Hello Autopians and welcome to another edition of Ask an Engineer. This week I thought we could talk about tires again since we had so much fun with them the other week.
A reader named Patrick asked me a question about recommended tire inflation pressures. He had just recently bought himself a shiny new Jeep Gladiator, and when he first took it on the highway it just didn’t feel right to him. It was sensitive to wind and drafts from passing semi trucks. It followed road grooves excessively, and he felt the handling was actually pretty scary.
When he checked the Tire Pressure Monitoring System reading it showed all four tires inflated to about 41-42 psi while the recommended pressure is 37 psi. When he pulled off the highway and adjusted pressures back to the recommended levels, the difference was instantly noticeable. The truck rode better, the cross winds didn’t bother it so much, and overall it handled like he expected from a vehicle of this type.
What might have happened here? How can the tire pressures in a new vehicle be so much higher than the factory recommendations?
Why An Automaker Might Over-Pressurize Its Tires Before Sale
One possibility might be that the dealer prep on this vehicle was not performed correctly. Many OEM’s will ship their cars from the factory with much higher than normal tire pressures. This helps to prevent flat spotting which can happen in any tire when a car that sits in one place for a long time, like on a transporter or in a storage lot. The tire develops a flat spot where it contacts the ground and will create a thump-thump sound as you then drive it. In most cases the flat spotting will disappear after driving for a few miles, but in extreme cases it can completely ruin a set of tires. I have seen some OEM’s inflate their tires as high as 50 psi to help prevent flat spotting and part of the dealer prep is to reduce the pressures back down to the factory recommended levels before the car is delivered to the customer.
How Tire Pressure Can Affect Handling
No matter how it happened in Patrick’s case, in order to understand how incorrect inflation pressure would have caused the behaviors that Patrick noticed in his Gladiator, we need to understand a little about how tires work — in particular how tires generate cornering forces. Thomas Gillespie explains this very well in his book “Fundamentals of Vehicle Dynamics.”
Slip Angle
Tires like to go in a more or less straight line when they are rolling. When we turn the steering wheel in a car, we are forcing the tire to point in a direction other than straight ahead, and this difference in the direction the car is going and the direction the tire is now facing creates a sideways force in the tire.
The force is a product of the friction between the tire and the road, and it pushes the car in the new direction the tire is facing. When we look in detail at what is happening between the tire and the road surface we see that the flexibility of the belts inside the tire and the rubber in the tread blocks causes the portion of the tire in contact with the road (called the contact patch) to deform slightly. Like this:
Here we see how the contact patch has deformed because of the side force created by a left turn (this image represents a tire in the middle of a turn). The deformation causes the tire to roll in a slightly different direction (in this case, a bit more to the right) than it is pointed. This is called the slip angle and it is critical to how a tire behaves in a corner and how the car handles, especially as you approach the limits of adhesion.
Imagine an element, or piece, of rubber in the tread of the tire as the tire rolls down the road. As Gillespie explains:
“As the tire advances and the tread elements come into contact with the road, they are undeflected from their normal position and therefore can sustain no lateral force. But as the tire advances further at the angle of its direction of travel, the tread elements remain in the position of their original contact with the road and are therefore deflected sideways with respect to the tire. By this process the lateral force builds up as the element moves rearward in the contact patch up to the point where the lateral force acting on the element overcomes the friction available and slip occurs.”
The slip referred to above occurs because the lateral force overcomes the friction between the road and the tread element, and also also because the curvature of the tire is starting to pick the element up off the road so it is not being pushed down as hard as it was earlier in the rotation of the tire.
Let’s look at this in more detail. Imagine two spots on the tire tread shown below as points A and B.
Image 1: Neither points A or B have reached the contact patch yet and are sitting in part of the un-deformed tread.
Image 2: As the tire rolls forward (i.e. towards the right in the image above), point A comes into contact with the road while point B is still on the un-deformed tread. Because the tire is being pushed sideways, Point A has already started deflecting slightly to the one side. At this point, point A can only move a little bit sideways since it is physically connected to the rubber just ahead of it that has not come into contact with the road yet and is still un-deformed.
Image 3: The tire has rolled a little further to the right and now both points A and B are in contact with the road. Since the tire is continuing to be pushed sideways by the cornering force, both points A and B have now deflected to the side although point A has gone further since it has been in contact with the road longer.
Image 4: The tire has rolled even farther to the right and now point A has reached the point where the pressure in the contact patch has reached its maximum. The friction between the tire and the road cannot get any higher and point A is deflected to the side as much as it can before it will start to slip.
