if necessary. The outcome of the experiment would provide the data to set up a TPMS to go with my next set of new tires.

I found it was possible, but NOT at Toyota's recommended pressures (which isn't news any more!). I prefer 44 front/44 rear PSIG, though I note that most people seem to prefer 42/40. (We do a lot of long distance traveling with a full load in the trunk.) With the higher pressure I get 48 MPG even though I have lead feet. If I bother to "baby it" I can easily get 55 MPG! And the existing Toyota-recommended Dunlop tires, having lasted over 30,000 miles, are worn out almost perfectly evenly. (Proper 4 wheel alignment is also essential to obtain this result!)

The higher pressure actually improved the handling while making the ride only slightly harsher. It also means the tires are a lot louder, with most of the noise coming from the rear! When the trunk is filled for our various road trips, the noise is greatly muted.

Two weeks ago I purchased a set of 4 new Michelin HydroEdge P185/65R14 85T tires for the 2003 Prius. According the Michelin, these luxury-class tires are among the quietest and smoothest-riding tires they have ever made. They are supposed to last 90,000 miles. If they really do last that long, they are a steal at just under US $100 per tire.

This was the only non-Toyota-recommended tire I could find that is properly rated to carry the unusually high front axle weight of the Prius. It's rating is in fact slightly higher than that of the OEM extra-load (XL) tires. The new tires are just slightly bigger than the OEM tires, so there will be a 1% error in the speedometer and odometer. The slightly larger bulk uses up space that was meant for the use of tire chains in winter. I never use chains… (If the roads are that bad I climb into my 1992 Previa with 4-wheel drive and chains!)

I delayed installing the new tires for the arival of the TPMS kit.

Last week I ordered an aftermarket TPMS kit, made by SmarTire Systems Inc. (www.SmarTire.com), from The Tire Rack (www.tirerack.com/accessories/smartire/smartire_all.jsp). Including the optional LCD module, the 4 wheel 2nd generation passenger car kit costs just under US $300.

Additional wheel kits are available for under US $60 (http://www.vulcantire.com/smartire_pass_sys.htm). And no additional tools are required beyond the LCD module to teach the TPMS new sensor serial numbers.

Tomorrow morning the new tires and the TPMS kit will be installed.

I learned the following along the way, which may fill in some of the info others are looking for.

All new cars in USA will be required by the TREAD Act to have TPMS factory installed after September 2007.

SmarTire Systems Inc. holds many of the essential patents for TPMS. It is possible that Toyota either buys their TPMS transmitters from SmarTire, or has licensed the rights from them to make their own. The photos of valve stem type sensors on the SmarTire website look strikingly similar to the photos of Toyota sensors… Check it out at http://www.smartire.com/oem/technologies.html

The SmarTire units I just received operate at 433.92 MHz. Although every transmitter is constructed alike each is programmed to transmit a unique serial number (there are millions possible). When the day arrives that all cars are equipeed with TPMS, the serial numbers will enable your car to ignore all those around you. The SmarTire units send both pressure and temperature, and can give an alarm if a tire is overheating even though the pressure is normal (as would occur if a brake is dragging or jammed, for example). With the optional LCD module you can read the actual temperature and pressure of each tire.

Because of the preceding, it appears to me that an 06 Prius owner who did not like the factory installed TMPS could install a SmarTire kit without causing a conflict. Black electrical tape can hide the idiot light on the dashboard. (And I'm pretty sure that it is a LED.)

The SmarTire kit, when outfitted with the optional LCD module, allows custom programming of pressure and alarm settings. (The default settings, without the LCD, are not appropriate for the Prius.) It can aprise you of as tiny a leak as 2 PSI drop below your preferred pressure. For my treadwear and MPG goals, this is an absolutely essential feature.

Some mention was made of cars from another company flipping over due to tire pressure issues. That certainly is NOT a concern with the Prius! Indeed, if a tire on the Prius is that low, I can't imagine how you could ignore it… and you certainly would not need a TPMS to detect THAT problem! I am very disappointed to see that Toyota's TPMS doesn't give an alert until the tire has lost 25% of it's pressure. By then, it should be visible to the owner that the tire is low. Worse however is that both the treadwear and gas mileage are being sabotaged at this point.

