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Old 2nd July 2017, 15:42   #16
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

Honda City recommends 32 psi front and 35 psi back when fully loaded. I use them as guides only and on long journeys with full load I go for 34 psi all round and for city runs with less load for 32 psi. Initially, I felt the ride in the Honda to be a little 'stiff' as compared to my old gen Elantra, with time I have gotten used to it.
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Old 2nd July 2017, 15:49   #17
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

Maruti recommends a 31F and 29F behind for 185/70/R14 for the Swift Diesel, since I Michelin's in the said size shod on my car, using this tyre pressure makes the Swift feel like Hulk is pressing it from top, steering is heavy, acceleration is slow and steering response is lethargic. I have been filling 36F and 34F rear since years now and the car just feels fantastic. Cornering is super sharp, acceleration is brisk, when on roads like the Kasara Ghats or the Ghats before Lonavala, you would never want them to end is how the road holding is, its perfect.
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Old 2nd July 2017, 22:14   #18
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

Quote:
Originally Posted by humyum View Post
since I Michelin's in the said size shod on my car, using this tyre pressure makes the Swift feel like Hulk is pressing it from top, steering is heavy, acceleration is slow and steering response is lethargic. I have been filling 36F and 34F rear since years now and the car just feels fantastic. Cornering is super sharp, acceleration is brisk
Manufacturer's spec is derived from a different set of tires which are harder (in most cases) and when using tires with softer compound (like Michelin) it is always better to go with a little higher pressure than the OE spec.
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Old 2nd July 2017, 23:26   #19
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

This is the recommended levels for Maruti Ignis:
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Wonder why the relatively lighter petrol needs 4PSI more at the front. I'm not sure if the owner's manual has more detailed info with respect to the load.

For Baleno, Maruti recommends 29PSI all around for both tyre sizes.

Can someone shed some light on why there's such a wide gap for Ignis, esp for the petrol

Last edited by BigBrad : 2nd July 2017 at 23:29.
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Old 2nd July 2017, 23:26   #20
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

Requirements: 1) Infra red temperature measuring gun or a 100 degree Celsius mercury thermometer, 2)a lot of patience 3)Nearly even road temperature for the period of the test which will be about three weeks at the bare minimum.

Travel each day on the same route at roughly the same road speed and car and passenger weight. Road temperature should roughly be the same.

Measure temps at end of journey at a certain tire pressure starting from manufacturer suggested pressure. Keep increasing by a point each day and log the readings at the end of the journey.

There will be a certain pressure after which the temp readings will remain more or less the same. That is your tire pressure most suited for your car and driving style. Each tire compound will have different thresholds. Loads in the car too will change the temps and so does road temps and how hard your foot is on the controls including hands on the steering.

Use the tire pressure that is the threshold for negligible change in temperature.

Example if after tire pressure 35psi in the front further increase in pressures did not change the temp readings at end of journey then 35 is the optimum pressure for that particular tire and car.

As an example I took three weeks to get at the right pressures for the Michelin 3st tires for the Cruze. It is 35 in the front and 33 in the rear. For spirited driving it is 36 in the front and 33 at the rear. This is with single passenger. With two adults inthe front and four adults in the rear( tight squeeze) and luggage on a long journey 37 is the figure for the rear. Though that figure is not accurate since I should have done this test over at least 10 days to get accurate readings. I am not going to get that load consecutively over 10 days but 37 was the pressure needed to equal the temperatures in the front tires. The front tires needed 37 to keep temps in check.

You need a heck of a lot of patience and I do. 4 years ago my daily office trip was 53 km one way and coming to 106 total.

Last edited by drpullockaran : 2nd July 2017 at 23:29.
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Old 11th July 2017, 16:49   #21
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

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Originally Posted by greenhorn View Post
Its running around 30psi in the back and 33 psi in the front for 175/65 R14 (higher variant)
Fyi, the tyre dimension and recommended pressure is identical with the eCS CR4 variant
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Old 29th November 2017, 15:00   #22
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

First and foremost function of the tyre is to carry the load. Load carried by the tyres is the work done by the tyre and that is pressure volume work done. W.D.=P X V.
Why in recent years the pressure has increased, as the suspension and vehicle geometry improved, vehicle manufacturers started to increase rim size, as the rim size goes up the space available for air reduces.
As the W.D is directly proportional to volume and pressure, as the volume would go down the pressure has to be increased.
This can be very well understood by following example : Tractor tyre uses 20 psi whereas road bicycle uses 110 psi.
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Old 23rd December 2017, 12:56   #23
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

Maruti recommended the following tyre pressures for Ritz:
165/80R14 - F36 R33
185/70R14 - F32 R29

Any logic behind different pressures for different tyre widths?
I have VDi that came with skinny 165s, changed immediately to 185s but kept same tyre pressures as suggested in B puller, ride was always harsh. After some years found that top model ZDi that came with 185s from factory had different pressure sticker. Kind of wierd.
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Old 23rd December 2017, 15:28   #24
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

That is a very good question: with many people upsizing the OE tyres, I doubt anyone has a good handle on what tyre pressures to run on these, as compared to what is said in the manual. For instance, what if the version of the Ritz that came with the 185 was to be up sized to 195; what then?
Also, does the 165/80 compared to the 185/70 not have the same volume of air in them via increasing one number but reducing the other? It may not cancel out fully, but the two changes are definitely doing so to some extent.

Last edited by Sawyer : 23rd December 2017 at 15:31.
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Old 31st December 2017, 18:45   #25
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

Is it safe to run higher pressures on my indica rims running tubeless tires? I had borrowed a friends wagon r, and was running 32 psi, and was advised by another bhpian with the same car to raise the psi to 36. There was a dramatic improvement in ride quality - very surprising as I was expecting it to become harsher

I have always gotten the under inflated type of wear (edges only) when running the recommended 28/24, so am currently running 32 in my indica. Can I bump it up to 34/36? Is it safe? Any other impact?

Last edited by greenhorn : 31st December 2017 at 18:48.
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Old 20th April 2019, 18:13   #26
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Default Re: Rationale behind the 'recommended' Tyre Pressure?

Quote:
Originally Posted by Durango Dude View Post
Honda City recommends 32 psi front and 35 psi back when fully loaded. I use them as guides only and on long journeys with full load I go for 34 psi all round and for city runs with less load for 32 psi. Initially, I felt the ride in the Honda to be a little 'stiff' as compared to my old gen Elantra, with time I have gotten used to it.
Is it same recommendation for 175 as well as 185 tyre size? I have City ZX with 185 sized tyres. Got 33 psi done in all tyres today.

Today I travelled 50 km and then parked car somewhere for an hour. Then went to nearby petrol pump and got air pressure checked in all tires. It ranged between 50-65 psi. I wondered how it can be. Especially after car was parked under shade for an hour post travel.

Now the guy reduced pressure to 33 psi in all tyres. I will get it checked in morning again so that tyres get ample time to cool down. Will see if pressure is still 33 psi or it goes down.
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