Image 5: Point A has slipped completely back to its original spot on the tread since the curvature of the tire has lifted that part of the tread off the road again, reducing the pressure at that point and eliminating the friction. This happens quite quickly and you can see how little the tire has to roll to the right before point A goes from maximum deflection to zero deflection. Point B is still stuck to the road, however, and has reached its maximum deflection.
Image 6: Both points A and B have gotten to the end of the contact patch, have been lifted off the road, and have returned to their original un-deflected positions on the tread.
Another way to think about this is to picture each element of the tire as a spring. As the element comes into contact with the road, the spring is not deflected yet and so it has no force in it. But, as the element is pushed sideways in the tread by the slip angle, it is as if we are pushing more and more against that spring. It takes more and more force to do it. The friction between the element and the road is what pushes on the spring. But as the friction reduces towards the back of the contact patch because that part of the tire is starting to get lifted off the road again, it can no longer push on the spring and it lets go. Take all the elements that make up the contact patch and add up all the forces in those little springs and you get the total side force the tire generates.
One thing to note is that the slip angle shown in the images above is greatly exaggerated for illustration purposes. An average tire has a cornering stiffness around 150-200 lb/deg, although this value is heavily dependent on the load the tire is carrying, the inflation pressure, and the tire construction, among other things. If we take a 4,000 lb car cornering at 0.5G (which is a higher than the average driver will ever corner in their life!), this means the tires have to provide a cornering force of 4000 x 0.5 = 2,000 lb. If we assume all four tires are doing the same amount of work, then each will need to provide 500 lb of cornering force. If the tire cornering stiffness is 200 lb/deg then the slip angle will be 500 / 200 = 2.5 degrees. You can see we are talking about small numbers here, not the large angle shown in the drawings above.
Now you might think that more slip angle would be better because all those little springs get deflected more and create more force, but that would not be correct. A soft spring will deflect more for a given force than a stiff spring, so the “stiffness” of the contact patch matters. The softer the little springs are, the more the contact patch has to deflect before it can generate the side force needed to steer the car, meaning a larger slip angle. T
The deflection of these little springs also takes time which means there is a delay between when the tire is steered to the time it can generate the required side force. This delay can be felt in the responsiveness of the car. A stiff tire will respond much faster to changes in direction than a soft tire because each element doesn’t have to deflect as far to get the cornering forces you need to navigate a turn. If you can make a tire with very stiff little springs, then it doesn’t have to deflect as much for a given side force and will be more responsive to steering input.
Cornering Stiffness
So what does this have to do with the inflation pressure problem Patrick had in his Jeep? For that answer we need to understand another characteristic of how tires work and it is shown in this graph:
Notice that as the inflation pressure increases, the cornering stiffness increases, meaning that the slip angle decreases. It takes more pounds of cornering force to get a degree of slip angle.
The increased inflation pressure will also lead to an increase in the vertical stiffness of the tire. This will make it ride harder and less able to absorb small imperfections in the road. Imagine the extreme where the tire is as hard as concrete. It wouldn’t ride very nicely
All of this translates into a stiffer tire that will respond to changes in the road more quickly and ride more stiffly, just like Patrick noticed in his Gladiator.
It is tempting at this point to conclude that increasing the inflation pressure of your tires will make the tire stiffer and therefore more responsive. To a certain degree you would be right but be careful. Every road car is designed to have a certain amount of understeer, which is the tendency of the car to want to keep going in a straight line when you corner. The opposite is oversteer, which is the tendency of the rear of the car to step out in a corner and cause the car to spin out. Understeer is best for most drivers since if you lose control you will go off the road nose first. An oversteering car will want to spin and go off the road sideways or backwards. The nose of the car is the strongest and designed to best absorb energy so that is what you want to hit something with, not the doors or trunk.
Getting back to our tires, keep in mind that the cornering stiffness of your tires works in conjunction with the springs, dampers and bushings in your suspension to create an overall lateral stiffness of the suspension and is a large contributing factor to the amount of understeer or oversteer your car has. Changing the cornering stiffness of your tires can upset this balance and lead to handling problems, so be careful.
I Generally Advise Sticking With Manufacturer-Recommended PSIs
You can, however, make some significant changes in the way your car handles by playing with pressures. If you participate in track days with your car then you are probably already well aware of this especially if you play with the front and rear pressures separately. It is also a great way to get yourself into trouble so doing this at a track is a great way to learn in a controlled and relatively safe environment. You don’t want to find out you’ve gone too far in an emergency situation on public roads.
