(T) Tyre Pressure

Just some thoughts...

When I went down to Colchester at the weekend I had two passengers plus the Baby and a very full heavy boot. I usually keep the tyre pressure at 2.1 Bar (17inch wheels 215/45 profile tyres) which the handbook says is the pressure for light to medium load. Because of the extra weight I increased the pressure - again according to the handbook - to the indicated 2.3 Bar. On the journey everything was fine.

My point is since increasing the pressure both under the heavy load and today driving around with just me and Amanda in the car; the road holding and handling seems to have improved. I went down some twisty roads at a fair pace and on corners where I'd previously get a bit of understeer there was none...Is this real or just my imagination? It appeared to be so improved I'm loath to decrease to 2.1 Bar now.

Also, since the tyres were scrubbing less I expect tyre wear would be less too. Is incorrect tyre pressure a factor in all these cases of premature tyre wear on Stilos? I can't remember tyre pressures being mentioned too much in these threads? As I say I check my tyre pressure at least every fortnight using a digital electric inflator and double checked with another digital gauge always at cold temp. Have people that suffered premature tyre wear checked pressures often? Perhaps using the upper 2.3Bar limit would help?

What do you guys think? thoughts comments please - sorry for another longish post I couldn't think how to condense it!

Usually higher pressure will cause less grip, but obviously less drag. I used to run my Escort TDi at the upper rating, i was usually the only person in the car, i drove mainly motorway so the slight loss in grip wasn't noted but the slight improvement in economy was worth it.

However higher pressure means less squidge in the tyres, and possibly more drumming, so more road noise.

True, I would have thought less grip - although in the five hundred odd miles I've driven at the increased presssure I haven't 'perceived' any loss yet. I suppose being only a 0.2 Bar increase any loss of grip would be very minimal, plus it's not like the tyres are operating outside the manufacturers' limits so it should still be perfectly safe. I suppose the added pressure and less drag you mention is helping give the effect of better turn in and less - initially perhaps - drag/understeer mid bend?

My manual says 2.3/2.3 for medium load and 2.7/2.5 for full load on the 17" tyres - 2.1 bar is for the 16" alloys on the Abarth!

Paul

BTW - the pressures in my tyres were around 2.1 bar, and I had to increase them to 2.3 myself!

Anyone know the PSI conversion? I got a digital meter, and it doesn't do bar.

yeah, 1 bar is equal to 14.50377399 pounds/sq inch,

so that would make 2.3 bar 33.35868019 psi.

Crap!! Your right!! You'd think after a decent education and four years of Uni I'd of learnt how to read figures off a page correctly (even more worrying given the job I do)!! I just went out to check the manual 2.3 it is, even for light-medium load. So, for almost a year now, I've been going around under inflated..........oops. Still, like I say, the car does feel better now!

:-) Thanks for pointing it out. :-)

Ive managed to misplace my manula and was wondering what are the proper air pressure settings for standard (factory fitted) fiat stilo wheels?

depends on the size of tyre!

If no-one does it by tonight, I will scan in the relevant page from the manual and host it on here

anyone know what pressure at tesco i need to put in my jtd (i.e. 36 on the lcd thing)?

I usually stick to 2.2 bar(32 psi) in the front & 2.0 bar(30 psi) in the back.
Seems fine, mind you I only have the 16" wheels.

I run mine at 31.5 psi all round (205/55/16). I check them every other week and the wear is even.

i put 34 all round (ro5/55/r16) bit too much you think?

I've an Abarth on 215/45/17 alloys. Rounding up it should be 34 PSI from the bar conversion, I go one up than that to 35 all round.

Both under and over inflation is dangerous, but I think +/- 5% should be ok. What I would do is get a proper calibrated hand held tyre pressure gauge as those in garages, supermarkets etc can be woefully inaccurate. A blow out at motorway speeds due to under or over inflation can be "fun" if not fatal!

Key here, as most people seem to do, are regular checks.

Who changes their tyre pressures when they go on holiday 4 up with loads of luggage? (bet hardly anyone).