Ding! A symbol that looks like a baseball bat dropped into a punchbowl appears on your dashboard. You have a tire that’s low on air, and your car’s alerted you to it far before the heat and friction of underinflation cause odd tire wear or a panel-bending blowout. Well, either that or one of your tire pressure monitoring sensors has died. But what if there was a better way of keeping tabs on tire pressure? One that perhaps trades some precision for being completely maintenance-free? Well, such a thing used to exist, then the federal government killed it, but now it’s coming back. May I introduce you to indirect tire pressure monitoring?
The tire pressure monitoring systems in most American cars feature four sensors and a receiver, or sometimes four sensors and a combination receiver-transmitter unit. See, those expensive little sensors are jam-packed full of tech, from the battery to the pressure sensor to the analog-digital converter to a radio frequency transmitter sometimes used in conjunction with a receiver inside each sensor to share data with the tire pressure monitoring system receiver or receiver/transmitter inside the vehicle. This system of wireless data transmission explains why you could theoretically build a cheap pressure chamber out of pipe and a schraeder valve, dump four sensors in there, pump it full of air, throw it in the trunk, and the TPMS system will be none the wiser. It also explains why these things cost a mint, adding three figures to the cost of, say, a winter tire and wheel package.
However, indirect tire pressure monitoring doesn’t add any hardware to a car, so they should be cheaper even factoring in the software development (and tire changes should be easier). In fact, an indirect system just takes signals the car’s already generating and uses them to discern if a tire’s low on air. An underinflated tire will have a smaller overall diameter than properly-inflated tire, which should get picked up on the wheel speed sensors used for ABS as a difference in wheel speed. If the difference is great enough, the vehicle’s electronics will notice and illuminate a warning light on the dashboard. In principle, “indirect” tire pressure monitoring is perfect for anyone whose last name isn’t Verstappen or Vettel. There are no expensive wheel-mounted sensors that eventually crap out or may get damaged in the tire mounting process, and winter tire swaps are extremely easy. However, there’s a reason why indirect tire pressure monitoring briefly disappeared from the American market.
In 2005, the federal government mandated a phase-in of tire pressure monitoring systems in every car, with a firm deadline of September 2007. However, talks about mandating TPMS started years earlier, due to a headline-making scandal involving Ford Explorers and Firestone tires. Underinflation, blowouts, and a whole lot of mud-slinging over a recall prompted Congress to pass the TREAD Act, a piece of legislation primarily focused on recalls and reporting. However, section 13 of the TREAD Act specified that:
Not later than 1 year after the date of the enactment of this Act, the Secretary of Transportation shall complete a rulemaking for a regulation to require a warning system in new motor vehicles to indicate to the operator when a tire is significantly under inflated. Such requirement shall become effective not later than 2 years after the date of the completion of such rulemaking.
Well, so much for the deadline. Eventually, this tiny little section of the TREAD act led to Federal Motor Vehicle Safety Standards section 138, a tire pressure monitoring system mandate with very specific criteria. A critical part of the test certifying tire pressure monitoring systems for use on American vehicles is to:
Stop the vehicle and deflate any combination of one to four tires until the deflated tire(s) is (are) at 7 kPa (1 psi) below the inflation pressure at which the tire pressure monitoring system is required to illuminate the low tire pressure warning telltale.
Sounds like simple criteria, right? Unfortunately, most older indirect TPMS systems can fail this test. From NHTSA:
There are two types of TPMSs currently available, direct TPMSs and indirect TPMSs. Direct TPMSs have a tire pressure sensor in each tire. The sensors transmit pressure information to a receiver. Indirect TPMSs do not have tire pressure sensors. Current indirect TPMSs rely on the wheel speed sensors in an anti-lock braking system (ABS) to detect and compare differences in the rotational speed of a vehicleís wheels. Those differences correlate to differences in tire pressure because decreases in tire pressure cause decreases in tire diameter that, in turn, cause increases in wheel speed.
To meet the four-tire, 20 percent alternative, vehicle manufacturers likely would have had to use direct TPMSs because even improved indirect systems would not likely be able to detect loss of pressure until pressure has fallen 25 percent and could not detect all combinations of significantly under-inflated tires. To meet the three-tire, 25 percent alternative, vehicle manufacturers would have been able to install either direct TPMSs or improved indirect TPMSs, but not current indirect TPMSs.
