Tyre Air Pressure

Hi All,

I have Maruti Zen 1996 with tyre size 145/70 R13.

I like to ask what is the right Air Pressure in tyres to drive on Highway (NH1) and What causes Low / high air Pressure?

Hi Gurpreet - The highway speeds are high, and so are the stresses on the tyre when moving at those speeds.

An underinflated wheel will flex repeatedly and rapidly, causing it to heat up as well as subject it to fatigue. This is the reason it hs recommended that the tyres should be pumped up a bit when on a highway trip.

If your regular inflation pressures are 30/32 PSI, I would recommend going up to 33/35 or even 35/37 PSI.

Do not overdo, as the tyres will heat up to some extent anyways, and the air pressure will go up further. If you are not careful, you could have a tyre failure at hand.

Bottomline is, an underinflated tyre is worse than a slightly overinflated tyre. An extremely overinflated tyre is very bad anyways, as common sense tells you!

Hi Krishna, thanks for experimental handy tips. It really helps.

My car is santro. As per op.manual recommonded tyre pressure is 30 PSI in front& rear. I am suspecting its on lower side since I read this. What's your call here?

Also, tell me should I opt 32PSI front & 35PSI in rear when long highway run. I am going on long drive(@800kms) just after 2 days. Tyre spec am not sure but 155/70 R13 (car model-Dec 2008)

pls suggest.

Mfr recommendations for tyre pressure are generally on the lower side because they expect the tyres to also act as ride cushions, in addition to the primary function of the tyres.

For tyre longevity, handling and FE gains, I would choose the recommendations of your friends over the mfr's.

Thanks Krishna, Your post is really helpful.

Quote unnecessary and hence removed-MODS

small stuff does not count - only you will get some rattling if you go higher than required. There usually a lot of variation in the pump pressure meter calibration, so do not bother to get it right within 0.1 PSI.

Tyre wear++ <------ 30 PSI recommended ------ (32 to 35) all tyres, what I would go for ---- (38) slight rattles------ (40) slightly impaired cornering ----- (45) chances of patches coming loose ----- (55+) Chances of blowout ---> DOOM!

This is the scale in which you play. FE goes improving up to 50 PSI, but then levels off. Tyre wear is less with higher pressure. 

I myself keep 45 to 50 PSI, for FE reasons. I do not recommend anyone to follow me unless he knows what he is doing. In any circumstances, do not go beyond the maximum sidewall pressure (pressure printed as maximum on the tyre sidewall) (in my case it is 51 PSI).

Also if you care too much about pressure to think about different pressure for highway and city, you may want to consider investing in your own tyre pressure guage. [Independently, they are good investment considering the variation in pumps - but this does assume that you are filling or at least having the guy use this and then show you the reading]

I drive a mix of highway and city (~800KM/week) - but keep the pressure same (= mfg recommneded with mfg recommended tyre sizes) - for driving condition and across the 4 tyres. Keeps life simpler

Higher pressures can also be detrimental to worn or older tyres, so be careful on going on the extreme with those.

thanks to all for info.

Krishna, u wonder boy...amazing to know u r surfing on 50!!! PSI tyres. very interesting. sometime,  somewhere would like to meet u with this stuff...

finally, I decided 33PSI for all 4 tyres..