The SmarTire kit also supports having multiple sets of wheels and tires for seasonal changouts. It allows rotation plans without a hassle. It even can monitor your spare tire, with a limitation: it will only give an alarm if the spare is *really* low, so you still need to check it manually anyway. And for larger vehicles that might pull a trailer, the SmarTire kit even supports monitoring duallys on the towing vehicle AND the tires on a trailer! Every axle can have it's own unique pressure settings.

A nifty extra: Each transmitter of the basic SmarTire 4 wheel kit has a different colored dot printed on it's label. The kit includes 4 color-coded rings you attach to the valve stems to help you remember which transmitter is on which wheel. The user does not need to pay any attention to the serial numbers (unless your OCD demands it). The basic receiver comes from the factory already knowing which serial number goes with which color.

The battery: 1 lithium cell per wheel transmitter. A motion detector built into each sensor shuts down the tranmitter if the wheel isn't moving to conserve the cell. But it is still monitoring; if it senses that a tire has lost a lot of air it will intermittently transmit the alarm even if the wheel isn't moving. The cells are NOT user-replaceable. About every 5 years (assuming 20,000 miles per year) you'll need to replace *ALL* of the transmitters, which currently cost US $47 per wheel.

Direct vs. Indirect: The indirect systems (which are inferior, IMHO) work by measuring and comparing wheel RPMs; there is no requirement that a radio transmitter be used at all, and likewise no requirement that some special gizmo be built into the wheel or tire. Often, these indirect systems take advantage of existing circuits installed as part of the anti-lock braking or traction control system. Direct systems place a pressure gauge and radio transmitter on each wheel, inside the tire. As I mentioned above, the SmarTire direct system adds a temperature gauge and motion detector to further improve the kit.

Hmm… My new 90,000 mile tires should last me about 5 years.

SmarTire is working on a 3rd generation design that will eliminate the lithium cell in the transmitter, yielding a system that will last the life of the vehicle. By the time I need new tires and transmitters they should have it perfected! Read about it at http://www.smartire.com/pdf/newsreleases/S...uly_28_2004.pdf

P.S.: At cold tire pressures above 45 PSIG, I could not detect any improvemment in gas mileage, BUT it did cause the tires to start wearing out faster in the center of the tread.

 

Out of curiosity, after work today I stopped by the dealer that sold my Prius. The salescreature talked me into taking a silver 2006 Highlander Hybrid for a spin, and overall it was an ok ride.

I then talked to the Prius tech who services my car, and he told me that due to the TPMS I couldn't run steel wheels and winter tires on that Highlander. That seemed dumb.

We then used my notebook computer to get into Tire Rack and discovered that there are no winter tires in the Highlander Hybrid size anyway. There is no way I'd drive on snow/ice with those skimpy "all season" tires.

The closest I could find was P235 65 17, which is wider than stock. Not desirable in deep snow. However, you can get a studded Cooper Discoverer M/S in that size, and I have experience with that tire on my old Ford pickup. Studded, they work very well on ice and snow.

I'd worry about eventual rim damage from seasonal mounting/dismounting from "all season" to winter tires. The Prius tech thought I'd get 5-6 years out of the rims.

I'm still trying to find an SUV as a second vehicle. The Highlander Limited is a bit steep - around $53,000 Cdn - but that price will get me a 1 year lease return Navigator with 22,000km on it.

More than likely, the Highlander hybrid will hold its value well, and the Navigator will continue to have steep depreciation.

 

You could get a Volvo XC90. It has the highest resale value retention of any vehicle.

 

Hmmm. I quickly went to the Volvo Canada web site. The base model is around $51,000 Cdn, but even the base model has the side and head curtain airbags. You have to "upgrade" to the Highlander Hybrid Limited to get that, which is then very similar in price.

I couldn't find any mention of the standard tire size though. If I could slap on some studded Nokian tires for winter, it could very well end up I'd have an XC90 as my second vehicle.