While it may be tempting to start playing with the tire pressures in your car, you will need to work within some limits. Every car now has a tire pressure monitoring system (TPMS) as standard equipment. These systems monitor the pressures in each tire and will give a warning to the driver if any tire falls below a specified minimum pressure. In the U.S., this is governed by regulation FMVSS 138 which became a requirement in 2007 in response to the Ford Explorer Firestone issues. It states that the warning must be given when the pressure in any tire drops below 75% of the recommended level, or below a minimum level as stated in table 1 below, whichever is higher. The result is that no tire will be more than 25% below the pressure of the other tires before a warning is made to the driver. The handling impact of an underinflated tire is thereby minimized.
Let’s look at an example of what FMVSS 138 requires. Here is one of the forms the OEM is required to fill out which sets the TPMS trigger pressure.
I own a 2015 Mustang with P265/35R20XL tires. The recommended pressure is 35 psi, or 240 kPa. Here is the form filled out for that car:
According to the regulation, my car should light the TPMS light if the pressure in any tire drops below 160 kPa or 26.25 psi. I know from experience that for my vehicle this is indeed the case.
Because the TPMS trigger pressure is not something we as owners can change, if you do decide to use tire pressures that are different from the recommended levels, you will be running at pressures that are either closer or farther from the trigger levels set by the OEM. If you go lower in pressure then you will be closer to the trigger point and you may find false activations of the TPMS light in colder weather. If you go higher in tire pressure then you will be farther away from the trigger point and it will take a much larger drop in pressure before the system will give you a warning. This means that any one tire can be more than 25% underinflated before you get a warning and the handling impact of having one underinflated tire will be that much greater.
My recommendation as an engineer is to stick with the recommended tire pressures, but if you do decide to experiment with your car’s tires, please do it in a safe way. As Patrick found out, tire pressures can have a significant impact on the way a car performs both in a positive and a negative way.
Please keep those questions coming to askanengineer@autopian.com!
When I set tires in my Wrangler to 37PSI cold tire pressure like sticker says, by the time I get off highway the dash will show tires are at 42PSI or more.
This person just underinflated their tires that gain pressure when driven.
The sticker on the door says 43PSI for my Rubicon 10a, which is insane. Driving over a manhole cover completely dislodges it and triggers traction control. I run ~33 PSI and it’s a much safer machine. Also very easy to flash the ECU to change the warning point with a phone app.
We didn’t discuss manufacturers who set recommended pressures artificially high to get better CAFE fuel economy numbers – looking your way Ford… The Focus RS recommends 46psi on the summer wheels. That car is oversprung as it is, and it’s undriveable at 46psi. Tires also wear incorrectly at that setting.
I run mine about 40-42 for regular street driving.
This tire overinflation during shipping is a common practice. Unfortunately, it also seems to be a common practice at dealerships to skip the tire pressure check during the prep process.
I am a Mazda owner, and on the Mazda forum that I belong to, there are continuous comments and complaints from new owners where the tire pressure was at 45-50 PSI. No matter how often this subject is brought up, it doesn’t seem to filter down to the dealers. Lazy techs that can’t be bothered to follow the checklist. So frustrating.
I have a 2021 Corolla and the only way to keep the TMPS light from coming on in the winter is to overinflate the tire. I was coming on as soon as it dropped below about 50 degrees Farenheit all winter and I would go to take the pressure and they would be right at the manufacturer recommendation and the light STILL came on.
Check your pressures when you rotate your tires as well, especially if you have it done by someone else. Some vehicles use different pressures for front and back tires. The tpms doesn’t know which is which, only if it’s within range.
Recently took delivery of a new Camaro SS 1LE. Tires were 39-40 psi, recommended 32 psi. Was wondering how they could be so high from the factory, makes sense now.
The mention of designing understeer into most new vehicles also has to do with the response on how to correct it, which is either letting off the accelerator or hitting the brakes to give the front tires more grip again. That is most drivers common response when losing traction with either the front or rear tires.
Rando, you are absolutely correct and in most cases the amount of understeer tuned into a car is such that even under heavy braking there is still enough understeer left over to ensure you exit the turn nose first.
I tried once, just for fun, to inflate the tyres on our 1965 VW T1 Bus to the maximum written on the tyre sidewall, I think it was 65: It got ridiculously low rolling resistance so you had to use the throttle much less, the steering got light as if it was power assisted, but the hard ride was more like a modern day Toyota. The grip and handling probably suffered severely, but we never really drove that thing to the limits anyway.
