# Tire Pressure Monitoring System (valve stem) **URL:** \ **Category:** Factual Questions\ **Created:** [December 20, 2015, 3:43pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926 "2015-12-20T15:43:37Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![crypto](https://avatars.discourse-cdn.com/v4/letter/c/b3f665/32.png) [@crypto](https://boards.straightdope.com/u/crypto)\ **Post date:** [December 20, 2015, 3:43pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/1 "2015-12-20T15:43:37Z")
If you have a TPMS attached to the valve stems, when changing the tire, is there a wire attached to the inside of the wheel and connected to the stem, or can the tire be removed without worrying about damaging the TPMS? Also, when buying new tires, does the tech need to reconnect any wires? Or does it work another way? Assuming the sensor doesn’t fail, is it something that should work normally for the life of the car, or do the sensors have to be replaced each time you get a new tire? (They usually put new stems when you buy a set of tires, but I doubt those stems have any TPMS built in. Based on this, I assume they must work differently than I am picturing) Thanks ---
**Author:** ![fubar.gr](https://avatars.discourse-cdn.com/v4/letter/f/898d66/32.png) [@fubar.gr](https://boards.straightdope.com/u/fubar.gr)\ **Post date:** [December 20, 2015, 4:03pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/2 "2015-12-20T16:03:00Z")
There are no wires. The sensor is simply a small black box connected to the other end of the valve stem. See here: [http://www.ebay.co.uk/itm/4PCS-AUTEL-433MHZ-UNIVERSAL-TPMS-TIRE-PRESSURE-MONITOR-SYSTEM-SENSOR-DIAGNOSTIC-/181927372271?hash=item2a5bb765ef:g:Ao8AAOSwf-VWaEB3](http://www.ebay.co.uk/itm/4PCS-AUTEL-433MHZ-UNIVERSAL-TPMS-TIRE-PRESSURE-MONITOR-SYSTEM-SENSOR-DIAGNOSTIC-/181927372271?hash=item2a5bb765ef:g:Ao8AAOSwf-VWaEB3) There’s nothing special in the tire removal process, same as normal, non TPMS wheels. However rims must be marked and put back at the same position. If for example a front left wheel is installed at the rear right position, this could potentially confuse the on board computer. TPMS sensors have a non-replaceable battery that will run out after 5 to 10 years. In that case the whole sensor has to be replaced. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [December 20, 2015, 4:08pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/3 "2015-12-20T16:08:15Z")
> **[Tire-pressure monitoring system](https://en.wikipedia.org/wiki/Tire-pressure_monitoring_system)** > > A tire-pressure monitoring system (TPMS) monitors the air pressure inside the pneumatic tires on vehicles. A TPMS reports real-time tire-pressure information to the driver, using either a gauge, a pictogram display, or a simple low-pressure warning light. TPMS can be divided into two different types – direct (dTPMS) and indirect (iTPMS). > TPMS are installed either when the vehicle is made or after the vehicle is put to use. The goal of a TPMS is avoiding traffic accidents, poor fuel economy, a... No need to connect or disconnect wires for changing a tire or wheel. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [December 20, 2015, 4:10pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/4 "2015-12-20T16:10:25Z")
> [@fubar.gr](#): > > TPMS sensors have a non-replaceable battery that will run out after 5 to 10 years. In that case the whole sensor has to be replaced. Yeah, I have that issue on my 2006 Nissan. Just haven’t messed with it yet. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 20, 2015, 6:24pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/5 "2015-12-20T18:24:53Z")
> [@enipla](#): > > [Tire-pressure monitoring system - Wikipedia](https://en.wikipedia.org/wiki/Tire-pressure_monitoring_system) > > No need to connect or disconnect wires for changing a tire or wheel. Just remember to always back up periodically, or the wires get all wound up. ---
**Author:** ![UberArchetype](https://avatars.discourse-cdn.com/v4/letter/u/2bfe46/32.png) [@UberArchetype](https://boards.straightdope.com/u/UberArchetype)\ **Post date:** [December 20, 2015, 7:54pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/6 "2015-12-20T19:54:15Z")
Replace valves/TPMS sensors with new tire sets in order to maintain warranty support for the tires and sensors and avoid things like battery issues and potential damage during re-installation. Some shops and dealers have declined warranty support for TPMS issues after discovering the sensors are not theirs, or not OEM. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [December 20, 2015, 7:57pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/7 "2015-12-20T19:57:42Z")
