[joybhowmik]

Originally Posted by Santoshbhat

I would advise against using such crude contraptions. These pressure indicators will constantly be pressing on the tyre valves, which is how they give out pressure readings. I don't know how durable these things are and for how long they will be able to withstand these kinds of pressures.

Moreover if these things give out wrong readings it can mislead the car owner to think that his tyres have the right pressure. I am sure its manufactured by some local company and is just sold by the local Bridgestone dealer. Doubt if Bridgestone has anything to do with it.

Tyres are one of the most critical safety parts of your car and maintaining correct tyre pressure is extremely important. I don't trust most petrol bunks gauges either. Most of their gauges are out of calibration and give out wrong readings. The digital ones are the most innaccurate. Its best to carry your own analogue gauge and check pressures with it on a regular basis.

Bridgestone are resellers of a tyre pressure monitoring system cum navi. It retails for around 12K in New Delhi at Bridgestone Select stores.

[headbanger]

Hello BHPians,

I am contemplating to change tube type tires of my Zen to tubeless tires. The car was shod with tube type tires and the first change of tires also happened to be with tube tires. The recommended tire pressure by manfacturer for tube type tires is 24psi for all tires. Various tire-marts are suggesting me to keep 28psi-30psi and when I mention that 24psi is the manufacturer recommended tire pressure, they disapprove it.

I am also considering to upsize the tires from R12 to R13, not sure though!!!

a) If I plan to keep the same tire configuration, do I need to change the tire pressure if I go for tubeless tires?
b) If I plan to upsize tire configuration from R12 to R13, do I need to change the tire pressure if I go for tubeless tires?

Please advise!!!

[saket77]

For a Zen, though the recommended tyre pressure is 24 PSI, inflate it to at least 28 PSI. I don't know why & how the company recommends 24 PSI as it feels under-inflated a lot and the car is sluggish & FE is worse. The only situation I can think of is that the recommendation is for tires not bearing the weight of the vehicle. But I am not sure about it.

Tube or tubeless, R12 or R13; since the tyre pressure is measured in PSI - Pound per Square Inch, it hardly fluctuates too much with tyre size.

For instance, I run my 145/80-R12 tubeless tyres at 28-30 PSI. The tubeless are Michelins XM1+ and of course, the car Zen.

Regards,
Saket

[headbanger]

Originally Posted by saket77

For a Zen, though the recommended tyre pressure is 24 PSI, inflate it to at least 28 PSI. I don't know why & how the company recommends 24 PSI as it feels under-inflated a lot and the car is sluggish & FE is worse. The only situation I can think of is that the recommendation is for tires not bearing the weight of the vehicle. But I am not sure about it.

Tube or tubeless, R12 or R13; since the tyre pressure is measured in PSI - Pound per Square Inch, it hardly fluctuates too much with tyre size.

For instance, I run my 145/80-R12 tubeless tyres at 28-30 PSI. The tubeless are Michelins XM1+ and of course, the car Zen.

Regards,
Saket

Thanks Saket!!! Even Alto runs on same profile tires with manufacturer recommended 28-30psi pressure. (I am not sure on the figure but its definitely above 24psi.)

But to be honest, for the last 10 years ever since Zen entered our garage, its been 24 psi till date. FE has always been good(16-20kmpl) and tires have given me good range. The current ones are from year 2008 with more than 65k.

On the contrary, there have been instances where the car was running on 28psi and I could figure that almost immediately.

Having said that, I am not able to find any concrete source of info which states whether I need to change tire pressure should I opt for tubeless tires. Hence the confusion!!!

[deetjohn]

No harm in sticking to the manufacturer specified reading when changing to tubeless tyres. I think the best way forward is to start at the specified reading of 24 and increase bit by bit if you feel the need. Do note to take the reading when the tyres are cold.

I agree, 24 looks bit low nowadays. And 13" will suit the Zen real nice. 165/65 R13 got the same outer diameter as 145/80 R12.

[saket77]

Dear Headbanger,

I hope you are not relying too much on the road side tyre wallas and their gauges for measuring the air pressure. Their meters show incorrect readings 90% of times. In case you don't have a personal gauge, get one and check air pressure in the morning when the car has been stationery at night.

Originally Posted by deetjohn

No harm in sticking to the manufacturer specified reading when changing to tubeless tyres. I think the best way forward is to start at the specified reading of 24 and increase bit by bit if you feel the need. Do note to take the reading when the tyres are cold.

I started with this theory only. I felt 24 PSI a bit too low and the performance & FE suffered. The steering felt heavy and as my car does not have a power steering (& I love the feedback!), it made matters worse. The ground clearance also went worse. In fact, MASS only recommended me to run 28 PSI and most of the above complaints were resolved. I think I have been running on 28-30 PSI for about at least 7-8 years now.

Originally Posted by deetjohn

I agree, 24 looks bit low nowadays. And 13" will suit the Zen real nice. 165/65 R13 got the same outer diameter as 145/80 R12.

