Tire pressure 20inch
03-30-2017, 12:33 PM
#1
Junior Member
Thread Starter
Tire pressure 20inch
I have GLS450 with appearance package, so i got a 20 inch wheel. Vehicle tire pressure reading shows 36/35 on front wheels and 42 on rear wheel.
What is the recommended tire pressure on my tires? Can the front and rear can have the same tire pressure?
What is the recommended tire pressure on my tires? Can the front and rear can have the same tire pressure?
03-30-2017, 03:57 PM
#2
Yes you can probably use 35 psi all around.
The advices on car are given mostly for fully loaded and maximum technical car speed, and behind some extra to cover overloading.
All a matter of covering the responcibility of the car maker.
Tirepressure advice is to give the tire a deflection that dont produce that much energy , that the rubber at any part of tire goes above a sertain temperature.
That heatproduction a second is made by the heatproduction a cycle X number of cycles a second.
Cooling down of tire is not dependent on speed, but on temperature differences between rubber and surounding rubber, rubber and in and outside air, and between in and outside tire air.
I am able to calculate a save pressure for every situation you come by in your use.
For that I need from car next:
Best seperate weighed wheelweights in the loading of the situation ( persons and load).
Second best axle weights for the situations.
But when you dont have one of that , we will have to use the GAWR's, GVWR,Enpty weight and the way you load it for the situation( so persons weight and load and where you place it.
Also need the maximum speed you use and wont go over for even a minute.
From tires next and can be read from the sidewall:
maximum load or loadindex,
Kind of tire to determine AT wich pressure the maximum load is calculated for.
But give sises and if P in front of that to , so I can google to check it.
Also nice would be the speedcode ( a letter Q,R,S,T,H,V,W,Y,(Y) )
The car advice is for GAWR's and maximum technical car speed calculated nowadays, but who drives that max speed and with maximum loaded .
99% of use is with 1 or 2 persons and a little load and speed not higher then 140km/86m/h. For that axle loads are much lower and mostly front higher then rear, wich gives advice front higher pressure then rear.
Before the year 2000 in Europe , normal advice was for axleloads determined by carmaker for 3 persons and a little load.
After 2000 also in Europe this was not given anymore, and normal was sayd for 4 persons and load and for that the GAWR's where filled in the formula to calculate the advicepressure, and for maximum tech carspeed.
to make a long story short, probably your 3 persons and a little load advice will come to about 30 psi front and 25 psi rear, that low .
But dont go using this before I calculated , its a gamble.
Greatings from a Dutch Pigheaded selfdeclared tirepressure-specialist
Peter
The advices on car are given mostly for fully loaded and maximum technical car speed, and behind some extra to cover overloading.
All a matter of covering the responcibility of the car maker.
Tirepressure advice is to give the tire a deflection that dont produce that much energy , that the rubber at any part of tire goes above a sertain temperature.
That heatproduction a second is made by the heatproduction a cycle X number of cycles a second.
Cooling down of tire is not dependent on speed, but on temperature differences between rubber and surounding rubber, rubber and in and outside air, and between in and outside tire air.
I am able to calculate a save pressure for every situation you come by in your use.
For that I need from car next:
Best seperate weighed wheelweights in the loading of the situation ( persons and load).
Second best axle weights for the situations.
But when you dont have one of that , we will have to use the GAWR's, GVWR,Enpty weight and the way you load it for the situation( so persons weight and load and where you place it.
Also need the maximum speed you use and wont go over for even a minute.
From tires next and can be read from the sidewall:
maximum load or loadindex,
Kind of tire to determine AT wich pressure the maximum load is calculated for.
But give sises and if P in front of that to , so I can google to check it.
Also nice would be the speedcode ( a letter Q,R,S,T,H,V,W,Y,(Y) )
The car advice is for GAWR's and maximum technical car speed calculated nowadays, but who drives that max speed and with maximum loaded .
99% of use is with 1 or 2 persons and a little load and speed not higher then 140km/86m/h. For that axle loads are much lower and mostly front higher then rear, wich gives advice front higher pressure then rear.
Before the year 2000 in Europe , normal advice was for axleloads determined by carmaker for 3 persons and a little load.
After 2000 also in Europe this was not given anymore, and normal was sayd for 4 persons and load and for that the GAWR's where filled in the formula to calculate the advicepressure, and for maximum tech carspeed.
to make a long story short, probably your 3 persons and a little load advice will come to about 30 psi front and 25 psi rear, that low .
But dont go using this before I calculated , its a gamble.
Greatings from a Dutch Pigheaded selfdeclared tirepressure-specialist
Peter
The following users liked this post:
solaris72 (03-31-2017)
03-31-2017, 09:05 AM
#3
Junior Member
Thread Starter
Thank you for the detailed explanation.
Yes you can probably use 35 psi all around.