I'll swing by the Volvo dealer today after work and see if they have one. You've stirred my curiosity.

 

Found the tire size info in the Build section of Volvo Canada: P225 70 16. Plenty of winter tire choices.

 

It wil be interesting to hear how much more quiet they are!

 

[catching up...] The fiberglass-rods thing certainly would hit the
ground on the occasional chuckhole or large bump, but they wouldn't
*stay* on the ground afterward. The low-pressure alarm would be a
continual dragging sound transmitted through the frame of the car.
.
I know what the mounting hardware I need would look like at this
point, but I think I'll need to fab it from scratch. I'm also a
little leery of drilling holes through any suspension part, even
small holes, and may try to come up with a way to use existing ones
if they're close enough to the wheel.
.
Also thinking about the indirect method tapping off the wheel-speed
sensors, but that's said to be less reliable and the jury is still
out on whether a low tire actually changes the effective rolling
circumference appreciably or not.
.
_H*

 

To Hobbit:
I too disdain drilling holes in vehicles I truly care about. (Old clunkers is another matter).
An optional method is glue, but I have serious doubts about how reliable it would be. For example, super glue is notorious for obtaining a death grip, then letting go with no warning later.
That said, I have had good reliability from an adhesive caulking called "Lexel", and any of the RTV Silicones from General Electric. I'm currently testing the urethane based glues. So far they seem good, but I haven't used them long enough to be sure. (Urethane glues include Gorilla and Elmers Ultimate.) Surfaces to be joined must be "surgically" clean to have a prayer of staying joined!
No matter how you decide to attach it, be aware that if a feeler detaches while you are on the road, causes damage or injury, AND can be traced back to you … (well, *I* would *NOT* want to go there!)
As a practical matter, since you sound like you really are going to do this:
If you attach the feelers to the body, as the load changes, even by as little as the difference between an empty and full tank, the accuracy af your scheme will vary. Adjust your feelers while assistants whose weight matches yours and whoever routinely rides with you sit in the appropriate seats. Provide a means to adjust them for those inevitable road trips with a full trunk.
If you attach the feelers to the axles or control arms, you can sidestep those issues, but then you might not hear them make contact…

To Everyone:
I got my new HydroEdge tires and SmarTire TPMS installed yesterday morning. It went well. I'm still evaluating the system and will post a more informative report later. So far I like it!

P.S.:
In many places in the US, studded tires were outlawed. I used them myself every winter until they were banned. Now I use chains with case-hardened cross bars. A bit of hassle, but quite effective. The ride is quite nice on snow or ice, but becomes intolerable on bare pavement, ensuring that drivers remove them when not needed.
In case some are wondering why the studs were banned, too many lazy people ran them on bare pavement, leading to greatly increased road repair costs. (Since the studs did not cause a rough ride on bare pavement, a few idiots even ran them in the spring and summer!)

 

Cool -- hydroedge and *some* sort of TPMS is one of the options
I'm thinking about, in fact, and the feelers thing is sort of a
cheap hack that is one more of several alternatives. Did you get
the SmarTire type that hose-clamps around the inside of the rim?
That struck me as a somewhat cockamamie mounting scheme, in contrast
to several other systems that seemed to elegantly mount it in a
compact little wart off the inside of the valve stem. And I really
think that *any* system should be able to directly read and display
pressure and temperature numerically, not just kick an idiot light
when one or the other goes past some threshold [leaving you, in
many cases, to figure out WHICH tire it is f'krissake].
.
_H*

 

Hello Everyone!

I've had the new Michelin Hydroedge tires and the SmarTire Gen II Passenger TPMS in service long enough now (1,260 miles) to draw several conclusions.

INSTALLATION

My favorite body, frame & tire shop had heard about these kits but never seen one; they were very much interested in doing the job. I've been doing business with them since the late 1960's. As I was already familiar with all of their safety requirements, they had no problem with me working side by side with their front end alignment specialist to install the kit.

