Tyre pressures

[NewMustangDE]

Thought i post a question here.

I have done a very extensive search and can find nothing relating to tyre pressures using 20" wheels.

While i have had zero problems with my car, i find the ride stone hard. It was like that even when car came with the standard 19" wheels and is now the same on my 20" wheels.

I am currently running 2.5 PSI but are condering lowering it to 2.2 PSI.

Does anyone recommend a setting or have played around with the pressures?

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[papinist]

Tire pressure is a question I have too.
Mine was set to 3.0 from the dealer, or it arrived this way and they did not check.
I could remember that manual says 2.2 so I need to lower it!

 

[Ericc B]

Pretty common value for this type of tires is 2.5 front and 2.2 rear.

 

[NewMustangDE]

Actually, mine is set to 2.2 all round but this rises to an equal 2.5-2.7 after a drive.

 

[Norm Peterson]

I assume you guys mean pressure in 'bar' or kg/cm².

What information does the sticker for tire pressures give?

If you have changed tire sizes since new, the pressure you need to inflate the new tires to may differ slightly. There is a way to determine this based on the tire load vs inflation tables, though I'd have to know the before and after tire sizes, load index numbers, and whether the tires are standard load or eXtra load.


Norm

 

[NewMustangDE]

I assume you guys mean pressure in 'bar' or kg/cm².

What information does the sticker for tire pressures give?

If you have changed tire sizes since new, the pressure you need to inflate the new tires to may differ slightly. There is a way to determine this based on the tire load vs inflation tables, though I'd have to know the before and after tire sizes, load index numbers, and whether the tires are standard load or eXtra load.


Norm

Thanks Norm!

Here's some details....

The EU cars come with the following specs:
(F) 19 x 9.0 255/40/19 ZR - 101Y Pirelli P Zero
(R) 19 x 9.5 275/40/19 ZR - 96Y Pirelli P Zero




My new HRE FF01 20" wheels & tyre specs:




[FONT=&quot](F) 20 x 9.5 [/FONT][FONT=&quot]265/35/20 ZR ET35 - 104Y Michelin PSS[/FONT]
[FONT=&quot](R) 20 x 10.5 285/35/20 ZR ET45 - 99Y Michelin PSS[/FONT]

[FONT=&quot][/FONT]
[FONT=&quot]Currently they are all set at 2.2 BAR (31.9 PSI) when cold. When hot, they are as high as 2.7 BAR (39.2 PSI).
[/FONT]

[FONT=&quot][/FONT]
[FONT=&quot]As far as XL tyres, I don't think they are. The originals were not.
[/FONT]

[FONT=&quot][/FONT]
[FONT=&quot]Hope that helps.
[/FONT]

 

[Norm Peterson]

I think you've got the load index numbers switched front to back and vice-versa - Tire Rack gives 96 (SL) for the 255's and 101 (SL) for the 275's, which makes logical sense that the bigger tire has higher load capacity.

The Michelin PSS tires are a little trickier. The 285/35 is an XL tire, as is the 99Y 265/35 tire . . . but there is also a 265/35 in 95Y that's SL (that you wouldn't want if the pressure requirement went much higher than it did).

For 2.2 bar in the OE sizes (I'm going to have to work in psi and convert back as my tables and spreadsheet work in psi), that's 32 psi. Do not try to make comparisons based on the load index numbers alone, because the SL and XL tables do not line up that way.

255/40-19 96SL @ 32 psi => 265/35*20 95SL @ 33 psi or about 2.3 bar
275/40-19 101SL @ 32 psi => 285/35-20 104XL also @ 33 psi (2.3 bar)

Basically you'll be adding 1 psi or about 0.1 bar to whatever the inflation pressure sticker says for the OE 19's.

Norm

 

[NewMustangDE]

Thank you very much!

I'll give it a go.

Yes, i had put the load figures the other way around.....

 

[2015 Silver GT]

"tire" not "tyre".

 

[NewMustangDE]

"tire" not "tyre".

British English is Tyre.....its what 15 years in the UK does to you ;)

 

[papinist]

"tire" not "tyre".

British English is Tyre.....its what 15 years in the UK does to you ;)

since I know that US and UK english have these differences, I used specifically "tire"
I prefer the american english because it's more 'informal'.

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