The advices on car are given mostly for fully loaded and maximum technical car speed, and behind some extra to cover overloading.
All a matter of covering the responcibility of the car maker.
Tirepressure advice is to give the tire a deflection that dont produce that much energy , that the rubber at any part of tire goes above a sertain temperature.
That heatproduction a second is made by the heatproduction a cycle X number of cycles a second.
Cooling down of tire is not dependent on speed, but on temperature differences between rubber and surounding rubber, rubber and in and outside air, and between in and outside tire air.
I am able to calculate a save pressure for every situation you come by in your use.
For that I need from car next:
Best seperate weighed wheelweights in the loading of the situation ( persons and load).
Second best axle weights for the situations.
But when you dont have one of that , we will have to use the GAWR's, GVWR,Enpty weight and the way you load it for the situation( so persons weight and load and where you place it.
Also need the maximum speed you use and wont go over for even a minute.
From tires next and can be read from the sidewall:
maximum load or loadindex,
Kind of tire to determine AT wich pressure the maximum load is calculated for.
But give sises and if P in front of that to , so I can google to check it.
Also nice would be the speedcode ( a letter Q,R,S,T,H,V,W,Y,(Y) )
The car advice is for GAWR's and maximum technical car speed calculated nowadays, but who drives that max speed and with maximum loaded .
99% of use is with 1 or 2 persons and a little load and speed not higher then 140km/86m/h. For that axle loads are much lower and mostly front higher then rear, wich gives advice front higher pressure then rear.
Before the year 2000 in Europe , normal advice was for axleloads determined by carmaker for 3 persons and a little load.
After 2000 also in Europe this was not given anymore, and normal was sayd for 4 persons and load and for that the GAWR's where filled in the formula to calculate the advicepressure, and for maximum tech carspeed.
to make a long story short, probably your 3 persons and a little load advice will come to about 30 psi front and 25 psi rear, that low .
But dont go using this before I calculated , its a gamble.
Greatings from a Dutch Pigheaded selfdeclared tirepressure-specialist
Peter
The advices on car are given mostly for fully loaded and maximum technical car speed, and behind some extra to cover overloading.
All a matter of covering the responcibility of the car maker.
Tirepressure advice is to give the tire a deflection that dont produce that much energy , that the rubber at any part of tire goes above a sertain temperature.
That heatproduction a second is made by the heatproduction a cycle X number of cycles a second.
Cooling down of tire is not dependent on speed, but on temperature differences between rubber and surounding rubber, rubber and in and outside air, and between in and outside tire air.
I am able to calculate a save pressure for every situation you come by in your use.
For that I need from car next:
Best seperate weighed wheelweights in the loading of the situation ( persons and load).
Second best axle weights for the situations.
But when you dont have one of that , we will have to use the GAWR's, GVWR,Enpty weight and the way you load it for the situation( so persons weight and load and where you place it.
Also need the maximum speed you use and wont go over for even a minute.
From tires next and can be read from the sidewall:
maximum load or loadindex,
Kind of tire to determine AT wich pressure the maximum load is calculated for.
But give sises and if P in front of that to , so I can google to check it.
Also nice would be the speedcode ( a letter Q,R,S,T,H,V,W,Y,(Y) )
The car advice is for GAWR's and maximum technical car speed calculated nowadays, but who drives that max speed and with maximum loaded .
99% of use is with 1 or 2 persons and a little load and speed not higher then 140km/86m/h. For that axle loads are much lower and mostly front higher then rear, wich gives advice front higher pressure then rear.
Before the year 2000 in Europe , normal advice was for axleloads determined by carmaker for 3 persons and a little load.
After 2000 also in Europe this was not given anymore, and normal was sayd for 4 persons and load and for that the GAWR's where filled in the formula to calculate the advicepressure, and for maximum tech carspeed.
to make a long story short, probably your 3 persons and a little load advice will come to about 30 psi front and 25 psi rear, that low .
But dont go using this before I calculated , its a gamble.
Greatings from a Dutch Pigheaded selfdeclared tirepressure-specialist
Peter
04-16-2017, 09:55 PM
#4
Tire pressure boils down to three choices:
a) believe the manufacture
b) measure the situation
c) go with some gut instinct (almost always wrong)
A tire pyrometer is the proper tool to perfor choice b. With it, you can determine if you are running the proper inflation pressures, if you have the proper camber, if you have the proper balance between toe front to rear, and a few more subtle suspension alignment questions.
A tire is properly inflated when, after driving for at least 10 minutes at a chosen speed, one exits the vehicle and immediately measures the tire temperature on the tread at 3 places on each tire (12 measurements), outer edge, inner edge, and center, on all 4 tires. If the the center has the same temperature as the average of the outer edge and the inner edge, the tire is properly inflated--period; otherwise it is not (even if it has the tire pressure recommended by the manufacturer.) Generally one wants the outer edge to be 10ºF to 10ºC cooler than the inner edge (hotter), as the outer edge gets cool air from ambient while the inner edge gets hot ir from the car's operating mechanisms.