Old french cars like the Citroën DS has a very low factory pressure setting, probably for more soft comfort. I usually put a little more air in those, because I don’t like the slow puncture slighty flat looks.
I had the bigass tires on my old CJ5 at 50 psi for road driving and could get a few more mpg’s. It rode like a lumber wagon already so firmer tires didn’t really matter for comfort.
When I picked up my Bronco a couple of months ago, I had the same issue. All the tires were inflated to 50psi. I dropped them down to the recommend 39psi and the truck handles much better!
Great piece. It’s worth noting that TPMS can be adjusted from factory specs in certain circumstances which is ideal when changing tires from OE.
Regarding pressures and ambient temps, manufacturers provide their guidance on cold tire temps for a reason.
> Regarding pressures and ambient temps, manufacturers provide their guidance on cold tire temps for a reason.
Sure. But over the possible (extreme) range of ambient “cold” temperature, going from -20F to +120F will raise the pressure by about 30%.
P = (nRT)/V, where n=amount of air (in moles, ugh), T=temp (in Kelvin, which is like Celsius but counting from absolute zero), V=volume of tire, and R is a constant (for our purposes, fortunately the only variable is T, so you don’t need to know how many moles of air is involved). I remembered that formula from HS chemistry, 60 years ago, weird thing memory.
BTW, Autopian, good on ya for making the comments thread/indent properly, unlike a certain other website.
On Gen 2 Prius forums (I owned an ’06 at the time) users were experiencing excess wear on the outer edges of tires when run at the recommended pressure. By raising the pressure to 42 front and 40 rear tire wear evened out.
If I remember correctly, one could adjust the TPMS trigger point through pressing a button u under the steering column. Inflate the tires to a higher than 42/40 pressure, hit the button, and lower the tire pressure to 42/40.
I just put the all-seasons (Goodyear Fuel Maxes) back on our Cruze Diesel for the spring/summer/fall and they’re clearly in need of replacement.
What is odd, though, is the outer edges are what’s really worn down…but this doesn’t quite make sense given we run these tires at ~46 psi.
I’d have to double check, but I’m pretty sure the Michelin Xi3s we run for winter (this past winter was their 8th and likely final season – I’ve continuously been impressed with their wear) did not have similar wear patterns.
Outside edge specifically and not inside generally means an alignment issue, not pressure-related. Could be the amount of toe, or worn suspension that’s letting things flex and move more than they should.
Thank you for this. More ways to conceptualize the contact patch at work is a good thing. I tend to slightly raise pressures to get that quicker reaction to steering inputs and seem to do OK maintaining the ballance just by maintaining the front / rear offset ratio, seeing the graphed curve lets me know my butt wasn’t lying, it’s linear enough in the region and magnitude I’m playing with.
I have also had TPI trip because the pressure was too high. Driving a rented Nissan Versa in the mountains, about halfway through, the light came on. Stopped to check, they all _looked_ ok. Drive slow to the next garage. TP all around was 50-60psi, IIRC. Let some air out, and the light went out. Assume it was a combination of some doofus at the (frost belt) rental place pumping them all up hard, and transitioning to warm-state mountains..
Thank you for the chart referencing bias ply tires. /s
That’s relevant for trailers. A lot of trailers run bias ply tires. And quite a few are driven like they’re on a racetrack. Every summer a fair number of camping rigs roll. Usually because the trailer broke traction “unexpectedly” when the nut behind the rig’s wheel did something abrupt. Hint: that stiff sidewall is to support the trailer, not so it can change direction quickly.
Well there’s something I did not know. I just assumed trailers would just have more axles or go dually is they needed to support more weight. Also, I guess I should update my idiot rating system. When I’m on the road, I’ll watch for trailer dangers in the following order from safest to not:
– Horse trailer, probably driven well because payload is precious
– Contractor/work tool trailer, probably driven well because payload is expensive
– Camper, maybe inexperienced driver, but probably not trying to mess up payload
– Boat or toy trailer, might depend on toys, but high likelyhood driver could not give a shit about others.
– Dump run trailer, “oh yeah, that’s back there” or “dad just tossed me the keys”.
– Empty trailer, stay the fuck away
– U-haul, dial 9 and 1 and when I tell you to dial 1 again.
– 1-ton dually with a gooseneck: hotshot driver, try to stay well clear as they blow past. Especially if you’re anywhere near an oil field or logging.
Cold weather activations of tire pressure warning systems are not false warnings. The pressure in cold weather actually is below recommended and the tires should be inflated when the alert comes on.