This kit is the type that uses stainless steel "hose" clamps to secure the color-coded transmitters. I too had doubts (i.e. "Mickey Mouse" kind of thoughts), but in practice it went very well and seemed absolutely secure. In the end, I very much liked it.

The kit instruction manual, which is outstanding, is available as a downloadable PDF (http://www.smartire.com/pdf/productliterature/owners english.pdf). You'll also need the LCD module's manual (http://www.smartire.com/pdf/productliterature/full func.display english.pdf). I recommend that you print them and give them to your preferred mechanic ahead of time.

We spent a half hour on the first wheel figuring out what the deal was. Second wheel took 10 minutes. 3rd & 4th wheel, less than 5 minutes each. Piece of cake!

Temporarily, we just plugged the receiver into the 12 volt courtesy outlet (formerly know as the cigar lighter) and laid it on top of the dashboard. The transmitters are easily tested before installation by shaking them and observing that the LCD shows the correct temperatures. I also programmed the LCD unit before arriving at the shop. I "permanently" Velcro mounted the LCD module on the side of the bracket that holds my cell phone car kit. That part looks great and is positioned perfectly for the driver's convenience.

Someday (maybe…) I'll hide the receiver inside the dash, and splice the power cord to an ignition circuit. There is plenty of room in the Classic Prius dash, near the top, inboard of the glove box. For proper operation, the receiver needs to be up as high as possible in the vehicle. When laid on the floor, it is unable to receive the signal from the left rear wheel.

Does anyone know how to take the Classic Prius dash apart without breaking it? (HINT: this is why I tossed the receiver on top.)

BALANCE

The TPMS transmitters weigh just under 1 ounce each and are almost perfectly centered from inside to outside on the rim. Although not mentioned in the instruction manual, my mechanic cleverly placed the worm gear screw of the "hose" clamp directly opposite the TPMS transmitter on each wheel, stating "It'll balance out some of the weight". We ignored the fact that part of the bands were slotted while part were solid.

We were delighted with the results, using his dynamic spin balancer (the kind that tells you exactly where to put weights on both inside and outside of the wheel).

One wheel was perfect, needing no extra weight at all!

One wheel needed less than 1 ounce on each side.

The other 2 wheels needed a bit over 1 ounce on each side.

Interestingly, *none* of the weights correlated with the location of either the TPMS transmitters or the worm gear screws.

PRESSURE SETTING

During the installation I discovered (to my great surprise) that my very reliable 0 to 60 PSIG 2-inch diameter dial type pressure gauge was reading 2 PSIG high. I've had it for many years, and *never* drive anywhere without it! The mechanic noticed that after I set the pressures with my gauge, the readings he got with his brand new professional gauge were 2 pounds lower. After he finished installing the TPMS and all 4 new tires, we were amazed to see all 4 TPMS transmitters agreed EXACTLY with his pro gauge!

All this time I believed I was running 44 PSIG, a setting arrived at by very meticulous monitoring of tread wear. Suddenly I find I'm running at 42, the same pressure everyone else has been quoting for ages!

NOISE

The Hydroedge tires, running with the trunk empty (worst case) produce about the same amount of noise (loudness) as the previous Toyota-recommended Dunlop tires, running with the trunk full (best case)! This is fantastic!!!

Furthermore the character of the noise produced by the Hydroedge tires is not nearly as irritating.

HANDLING & HARSHNESS

The Hydroedge handling is comparable to the Dunlop, which is to say very good to excellent. In fact, I got to try it during a snow storm shortly after installing them. While many people around me where slipping (a few even wiped out) I felt completely secure. (When new, the Dunlops were also fine; it is totally improper to even think about driving worn out tires in snow.)

Both sets of tires (old & new) seem to ride about the same but the Hydroedge seems to give a slightly smoother ride to me. This is a subjective thing… When you can find truly smooth pavement (e.g. a brand new lane) and are cruising in electric-only mode, you don't feel anything at all with these Hydroedge tires. I don't guess it can get any better than that.