As I mentioned before, early indirect tire pressure monitoring worked simply by referencing the speed of all four tires against each other using a vehicle’s wheel speed sensors. The theory is that an underinflated tire has a slightly different diameter than a properly inflated tire, and will therefore spin at a different speed. While this eliminates pesky TPMS sensors, it does come with a blind spot — if the pressure in all four tires is reduced by the same amount, the TPMS light won’t come on. After all, if all four tires are rotating at the same speed, a computer only referencing relative wheel speed won’t notice anything’s wrong. Early indirect tire pressure monitoring also has a limitation when it comes to certain staggered tire setups that run different overall tire diameters on each axle. For those vehicles, similar deflation across any one axle may cause a false negative.
However, since the advent of FMVSS 138, indirect tire pressure monitoring systems have evolved substantially, with Brake & Front End reporting that “New systems are taking advantage of better wheel speed sensors and modules to make indirect systems work.” A specific example is how Infineon Technologies has a patent on indirect tire pressure monitoring using “an electronic control unit (ECU) coupled to the ABS and configured to process the sensed signals using a multidimensional resonance frequency analysis (MRFA) that includes a spectral analysis identifying at least two tire vibration modes in the wheel speed signal and isolates at least one characteristic affecting the at least two tire vibration modes.” Translation? By using spectral analysis, this system can detect if all four tires are losing pressure simultaneously.
Modern Tire Dealer, a website that’s apparently the “premier source of news, research and market trend analysis,” breaks all this down further, discussing Audi’s new indirect system from supplier Nira Dynamics AB called “TPI.” After noting that it’s easy enough for an indirect system to use wheel sensors to figure out if one, two, or three wheels are deflated (since the tire radius changes, and thus the deflated wheels will have to rotate faster to “keep up”), the issue of four simultaneously-low wheels comes up:
TPI also features other components analyzing high-frequency components of the wheel speed signals stemming from different vibration modes of the wheel. These approaches are applied to each wheel separately, and by combining this with the previously mentioned radius analysis, TPI can detect under-inflation in one, two, three and four tires simultaneously.
The article goes on to say that there’s an “initial calibration or learning phase” to figure out what the normal “characteristic parameter values” should be with fully inflated tires. Those are later used to compare what the vehicle is reading from the sensors as a user drives the vehicle. “The driver should reset the system and re-initialize calibration whenever he or she has made a change to the tires, the tire pressures or, in general, to the wheels,” the article continues before saying:
TPI is designed to give a warning for under-inflations of 25% or more compared to the nominal pressure level, which the system learns during the calibration phase (25% is the required detection level under FMVSS 138).
The best statement regarding the reliability of the system at this point is probably that TPI (has been) in production for the Audi TT since 2006 and for the Audi A5/A4… and has received positive reactions from customers and quality assurance people alike. Further, since TPI is a software-based system using existing and well-proven components of the ABS/ESC system, in particular the wheel speed sensors, it’s optimally simple and robust. The key point here is that software doesn’t break!
These developments allowed these indirect systems to slowly start trickling back into the American market in the 2010s. The first-generation Mazda CX-5 (see above) used an indirect tire pressure monitoring system, as do many Volkswagen Group cars and most newer Hondas. For the vast majority of drivers, it’s simply a better, more cost-effective, maintenance-free solution compared to direct tire pressure monitoring.
So what if you’re a tire pressure gauge-carrying scofflaw with a car from the late aughts and don’t need no stinkin’ TPMS sensors? Well, depending on the make and model of your car, you may be able to “code in” indirect TPMS. For instance, most Bangle-era BMWs will let you code in Flat Tire Monitoring, an indirect tire pressure monitoring system that uses relative wheel speed derived from wheel speed sensor data instead of an expensive tire pressure monitoring sensor in each wheel. Of course, we don’t advise breaking any laws, but we do think it’s funny that tire pressure checks used to be part of normal driving routine, and now many people simply don’t carry a cheap tire pressure gauge in their car.
(Photo credits: Thomas Hundal, Amazon, Mazda)
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Mazda has been using an indirect system for a while now, starting in like 2015ish, maybe even a little sooner, I don’t remember exactly.
No it isn’t good that indirect systems are making a come back. OE sensors can often be found for less than the universal one size fits all sensors and often last much longer than the universal.
What is good are the newer direct systems that use PAL (ABS + Sensor Data) or WAL (directional antennas and signal strength) to automatically learn positions or new sensors and display actual pressure.
The older systems didn’t display pressure since that would rely on people doing the relearn process when necessary so that the position the vehicle thinks sensor is in matches the actual location of the sensor.
They did. My 2009 G8 showed exactly which corner had what tire pressure if I taught car to tires.
If you rotated tires without teaching it would show wrong tire pressure on wrong corner.
What if you are running tires with tubes in them?
I didn’t know Stutz Bearcats came with TPMS. The more you know. 😀
Well I was thinking heavy duty trucks and the like. I know my local tire dealer still has always has a pile of old inner tubes , mostly with those long valve stems like on dualies. Probably a lot of tractor tires too.
