Are TPMS sensors the new timing belt?


#1

A few years ago we used to see threads about “Do I really need a new timing belt,” as owners discovered this unexpected high-cost maintenance need.

Now, I see several threads (including mine) with similar reactions to replacing TPMS sensors. For myself, I feel like I should have realized that the sensors would have to be replaced, and I should have realized that it would be pricey. But I understand why most owners are surprised at the need and cost to maintain this “new technology.”


#2

I’m not sure how common this actually is. My wife and I keep our cars for eight to ten years and I have yet to replace a sensor on any car.


#3

I’m going to say No, this is not the equivalent to replacing timing belts.

If a TPMS sensor fails, nothing happens except a yellow light appears on the dash. You drive happily onward.

If a timing belt breaks, on many engines the light that appears on the dash is red and the car stops. And won’t go again until large plies of money are involved.

My last Mustang got all 4 replaced at 8 years old because I bought a set of larger wheels and the original bands wouldn’t fit. But the olds ones still worked. New aftermarket ones were $160 for the set. Not huge money but the tires I bought cost $250 apiece so comparatively, the TPMS sensors were not expensive


#4

I guess we’ve been lucky…My 05 4runner was the first vehicle to have the sensors on. After 300k miles when I gave truck away I still had never replaced any of the sensors. And they were working fine.

My wifes Lexus and my Highlander all have the original sensors.

I know my tire shop can replace sensors and reprogram them. I’ve seen them do it while I was waiting for new tires on my truck. They said with the right equipment they’ve been able to reprogram all makes and models. Far cheaper then going to the dealer.


#5

Tire sensors and timing belts is an apples to oranges comparison. I think Art is just noticing the threads because it is on his mind.


#6

"Are TPMS sensors the new timing belt?"
IMHO no, because their cost of replacement is minor and simply an inconvenience. And the effects of their failure don’t propagate through any major system… when they fail, they don’t start taking other systems down with them.

I suspect that CVTs are going to be the new timing belts. They’re just not old enough and ubiquitous enough yet for us to start seeing the problems. Just a prognostication, you understand.


#7

Not even close. You can replace all the TPMS sensors for under 200 bucks. A timing belt will easily run you over a grand in some cars. And the ones in my car have outlasted the timing belt.

This is like asking if having to put gas in the car is too burdensome.


#8

I suppose for some folks the idea that a car needs maintenance is offensive, at whatever level. The goal seems to be that a car should be like a refrigerator, plug it in and forget about it for 15 or 20 years, then complain when it stops working.


#9

Personally, I think it’s ridiculous that they still have a self-contained battery. Seems to me someone should have figured out how to utilize the free energy from rotation or perhaps wireless charging of a super cap to power them by now.


#10

yes, you could use the same inertial type mechanism used in self winding wrist watches. The energy would come from starts and stops.


#11

Yep.
None of it is anything earth shattering either, it’s all well known technology that exists today.


#12

Regenerative braking systems do recoup some of the inertial energy from both the car’s mass and the rotational energy from the wheels. However, none of this energy is free, and none of it is being wasted as the car traverses the tarmac. It’s all transferred to the car’s mass and to the wheels from the burning of gasoline (in traditional cars), or from batteries (in EVs) or some other form of power (hydrogen, French fry grease, or whatever). And the transfers/conversions all have losses. As the car traverses the tarmac, the energy is used to overcome resistance from the air, the friction and fluid resistances in the mechanical stuff in the powertrain, and from the rolling of the tires on the pavement. And few other details.

Ergo, the best approach rather than to attempt to recoup inertial energy is to attempt to minimize resistances that is has to overcome. Low rolling resistance tires, aerodynamics, and weight reduction are all attempts to do this. And they all come with tradeoffs. LRRs sacrifice traction. Aerodynamics can sacrifice utility. Weight reduction sacrifices ride, traction, and often utility… and when exotic materials are used to do it the cost rises.

In summary, inertial energy isn’t free. It has to be transferred from another power source to be there to recoup. It’s better to focus on reducing the amount that has to be transferred.

Oh, I almost forgot: a battery is sort of a super capacitor. Both store electrical energy by piling excess electrons on one side of a dielectric and leaving a relative electron deficiency on the other side, and both release that power through circuits when the two sides are connected. If resistance is in the circuits, they both release the surplus electrons in a controlled fashion. If the two side are shorted, both will discharge immediately.


#13

Everything you listed is correct. However, the energy required to keep a TPMS sender’s battery charged is very tiny compared to the energy in the rotating wheel. Probably in the microwatt region.


#14

My 2014 Mazda6 uses the ABS sensors to operate the TPMS system. No sensors inside the wheel. Pretty slick and I was able to buy snow tires on wheels without dropping an extra $200 for new sensors. The system works great. I forgot to reinitialize the TPMS when I put on my snow tires and within a few miles the system squawked at me because it could tell there was a problem (or it thought there was).

TPMS sensors have a service life of 7 to 10 years and 150,000 but many go much longer so, for most people it is most likely a one time repair, if the need arises. If you have sensors in your wheels I would think it is not that big of a deal and certainly not comparable to the cost and complexity of a timing belt replacement.


#15

It is. But I wouldn’t want to pay for the system necessary to convert the wheels’ rotating inertia into charging of the TPMS senders’ batteries. Just thinking that challenge through makes my brain hurt. :grin:


#16

I’d beg to differ… not the wheel’s inertia, but the change in momentum that comes with starting and stopping. As I said, the mechanism used in a self-winding watch would work just fine.

edit, but inertia and change in momentum are similar.


#17

Its not that bad, I think. Mount the weight of the battery on a piezoelectric stack and use the changing direction of the earths gravity the battery “sees” as it rotates to compress and relax the piezo creating voltage and a tiny bit of current to recharge the battery. All solid state, no spinning parts except the wheel itself.

Or just replace them every 10-15 years! :grin:


#18

Replacing a tire pressure sensor is pretty easy compared to the timing belt job. All that is required is to de-bead the tire and replace the part with a new one. And it’s a job that can be given to shop employees who are still in training.


#19

The energy you’re suggesting recovering IS inertial energy.
The pendulum in watches and similar devices that swings and (in a watch) gets stored in the hair spring is the energy contained in the static mass. Remember that mass IS energy.
The energy transferred to the spring when the mass’ momentum is changed is the energy of the pendulum’s mass wanting to either stay in one place (if the momentum is increasing) or continue moving (if the momentum is decreasing).

Mustang’s idea sounds interesting. But I wonder what it would take to make it meaningful.
You could test it. An antiknock sensor is a piezoelectric device. If you could mount a sensor to a wheel and somehow create a continuous circuit to a multimeter that has the ability to record data you could theoretically measure the amount of output from the crystal and calculate its ability to keep a TPSM sender charged. The output of the knock sensor could probably be obtained from its manufacturer and the voltage of the pressure sensor from its manufacturer.

I have to tell you, though , that in all my years I’ve never run such an experiment that was anywhere near as simple as the initial concept statement. I wish only the best to anyone willing to take this one on. Succeed and you might make a fortune. Fail and the things you learn in trying might have value of their own. :stuck_out_tongue_winking_eye:


#20

The tire places around here try to get you to pay to rebuild your sensors every time you get new tires. Even the ones that give you an out the door with everything included price try to charge you extra.