Keep an eye on your tire pressures folks (PSA)
12-28-21, 10:46 PM
#1
Racer
Thread Starter
Keep an eye on your tire pressures folks (PSA)
tl;dr I don't work on my own car. Randomly decided to audit tire pressures to see what has been maintained in my tires.
All numbers are cold inflation pressure with the car not driven that day, on stock OEM wheels and Michelin Snow tires.
It's 17 degrees outside and my pressures were reading 33-36 PSI. My front left tire measured 40PSI during the day when the ambient temps are in the 50's and 60's. This is way too high above specification - especially considering these are not performance tires on a performance vehicle. It looks like the last person who touched my tires (ironically the Lexus dealership for a wheel balance) over-inflated them.
Owners manual calls for 29 PSI. 32 if the vehicle is fully loaded, and ontop of that, an additional 12 PSI if traveling for extended periods above 100mph. Now sadly I don't live in Germany with access to the Autobahn, so while I've had times where I've touched 100+mph, it's never for extended periods.
Dropped the pressures on all 4 corners to 31 PSI @17 degrees ambient. Pressure raises to 34 @ 50 degrees ambient. I may lower it further depending on feedback in this thread - I'm curious to hear your thoughts.
Small, but not insignificant change to ride quality. The car is way less "bouncy" and the tires are doing a lot more work in conjunction with the suspension - though the handling is a slight bit more vague at higher speeds. I'm sure the tread will wear a bit faster and my fuel economy will get worse - but these things are fine for me to gain more ride quality and have a "fatter' tire which will provide better grip in the snow.
Don't forget about tire pressures now that the northern hemisphere is headed into cold temps folks! If you're still running summer tire pressure, the drop in temperature will expose the opposite problem I have - you'll be significantly under-pressure. Temp goes down, so does pressure.
All numbers are cold inflation pressure with the car not driven that day, on stock OEM wheels and Michelin Snow tires.
It's 17 degrees outside and my pressures were reading 33-36 PSI. My front left tire measured 40PSI during the day when the ambient temps are in the 50's and 60's. This is way too high above specification - especially considering these are not performance tires on a performance vehicle. It looks like the last person who touched my tires (ironically the Lexus dealership for a wheel balance) over-inflated them.
Owners manual calls for 29 PSI. 32 if the vehicle is fully loaded, and ontop of that, an additional 12 PSI if traveling for extended periods above 100mph. Now sadly I don't live in Germany with access to the Autobahn, so while I've had times where I've touched 100+mph, it's never for extended periods.
Dropped the pressures on all 4 corners to 31 PSI @17 degrees ambient. Pressure raises to 34 @ 50 degrees ambient. I may lower it further depending on feedback in this thread - I'm curious to hear your thoughts.
Small, but not insignificant change to ride quality. The car is way less "bouncy" and the tires are doing a lot more work in conjunction with the suspension - though the handling is a slight bit more vague at higher speeds. I'm sure the tread will wear a bit faster and my fuel economy will get worse - but these things are fine for me to gain more ride quality and have a "fatter' tire which will provide better grip in the snow.
Don't forget about tire pressures now that the northern hemisphere is headed into cold temps folks! If you're still running summer tire pressure, the drop in temperature will expose the opposite problem I have - you'll be significantly under-pressure. Temp goes down, so does pressure.
Last edited by 400fanboy; 12-29-21 at 09:50 PM.
The following users liked this post:
Lavoisier (12-29-21)
12-29-21, 05:29 AM
#2
Personally, I prefer a bit of a stiffer ride for better mileage and handling. I have them at around 33psi, cold.
The best test would be to draw chalk lines on the sidewalls, next to the tread pattern and then drive some aggressive S curves and see if the chalk lines got erased. If so, then your tire pressure is too low. Somehow, I have a feeling, Lexus was after comfort over safety on this one. To me, safety comes first. (Why do I have a feeling I've just opened a big can of warms?
)
The best test would be to draw chalk lines on the sidewalls, next to the tread pattern and then drive some aggressive S curves and see if the chalk lines got erased. If so, then your tire pressure is too low. Somehow, I have a feeling, Lexus was after comfort over safety on this one. To me, safety comes first. (Why do I have a feeling I've just opened a big can of warms?
)
12-29-21, 06:37 AM
#3
Racer
Thread Starter
I think the engineers who design the car and set the tire pressure recommendations in the owners manual are a lot smarter than myself - so I'm just going by what is recommended by Toyota\Lexus.
THIS BEING SAID - tire technology has come a LONG way in the last 25 years. Specifically in tire sidewalls and tread compound. So this isn't such an easy question to answer and I've never come across any good information about what changed and whether you should adjust specifications on older vehicles.
All I know is that 40 PSI peak during warmer temps is just too high so I took the edge off.
THIS BEING SAID - tire technology has come a LONG way in the last 25 years. Specifically in tire sidewalls and tread compound. So this isn't such an easy question to answer and I've never come across any good information about what changed and whether you should adjust specifications on older vehicles.