Are there any aftermarket indirect systems? My Juke doesn’t report which tire is low, so it’d be great if I could install an indirect system that could provide that information through a phone app or a little display panel stuck to the dash.
Just curious how much you would be willing to pay for what you described, as opposed to a $10 tire gauge that you keep in your glove box?
Ssshh, you’re supposed to try to sell him a $300 tire gauge you picked up at the gas station for $5.
The system in my 2014 Sportwagen is indirect, but avoids the blind spot that comes about if all four tires lose pressure at an equal rate (like during a cold snap). When your tires are properly inflated, you press and hold a button in the glove box which sets the current pressure as the comparison point. You have to do this any time the warning light comes on, after you’ve reinflated the tire(s). Is it an extra step? Yes. But I prefer it to the expensive TPMS sensors that are the alternative. On my last water-cooled VW (2012 CC) I didn’t bother putting the sensors in my aftermarket wheels, I just tweaked the code (VCDS is a godsend) to turn off the system so the warning light would go out.
My friend discovered the passive system in her 2012 Beetle just yesterday, and thought it was the coolest damn thing.
To avoid installing and teaching new pressure sensor to remove TPMS light, G8 and SS guys used to put pressure sensors that were taught to car in PVC pipe, then seal it and add Schrader valve.
Pressurize that to 40 PSI and leave it in the trunk
My wife has a 2015 Mazda CX-5 and I used to have a 2015 Mazda 6. Anytime I had to replace the tires, I looked over the estimate and made sure to point out my car had indirect TPMS and I expected the final invoice to have that line item removed. I felt smug doing it, but there was no reason to pay for something they wouldn’t be doing. One guy when I told him replied “well, we’ll see about that.” It was not in the final bill.
I also ask them to remove “tire disposal fee” when I just change tires and take all of them back.
When they add TPMS to new tire install (they say so I can have new batteries in them) I ask for old ones back and keep spares 🙂
For most drivers I don’t think tire pressure checks were a routine part of vehicle ownership. At best, if a shop checked them at oil change time.
I’m not sure if my 2015 Optima was direct or indirect as it didn’t read the PSI but would blink which tire was low in the dash readout, which is a fair compromise if possible with indirect. However I want to say SX/Limited models did read the PSI, so probably direct.
My GTI once pinged for low pressure on a road trip a couple years ago, but when I pulled over at a gas station and checked every tire, none were below recommended PSI. That said, it was before I really knew the differences between the TPMS types, so maybe it was just enough of a difference between them to set off the sensor between the readings despite being above spec, because I likely had it a couple PSI over.
I can’t remember the last time I had low tire warning, but also just made it a habit after I got new tires to pop into the tire fill stations at Costco and check and fill in one swoop.
in my GTI there is a button to teach the VW that right now current tires have correct tire pressure.
So sticker calls for 39 PSI. I set tires at 32, press teach TPMS button, and GTI knows that 32 PSI is correct and alarms me when it is lower from that setpoint.
Maybe you taught your VW with too high tire pressure
Yes, I’ve used the set tire pressure function, I’m familiar. Thinking about it again from say, the 20% differential, that would have required them to be set at 45 PSI – which I didn’t and doubt the dealer or a shop would have either. But, whenever I’ve checked and filled ever since Costco, I’ve never lost more than 4-5 PSI, so it seems they’ve also just been not susceptible to much air loss (knock wood).
It certainly is an impressive amount of technology to replace a $3 gauge from Harbor Freight
Those owners of 1996 Ford Explorers with Firestone all terrain tires sure could have used TPMS since that $3 gauge didn’t prevent them from roll over after tire thread seperated from too low air pressure at high speed
That’s assuming a) the tire pressure was fine before they got on the road, and b) there was even enough time between when the tread starting failing and when it totally failed to even get safely to the side of the road. In that situation, by the time the warning light came on, the tire was likely already self destruction
And it was also a highly isolated incident involving one specific manufacturer and brand of tire (Firestone Wilderness A/T) installed on one specific model vehicle (Ford Explorer) that involved a factory defective, which was eventually dealt with through the recall process, fines, penalties, and civil litigation, and the problem has not recurred on other tires or SUVs since
Yes, because Ford told Explorer owners too low tire pressure for better ride vs Firestones recommendation.
My flat’s thread seperated too when I tried nursing it home but I knew it was flat from TPMS and went 15MPH instead 60MPH
There were also quality control problems at Firestone’s factories, especially the one in Illinois, and specific details with the tire’s construction that made it more prone to failure under the exact same conditions than the Michelins installed on certain Explorer, Mountaineer, and Navajo models, which didn’t have tread separation issues despite the same PSI recommendations.
