Tyre Comfort Calculator

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stallturn
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Post by stallturn »

A couple of years ago, I found a 'Tyre Comfort Calculator' on the internet.
Inputting the tyre parameters, eg 245/35 R19, this calculator gave a notional 'Comfort Index' - the lower the number, the more uncomfortable was the ride given by the tyre. Obviously the lower the profile, ie sidewall, the more 'uncomfortable' was the tyre and the lower the index. Tyres could thus be compared for comfort.
For the life of me I cannot find this calculator again.
Does anyone have a link to anything similar?

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Paul
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Post by Paul »

http://www.stealthmotorsport.co.uk/wheeldiam.html

This returns a “comfort” value....
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Orangebulldog
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Post by Orangebulldog »

265/45 R20 means the tire height in millimeter is 45 percent of the tire width in this case 265 millimeters. This gives 11,925 centimeters tire height. The actual height you can see is less, because part of the tire is inside your rim.

My experience with different SUVs and brands has thought me sticking to 12 cm or above is just fine for comfort. Below you start to feel the road imperfections a bit more.
DJMCUK
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Post by DJMCUK »

I've reawoken this thread as I'm trying to work out where to set the pressures om my 2019 Macan S, 20" wheels.

From when we bought it Oct'23 the warm TPMS readings were around 2.1 front; 2.3 rear.
The door sticker says 2.3 front; 2.5 rear at 70 degrees F.
As a starting point I've inflated them to 2.3/2.5 today (at around 37 degrees F).
When I next drove the car, TPMS showed the same 2.3/2.5 cold which, when fully warmed after 30 mins drive, increased to 2.5 front; 2.7 rear.
The car felt as thought the tyres were over inflated.

I'm conscious there's also a "comfort" pressure setting, perhaps 0.2 BAR under the normal pressures.

So, what should I set them to when cold (at 37 degrees F) which will presumably rise by 0.2 BAR when fully warm, same as they rose today.
NB. I have no idea what the fully warmed air temp inside the tyre is. Pretty sure it's more that 70F.

Thanks for any help.
AllanG
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Post by AllanG »

I just set my pressures at whatever it says on the door sticker, but not comfort setting, and I don’t worry about what the air temp is, as it’s very rare we get temps of 20C in the UK 😁
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Jon A
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Post by Jon A »

AllanG wrote: Mon Jan 08, 2024 5:49 pm I just set my pressures at whatever it says on the door sticker, but not comfort setting, and I don’t worry about what the air temp is, as it’s very rare we get temps of 20C in the UK 😁
Same here, too much in life to worry about without adding this to the list. Whatever it says on the door sticker, inflate, drive off - end of. 👍
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Bluesnose1812
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Post by Bluesnose1812 »

DJMCUK wrote: Mon Jan 08, 2024 5:36 pm I've reawoken this thread as I'm trying to work out where to set the pressures om my 2019 Macan S, 20" wheels.

From when we bought it Oct'23 the warm TPMS readings were around 2.1 front; 2.3 rear.
The door sticker says 2.3 front; 2.5 rear at 70 degrees F.
As a starting point I've inflated them to 2.3/2.5 today (at around 37 degrees F).
When I next drove the car, TPMS showed the same 2.3/2.5 cold which, when fully warmed after 30 mins drive, increased to 2.5 front; 2.7 rear.
The car felt as thought the tyres were over inflated.

I'm conscious there's also a "comfort" pressure setting, perhaps 0.2 BAR under the normal pressures.

So, what should I set them to when cold (at 37 degrees F) which will presumably rise by 0.2 BAR when fully warm, same as they rose today.
NB. I have no idea what the fully warmed air temp inside the tyre is. Pretty sure it's more that 70F.

Thanks for any help.
Just look at the my porsche app tyre info. It shows the +/- to normal regardless of the temperature. Mine is showing - 1psi all round. So all I need to do is add a little bit. In the current climate the fronts start at 30 on the PCM. But I don't worry too much about it so long at I'm within 5% of 33/36. On a run they vary 2-3psi depending on how twisty the road is or if I am scrubbing off speed to save the brakes :D
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SAC1
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Post by SAC1 »

Start off by leaving the pressures as now. Then go for a reasonably long drive- at least 15 minutes at above 50 mph. Bring the car to a halt. On the thumb wheel, scroll to tyre pressures (TPM). Press the thumb wheel and it will show how much air to add / remove from each tyre.

A fuller description can be found on the Porsche Good to Know App plus a video showing the checking sequence.
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SAC1
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Post by SAC1 »

Screenshot from PGTK app...

Screenshot_20240108_175533_Porsche Good to know.jpg

Steve

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DJMCUK
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Post by DJMCUK »

Thanks Steve. Is the Good to Know App already in the car's PCM unit? If so, how is it accessed?
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