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Old 6th February 2005, 00:06   #1
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Default Tyre pressure indication on the sidewall!!

Well, i've been through a few sites where all the markings on the sidewall of a tyre have been explained but, there seems to be no way of finding out the recomended pressure for that tyre. Only the max allowable pressure is given.

Most sites say that even when you replace your OE tyres with new ones, the car manufacturer's recomended pressure applies to the new tyres also, this has got me into a fix now.

Do they mean tyres of the same model and make, or any tyre with the OE size or any tyre irrespective of size and profile?

Here's what a website has to say :
Quote:
Maximum Inflation Pressure is the highest inflation pressure that the tire can withstand. This is not, however, the recommended inflation pressure. Inflation pressures should never be below the recommended pressure or above the maximum pressure branded on the sidewall. Also see Air Pressure.
I plan to go in for new tyres very soon and unless i find a way to determine the recomended pressure, i'm never gonna be comfortable with them.

Shan2nu

Last edited by Shan2nu : 6th February 2005 at 00:08.
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Old 6th February 2005, 10:45   #2
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Its not possible for a tyre manufacturer to stamp recommended pressure on its sidewall. The simple reason is that this is a variable. This changes with every car as well as the weight you are lugging around in the form of passengers and luggage. That is why your manual gives you atleast 2 different pressure, one for when the car is empty, the other for when you are driving with a full load.

The maximum pressure marking is not a variable, hence it is stamped on the sidewall. This would be as a safety measure, as driving with pressure's exceding that figure would increase the risk of a blowout by a fair margin.

Basically, the recommended pressures for one particular car model would remain the same no matter what tyre you put on.
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Old 6th February 2005, 11:49   #3
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Quote:
Basically, the recommended pressures for one particular car model would remain the same no matter what tyre you put on.
Wow, didn't know that. I thought the recomeneded tyre pressure was to be given by the tyre manufacturer.

So if Honda recomends 29psi, it's ok to use the same for the GSD2s that i might be going for, in a few days time?

Shan2nu
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Old 6th February 2005, 12:20   #4
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Yes. The vehicle recomended pressure is the safest point to start from. Ofcourse, you would then adjust a psi here or there depending on your driving style.
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Old 6th February 2005, 12:46   #5
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the pressure for a particular tire varies according to the vehicle weight.
for example,145/70 r13 is used on both the wagon r and the carb zen
maruti says 33psi for the wagon r and 28 psi for the zen with same tires as the zen weighs less.
same with 145/80r12 .maruti says 24psi for the zen and 28psi for the wagon r.

so the vehicle weight plays an imp part in the right tire pressure ,if you want a good ride as wellas handling.

the max pressure mentioned is the max that can safely be inside the tire.
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Old 6th February 2005, 13:08   #6
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Hmm, interesting. So hypothetically speaking, if i fit the Vtec tyres on the Wagon R (LOL) will it still need 33psi?

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Old 6th February 2005, 13:13   #7
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Quote:
I plan to go in for new tyres very soon and unless i find a way to determine the recomended pressure, i'm never gonna be comfortable with them.
Shan, assuming that you are going with one upsize, dont worry about the PSI. You are safe with Hondas recommendations.

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Old 6th February 2005, 13:21   #8
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Quote:
Originally Posted by Shan2nu
Hmm, interesting. So hypothetically speaking, if i fit the Vtec tyres on the Wagon R (LOL) will it still need 33psi?

Shan2nu


do the wagon r and the Vtec weigh the same.if yeas then u can do so.
u can fill more air but then the ride will be bumpy and the hadling may be affected .and on wet roads you also run the risk of aquaplaning.

if u fill less air,the tire wear will be accelerated,but you might get more grip.the ride will be good.
but at higher speeds you can overheat the tire.
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Old 7th February 2005, 01:15   #9
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Quote:
Originally Posted by speedsatya
u can fill more air but then the ride will be bumpy and the hadling may be affected .and on wet roads you also run the risk of aquaplaning.
Actually its the opposite, you decrease the risk of aquaplaning if you run a slightly higher tire pressure.

cya
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Old 7th February 2005, 10:45   #10
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Quote:
Originally Posted by Rehaan
Actually its the opposite, you decrease the risk of aquaplaning if you run a slightly higher tire pressure.

cya
R

hey rehaan,
can you explain ?????as when u fill more air the contact area of the tire with the road surface will decrease.the only part of the tire in contact will be around the center of the tire surface.whereas when u have lesser air,the area on the road will be more.
correct me if i am wrong
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Old 7th February 2005, 11:08   #11
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Quote:
Originally Posted by Shan2nu
Wow, didn't know that. I thought the recomeneded tyre pressure was to be given by the tyre manufacturer.

So if Honda recomends 29psi, it's ok to use the same for the GSD2s that i might be going for, in a few days time?

Shan2nu
Umm the pressure on the sidewall is the highest recommended as we all know, but what the manufacturer recommends is actually the "lowest" recommended tyre pressure. So if you want to do 120+ have the tyre pressure upped by 3-4psi. Slightly harsher ride, but you will reduce risk of blowout. Indica recommends 28psi, but on highway i run 32 in front and 30 in rear. So i guess no matter what the tyre, use 32psi . And if you think your tyre pressure is lower than the recommended one, dont exceed 80 till you reach the nearest filling post!
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Old 7th February 2005, 15:37   #12
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Quote:
hey rehaan,
can you explain ?????as when u fill more air the contact area of the tire with the road surface will decrease.the only part of the tire in contact will be around the center of the tire surface.whereas when u have lesser air,the area on the road will be more.
correct me if i am wrong
That's exactly why tyres aquaplane when tyre pressure is low. With a bigger contat patch the weight of the car is distrubuted over a larger area, this reduces the pressure per square inche or cm (what ever unit it may be).

Watch a WRC stage where the tracks are covered with snow, the cars run on ultra small 165 tyres, that's bcoz when the pressure per square inche increases the tyre is able to penetrate through the layer of snow and not just float over it, giving the car lot more grip.

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