TIRE PRESSURE FOR staggered 19s
03-09-2014, 08:52 PM
#1
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2009 C300 Sport 4Matic
TIRE PRESSURE FOR staggered 19s
2009 C300 4 Matic Sport- I just bought some new tires (Goodyear F1 asymmetric 2) for my wheels- 19x8.5 front; 19x9.5 rears. The tires are 235/35/19 (F); and 265/30/19 (R).
My stock & staggered 17s recommend the tire PSI be 30 front; 35 rear.
For all you guys driving on 19s, any idea what the correct PSI should be?
Btw, tire rack.com said I should keep the psi to at least 42psi. That seems a bit much, but then again, I am clueless about the matter. Thoughts?
My stock & staggered 17s recommend the tire PSI be 30 front; 35 rear.
For all you guys driving on 19s, any idea what the correct PSI should be?
Btw, tire rack.com said I should keep the psi to at least 42psi. That seems a bit much, but then again, I am clueless about the matter. Thoughts?
03-10-2014, 04:43 AM
#2
I can calculate that for you , but need some more data.
Made spreadsheets for it , but already came to new information wich I have to implement in it, so best it to let me do it for you.
One thing is for instance that your low aspect ratio tires ( the 30 and 35 in the sises) are given to high maximum load by the tire makers.
Best is to substract 8 from the loadindex give ( so fi 98 gets 90) or substract 20% from given maximum load ( so 750kg goes to 600kg).
Also the low AR tires are more sensitive to sideward road/treath angles ( wheels like this on the axle /-\ or riding in a truck track for miles).
The rest is copyd from another topic I answered too yust now.
For calculating the lowest pressure at wich the tires dont get damaged by the 10 to 30 times a second deflecting and flexing back of every segment of the tire , I need the next.
From tire :
maximum load or loadindex
Pressure needed for that called the reference-pressure ( Pr) and is not the maximum pressure of yours 51 psi. If you see XL/reinforced/ Extraload on the tire, then its such a tire and needs 41psi /2.8bar for the maximum load to ride up to mostly 160km/99m/h with camber angle of below 2 degrees.
Normal car tires , called P-tires in America need 35psi Pr.
For higher speed the Pr has to be highenend up with a system depending on the speedcode of tire ( V to Y ,(Y)).
Also need the sises and that speedcode.
From Car :
Empty weight and the way you load it ( persons and load) .
Motor in front or back.
This is to estimate the axle loads in your normal use.
For fully loaded the GAWR and GVWR ( gross axle/vehicle weight rating).
Camber angle of mostly rear wheels done ( wheels like this on the axle/-\)
Maximum technical car speed or speed you sertainly wont go over in your use.
Try to find all that or most of it and give it here, and I will calculate that lowest pressure , wich you can play with above that for handling and over and under steer.
Made spreadsheets for it , but already came to new information wich I have to implement in it, so best it to let me do it for you.
One thing is for instance that your low aspect ratio tires ( the 30 and 35 in the sises) are given to high maximum load by the tire makers.
Best is to substract 8 from the loadindex give ( so fi 98 gets 90) or substract 20% from given maximum load ( so 750kg goes to 600kg).
Also the low AR tires are more sensitive to sideward road/treath angles ( wheels like this on the axle /-\ or riding in a truck track for miles).
The rest is copyd from another topic I answered too yust now.
For calculating the lowest pressure at wich the tires dont get damaged by the 10 to 30 times a second deflecting and flexing back of every segment of the tire , I need the next.
From tire :
maximum load or loadindex
Pressure needed for that called the reference-pressure ( Pr) and is not the maximum pressure of yours 51 psi. If you see XL/reinforced/ Extraload on the tire, then its such a tire and needs 41psi /2.8bar for the maximum load to ride up to mostly 160km/99m/h with camber angle of below 2 degrees.
Normal car tires , called P-tires in America need 35psi Pr.
For higher speed the Pr has to be highenend up with a system depending on the speedcode of tire ( V to Y ,(Y)).
Also need the sises and that speedcode.
From Car :
Empty weight and the way you load it ( persons and load) .
Motor in front or back.
This is to estimate the axle loads in your normal use.
For fully loaded the GAWR and GVWR ( gross axle/vehicle weight rating).
Camber angle of mostly rear wheels done ( wheels like this on the axle/-\)
Maximum technical car speed or speed you sertainly wont go over in your use.
Try to find all that or most of it and give it here, and I will calculate that lowest pressure , wich you can play with above that for handling and over and under steer.
03-10-2014, 12:49 PM
#3
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2009 C300 Sport 4Matic
I can calculate that for you , but need some more data.
Made spreadsheets for it , but already came to new information wich I have to implement in it, so best it to let me do it for you.
