Focus Fanatics Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
90 Posts
Discussion Starter · #1 ·
Tire Pressure - 16"oem-2012 foucus Conti procontacts 215-55-16
The sidewall indicates a max inflation of 51psig.
The doorplate says 34 psig.
My other car a honda civic hybrid I run the tires at 40 psig, it handles better,
and of course the 48mpg isn't bad :)

Is anyone running their focus Conti's at 40 psig ?

I'll bet that the same results will occur EXCET the 48mpg part :)
 

·
Registered
Joined
·
4,475 Posts
I have the 17" wheels on my 2012.
I am running 43 front, and 37 rear.
The rear tires are less heavily loaded and the ride is a lot better with them at 37 or less.
 

·
Registered
Joined
·
8,023 Posts
This is the best analogy I can give you with regards to tire pressure. A tire is like a basketball. The more you fill them the more they will bounce (if you've every played basketball you know an overfilled ball bounces more, and as such, is far more difficult to control than a properly inflated one). The same principal holds true for a tire. That bouncing is, however, controlled by the shocks and to a degree the springs. On cars that come with the new eco tires (specifically designed for higher pressures and less rolling resistance) will also have shock valving that has been recalibrated to better control them. Unless you have a heavy duty shock or preferably one that is rebound adjustable, significant increases in tire PSI can take a toll on stock suspension components.

The "car" manufacturers recommended PSI is based on a lot of testing. It is a compromise based on car weight, maximum load, desirable handing traits (performance car vs family sedan for example), ride quality, economy, safety, etc. The "tire" manufacturers rating is simply the maximum cold temp PSI that will maintain the maximum load rating of the tire. It does not address any of the "car" manufactures qualitative requirements. The engineers from both know a thing or two more about this process than we do and neither of their recommendations should be taken lightly. The car manufacturers numbers while not necessarily cast in stone, can be adjusted in small incremental changes to "refine" one or more of the intended design perimeters previously mentioned.
 

·
Registered
Joined
·
5 Posts
I dont believe that tire-pressure advice by the car manufacturer is based upon a lot of testing. It is all calculated with a formula in wich weigth on tire , maximum load and reference pressure of tire ( for normal car tires 36 psi in Europe) is filled in.
Only other factor is camber-angle, but seldomly needed, and the maximum speed of the car.
I once got hold of thay European formula, and went running with it.
Later discovered an article about other formula from an American, wich comes to saver answers, with conclusion that the old European one is save for normal car tires.

https://skydrive.live.com/?cid=a526e0eee092e6dc#cid=A526E0EEE092E6DC&id=A526E0EEE092E6DC!235
This links leads to a map on my public map of skydrive/hotmail, with spreadsheets and examples for re-calculating tire-pressure advice for other then original tires , but also for checking the original, and see if you can go lower savely for sertain conditions.
To use a spreadsheet , click on the I in a circle at the end of the line, the in the right bar a Download. After downloading open in Excell or compatible, and not in the browser.

After 2000 the advices ar verry high , in the 90s they calculated good, is my opinion. So old advice of the car is better then the higher mentioned here.
 

·
Registered
Joined
·
90 Posts
Discussion Starter · #5 ·
Update

I put 40 psig front & rear..
Handles better, and imo rides better..

imo I found the magic combo

I'll give it some time to see if more fuel effcient
 
1 - 5 of 5 Posts
Top