Nitrogen versus air

[tannat]

So I've had my Focus for 3 years + and about 44k miles. A few track days- I feel i know thee car pretty well.

Until the most recent set of tires (replaced at 38k) all tires have been filled with compressed air.

The current set has nitrogen. I had these tires installed in the spring when temps were in the high 20s (Celsius). Recently temps have dropped significantly (as well as humidity). Now the car bounces like a rubber ball after hitting a bump. Its a bit unsettling and reall hurts the 'seat of pants' feel of the car.

Granted-it could be any number of other factors (suspension, driver, etc) and I have considered these, but Occam's razor points to the nitrogen.

Has anyone else experienced a similar phenomenon with nitrogen filled tires and drops in temps?

[Zico]

Nothing to do with grip levels then? Sounds like the dampers to me.
Nitrogen is obviously far more stable than air, the water content will be far lower and the pressures dont fall as much when the temperatures drop... but Isn't a lower tyre pressure what you want when the ambient temps drop? I know I always drop my tyre pressures a couple of PSI over the winter months.

There is an interesting thread on the subject here.. http://www.ten-tenths.com/forum/show...light=nitrogen

[tannat]

Cheers Zico. Thanks.

I plan to give it the car a good hard look this weekend...

[Daniel]

Why would you drop pressures in the winter?

[Zico]

Why would you drop pressures in the winter?

With normal garage forecourt air, tyre pressures drop by 1 PSI for every 10 deg drop in temp.

I also always make sure my tyres are set a couple of PSI lower in the winter anyway, its not only cold but wet 90% of the time here, If I keep them at summer (F34-R32 PSI) pressures I find the car much more nervous, less comunicative and the grip much less progressive, probably to do with the increased tyre roll suiting the lower grip levels better. Does no one else find that?

[Easy Drifter]

Nitrogen is far less affected by temp. than compressed air.
Unless you have a leak(s) there should be no noticable difference in handling with a drop in temp.
I would, of course, check presssures but I suspect your problem is elsewhere.
As suggested quite likely shocks. Worn bushings in the sway bar links or control arms are another possiblity. As you have used the car in limited competition plus age these are distinct possibilities.
But shocks are most likely.
AKA Dampers

[Hondo]

Lower tire pressure does give you more traction, grip, and feel. Check out the air pressures on the tires of a trials motorcycle. They run just enough to keep the tire on the rim.

[janneppi]

Why would you drop pressures in the winter?

From what I've heard it's the opposite, as pressure in tyres drops in colder climate, you need to counter it. If you have 2.2 bar at 20C , it drops to 2.0 bar at 0C.

[Daniel]

With normal garage forecourt air, tyre pressures drop by 1 PSI for every 10 deg drop in temp.

I also always make sure my tyres are set a couple of PSI lower in the winter anyway, its not only cold but wet 90% of the time here, If I keep them at summer (F34-R32 PSI) pressures I find the car much more nervous, less comunicative and the grip much less progressive, probably to do with the increased tyre roll suiting the lower grip levels better. Does no one else find that?

I really don't agree with that at all.

You will always want the same pressure (when cold) in your tyres regardless of temperature.

In the snow you definitely don't want tyres which are narrower because it'll be harder for them to bite down. You also don't want a wider tyre in the wet either because a narrower tyre will displace water better.

I'd be very sceptical about anything in that thread, there's a lot of crapola in there like that nitrogen inflated tyres lose pressure more quickly because nitrogen molecules are smaller than oxygen molcules which is rubbish.

http://www.theaa.com/motoring_advice...-nitrogen.html

As for the OP, I'd check the car out. That said is it possible you're just feeling a reduction in lateral grip? I find the Fiat bouncier around certain corners when it's colder.

[tannat]

Nitrogen is far less affected by temp. than compressed air.
Unless you have a leak(s) there should be no noticable difference in handling with a drop in temp.
I would, of course, check presssures but I suspect your problem is elsewhere.
As suggested quite likely shocks. Worn bushings in the sway bar links or control arms are another possiblity. As you have used the car in limited competition plus age these are distinct possibilities.
But shocks are most likely.
AKA Dampers

I'll have a check, ED, but she's a young car, and limted track use, but who knows..

We give me an excuse to upgrade the shocks