Just our government trying to keep you safe...

Does anyone know of an inexpensive source for the TPMS sensors? I've got a base 2007 cayman - which I hope counts as a boxster

The tire rack folks have them, but they are $90 each. I thought there might be another source out there.

I tried driving on sensor-less wheels for a while, and the car just complained that the system wasn't working. Now that I'm replacing the tires on those wheels, I thought I'd put the sensors in. I wasn't expecting ~$400 though, so I'm debating going without. Anyone else do that? Is it harmful to anything?

I like knowing the tire pressures, but jeez...$400 for it is a downer.

units that are compatible with the Porsche TPMS but they may exist.

If I were in your shoes I'd just spring for the $90/each units and be done with it. My time with my 08 Cayman S with TPMS was short lived but I really appreciated the TPMS feature and would have kept it in tip top shape had the car remained on the road.

Oh I agree that it's a great feature, and I don't mind that it's mandated etc. However, after some pricey christmas travel and just buying a new house, for that cost I can go at least this one winter measuring the old fashioned way. I'll have to get the tires mounted on my 986 rather than the 987 though, since the tire store folks tell me they aren't allowed to mount sensor-less wheels onto a car with the monitoring system.

on eBay. I purchased rims (take offs) and snows a few years ago and needed TPMS transmitters. I went to my local Lexus dealer and they wanted around $110 each!!!! A piece of black electrician's tape on the dash is less than 1/4 cent. On eBay, I discovered these monitors are pretty much all the same for Japanese cars as they are not a market differentiator for them... the price on eBay?? Wait for it........ all four were around $70 total. Yep, you read that correctly. I took the car to a Toyota dealer to program... no way am I paying Lexus labor rates for this. Working fine for four years on now.

Bruce in Philly.

There seem to be several offers for about half the price of what tirerack had. I wouldn't be surprised if the batteries were near dead in some of those, but who knows.

I think I'm resigned to going sensorless. It occurred to me that the wheels I'm using are from the 986 era, so the sensors may not even fit on them. Besides, my new house has a lot of sidewalk, and I've been drooling over the snow blowers on display at the local hardware store. When looking at a wide sloping driveway and 300 feet of sidewalk, and all you have is a shovel, it isn't hard to decide between a snow blower and a pretty digital display of tire pressure

...at any cost.

I wonder why tire pressure sensors don't use self winding technology of simple wrist watches to function?

dghii
2000 Boxster S 6speed 112k miles

operating conditions. Big difference between a self winding mechanism in a wrist watch on a human's arm and one inside a tire rotating at God only knows what speed. A self winding mechanism that could withstand this environment would make the cost of battery powered TPMS devices about the same as Susan B. Anthony $1 coin to a Nancy Pelosi $1,000,000,000,000 coin.

What exactly would be getting wound? It's not like the transmitters are mechanical. Besides, I thought those watches were wound by the oscillation of our arms, not a regular rotation. Anyhow, given that these are only recently required elements of cars, I'm sure that the sensor designs will evolve over time. Tossing out "why didn't they just ..." statements usually underestimates the amount of thought that went into the current designs. "Why not use induction like on bicycle lights?" or "Why not use live connections" etc. I'm sure ideas that vague have been explored and that none worked out, so far.

a small generator has been spun at sufficient speed to generate the necessary electrical power. This is done by in the case of a self-winding watch that runs on electrical power by arm movement that causes an imbalanced rotor to spin and generate electricity which is used to top up a rechargeable battery or capacitor. Designing a mechanism that can tolerate the relatively low g-forces produced by the human arm in normal conditions (I imagine a major league baseball pitcher would have to remove his self-winding watch while he was pitching) is not that hard (though of course beyond my less than meager design abilities).

Designing one that could withstand the g-forces inside a spinning wheel is something else. There is also the problem -- at least to me it appears to be a problem -- of how to deal with the considerable variation in output from a wheel rotating at low speed vs. one spinning at high speed and for a prolonged period of time.

Also, please note that there is still a battery/capacitor in the electrical circuit and these have limited service lives. Plus if a car is parked a while this battery/capacitor could run down and it would take some driving time to recharge it so the TPMS worked again. I'm assuming this rechargeable battery/capacitor would not be harmed by fully discharging too.

I know for those that own a TPMS equipped car this periodic TPMS module with a new battery replacement is an expensive surprise at tire replacement time -- service managers at dealers tell me the subject of TPMS has resulted in some of the most upset customers ever -- the design is a pretty good one considering.

I have to point out we only are faced with dealing with TPMS module replacement because of a government mandate.

Good discussion but remember that the energy may only be needed augment, as opposed to replace a power source (as stated above in MarcW's post). Unllike a watch, the 'self winding' movement would not need to power any mechanical device. Oscillation motion of a human arm is not required....think regenerative brakes, not fragile watch. What if the 'device' kept a doubled or tripled the battery life of the sensor...wouldn't that be great?

dghii
2000 Boxster S 6speed 112k miles

Forget the self winding feature, just make the darn things so that the battery can be replaced instead of the entire unit. That's the real issue--$90 times four vs $8.99 times four.

--db

to be replaced it can come out other times. Remember the environment the TMPS lump has to exist in. Horrendous g-forces. Heat. Cold. Vibration.

And chances are the labor to remove the battery and replace it would be nearly as much as the cost to replace the units anyway.

and it all came about to fix a problem that wasn't actually there... Ford Explorers were having blowouts, rolling over and killing people, remember that? Turns out the extra heat caused by the "low" tire pressure was two much for the Firestone tires they came equipped with so the tread was separating from the core. This went on for several years until someone sued. The court finding found that the pressures weren't actually low they were what was called for by Ford. Firestone had warned Ford that the pressures were too low but Ford wanted those pressures to soften the ride in what was really a truck with a car body. Well Firestone took more heat then Ford and ended up being bought by Bridgestone, Ford payed off, no one went to jail and is doing fine today. The government of course had to act so they mandated tire pressure sensors which would have done nothing to stop the problem as the pressure show were too low so Ford wouldn't have to build a new softer platform for their truck.

The government rather then prosecute one of their big donor favorites they made up a costly, unnecessary law.

...I just wonder how I survived without this wonderful feature. Remember car seat belts that put themselves on automatically? Now that was a cool design!

dghii
2000 Boxster S 6speed 112k miles

Personally, I am looking forward to driving a Google self-driving Boxster. The excitement of taking a clover leaf at the recommended speed; seeing my pdk tranny automatically shift every time with stunning precision at 2,500; never changing lanes; and enjoying my cd player like never before because there is nothing else to do. Hmmm. Maybe I'll take the bus.

Quote
Bobtesa
Personally, I am looking forward to driving a Google self-driving Boxster. The excitement of taking a clover leaf at the recommended speed; seeing my pdk tranny automatically shift every time with stunning precision at 2,500; never changing lanes; and enjoying my cd player like never before because there is nothing else to do. Hmmm. Maybe I'll take the bus.

You're forgetting the excitement of texting, checking your email, brushing your teeth, maybe even taking up knitting while driving. The ultimate would be to have an in car Xbox car racing game to play while your Google car takes you to your destination.