While it is true that once the tires warm, the pressure will often rise to within the acceptable range, it will almost always be at the lower end of the acceptable range.
You should add pressure when the tires are cold, but do not overfill them. Bring them up to minimum acceptable pressure, and then top them off to the desired pressure once the tires are warmed up.
Manufacturers crank up tire pressures for shipping because the vehicles are tied down hard enough to compress the suspension during rail shipment and carrier transport. Low inflation pressures don’t jive well with that much force on 4 contact patches the size of post cards..
(The next time you pass a transport truck, take a close look and you’ll notice the vehicles are absolutely cranked down to somewhere close to full compression to keep them from moving around.)
Also, all manufacturers pay the dealers prep time to do things like making sure the lug nuts are tight and to properly set inflation pressures to the spec on the door placard.
If your car is shipped with improper tire pressures, IT’S ENTIRELY THE DEALER’S FAULT, not the manufacturer.
Correction: If your vehicle is DELIVERED to you with with improper tire pressures, it’s entirely the dealer’s fault, not the manufacturer.
Related to TPMS, how do ambient temps affect the sensors themselves?
On one of my cars, when the temps drop below freezing, I often get a TPMS “general” malfunction warning.
The tires themselves are at proper pressure and as soon as external temps rise, the general fault notification goes away.
I’ve learned to live with it, just wondered why.
Ambient temps should not affect the sensors at all. Sounds to me like you’ve got one that’s malfunctioning.
Temps don’t affect the sensors, but the air in the tire. Cold temps cause the density to increase and, because there’s a fixed number of molecules of air in the tire, the pressure to drop. Think of what happens when an empty, sealed bottle (water, 2L, etc.) is exposed to cold. It contracts and sometimes collapses. Your tires do the same thing on a less noticeable scale.
Generally speaking, you need to add air when temps drop and then let some out when it warms back up. Just because you filled them to the proper pressure at one point in time doesn’t mean that pressure will always be maintained.
Hopefully someone can confirm that I remember a little bit from college and I’m not totally talking out of my ass…
The ideal gas law says that PV=nRT, and in a tire V, n, and R are constant. So pressure varies linearly versus temperature (in Kelvin).
So:
70 degrees Fahrenheit = 294 K. Lets say you filled up your tires to 35psi at that temperature.
40 degrees F = 257K. The temperature went down by 12.5%, so your pressure will go down by 12.5% to 30.625psi.
All rough math, because air isn’t an ideal gas, but you get the idea. Best care scenario is that filling up tires to the recommended pressure should be done with a cold tire (as in, not having been driven around) and at roughly the ambient temperature that you intend to be driving.
Maybe the sensor batteries are getting old and the cold weather causes them to stop working? Although if that’s the case I would expect it to start working again once you’re driving and get some heat in the tires.
TIL that TPMS sensors have non-rechargeable batteries in them. That sounds dumb; why aren’t they powered inductively by a transmitter in the car, or fitted with a kinetic generator (like what you get in a self-winding watch, or one of those emergency shake-lights) so they can charge as you roll along?
That would make a lot of sense, but then the manufacturers couldn’t charge through the nose for replacement sensors. 🙂
So they can last longer than rechargeable batteries. In the car I sold recently they worked fine after 13 years
“The tires themselves are at a proper pressure….”
Are you inflating them before you start the vehicle, but using some external gauge?
I am wondering about the notification going away as external temps rise, because, without knowing what “general” malfunction looks like, it sounds like you are just taking part in the ideal gas law.
Wow, that was way more than 1.5PSI off. He’s lucky to still be alive!
Illustrating the need for a digital tire pressure gauge
If I put different tires on my truck that call for higher inflation than what the vehicle manufacturer states, which number should i use?
Tires have a maximum inflation pressure on them, not the recommended pressure, so you will stick to the OEM
My understanding is that the pressures embossed on the tires are maximum ratings for what the tire can safely handle without bursting at speed. Huibert can correct me if I am wrong, but I’ve always followed the cars rating, not the tire.
This assumes that you are replacing with same size tire. I’m not sure what to follow if you are replacing wheels with a different diameter along with the new tire.
I’ve always treated the tire numbers as the high end of the maximum range, and the car’s recommended ones as the low end. You probably don’t want to go around with anything less than what’s in the doorjamb, but you don’t EVER want to go over what’s embossed on the tires.