Camber is used to adjust the difference between the temperature of the inner edge of the tire and the outer edge of the tire; and to a certain degree, set the operating temperature of the tires as a whole. The proper tire temperature of a tire rolling down an interstate at 65 MPH is about 165ºF. The proper tire temperature of a car circulating a race track is about 200ºF.
Toe adjustment is used to set the difference between the temperature of the front tires and the rear tires to balance out the traction front to rear. Whereas tire pressure can adjust the balance front to rear, this is done by loosing grip on the tire being ask to do less work. Far better to balance the tire temperatures so both ends do similar amounts of work, here a bit of work on toe and air pressure works best.
Attempting to set tire pressure without some measurement device is simply not a correct way to make forward progress. Although for those who cannot be bothered to perform a few simple measurements and especially for those who don't want to get 50% more tire mileage between new replacements, you can simply use the manufacturer's recommended pressures. I should note that the cost of a decent tire pyrometer is about 10% the cost of a set of tires, and will last you your whole adult lifetime. So, it will have paid for itself by the time you get 10K miles on the second set of tires you put on the car.
a) believe the manufacture
b) measure the situation
c) go with some gut instinct (almost always wrong)
A tire pyrometer is the proper tool to perfor choice b. With it, you can determine if you are running the proper inflation pressures, if you have the proper camber, if you have the proper balance between toe front to rear, and a few more subtle suspension alignment questions.
A tire is properly inflated when, after driving for at least 10 minutes at a chosen speed, one exits the vehicle and immediately measures the tire temperature on the tread at 3 places on each tire (12 measurements), outer edge, inner edge, and center, on all 4 tires. If the the center has the same temperature as the average of the outer edge and the inner edge, the tire is properly inflated--period; otherwise it is not (even if it has the tire pressure recommended by the manufacturer.) Generally one wants the outer edge to be 10ºF to 10ºC cooler than the inner edge (hotter), as the outer edge gets cool air from ambient while the inner edge gets hot ir from the car's operating mechanisms.
Camber is used to adjust the difference between the temperature of the inner edge of the tire and the outer edge of the tire; and to a certain degree, set the operating temperature of the tires as a whole. The proper tire temperature of a tire rolling down an interstate at 65 MPH is about 165ºF. The proper tire temperature of a car circulating a race track is about 200ºF.
Toe adjustment is used to set the difference between the temperature of the front tires and the rear tires to balance out the traction front to rear. Whereas tire pressure can adjust the balance front to rear, this is done by loosing grip on the tire being ask to do less work. Far better to balance the tire temperatures so both ends do similar amounts of work, here a bit of work on toe and air pressure works best.
Attempting to set tire pressure without some measurement device is simply not a correct way to make forward progress. Although for those who cannot be bothered to perform a few simple measurements and especially for those who don't want to get 50% more tire mileage between new replacements, you can simply use the manufacturer's recommended pressures. I should note that the cost of a decent tire pyrometer is about 10% the cost of a set of tires, and will last you your whole adult lifetime. So, it will have paid for itself by the time you get 10K miles on the second set of tires you put on the car.
The following users liked this post:
knpnj (04-17-2017)
04-16-2017, 10:38 PM
#5
Tire pressure for cars and trucks is weight driven!. the tire manufacturer publishes tables for each tire what the pressure should be for that tire for that weight. aside from the min and max, the min to prevent it from rolling off the rim and max for the obvious (all stamped on the tire...) for cars.. use the numbers posted on the drivers side pillar as a guide.
Not related, but F18 Jet uses 150 PSI on the nose, 300PSI for Carrier ops😎 The retired Concorde used 240PSI on the mains.
Not related, but F18 Jet uses 150 PSI on the nose, 300PSI for Carrier ops😎 The retired Concorde used 240PSI on the mains.
Last edited by nookie; 04-16-2017 at 10:42 PM.
04-17-2017, 08:19 PM
#6
MBWorld Fanatic!
Well... thanks for for all the self-taught-kindof-tech-speaks..
I have my techs set 20" rigs at 38psi... then after 1/2 weeks of driving we encourage the owner to experiment up/down in 2PSI increments
I have my techs set 20" rigs at 38psi... then after 1/2 weeks of driving we encourage the owner to experiment up/down in 2PSI increments
04-18-2017, 02:51 AM
#7
Trending Topics
04-28-2017, 06:24 AM
#9
Senior Member
FWIW, I started at 36 with 20s, found 35 a bit more comfy and seemed like overinflation could wear tire centers more based upon my lightly loaded use of this car and the actual tread depths after a while. No science here.
