Correct tyre pressure for low profile tires

[Getafix]

Hi guys,


I'm a little confused about the correct tire pressure for my 195/50/15 tires. I get different answers from people ranging between 26-28 psi. Anyone knows what's the optimum/recommended psi for 195/50/15 tires?

[mafzaltareen]

i keep hte pressure of 28psi.
the ride remains smooth

[Storm]

tyre pressure has nothing to do with the tyre size, it has to do with the useage and the vehicle.

for example the tyre pressure of the front tyre of my VW is 18 whereas the rears are 27. these tyres are exactly the same size as the ones on the corolla.

[vampires]

28psi..(Y)

[spangle]

i always use 26/28 tyre pressure in my 205-40-17

[Spano]

agreed with storm


@Getafix


can you please tell me which car do you have. I will tell the exact pressure you require to keep in your tires.


Being an Electrical Engineer let me tell you about its scientific calculation.


there is a little physics and chemistry involved it in


Suppose the weight on your front axle is 600kg


means ...its equaly divided on each front tyre that is 300kg each.


now the the size (normally the width) of the tyre is responsible for the contact area.


if the tyre is has to lift 300kg of weight the contact area will vary with change in tyre pressure.


more tyre pressure will decrease the contact area.


Mathematically:

dldd /dd/dl

where:

dldd
p
is the pressure, /dddd
F
is the normal force (weight of the car), /dddd
A
is the area /dd/dl




According to Oscar Pereda, an engineer for BFGoodrich, a thumb rule and a realistic starting point is:

(Vehicle Weight in lb/100) + 2 psi at heavier end + 2 psi all around if suspension and alignment are stock.

Oscar also adds that there is no 'golden' tyre pressure. The optimal setting depends on the individual driver's preferences. For those inclined to find the ultimate setup, he recommends detailed tests, see
http://www.sportcompactcarweb.com/tech/0208scc_tires/
for details.

[rozzzzz]

^^^good reply

@poster

i keep 25 in all

[accord7362]

sapno & strom well said

As the gear box of steermatic is heavy so as the car from front I used to drive it with 32 on front tires & 30 in rear

to give my santro a power steering feeling I kept 30 in front & 28 in rear

[panicslayer]

@accord


Keeping high in front and low in rear is not good safety wise. It compromises handling. Always keep same pressure or swap the numbers like 28 in front and 30 in rear / 30 in front and 32 in rear

[Getafix]

Spano,
I have a 97 Honda Civic.

[jadatis]

I have been busy with re-calculating tire-pressure since 2007 ( not every day)


This with the formula of the European tire and rimm technical organisation.


The TRA uses other formula wich gives lower pressures, I recently discovered.


My last made Excell-spreadsheet is for re-calculating tire-pressure when other tires are placed then the original.


http://cid-a526e0eee092e6dc.skydrive...0tyre-pressure


The sheet gives , when you fill in everything right, always the correct advice-pressures for Heavy use and vacation use with tow-bar load. Those for normal use can go wrong if TRA formule is used for the plackard with advice-pressures. But nowadays the normal -advice pressures are mostly not given, so you dont miss them. You can always weight the seperate Axles with the load you use and add say 10% for measure-diferences. This you can fill in at "your own import".


from car you need;


1 Max axle loads ( on plancard under the motor hood or 1 of the door styles)


2 Maximum speed of the car ( in manual or estimate)


3 From the old advice-pressure plackard the advice-pressures for normal and heavy use for the original tires that are meanth for the specific car. Without this you will miss the normal-advice-pressures, so you can do without.


4 The camber angle only if above 2 degrees. This is when the alignment is like this /-\. so mostly not needed.


from the tires. Example P195/65 R 15 90T


1 . The maximum load of the tire in example 90 is the load-index and stands for 600kg


2 . The letter that stands for the maximum speed of the tire. In example T stands for up to 190km/h


3. The reference pressure or kind of tire. If you see somewhere on the tire side wall "at 250kpa"or "at 35psi"then this is always the reference pressure but you can select a kind of tire in the sheet. It is not the maximum pressure of the tire wich is with normal car tires higher ( 3 to 3.5 bar)


If there are questions or you might find some bugs ,then react here.

[jaggi]

28 psi