One thing is for instance that your low aspect ratio tires ( the 30 and 35 in the sises) are given to high maximum load by the tire makers.
Best is to substract 8 from the loadindex give ( so fi 98 gets 90) or substract 20% from given maximum load ( so 750kg goes to 600kg).
Also the low AR tires are more sensitive to sideward road/treath angles ( wheels like this on the axle /-\ or riding in a truck track for miles).
The rest is copyd from another topic I answered too yust now.
For calculating the lowest pressure at wich the tires dont get damaged by the 10 to 30 times a second deflecting and flexing back of every segment of the tire , I need the next.
From tire :
maximum load or loadindex
Pressure needed for that called the reference-pressure ( Pr) and is not the maximum pressure of yours 51 psi. If you see XL/reinforced/ Extraload on the tire, then its such a tire and needs 41psi /2.8bar for the maximum load to ride up to mostly 160km/99m/h with camber angle of below 2 degrees.
Normal car tires , called P-tires in America need 35psi Pr.
For higher speed the Pr has to be highenend up with a system depending on the speedcode of tire ( V to Y ,(Y)).
Also need the sises and that speedcode.
From Car :
Empty weight and the way you load it ( persons and load) .
Motor in front or back.
This is to estimate the axle loads in your normal use.
For fully loaded the GAWR and GVWR ( gross axle/vehicle weight rating).
Camber angle of mostly rear wheels done ( wheels like this on the axle/-\)
Maximum technical car speed or speed you sertainly wont go over in your use.
Try to find all that or most of it and give it here, and I will calculate that lowest pressure , wich you can play with above that for handling and over and under steer.
Made spreadsheets for it , but already came to new information wich I have to implement in it, so best it to let me do it for you.
One thing is for instance that your low aspect ratio tires ( the 30 and 35 in the sises) are given to high maximum load by the tire makers.
Best is to substract 8 from the loadindex give ( so fi 98 gets 90) or substract 20% from given maximum load ( so 750kg goes to 600kg).
Also the low AR tires are more sensitive to sideward road/treath angles ( wheels like this on the axle /-\ or riding in a truck track for miles).
The rest is copyd from another topic I answered too yust now.
For calculating the lowest pressure at wich the tires dont get damaged by the 10 to 30 times a second deflecting and flexing back of every segment of the tire , I need the next.
From tire :
maximum load or loadindex
Pressure needed for that called the reference-pressure ( Pr) and is not the maximum pressure of yours 51 psi. If you see XL/reinforced/ Extraload on the tire, then its such a tire and needs 41psi /2.8bar for the maximum load to ride up to mostly 160km/99m/h with camber angle of below 2 degrees.
Normal car tires , called P-tires in America need 35psi Pr.
For higher speed the Pr has to be highenend up with a system depending on the speedcode of tire ( V to Y ,(Y)).
Also need the sises and that speedcode.
From Car :
Empty weight and the way you load it ( persons and load) .
Motor in front or back.
This is to estimate the axle loads in your normal use.
For fully loaded the GAWR and GVWR ( gross axle/vehicle weight rating).
Camber angle of mostly rear wheels done ( wheels like this on the axle/-\)
Maximum technical car speed or speed you sertainly wont go over in your use.
Try to find all that or most of it and give it here, and I will calculate that lowest pressure , wich you can play with above that for handling and over and under steer.
Thank you VERY MUCH for taking the time to respond in detail!!!
Here is some more information:
1.) Tire specs:
FRONT: 235/35R/19 (91Y) XL. Max PSI -50. Max load - 1,356lbs.
REAR: 265/30R/19 (93Y) XL. Max PSI - 51. Max load - 1,433lbs.
2.) Empty weight of vehicle - 3,740lbs.
3.) My typical load adds 220lbs to empty weight of vehicle.
4.) GVWR - 4,672lbs.
5.) GAWR Front - 2,358lbs.
6.) GAWR Rear - 2,391lbs.
7.) Engine mounted in Front.
8.) Camber settings - unknown
9.) Max speed vehicle would be driven at - 145mph.
Just want to point out that my car is a 4matic (all wheel drive) not sure it matters, but figured I'd tell you.
Thanks again for your help!
03-11-2014, 05:25 AM
#5
Wont quote your post Bunkx9 because this post would take to much space.
But used my motorhome-calculator and adyusted it in the percentages reserves , and for the maximum speed I compensated the reference-pressure with the official system for W speedrated tires , so first conversed 145m/h to 235km/h wich is 45 km higher then reference speed of 190km/h for W speedrated tires.
Official system says for every km 1kpa higher Pr ( reference pressure) of used European 2.9 bar/290kpa becomes 335kpa/3.35bar and filled that in the calculator. American is 2.8 bar
Devided your loads with key I decided and came to empty 1990 lbs front and 1750 rear added asuming your weight right between the axles devided.
