Tire pressure, Any guesses ?

Yeah, always check your tire pressure again AFTER the dealership touches it. One time I found that my front tires were 36 and my rears were 32. When they did the tire rotation, they didn't check the pressures afterward.

But, on to the tire pressures. You should fill and then set them at the coldest part of the day after the car has been sitting for hours.

 

i set mine at 42f/40r, but admittedly don't maintain them regularly. the good thing is, when i do check them, they are way above the tpms set point.

i think you might pick up an mpg or two

 

I put 38 all round - promising myself to drop them the next morning when they're cold.

But I've been practising procrastinating - why do this week that which can be put off till the week after next.

 

oh my, you've copied my playbook

 

Might need to "reset" the TPMS too.
Most people find that there is no significant increase in mileage from higher tire pressures.......unless you make them ridiculously high.
The key words are "significant" and "ridiculous".

Side note: Just rented a car last week in St. Louis.
Immediately noticed that the ride was harsh and it was hard to hold a straight line at speed.
Stopped at one of the rental locations to have the pressures checked.
ALL were over 50 and two were over 70 !!!!!

 

Don't confuse the pressure that the tyre manufacturer prints on the sidewall of the tyre. That is just telling you what the maximum safe pressure the tyre is designed for - not what pressure you should run. Note that the tyre manufacturer prints the same pressure on the tyres, not knowing which vehicle it will be fitted to - nor whether it will be on the Front or Back axles.

The pressure that TOYOTA prints on the tyre placard is the relevant one.

My FOCUS - FORD specifies 33 PSI Fr/Rear - but the tyre sidewalls have 51 PSI MAXIMUM marked. That car would be terrible with 51 PSI - I usually ran about 35 which was the high-speed recommendation.

In the case of my older MAZDA 929 wagon - 26 PSI front, 32 PSI back - but the tyres said 44 PSI maximum. I think MAZDA said to add 4 PSI for higher speeds, which is what I did - not 44.

 

TPMS light comes on when there's around a 20% drop in pressure from whatever you set the TPMS at. Whilst cold, I pump my tyres up to around 25% higher than recommended, set the TPMS, then drop them to about 2 psi above the recommended. This means the TPMS will warn me when the pressures drops by about 2 psi. I like an early warning rather than waiting for a 20% loss.

 

Do our gen 4's have a TPMS readout at all on the data screen? My 2015 truck would tell me the pressure in each tire (a base-model feature), but I haven't found that yet on my 2019 Prius.

 

Nop. Never did, and probably never will.

 

That's pretty archaic of them, but then my 2019 radio is based on 2013 tech.

I'd bet that Gen 5's will get it.

 

I hope so. All TPMS sensors (internal ones) are sending pressure and temperature data, and ECU is receiving them. It is just a matter of displaying it on the screen. But somehow, Toyota do not want to do that on PRIUS. I have no idea why. You can capture the data and display it by using TechStream or other OBD apps including ScanGauge II.

 

I agree that folks should not confuse max pressure for max load info with what they should run (unless they are running five people + gear in their Prius most days).

Likewise, especially true for pickup trucks and station wagons that aren't treated like work-vehicles (my father's station wagons, for example, were work cars - they were loaded to the max at in the rear and rear-seats with brochures, equipment, and sales products), the running tire pressure for the rear should often be lower than the front tires. The front tires carry the weight of the driver, the engine, much of the transmission (or, again, nearly all of it), plus the additional loads of braking (75% to 95% of braking traction and braking come from the front two tires) and cornering. In a commuter vehicle, like my Prius or my Ram 1500, the front tires were the ones that should have had - and did have - the higher pressures (compared to the rears). If I knew I was going to load my truck down, I'd pressure-up the rears. Now, on the work-trucks I've used, we ran max pressure on the rears all the time, as - day in and day out - each was loaded with equipment and trailers.

 

The other thing that tyre pressures do is change the handling (by changing the grip) - to balance out understeer or oversteer. My 1977 Renault 12 wagon, front engine, FWD ran 23 Fr, 27 Rear (or 24/29 if laden) - it understeered, but was safe.

I rotated the tyres front to back and drove to the Service Station to adjust the pressures - and on the way the car oversteered quite noticeably - at higher speeds would have been verging on dangerous (or like a rally car!!).

 

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I suggest that you read at these three links.

Why Proper Tire Pressure Matters | News | Car and Driver

What is the Right Tire Pressure & Why Maximum is not the best

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=8