It is the pressure to use at the tire’s maximum rated load. In non-commercial use, passenger car and light truck tires almost never get close to maximum load. I would have to load my F150 up to a GVW of about 11,000 pounds to load the 4 tires to their max rated load.
When changing tire size, and especially when changing wheel size, consult the tire manufacturer for recommended PSI for your application.
Depends on what you are doing. If towing pump up that tire. If off road lower the pressure. Otherwise stick with recommended pressure.
Frodo, always follow the OEM recommended tire pressures. As some of the other commenters have said, the pressure shown on the tire sidewall is the maximum safe pressure for that tire. It has nothing to do with what is right for that particular vehicle.
Great article on tires, should be mandatory reading for all drivers. New drivers would certainly benefit from understanding their function.
Some TPMS history. In the late 80’s Porsche came out with the 928 GT, I think the first production car with TPMS. I was just an apprentice in a Porsche / Audi garage. The sensors in the rims displayed to the dashboard. The sensors were also very inaccurate, low by 8-10 psig. Porsche factory bulletins directed to increase air pressure until the warning message cleared and add 5 psig. This resulted in pressures above manufacturers labeling, which was 44 psig. Most tires ended up at 55 psig. When Dunlop Tire found out what Porsche was doing, they pulled their tires from production deliveries and let them scramble for a new supplier. Sensors were updated about 12-16 months later.
I drive a Ram 1500 Rebel with 295-70-17 AT tires. It’s a little bit interesting because the factory inflation is 55 psi front, 45 psi rear. It’s the first I’ve encountered staggered inflation as standard. An inattentive tech failed to adjust the inflation following an oil change and tire rotation. The truck was a scary mess. Back end was loose and bouncing all over, front end was slow and wallowy. It was a dangerous prescription for seasickness until corrected. I knew in the first 1/2 mile something was wrong.
That’s really bizarre on a square set up. Those pressures also seem quite high for such a wide tire. I’d be wary of high center wear compared to the shoulders.
Particularly odd (at least from my limited experience with trucks) that the front is higher than the rear. A higher PSI in the rear would make sense from a towing/hauling perspective, and also because the harshness of the extra pressure isn’t going to be as noticeable as on the front.
I have see in a lot of Ram 1500 trucks where they will install P rated tires to give them better feeling ride rather than an LT.
I would assume they are essentially doing the same, font is heavier thus requiring more pressure, but keeping as low as they feel safe to make it ride better.
I find a lot of people run way to much air in their tires epically in trucks, its crazy how big of a difference it makes in ride comfort. I run my F350 around 40psi most days. Just don’t for get to increase it before you hook on a trailer or load the bed. you will have a bad day.
The most likely reason for the difference in front to rear has to do with the unloaded bed. It probably has to do with weight distribution being mostly front heavy and making a similar contact patch for all the tires.
This happened to me once at a quick lube joint. ’95 Geo Tracker with placarded tire inflation of 25PSI, the kid pushed it up to 35PSI and was so proud to tell me how he “fixed” it. Then I told him to back it down again and showed him the sill plate with the 25PSI recommendation. His manager had never told them to check these things, just put everything at 35PSI.
That car with 35PSI in the tires was like trying to navigate a ping-pong ball down the highway.
I’d venture a guess that the manual says to bring that rear pressure up when towing or hauling a heavy load in the bed
In that techs defense you are no longer running the stock tire size.
can you really still go by the label?
Math Hard
This gets tricky (annoying) with iTPMS systems as well
“If we take a 4,000 lb car cornering at 0.5G (which is a higher than the average driver will ever corner in their life!)”
I mean. Yeah, it kinda is when you consider that most drivers are just going to work, the grocery store, and such. But c’mon, most of us are hooners. You gotta caveat that statement a little better.
Good article though.
It’s not just hooning, I’ve heard it said that the average driver will drive straight into a tree under brakes rather than try to steer around it. Most people just don’t have an intuitive sense of what their car is capable of, cornering-wise. Just because we’re all hoons doesn’t mean most people are.
True that. I once watched a bog-standard, 2nd-gen RAV4 basically teleport itself into a different lane when an inattentive driver tried to change lanes right into it. Never expected an old Rav to move like that. Might’ve saved my life; me and my NA might have plowed right into the accident if those cars had collided right in front of me.
“Because the TPMS trigger pressure is not something we as owners can change”
In the interest of completeness (not necessarily endorsement), this threshold can be changed by tools like Forscan.
I believe if you want a higher psi to make cornering harder you need to use the foreskin tool lol
Haha, I also read that as foreskin. Glad to see there are others stuck with a middle school sense of humor.