For the last 3 tire sets I wanted to get Firestone tires and then Discount Tire won’t sell them to me because Firestone has a store that installs tires, and DT won’t carry competition’s brands and I like having DT’s road hazard warranty on tires.
Maybe that is why DT won’t sell them – poor quality?
Maybe for some summer 18s for the GTI I’ll get some Indy 500s since I scored a sweet deal for 33″ BFG KO2 AT take offs for the Jeep instead of Destination AT
I don’t think its a wider issue, this was something that happened 25 years ago on two specific models of Firestone tires from two factories that were sold to Ford as OEM equipment
I wish my 20 year old Lexus had indirect TPMS. Instead, it came with direct TPMS, which wasn’t an issue until recently, when shortly after replacing all five pressure sensors the main control module failed. Replacing it is a pain, so I disabled it and now use a mechanical pressure gauge to make sure my tires are inflated….just like I did when the TPMS worked, because it only had an idiot light instead of individual pressures.
I still carry a mechanical tire pressure gauge. The indirect TPMS on my car will occasionally show a false positive when we drive a lot on gravel roads. Oddly this only happened after we replaced the tires with a different brand.
Did you check tire pressures when wheels are cold?
All tire shops inflate to 32 PSI and call it good even when minium tire pressure is at 39PSI
Yeah I carry a tore gauge and check
Hm, I just use my trusty PKE meter, which is “…configured to process the sensed signals using a multidimensional resonance frequency analysis that includes a spectral analysis identifying at least two vibration modes in the signal and isolates at least one characteristic affecting the at least two vibration modes.”
Man, this thing reads like stereo instructions!
Great timing on this article. I just had my indirect system alert me before a catastrophic flat. I always do a visual at every fill up or more often if the car has been sitting and there have been major temperature swings. I use my analogue gauge roughly monthly. I don’t drive a whole lot, so some of this is just to stay on top of my tires aging.
I was on a long road trip this week and had done a visual, but my light came on. I was about to stop anyway and I did. I noticed my tire was down ever so slightly and thought, wow, that’s pretty sensitive. Then I noticed the hunk of metal jutting out of the inner sidewall. That tire wasn’t going to hold long!
Not only do I carry an analog gauge in my car (the digital ones are nice until winter hits and the battery is kaput) but I keep a cheap one in my laptop bag and travel electronics case. After two rental cars that threw a TPMS light and no idea if it’s a “hmm” or an “oh-shit” moment, I learned my lesson. I actually forgot one in a rental the other week and told my wife “it’s ok, I have a backup in my suitcase”. Her response? “You have a backup tire pressure gauge to your backup tire pressure gauge??”
I do the same. After traveling on business, I’ve found out the hard way that checking tire pressure was the renter’s problem and not the rental agency’s problem (unless the tire was flat to begin with – at least that’s the way they make me feel). Even used it to help a coworker out when he got a flat.
Ask her what’s in her purse. I bet there’s a fair bit of redundancy there if she’s anything like my wife.
I’ve gone in there. It’s her wallet, chapstick, receipts from 2017 and a dead leaf or two.
With rentals for work I turn around and request another vehicle that is road worthy and return the broken one back
I admit I skimmed quite a bit so maybe you addressed this but how well will this indirect system work with runflat tires?
I would imagine it still works. I don’t know much about run flats but I suspect the tire deforms at least some when flat, which would trigger the sensor.
There is only one way to find out! Run flats are good for 50 miles without air in them so that is the limit for the test (I don’t have run flats)
I find that just having an idiot light is highly annoying though. I much prefer when I can see the PSI of each individual tire so I can gauge how severe it is (like, am I just a couple PSI out of spec and I’m fine to keep going for a bit) and also so I know exactly what tire needs air when it is time to top it off.
It also allows you to monitor a slow leak, sometimes you get a low pressure due to cold weather which can muddy the waters if you don’t have individual pressure readouts
Tires with low air pressure at cold weather need to be filled to correct pressure.
Air pressure naturally changes with temperature. It is normal and needs to be topped off
The Aventador I used to have had indirect TPMS which was extremely annoying. You never knew if it was because the sensor died, you had a puncture, or if the temps simply dropped because it got cold. I’d very much rather know what all my pressures are instead of seeing “low tire pressure”
Tires with low air pressure at cold weather need to be filled to correct pressure.
Air pressure naturally changes with temperature. It is normal and needs to be topped off
Tire temps drop when at high speeds. I’d like to know if theres a puncture or if it’s just because I’ve been doing over 130
Yet my wheels and tires are dry first of the whole car after driving in the rain, and tire pressure does not decrease until it is parked for few hours.