SPEEDOMETER & ODOMETERS

After testing for more than 500 miles with my Magellan SporTrak Pro GPS Receiver's odometer mode, I find the Tire Rack's published differences in tire revolutions per mile do NOT correlate with actual driving experience. Although the published numbers (which I have no doubt are true) suggest an error of 1%, my real world measured error is better than 1/10 of 1%. That's less than 1 mile of error for every 1,000 miles driven!

Furthermore, that is nearly the same result I used to get with the Dunlop tires.

By the way, I've also conducted tests with the GPS Receiver's odometer, walking known metered courses and found the GPSR to be accurate within 1/50 of 1%. That's less than 1 mile of error for every 5,000 miles driven! (If you hadn't already thought about it: GPSRs make a dandy outdoor exercise pedometer!)

MILES PER GALLON

Once we know the odometer's accuracy, we can correctly evaluate the fuel economy.

The short report: it is unchanged!!! Hurray!

DAY TO DAY EXPERIENCE

The first few days I fooled with it a lot. Now I am beginning to ignore it. I greatly enjoy the convenience and confidence of knowing my tires are good to go without having to use my gauge.

The gauge is still needed when the time comes to actually add air to a tire. More about that in a minute…

On one occasion the TPMS incorrectly showed a tire leak on the right front and sounded the alarm beeper, but corrected itself 7 seconds later.

Once in a while it appears to have trouble receiving the left rear signal, but it *always* recovers in less than 10 minutes, and typically recovers in less than 1 minute. Experimenting with the location of the receiver might eliminate this issue, but it is a very minor one, and I haven't had time to fiddle with it. In theory, it could be a transmitter defect. If it is, when I rotate the tires in a few thousand miles, the problem will move to the left front. If it does, I'll petition SmarTire for a replacement transmitter.

The system had a delightful surprise. The LCD manual describes a "+ & -" display mode, but I didn't understand it until after the system was installed and I'd had time to play with it. I deliberately slightly over-inflated a tire and drove it far enough to get a reading from the TPMS (less than 1/10 mile). It showed a +3, lit the red alarm light and briefly sounded the alarm beeper. Cool, but I expected that.

Next I drove a while until the tire's temperature stopped rising, 30º F above ambient. Now it showed +6, with the red light still lit.

I stopped and got out my gauge. With the tire still hot, I immediately used the gauge to carefully let out exactly 6 pounds.

Driving again the alarm was gone and the +- display was blank. Pretty cool. But what happens when the tire is cold again?

The next morning, the TPMS reported the tire pressure was perfect. Checking with my gauge (and allowing for the newly discovered error) the pressure was indeed perfect!

Further experiments showed it works the other way, with one caveat. Lets say the TPMS reported the tire was -6 when hot. You might want to add 4 pounds. Why only 4? Because the added air might be colder than the air in the tire; after heating it might actually yield an increase of 6. In any case, even if you decide to add 6 all at once, further driving will reveal if you added too much or need to add a bit more.

WARNINGS

Do NOT use Fix-A-Flat or any of it's competitors with *any* direct TPMS, no matter who makes it, factory installed or aftermarket. It can (very probably will) clog the pressure port, ruining the transmitter. SmarTire will NOT give you a free transmitter if this happens.

Filling the tires with pure dry nitrogen instead of air, as some shops now do, won't hurt it but might change the calibration of the "+ & -" mode slightly. The LCD module has a "Slope" feature to allow for that. Call the factory for instructions if this applies to you.

I carry a portable 12 volt compressor in the trunk every where I go, in lieu of Fix-A-Flat. Don't plug your compressor into the 12 volt courtesy outlet (formerly know as the cigar lighter) because these babies are capable of popping the fuse. I learned this the hard way. Instead get an adapter with pygmy clamps and hook it directly to the auxilliary battery posts. Make sure the engine is running! You don't want a dead battery. Classic Prius auxilliary batteries are only 33 AHr. They are very easy to run down.

SUMMARY

I am very happy with both the Michelin Hydroedge tires and the SmarTire Gen II Passenger TPMS.

DISCLAIMER

My only affiliation to Michelin and SmarTire is that of one very pleased customer.

ANY QUESTIONS?

If I missed something, please speak up!