+1 to above. The old Zen (pre-mpfi ones) actually came factory fitted with these specs. They handled a lot better but the ride quality suffered. Also many had complains of bent rims which provoked the company to shift to broader side profiles but without changing the overall circumference of the tires. In turn the ride quality became much better and the problems of damaged rims was addressed, but a bit of handling was compromised. Also, this enabled the company to mass procure & produce same tires & rims respectively for many vehicles across its range at that time including the 800, Alto, Zen and probably Wagon-R too (not sure about wagon-R though).
However, I think that despite the same size of rims across the above cars, some were not interchangeable because of the different hole pattern.

Regards,
Saket

[JoseVijay]

Reving an old thread.

What would be the correct tyre pressure for Ford Fusion? The car is running on MRF Zvts 195/60/R15. Help .

[sourav9385]

Originally Posted by JoseVijay

Reving an old thread.

What would be the correct tyre pressure for Ford Fusion? The car is running on MRF Zvts 195/60/R15. Help .

Tyre pressures are normally 30-32 psi in passenger cars, unless specified otherwise by the manufacturer.

For your Fusion, I'd suggest around 32 psi. Not too much, not too less.

Also, please check the front passenger/driver side door. Usually the recommended tyre pressures are mentioned there on a plaque.

[JoseVijay]

Originally Posted by sourav9385

Tyre pressures are normally 30-32 psi in passenger cars, unless specified otherwise by the manufacturer.

For your Fusion, I'd suggest around 32 psi. Not too much, not too less.

Also, please check the front passenger/driver side door. Usually the recommended tyre pressures are mentioned there on a plaque.

It is a pre-owned car. The previous owner might have taken off the sticker that mentiones the recommended tyre pressure. I will stick to 32 psi.

[SyncNest]

Hi All,

for my swift vxi, with the regular tyres it came with, this happened recently - I got a flat tire fixed in a small local garage. this was between hyd-mahabubnagar. since this was a small place the guy was only equipped with the hand held pressure gauge and I told him to fill all tryes with 35.

for days I didn't check anything. but my dad pointed out that the car was not smooth so we got it checked in a petrol bunk in dilsukhnagar where we stay. the guy looks at me and he says why 50. all the tyres had 50 and he deflated them.

question: I was only driving in the city in the interim period (when I did not know all tyres ahd 50 psi)
would it have been risky if I had gone on a long drive?

[Chetan_Rao]

Originally Posted by SyncNest

......
would it have been risky if I had gone on a long drive?

Possibly. Tire pressure increases with temperature (also why it's recommended to check/inflate on cold tires), and the number you mention is dangerously close to the max rated pressure of small passenger car tires (e.g. the 175/70 R13 Michelin XM2s on my car are rated for max 51 PSI). Long drives mean sustained loading and friction over longer periods, so make doubly sure of the readings before such outings. Not to mention over-inflated tires will unnecessarily strain the suspension and other related components.

Best if you buy a pressure gauge of your own (reliable digital ones are available these days at most reputed tire dealers or online). Don't trust the calibration of road-side gauges, it could prove harmful (even fatal) in certain situations if not spotted/corrected ASAP.

[a4anurag]

Originally Posted by SyncNest

question: I was only driving in the city in the interim period (when I did not know all tyres ahd 50 psi)
would it have been risky if I had gone on a long drive?

More the pressure, more the temperature the tyre generates during motion. Now with more temperature, the air in it gets pressurized so any pot-hole/stones will lead to a blow-out.

With 50psi all round, there would be higher abuse to the suspension components + it is a rattle inducer!

[humyum]

Originally Posted by a4anurag

More the pressure, more the temperature the tyre generates during motion. Now with more temperature, the air in it gets pressurized so any pot-hole/stones will lead to a blow-out.

With 50psi all round, there would be higher abuse to the suspension components + it is a rattle inducer!

Hey, not always true for all pressures. Say if you fill 36 PSI in the front and 34 PSI in your Swift for 185-70-R14, it will heat the tyre up less than if the pressure was 31PSI in the front and 29 PSI rear as Maruti has specified. This is because the contact patch is less.

Of course the situation remains the same with the 50 PSI too, but here the difference is, you are closer to the maximum inflation pressure of the tyre and hence like you rightly said a hit at a pothole or a stone will lead to a burst.

Underinflation causes way more tyre bursts than over inflation ever does, of course if you overinflate by insensible margins then that will burst too.

[saket77]

Originally Posted by SyncNest

question: I was only driving in the city in the interim period (when I did not know all tyres ahd 50 psi) would it have been risky if I had gone on a long drive?

Over inflation of tires, apart from what Chetan, Rohan & Anurag suggest, also lead to poor road grip. Also, the wheels will lock up easily (in a non-ABS car) in case of hard braking. The tire itself will also take a beating and wear off at the center area.

Plus, as other members suggest, your suspension will take a beating and the ride will be very bouncy. I suggest you to get a good tire pressure gauge so that you can check 'cold' tire pressure, preferably in morning (before the car has been driven around).

Regards.

[alpha1]

Originally Posted by humyum

Underinflation causes way more tyre bursts than over inflation ever does, of course if you overinflate by insensible margins then that will burst too.

Actually, if we see a tyre is under-inflated, there fore it generates more heat.
Because of heat the air temperature inside the tyre also rises.
Rising air temperature leads to higher pressure.

Thus we should be at the same situation as what we would be if we had filled higher pressure air at the beginning!

How will this lead to over heating or tyre burst?