Maybe my Wrangler has more down force or I am driving faster (up to 65MPH) than you since you tire pressure goes down when driving
Perhaps you should drive your Wrangler at 130 and let me know what your tire temps look like. Here’s a simple photo of what pressures a Bentley uses if you do high speeds. https://cimg7.ibsrv.net/gimg/www.6speedonline.com-vbulletin/1024×1365/img_20191008_135845_1299c014b400b56de8909efc3a022c393a44287e.jpg
Can’t. It tops out at 99MPH but speedo only goes to a 100MPH so I got my monies worth.
THe picture does not show air pressure decreasing at high speed.
Even if your magic wheels and tires get cold at high speed they won’t get colder than ambient temperature, so their air pressure still won’t be lower than when tire is cold and not driven on.
My spouse hates the indirect TPMS system on her Mazda compared to the direct system on my Hyundai because her system doesn’t inform her which tire or tires need to be checked.
And if it’s a good sensor with live updates, you don’t need any gauge at all. Just leave the car running and look in the window as you fill.
They’re a pain in the ass. I can buy a set of Amazon for ~$50, and thankfully, my local garage will install parts I buy elsewhere, but now I have to pay ~$100 to have them installed. Since, I run summer/winter rims I also need to have the car reprogrammed twice a year.
I just leave the light on during the winter.
To avoid installing and teaching new pressure sensor to remove TPMS light, G8 and SS guys used to put pressure sensors that were taught to car in PVC pipe, then seal it and add Schrader valve.
Pressurize that to 40 PSI and leave it in the trunk
I guess the TPS in my 2010 RX-8 is the indirect kind. It is just a light with no indication of which tire(s) are low or by how much. It has worked fine for me and must be fairly forgiving as it has only come on a few times (a tire was low.) When I switch to snow tires (on their own rims, an inch smaller) I have to live with the light, but the warning beep only comes on once a season (and not everytime I start the car.) I like it, it has warned me when it needed to and not when it didn’t.
That’s an odd one. My ’06 Mazda3 had an indirect, but I didn’t run separate wheels to know if it behaved the same way. Is it set to a specific pressure, like 32 psi, and throws a light when it sees it as out of spec (low out of spec if it’s like the 3, since I usually run a little higher psi and never got an alert for it) and the smaller diameter wheels always seem that way? That almost sounds like the garbage direct type that doesn’t ID the wheel or the pressure, but I can’t imagine you wouldn’t have had to replace the sensors at some point in the last 13 years.
what I don’t like about TPMS sensors is you have to dismount the tires to change them. Say you already own a very capable scan tool that can program TPMS sensors….So you get on the web and find replacement sensors for 18 bucks each, order 4 of them and take them with you to your tire appointment. Then you run up against the greedy shop who “cant install those sensors, have to use ours for $75 each” and the $75 dollar sensor is an inferior cheapo with a 3 year battery opposed to the 7 year units you bought…. Its infuriating.
I know this is a privileged position but long term having two distinct complete sets of wheels is a better long term play. Extra set of rims is a one time buy and could be sold to recoup some of that money if they no longer fit a car change. There is only one instance of mounting which is at the time of purchase of new rubber and that cost is typically already factored into the price of the new tires. Then you can swap summers for winters on your own schedule at no cost and it’s all of 5 minutes to get the different set of TPMS sensors paired up to the car.
I would but I am in Texas. All tires and wheels are summers.
Technically don’t need to fully dismount, just unseat the bead.
What other cars can be coded for indirect? Fords?
-asking for a me with a Focus with some malfunctioning TPMS sensors.
Holy &^% did those drive me nuts on my Focuses! I never had more than a few months without another one going out. Eventually gave up on them as state inspection DGAF about the tire light as long as the tires are inflated. They’re basically worthless, anyway, as they don’t ID the offending tire, just say some tire(s) are low (though I usually only got the dead sensor light). If the problem is bad enough, it’ll be obvious without the system, if it isn’t a major problem, then I don’t need to be harassed by it. And of course, when one dies, it’s a PITA to figure which one is bad. The procedure is to deflate the tires in a specific order until the horn beeps. No beep, sensor dead, but it takes a lot of deflation to set it off and it’s easy to get dangerously low before realizing it’s not going off because it’s the dead one . . . or are there dead ones? Once you find an initial dead one, you can’t proceed to the next tire until the bad one is replaced or you rotate that tire to the last in line. Worse than useless. I can’t state how much cursing of parasite lawmakers mandating this crap and allowing such half-assed malicious compliance “solutions” I yelled during the almost 400k miles I put on the two cars.
