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-   -   Filling the right 'Pound per square inch (PSI)' (https://www.team-bhp.com/forum/technical-stuff/52058-filling-right-pound-per-square-inch-psi-5.html)

Is there any proper way to calculate PSI for non OEM tires and rims? Case being my car I keep it at 32 the gentleman I bought it from recommends it to keep the rims from getting damaged.

Hi,
I wanted to know what is the preferred tyre pressure for the 195/60R15 Bridgestone Potenza Tyre pressure for City and Highway Drive.
I tried keepng thr tyre pressure at 33 psi but I am seeing uneven wear on the tyre ..there is a difference of about 1 mm between the threads ( along the same line). So before the damage is done I would like to keep the tyre pressures at normal level.
Note : Most of my driving is in the city.

Regards
Dhananjay

Note from Team-BHP Support : Thread MERGED. Please use the search feature before creating a new thread on a topic that might already exist. Please continue your discussion in an existing thread. This will keep all the relevant information in one place and make it easier for readers in the future.

I have provided some inputs in this area that might be helpful. Please see my post at http://www.team-bhp.com/forum/test-d...automatic.html.

Regards,
Sandeep Menon

the recommended psi for 175/185/195 60 R15 is 30.
with this pressure the tire wear will be even and not focused on the center in case of 33/34 psi.

with the tire of 60hight rubber, the rims/ alloys can be dented in highway sudden potholes, but withing the city 30psi is sufficient to save the rims and also the tires.

um

I use an Accutire digital pressure gauge for my cars. Bought it in the US (From Costco) and brought it with me to India. Very accurate. Now I know which petrol pumps in my area have an accurate air pump. For some pumps where I regularly visit but whose pumps have wrongly calibrated gauges, I know the zero error. For example there is one enroute home from office, where I ask for 37 with a warm tire, and I know I'm getting 33 cold. I double check it the next day at cool air temperatures using my digital gauge, and confirm that it is indeed 33.

i never knew there would be such a huge difference in the cold and warm tire psi.

So when the car companies recommend 32 front and 30 rear, do they mean cold or warm psi ?

Anyways while driving and what really matters - tires will be warm, so the psi should be around 32 front and 30 rear (for Santro).

By the time one drives to a pump, the tires would be warm and get the correct driving psi required. after parking overnight the tries may look low.

UM

I think I did not word that accurately. What I meant was that, the pump has an error of about 3PSI, and the temperature perhaps causes another 0.5 or 1 PSI difference.

Speaking about cold and warm air pressures, all manufacturer recommended tire pressures are cold. Hyundai defines that as 1.6km or 1 mile driving distance. So the manual says that you must check pressure when you have driven less than 1.6km.

Also, after a 10 to 20 km drive in the city (not long drives on the highways), feel your front and rear tires with the back of your hands. You will notice that the front tires are warmer due to the engine heat, and the rear tires are cooler. This too will make a difference if you check air after driving such distances.

If you have your own gauge, then top up a little excess air at the pump and correct the pressure during early mornings before driving. This is what I do. In case you don't have your own gauge, then drive less than 1.6KM to a pump, and then check air pressure. Of course, this is not going to make a huge difference, and matters only if you are a perfectionist. (I certainly have that weakness).

Also, more significant than the temperature is to make sure your petrol pump digital gauge is accurate. Many digital gauges at our petrol pumps are wrongly calibrated. I have found differences up to 5 PSI between pumps.

Sorry, I think you've got it wrong.
It's not because of engine heat but because the front wheels do MOST of the braking, discs in modern cars! :)

Are you sure? My Verna has all 4 discs (since it has ABS) and why do you think front brakes generate so much more heat than the rear so much so that one can feel it on the tires? Because the weight of the car is thrown onto the front brakes? I find that difficult to believe. Cannot think of any other reason than engine heat.

Weight transfer to front will put more stress on front tires & brakes, hence the front disc's are bigger compared to rear's. Engine heat will have minimal effect on tire temp since the car is moving and cool air keeps the hear away, also the firewall/engine bay does a pretty good job at insulation ;)

See! You knew it all along! This has to do with the laws of Physics, not so much with ABS and EBD! The front brakes ALWAYS have to do more work. Assuming, of course that you travel AHEAD most of the time, LOL!

^^^Ditto in my Esteem. The front tyres are always hotter. And I'm pretty sure this isn't just because of the front discs. The rims feel even hotter... and I'm sure they transfer heat to the tyres.

This heating happens even on rides where the brakes are seldom used!

Interesting...but tell me...is the difference so much that during the short durations of braking, the temperature difference is so much that you feel the heat in the front tires and do not feel it in the rear tires? Sure that's not engine heat? Remember, I'm asking about 10 to 20 kms in the city, when air flow is not great under the car.

Yup take a 2 wheeler (engine is far away from brakes) and replicate, if you want in neutral, front will become hot compared to warm at rear.

I would give some 5 to 10 % more for engine bay heating the front brakes in a car, my own guess estimate no scientific instrument involved in this :D

EDIT: 5% is max dont think even 10% is possible

Pointers to any credible web site will of great help to understand. In a quick Googling attempt, I could not find anything.