All I know is that 40 PSI peak during warmer temps is just too high so I took the edge off.
01-01-22, 05:11 PM
#4
Driver School Candidate
Had the same problem, went to a garage because one of the valve on a tire was about to tear off (it did hold air, but barely) and another tire was leaking around the wheel.
The next day I checked and all 4 tires where at 40 psi.
I dropped them to 32 front/31 rear.
My tires seems to have soft sidewalls, and at 29 psi they look like they're too low on air. I like a little stiffer ride.
The next day I checked and all 4 tires where at 40 psi.
I dropped them to 32 front/31 rear.
My tires seems to have soft sidewalls, and at 29 psi they look like they're too low on air. I like a little stiffer ride.
01-01-22, 07:28 PM
#5
Racer
Thread Starter
We had our first snow of the season not too long ago.
Man this car handles incredibly. The double wishbone suspension really does wonders keeping the front end sorted during cornering. I put 2x50lb steel plates in the truck (they take up way less space than sandbags) to add a little more traction in the rear for acceleration. Overall once you're moving it's incredibly stable - You need to use power to make the rear slide, otherwise there is simply too much grip and the natural balance of the car will just understeer. It makes it feel extremely confident driving down the road, steering inputs don't unsettle the balance of the car in the snow.
They don't use salt on the roads here so they get covered in snow and stay that way. In the rust belt you can get away with all-seasons because it will all melt away - but here it stays (until the sun melts it eventually). The tires really make a huge difference, the lateral cornering grip and braking ability is just staggering.
I lowered my pressures 1 more time after making this thread, 29 PSI @15 ambient. Made the ride quality even better. As Krakrak said, the sidewall does seem a little spongey and they look visually like they're a touch low on air. But I mean such is life with a 60 profile tire - I don't think you're getting away from that. I would prefer lower pressures during the winter to make the tire a bit fatter to give better snow grip.
Man this car handles incredibly. The double wishbone suspension really does wonders keeping the front end sorted during cornering. I put 2x50lb steel plates in the truck (they take up way less space than sandbags) to add a little more traction in the rear for acceleration. Overall once you're moving it's incredibly stable - You need to use power to make the rear slide, otherwise there is simply too much grip and the natural balance of the car will just understeer. It makes it feel extremely confident driving down the road, steering inputs don't unsettle the balance of the car in the snow.
They don't use salt on the roads here so they get covered in snow and stay that way. In the rust belt you can get away with all-seasons because it will all melt away - but here it stays (until the sun melts it eventually). The tires really make a huge difference, the lateral cornering grip and braking ability is just staggering.
I lowered my pressures 1 more time after making this thread, 29 PSI @15 ambient. Made the ride quality even better. As Krakrak said, the sidewall does seem a little spongey and they look visually like they're a touch low on air. But I mean such is life with a 60 profile tire - I don't think you're getting away from that. I would prefer lower pressures during the winter to make the tire a bit fatter to give better snow grip.
03-14-23, 12:56 PM
#6
This thread was helpful, thanks all! I have upgraded from the stock 16's to 18's
I asked ChatGPT: "What is the recommended tire pressure for a 1997 Lexus LS400 with tire size 245/45R18?" And this is what it spit out the following - "For a 1997 Lexus LS400 with tire size 245/45R18, the recommended tire pressure is typically 32 PSI for the front tires and 30 PSI for the rear tires. However, please note that this is a general recommendation and you should always refer to the tire pressure specifications indicated on the tire information placard located on the driver's side door jamb or in the owner's manual for your specific vehicle."
Does this sound pretty accurate to yalll?
I asked ChatGPT: "What is the recommended tire pressure for a 1997 Lexus LS400 with tire size 245/45R18?" And this is what it spit out the following - "For a 1997 Lexus LS400 with tire size 245/45R18, the recommended tire pressure is typically 32 PSI for the front tires and 30 PSI for the rear tires. However, please note that this is a general recommendation and you should always refer to the tire pressure specifications indicated on the tire information placard located on the driver's side door jamb or in the owner's manual for your specific vehicle."
Does this sound pretty accurate to yalll?
03-14-23, 03:25 PM
#7
Racer
Thread Starter
I think those pressures will be fine. Everything is a compromise.
Higher pressure = more upright tire, stiffer sidewall, less compliance, sharper steering and handling, better fuel economy because of smaller contact patch
Lower pressure = more wobbly tire, spongier sidewall, more compliance, higher temperatures during extended cornering (Twisty road), worse fuel economy because of larger contact patch
Higher pressure = more upright tire, stiffer sidewall, less compliance, sharper steering and handling, better fuel economy because of smaller contact patch
Lower pressure = more wobbly tire, spongier sidewall, more compliance, higher temperatures during extended cornering (Twisty road), worse fuel economy because of larger contact patch
Thread
Thread Starter
Forum
Replies
Last Post