Thank you for this – I feel less alone screaming into the void!
It was just one at first (I was convinced when I had new tires put on, the tech dropped it and “eh, it’ll be okay”…) but now it’s two of them.
So I looked up the test procedure, and yeah, even actuating it, much less carrying it out, is hugely complicated.
Invest in an OBDII dongle, ForScan and a Ford TPMS tool. The car knows which sensor is bad, and if you go through the process of reprograming the vehicle when you rotate the tires you can see which one is bad as well as read the tire pressures in real time. Plus now you can check other things and change some programing, including turning off the TPMS entirely on some models but no you can’t convert a direct system to indirect since Ford never used indirect in any market.
Thanks – I kinda figured as much, but good to know for sure!
So will this calibration allow the system to display on the dash the pressure in psi for each tire? Because a warning light where I still have to get out and check each tire with a gauge to see which tire is low and by how much is not an improvement in my eyes.
As I’ve said here before many times, the incessant bitching about TPMS from enthusiasts is just inexplicable. It’s useful to know your pressures at all times, and it’s annoying to carry a gauge with you when a better solution exists.
The label on my door recommends 32 psi, but the warning light comes on at 31 psi. I have to walk around my car at least once a week with the tire gauge.
That’s what I mean, if the dash told you it was 31 psi all around, you could just ignore the light.
I complain about it simply because I have never experienced a tpms system which functioned correctly, and it’s really not a big deal to LOOK AT THE TIRE
I challenge you (or anyone) to accurately tell a tire with 27 psi from one with 32 psi by sight, especially when dark or raining.
If the mere presence of TPMS bothers you so much, just cover the light with tape and don’t replace sensors when they fail. You can always get out and check with a gauge like we did in 1950. I appreciate knowing tire pressure at all times without doing that, and am willing to pay a bit for that feature. TPMS has worked well in every car I’ve owned 99.9% of the time and hasn’t cost very much to keep working.
Or if you’re running any kind of stiffer sidewall performance tires. My Mustang’s pretty common Goodyear Eagles look the same whether properly inflated or not.
I do enjoy using my tire gauge though.
Which kind(s) do you like?
I grew up using the pencil type gauges, and still have some, but discovered I like the dial type better.
The dial type, increasingly just b/c I can’t read the absolutely tiny type on the pencil ones so well anymore. Damn getting older. I still do have them as backups, usually squirreled away in the bag with the jumper cables and flares.
My fav is a Meiser accu-gauge I bought in the ’90s, made in the USA, that still works great to this day. I even clipped the box top back then and sent away for a free rubber boot for it that arrived 6-8 weeks later.
*looks on eBay*
Hey, those look pretty nice! I like the legibility of the dial with the 90-degree-to-the-valve connection of the pencil type. I still use the pencils on the one modern motorcycle because it gets a little awkward finagling the dial past the brake discs.
I joined the reading glasses club several years ago and keep them distributed all over the house, car, workshop, etc. 😐
I have a motorcycle-specific one for my bike too! It’s the length of a golf pencil, got it at a motorcycle show.
It’s not one of the most useful little things I keep with the bike (the other being a tiny flashlight so I can peer incredulously into the tank).
I just had a flat. Tire with 23 PSI looked the same as the one with 39 PSI on a sunny clear day on my GTI. Same with G8, Wrangler, F350 that I experienced flats
I think back in the day, when more tires were just “all season” in a generic sort of way you could see when one was noticeably flat, but now, as the manufacturing has improved, it’s way harder to tell.
But on the plus side, it’s also why blowouts are a lot less common than they used to be.
I miss those tires. All seasons I buy still have a harsh ride when you deflate tires by 10 PSI
You can’t tell by sight. You need to use a combination of hearing and smell. I have trained my ears to detect a 2 psi variance when the tire is tapped with a #2 pencil. If I am still not sure, I let a puff of air out and take a deep whiff. The low pressure heats the tire and releases slightly more volatiles from the rubber.
???????? this is best answer!
(Laughing emojis) this is best answer!
But if 32 is enough 27 is also enough, except maybe for sustained high speed driving, and I do check accurately with a gauge before road trips. Realistically, there’s a 10 psi range that’s acceptable under most conditions.
So yes, I will continue to check my tire pressure with a gauge like it’s 1950, and I will continue to check my oil with a dipstick like it’s 1950, and I will check my axle oil with my finger in the fill hole like it’s 1950. Not everything needs to be from the future.
Tell that to 1996 Ford Explorer owners on Firestone tires
Yeah but 32 isn’t enough and so 27 is also not enough for that vehicle
The solution was TPMS for everyone
Have you ever driven a BMW E60/E61 with a malfunctioning TPMS?