> [@fubar.gr](#): > > However rims must be marked and put back at the same position. If for example a front left wheel is installed at the rear right position, this could potentially confuse the on board computer. On the TPMS systems that keep track of which sensor goes to which wheel (many of them don’t) there’s usually a fairly simple procedure to re-learn which sensor is at which position. Otherwise tire rotations would become quite a lot more labor intensive! ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [December 20, 2015, 8:12pm UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/8 "2015-12-20T20:12:11Z")
> [@beowulff](#): > > Just remember to always back up periodically, or the wires get all wound up. My shop does that for me every time I take it in to replace the blinker fluid. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [December 21, 2015, 1:08am UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/9 "2015-12-21T01:08:14Z")
> [@beowulff](#): > > Just remember to always back up periodically, or the wires get all wound up. When you drive a car in reverse, does the odometer run backward? To keep the wires from getting all wound up, you would need to drive as many miles in reverse as forward, in the long run anyway, so you’d want your odometer to keep returning to zero. Also helpful to maintain your car’s near-new resale value! ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [December 21, 2015, 1:44am UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/10 "2015-12-21T01:44:23Z")
> [@GreasyJack](#): > > On the TPMS systems that keep track of which sensor goes to which wheel (many of them don’t) there’s usually a fairly simple procedure to re-learn which sensor is at which position. Otherwise tire rotations would become quite a lot more labor intensive! yeah, and you can get TPMS “triggering” tools from pretty much any tool vendor, or even Tire Rack for some inexpensive ones. > [@Senegoid](#): > > When you drive a car in reverse, does the odometer run backward? To keep the wires from getting all wound up, you would need to drive as many miles in reverse as forward, in the long run anyway, so you’d want your odometer to keep returning to zero. Also helpful to maintain your car’s near-new resale value! That reminds me of when Bob Lutz was on _The Colbert Report;_ when Colbert asked if the Chevy Volt’s 40 mile electric range meant the car had a 40-mile long extension cord. Lutz replied “We were going to include one, but people kept running 'em over.” ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 21, 2015, 2:10am UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/11 "2015-12-21T02:10:04Z")
> [@Senegoid](#): > > When you drive a car in reverse, does the odometer run backward? To keep the wires from getting all wound up, you would need to drive as many miles in reverse as forward, in the long run anyway, so you’d want your odometer to keep returning to zero. Also helpful to maintain your car’s near-new resale value! I all seriousness, no. Years ago a friend and I rented a car for a long road trip. We exceeded the allowed milage by quite a bit. I came up with the (brilliant) idea to disconnect the speedometer cable from the transmission, and chuck it into a drill, which we then set to run backwards. The odometer backed up until the tenths digit was 0 and then stopped. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [December 21, 2015, 8:09am UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/12 "2015-12-21T08:09:22Z")
> [@beowulff](#): > > I all seriousness, no. > > Years ago a friend and I rented a car for a long road trip. We exceeded the allowed milage by quite a bit. I came up with the (brilliant) idea to disconnect the speedometer cable from the transmission, and chuck it into a drill, which we then set to run backwards. The odometer backed up until the tenths digit was 0 and then stopped. There’s a reason why that happened. Less-than-honorable car sellers (many of them ‘Dealers’) found the ‘back-off-the-milage’ trick many years ago. Laws were, IIRC, passed requiring odometers to be tamper-proof - at least for mechanical odometers. Lord knows what a clever geek could do with an electronic display. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [December 21, 2015, 10:16am UTC](https://boards.straightdope.com/t/tire-pressure-monitoring-system-valve-stem/740926/13 "2015-12-21T10:16:01Z")
> [@usedtobe](#): > > There’s a reason why that happened. > > Less-than-honorable car sellers (many of them ‘Dealers’) found the ‘back-off-the-milage’ trick many years ago. > > Laws were, IIRC, passed requiring odometers to be tamper-proof - at least for mechanical odometers. > Lord knows what a clever geek could do with an electronic display. Well, they had this clever feature that you could wind back the first 50 miles or so! So that the new-car dealers could reset the odometer to not show the shipping and delivery miles (and, in theory, so that you got full millage on your warranty). But those dam sneaks in the press and consumer affairs got wind of this, and though it was misleading (or even … dishonest …) so that feature’s gone too.