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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-6.html)

The best way to verify this is to drive 10-20 km without applying brakes and check the front and rear tyres.

I'd say make it a straight drive without turns.
Even then, purely on gut feel, I'd imagine the front tyres would be a wee bit warmer than the rear tyres in a FWD car. Possibly some heat from the differential gears will get conducted to the rims/tyres. ?

This is what I said! At the end of the day, the engine heat will make its way to the tires, by conduction or radiation! :)

Nope/again negligible, drive shaft conducts very minimal heat to the wheels. Have never seen drive shaft becoming Super HOT unless there is an issue with the tranny. Partly due to the fact that tranny itself is filled with oil.

See in a front wheel car, the steering, braking and the power delivery all happens through the front tires. More work done = more heat. Have read that in panic braking, the brake force can go upto 85-90% to front wheels, so weight transfer (steering/braking) and power transfer will tend to heat them up quicker.

Side wall flex (low air pressure situation) also heats up the tires. I generally do a quick check on air pressure by touching them, while on long drives. If they (tires and NOT rim) are heating up, air pressure is low. Same holds true for rear tires also.

To do a check if engine heat actually contributes to tire heating up, check on the inner side wall will be a better idea. Somebody with a digital thermo meter can maybe measure and post ;)

Thanks, Jaggu. I too felt that the difference could only be a wee bit, as I said before.
If the temp difference is large, it can only be through heating caused by the brakes, or low air pressure, as you have mentioned.

I was on 500+ kms highway trip last week end & stopped at a tea shop located next to a puncture shop. A guy in his esteem wanted the puncture wala to test the pressure of the air in all the tyres. He had one hand held gauge to check the pressure & it was only 20 psi in firs tyre.

Instantly he questioned whether the pressure was set in petrol bunk digital gauge & continued that it was always useless. Pumped in extra air till his gauge showed in 33 psi. Esteem guy promptly filled all his wheels with 33 psi.

I wanted him to check the pressure in my car tyre & it Showed 18 psi. I was pretty much sure it wont be 20 psi as there were no visual symptoms & only just before 2 hrs, I filled 28 psi at a bunk.

After around 30 minutes, when I was traveling at around 100 kmph, this esteem flew past me at 130 kmph (approximately)

Iam sure his tyres were with additional 15 PSI minimum & traveling at those high speeds never had him at any trouble. Infact I met him after 4 hrs at a restaurant.

Now will this 2-3 psi really make any difference?

i have 185/70 R13. i normally fill all 4 with 30psi. is it correct ?
is there a tyre-pressure calculator just like EMI calculator ?? :)

Here's my post on another thread that I provided to an i10 owner. This must help:

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If you're asking for the tire pressure because you upgraded your tires to wider ones, then sharing my experience might help. My Verna CRDI came with Bridgestone B250 185R14 stock tires. I did the recommended upgrade, to Bridgestone Turanza 195R14 sport. After delivery, I emailed Bridgestone India as well as Hyundai asking them what pressure I must maintain given that I had done this upgrade. Hyundai never replied, but Bridgestone sent me a prompt reply asking me to maintain the same pressure as recommended in the manual.

I did some more reading on this topic at that time. This is what I understood:

Like all parameters in an automobile, the recommended tire pressure is also a compromise formula, an optimized value. If you have high pressure, you will face lesser rolling resistance and consequently that will get you more fuel mileage. However, your ride will not be smooth. Too much pressure can make your tire a stone and can even damage the car due to excessive vibrations. On the other hand, a lower tire pressure will give you a smoother ride, but will increase rolling resistance, thus reducing your fuel mileage. Manufacturers give you a middle value as recommended pressure so that the ride is smooth as well as the mileage is good. Not to mention that too low pressure can affect handling as well as damage the tires.

Also, in general, the wider the tire, more your friction, since friction is proportional to the surface area of contact. So by just upgrading your tires to wider ones, you get better handling, but at the cost of some drop is fuel mileage (not significant if you upgrade within the recommended 10 to 20mm range).

Therefore in your case I guess using the same pressure as what Hyundai has suggested should help.

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Warm regards,
Sandeep Menon

Swift VDi with Bridgestone Turanza ER 60 185/70/R14. I use 33psi in the front and 31psi in the rear. Ride is good. Mileage is between 19-20 kmpl with AC on.

I bought this digital Michelin tyre pressure gauge from ebay.co.uk in July 2010. Cost me around 26 pounds. Works fine so far.

I keep my Dzire VDI at 33 front and 29 rear as recommended by the manufacturer for 185/70/14. I generally drive with only me and wife in the car. I get 18 kmpl in city and 23+ on highway sedate driving.

What i notice is the rear tyre is not in complete contact with the road surface. About 1 cm of the tread towards both the shoulders has a different color than the rest. Front tyre the whole tread area has the same color. Maybe I should try with 26/27 psi and check

Just a question for all members.

When do you check your tyre pressure.

1) As soon as you leave home/ office after car has been stationary for a couple of hours at least.
2) At the petrol bunk after driving around for some time?
3) At a tyre shop more than 2 kms from home.

Forgot to add. There is a reason behind asking this.

How many of these pressure gauges are calibrated regularly?
And how often?

I don't believe most of the digital or mechanical ones are ever calibrated after their purchase. Which makes their readings almost worthless.

The best way to check tyre pressure is to check them when they are cold.

I had upsized my Baleno RS tyres from 195/55 R16 to 205/55 R16. I have done the same on all my cars and in general I have always stuck to manufacturers tyre pressures without much issues.

However with the RS I noticed that the overall behavior of the car improved (better handling, felt lighter on it's feet) when the tyre pressure was higher. I first realised this when my alignment center inflated my tyres to a higher 32 PSI compared to the standard 29 PSI. On my Polo that had been upsized from 185 to 205 a higher PSI always messed up the ride. However in the Baleno I noticed that it had a positive impact on the composure of the car.

I was curious about this and stumbled up this link and through it this paper from TOYO tyres. The paper based the pressure to be maintained on the load that needs to be supported. It has a chart that lists tyres sizes and the loads that the tyres can support at each pressure.

Th explanation kind of made sense to me.

Drive on,
Shibu.