It chimes EVERY 15 SECONDS, for as long as the car is on – hours even – to remind you that it’s not functioning correctly, and a warning pops up on the center screen and IIRC the nav screen as well each time it chimes.
Putting a piece of tape over that is not gonna work.
When you actually have a low tire it doesn’t even nag you that bad. It just chimes once, a light comes on, and the nav screen tells you which tire is low. Then you can clear it out from the screen and ignore it without any nagging.
Damn, that’s even worse than my Ford, which would do an audible alert, additional yellow warning light, and display a message for a bad sensor after about 10 miles of driving and every damn time that happened, my heart rate jumped as it registered it as an actual problem for just a moment before the brain slapped it down again. In the heart’s defense, it was a Ford, so it wasn’t dumb to assume a serious fault (though both were actually extremely reliable except for the shitty TPMS sensors).
Sounds like a reason not to drive a shitty BMW, not a reason to hate normal TPMS systems that aren’t designed by idiots.
Mercedes makes E class cars, not BMW.
But both of them are made in a country with Autobahn that has no speed limit. Of course it will beep more when TPMS is broken than low tire pressure because it cannot tell if any tires are inflated for 155MPH random sprint at any time
Read the post I’m replying to carefully before weighing in on what I might or might not know please.
Sounds exactly like the E9X
Correct! The PSI readout is invaluable. With colder weather moving in I can check with the push of a button to see if I am +/- of where I should be over the coming weeks rather than get the gauge out and walk around my car for a few minutes. I will add a little air a few times going into winter. I actually use the read out in my car to inform me when I should go and check my wife’s VW since that only has the indirect system which frustrates me. I think most people who deal with the winter tire swap do so with an extra set of wheels. I just pop those on my Sonata N Line and within a few minutes the car picks up the new sensors and off I go for the season.
My Honda CTR doesn’t show you the tire pressure. It can’t even tell you which tire is low. Also TPMS will get confused if you have excessive tire slippage.
TPMS alerts when you want to run some different tire pressure from what the manufacturer suggested is always a popular reason to not want TPMS. This is especially true for enthusiasts who track their cars.
I agree 100%. We have two late model Audi’s and retrofitting real TPMS sensors is a common mod. We just took one to the mountains from FL and even with the huge temp change we never got a warning about tire pressure. As an Autopian reader, I know better, so I checked them all when we got there and pumped them up real quick. Someone like my mom would drive all over on 8psi low tires until the temps came back up unless a light came on to tell her. I’ve also gotten false alarms on both cars, which involves checking all the tires, finding out they’re fine, and storing the pressures…for no reason. Indirect TPMS saves the manufacturer money at the expense of your convenience.
If it doesn’t give me individual tire pressures I don’t want it. That was one of the requirements when I bought my most recent car after dealing with the good luck light as I used to call it. I would always pull over immediately and check when it kicked on and usually it was just one tire that was a few PSI lower than the rest.
Now if it kicks on I can see the individual pressures and monitor it for changes. If it keeps dropping pull over, if it stays the same it can wait until I get to my destination.
My GTI does not show tire pressures, but does show which tire is low on air.
I don’t miss the PSI readouts for the last 2 years and my G8 and Wrangler had PSI readouts on dash
And the dash readouts were always 2 or more PSI higher than my gauges so I would double check with gauge anyway and try to offset the errror in my head
Some direct read TPMS also don’t give individual tires. There are actually three kinds of direct:
One: the system like my Fords used that just says a tire is low. (Or mostly, IME, that another worthless sensor has died, but which one? You think a tire gauge is bad—which you still need anyway? Try the procedure to ID the bad one with that POS system and you can’t see if there’s more than one until you either replace the first found bad sensor or swap that tire around to the end of the sequence. Oh, and they all went out one at a time about every year in mine.)
Two: the system like my GR86 has that measures pressure keyed to a specific sensor, but it doesn’t know tire position when rotated or swapped between two sets of wheels. I suppose one could mark each tire and write it down so you can remember LF is now LR and so on, but if one is that diligent, they’ll just get the programmer like I did and relearn the new sensor and position every time since it only takes a couple minutes to do. This is useful, if a bit cumbersome as well as difficult for some enthusiasts on the forum for these cars to understand in concept, so certainly it’s going to be neglected and misunderstood by the average person who isn’t going to realize the low tire on the RR in the gauge cluster is now really on the RF and wonder why the tire seems fine when they go to fill it, but the sensor keeps saying it’s low. I’m sure there is plenty of: must be a bad sensor, screw it, I’m not wasting my time and money replacing the damn thing.
