Radically different tire pressure. Euro vs NA

[Doozer]

So I just picked up my Fiesta ST this week. The dealer delivered the car with 34 psi at all four corners. Door sticker says 39/36 is normal. I've done some searching online and seen UK door stickers at 31/26. Why such a difference for the same car? I think the 39/36 would be fine for auto cross, but seems harsh for day to day...
Tires are supposedly common in Europe and North America, so I can't understand an 8-10 psi difference.

 

[rodmoe]

Don't the Euro cars use the Metric pound ?? J/K I couldn't resist Is it the same though I never look at air/tire pressure in the UK so I am just being funny . Good to know though . for MPG bump your tires up a few lbs cold as they will air up more as the get warm from driving.. but your ride may suffer and get harsher with more air in the tires

 

[Doozer]

I'll probably try 35/32 for a few days and see how that goes. I've had a 2006 Mini Cooper S (run-flats are the devil), 2011 VW GTI, and 2012 Fiat Abarth previously, so I'm no stranger to stiffer rides. But the road conditions around here are crap at the moment.

 

[scottiemac]

After the first little while having my fillings rattled I lowered both front and back by 5 psi. I may knock them down another 2 and give them a try. Makes a small difference in ride quality. Personally can't see why they want them so high other than the fact that the Murkins are so litigious and there have been so many law suites about under inflated tires exploding.

 

[Perry]

On a related point, I find that if I run the recommended pressures (39/36 or so), and then go about on the highway for a while, I get a TPMS fault warning, I presume from an over-pressure situation of some sort. I've got a good gauge, and on checking the pressures, they'll be up a bit, but not dangerously so. The warning goes away after the car sits for several hours. Anyone else running into this? [BTW, for autocross I'm running 42/36.)

 

[Doozer]

My Abarth was delivered with 44 at all four corners. I yelled at my dealer since I paid some ridiculous prep fee and all they said was "well the tpms didn't show any warnings". Sigh. The ride was so squirrelly I thought the back end was going to bounce off the road. 32 is the recommended rear pressure, FYI. Needless to say, the car changed radically after adjusting properly.

 

[lessard.dcj]

I just run what the door says. The ride quality is what i would expect.

 

[Savant]

Aus spec euro model. FYI I run 40psi all corners. Placard does read 39 if driving at high speed. I drive 80-90% freeway. Rougher ride on slow roads and city roads which if they were the majority would drop them to 35-6 psi.

 

[NorthernProducer]

Tire pressure "always" seems to be an issue...too high, too low, TPMS false reporting and dealers that don't correct tire pressures on prep. Tires are over-inflated for transport to prevent tire flexing and rim damage when being "tied down" to the transporter. Dealer prep tech's are suppose to adjust the pressures down to the recommended levels before delivery to a customer, but I have often found they "forget" which results in a rough ride, poor handling and at times, TPMS warnings. My FiST was delivered with 44 psi in each tire...the same as used for transport. I ALWAYS check tire pressure on delivery of new vehicles and find them overinflated most of the time (all makes...not just Ford products). My advice...for normal driving, use an accurate tire pressure gauge and run the factory recommended pressures. High speed and competition events will require a different recommendation and I have found that the high performance engineers with the major tire manufacturers and even some at the auto manufacturers will help you find the best pressures for your event.

As for the differences in pressure recommendations between Europe and North America, I suggest that is a result of differences between the DOT ratings and EU regulators ratings. To obtain certain ratings, tires must be tested and run at particular pressures which can result in an auto manufacturer giving different recommendations...even though the tires may look and even have the same model names...(source: a friend who is a high performance engineer at GM).

I hope this helps...

 

[XuperXero]

38/32 here. Front definitely needs higher pressure especially on hard cornering. Rear's light so doesn't need as high pressure.

Best way to find proper tire pressure to suit your personal driving style: Wash car. Go for drive. Observe contact patch of tire and road from the dirt on the tire (you just washed the car so tire should be nice and black). If contact patch is narrow, you need to lower your pressure. If contact patch is wide, you need to inflate it more. You want even coverage across all tread. Do this for front and rear.

Track driving requires lower tire pressure than street driving as the heat will expand the air pressure. Autocross requires higher pressure since you only go for short runs at a time, they wont have time to heat up.

Inflated to 44/45 psi is for transportation purposes only as NorthernProducer said, there should be a sticky telling people to set tire pressure correctly after purchasing their ST. I drove mine for a week before I discovered the tire pressure was ridiculously high.