So came to 1990+110= 2100 front and 1750+110=1860 rear.
Left part 2 open so using GAWR's and reserve set to zero % because these kind of cars get seldomly overloaded . Advice in part 2 so is for fully loaded.
Part 3 originally is for when seperate wheels weighing but because your are sitting as driver left I gave a weightdifference of 10 lbs more to left.
Then using different system , no reserve but giving percentage to use of weight the pressure is calculated for called it Load% of 95%, wich is almoast the same as adding 5% to the weight for reserve.
Did not include camber angle but fi 2degr45min camber angle needs 5% higher pressure, mostly only alighned for rear. So you have to calculate that yourselfes.
So now here the picture , for your normal use take part 3 , and this is calculated asuming I determined the axle loads good, and the tire-specifications the tire maker gives is to laws of nature, wich it is not .
so next post will be with the tire-specifications I think it has to be for savety to laws of nature.
But used my motorhome-calculator and adyusted it in the percentages reserves , and for the maximum speed I compensated the reference-pressure with the official system for W speedrated tires , so first conversed 145m/h to 235km/h wich is 45 km higher then reference speed of 190km/h for W speedrated tires.
Official system says for every km 1kpa higher Pr ( reference pressure) of used European 2.9 bar/290kpa becomes 335kpa/3.35bar and filled that in the calculator. American is 2.8 bar
Devided your loads with key I decided and came to empty 1990 lbs front and 1750 rear added asuming your weight right between the axles devided.
So came to 1990+110= 2100 front and 1750+110=1860 rear.
Left part 2 open so using GAWR's and reserve set to zero % because these kind of cars get seldomly overloaded . Advice in part 2 so is for fully loaded.
Part 3 originally is for when seperate wheels weighing but because your are sitting as driver left I gave a weightdifference of 10 lbs more to left.
Then using different system , no reserve but giving percentage to use of weight the pressure is calculated for called it Load% of 95%, wich is almoast the same as adding 5% to the weight for reserve.
Did not include camber angle but fi 2degr45min camber angle needs 5% higher pressure, mostly only alighned for rear. So you have to calculate that yourselfes.
So now here the picture , for your normal use take part 3 , and this is calculated asuming I determined the axle loads good, and the tire-specifications the tire maker gives is to laws of nature, wich it is not .
so next post will be with the tire-specifications I think it has to be for savety to laws of nature.
03-11-2014, 05:53 AM
#6
Edit: saw I took 84 LI behind instead of 85 LI . Gives 1 psi lower advice so wont make a new picture.
So now how I have determined , what the advice pressure should be .
Reduced 20% of the maximum load by taking 8 LI steps back .
Set the Pr back to 2.9 bar and assumed this to be for only 160km/99m/h.
For S to V speedrated tires are using Pr for up to 160km/99m/h and I suspect the W speedrated to be calculated in its maximum load also for that speed and not as the system says for up to 190km/h. I make that of that there are V and W speedrated tires of same sises and XL ( mostly XL for low AR tires( 30/35 yours), with same maximum load or loadindex, and for higher speed it has to be lower with same Pr.
So advice in new picture is for up to 99m/h wich you can also keep yourself too I think. The reduction of 20 % gives the tire a deflection that gives to my estimations ( I dont have a laboratory in my backyard, so pure administrative research) zero chanche on tire damage by driving, and a livetime of 6 years or 80000miles . Comfort and Gripp are totally gone then, but savety first.
These low Aspect ratio tires are not for gripp and comfort designed, only for good looks, is my opinion.
How many miles or years do you make with your tires average?
So now how I have determined , what the advice pressure should be .
Reduced 20% of the maximum load by taking 8 LI steps back .
Set the Pr back to 2.9 bar and assumed this to be for only 160km/99m/h.
For S to V speedrated tires are using Pr for up to 160km/99m/h and I suspect the W speedrated to be calculated in its maximum load also for that speed and not as the system says for up to 190km/h. I make that of that there are V and W speedrated tires of same sises and XL ( mostly XL for low AR tires( 30/35 yours), with same maximum load or loadindex, and for higher speed it has to be lower with same Pr.
So advice in new picture is for up to 99m/h wich you can also keep yourself too I think. The reduction of 20 % gives the tire a deflection that gives to my estimations ( I dont have a laboratory in my backyard, so pure administrative research) zero chanche on tire damage by driving, and a livetime of 6 years or 80000miles . Comfort and Gripp are totally gone then, but savety first.
These low Aspect ratio tires are not for gripp and comfort designed, only for good looks, is my opinion.
How many miles or years do you make with your tires average?
Last edited by jadatis; 03-11-2014 at 05:58 AM.