Three: like TPMS type 2, but with a separate small RFID for each wheel that can discern which sensor is at which position. This system is the only direct one that should exist along with the modern indirect one talked about in the article.
While you are correct that there are three types of systems but miss on what is what. They are in two groups.
Systems that learn positions on their own via one of two methods.
Some of those systems will tell you pressures on the dash and/or the specific tire that is low, since it doesn’t rely on positions being relearned any time a wheel is moved to a new location.
I didn’t know about the PAL system, which is pretty cool and seems like a better solution than an antenna at every wheel location, but I don’t think the exact how they function is as important to the comment as describing how the different systems work as they relate to the driver: 1 is worthless, 2 useful, but a little annoying, 3 how they should all be in providing proper pressure and location without any rigamarole (except maybe if one is adding new sensors).
I don’t know if you’re describing a different Ford system (I’m sure there are multiple types), but that’s not how mine (mk3 Focus SE & ST) worked: there was no relearn procedure or provision for it to provide pressure data or location to the driver and it didn’t factor the spare tire at all, since I’ve taken them out without causing an error. I also ran a second set of winters and, for one winter before one of those sensors failed, those also worked and they were never taught to the TPMS and the tire shop didn’t do it without my knowledge as I dropped the wheels off for new tires and swapped them myself. While the TPMS must have known the pressure to some degree to know if a threshold had been reached, I don’t think there was anything but a single RX taking in readings from the four wheels without capability to know location. There would be no point for it to know, anyway, as the driver only got a dummy light—two if a sensor was bad—and an obnoxious audible alert and gauge cluster message that would come on after 10 miles or whatever in the latter case to momentarily make the driver think there was an actual problem. Combine that with sensor lifespans of fruit flies, it was worse than nothing at all.
I just mentioned in a comment above that I’d accept a notification on which tire at least as a compromise, but then I thought, I am one to casually scroll through the dash readouts to see what levels they are at, such as if I’m borrowing one of my parent’s cars. And like you said below, I can’t remember any issues we’ve had with the sensors in any cars (knock wood), dating back to my dad’s 2008 Aura with direct readouts.
Yeah I prefer the ability to see the numbers on the dash or in my app on the one car we have with that feature. On the others which have direct TPMS but just tell you low tire, I use my a scanner app and obdII dongle to regularly check pressures from the driver’s seat.
My VWs and Audis all use an indirect approach to TPMS. I think there are few exceptions (like the Cayenne/Touareg brothers), but I like it because I’m not constantly worried about tire pressures varying by 1 PSI and the added expense of changing out sensors since I live in one of those states that gets snow. I can’t tell you how many times I’ve had to fight with a tire store to take the “TPMS sensor changeover” charge off my invoice since there is literally no sensor in the tires. I wonder how much profit these shops make over underinformed vehicle owners….
I had a shop try to charge for changeover on new tires for my 1988 Volvo 240. Don’t know if it was a deliberate attempt to defraud or just stupidity.
I was really confused when I checked the tire monitoring on my Mk8 GTI. I aired the tires to the correct pressure, then hit “OK” on the screen, expecting to see the read out. poking, searching, finally googled it. “Oh neat no expensive sensors to replace!”
One of the only times us VW owners have no sensor to replace!
This sounds dangerous to the point of negligence! It doesn’t alert until there is a 25% reduction in pressure .Everyone knows what catastrophes can occur when underinflated by even 1.5 psi!
Well Mustang owners know it.
No, this is a BMW specific issue.
*Autocrossers flood into the chat*
A very well done article here! Thanks, learned a lot.
A couple years back I had new tires installed, and of course my system did not work when they were done. But for the “low price” of over $300 bucks they could fix it.
When I quit laughing at this bullshit just went home and kept my cash.
Upon discussion with friends I learned that this bullshit has become standard procedure at the majority of tire shops these days. WTF?
Now the always on dash light is used to remind me to check and adjust tire pressure all the time. I can live just fine with that.
BTW, always check your tire pressures before you leave the tire store. I have never seen them filled to the correct pressure, never. And running with twice the recommended pressure usually does not end well.
The ones I’ve gone to usually set them either by the door or the max tirewall when I like it somewhere in between, so I always end up changing them. One time, though, I did have them way over, but at least it was easy to tell as soon as I left the lot. Don’t know how high it was over because it slammed the 50 psi gauge to max and I had to air them down for a disconcerting amount of time for it to even register.
I can’t wait for Michelin’s Uptis airless tire to get DOT approval and go into mass production so I don’t have to deal with TPMS BS!
That must be a British car pictured in the topshot.
The speedo is in kilometers and the dash says “TPMS, innit?”.
I just have to say how much I enjoyed this…a bit of Friday afternoon all right.