[baroudeur]

Personally, I don't think it is possible to over-inflate the (front) tyres in any sensible way.

Then perhaps   you are living in cloud cuckoo land? Over inflation can lead to loss of grip earlier than a correctly inflated tyre.

Car and tyre manufacturers spend millions on research.  Do you really think they do not know what they are doing?
In the event of a serious accident it may well be that an under or over inflated tyre may be considered a contributory factor.

Personally, I don't think it is possible to over-inflate the (front) tyres in any sensible way.

Then perhaps   you are living in cloud cuckoo land? Over inflation can lead to loss of grip earlier than a correctly inflated tyre.

Car and tyre manufacturers spend millions on research.  Do you really think they do not know what they are doing?
In the event of a serious accident it may well be that an under or over inflated tyre may be considered a contributory factor.

Interesting that you should wake this old thread but I stand by what I said.

Underinflation (of the front tyres) is much more likely to be the cause of poor stopping distance in an emergency braking event: I expect overinflation would be negligible.

I'm not going to quote any supporting evidence (but I'm sure I could find it ) partly because it's almost obvious that when you brake (really, really) hard the weight transfer to the front wheels is several times the normal load such that these tyres would ideally be inflated to maybe 50psi or even more. I'm happy to use 40psi.

It's a compromise between what (harshness) can be tolerated for normal driving and what needs to be available in an emergency.

Perhaps if the road is wet/icy the ability to generate sufficient friction to cause the weight transference is limited... but even so, if this were the case, then no tyres will grip well, no matter what the footprint.

[Surferdude]

Pip, what you say above is pretty spot on. Under heavy braking, you could have 50 psi in your front tyres but of course that's not practical under normal conditions, so the compromise of around36 to40 is fine (IMHO).

I wonder though, if in wet conditions, a bit less pressure wouldn't be more useful as the footprint would be spread out a bit more.

On sand for instance, 4WDs lower their pressures sometimes down around 15 psi to widen the footprint and give more traction (as well as help the tyres not to spin and dig holes)/

[RamblinR]

New here but been reading a bit here and there.

Picked up my new car just under a week ago and decided to check the tyre pressure today.
Tyres were filled to 36psi by the dealer.

[Surferdude]

New here but been reading a bit here and there.

Picked up my new car just under a week ago and decided to check the tyre pressure today.
Tyres were filled to 36psi by the dealer.

Sensible dealers up here on the Sunny Coast.

[snakoil]

tire pressure should be defined by the tire and not the car IMO
over here  the i30 comes with hankook solus (Crappy soft tires) and Running 34psi would be no problem on 17"
however when I used to do lapping I would have real sport ire like Falken Azenis I would run 28 on the street and 45  on the track
(actually 45 only for the back to compensate the oversteer and weight distribution of a FWD car)
32 on the street with stiff sidewall was just not tolerable.

[wardfam]

What works for me is front 38psi cold , rear 35psi cold for 40,000 km ,diesel slx hatch , Cheers Craig

[MGS]

I think Baradeur is right. I have an i30 Diesel 1.6, and it came with 42psi in the Hancook tyres when supplied new, and I'm convinced this is way too much pressure.
After quite a bit of driving It seemed really noisy and bumpy especially on motorway trips, I'd heard this was mainly due to the Hancook tyres and assumed they were just rubbish. I had to do an emergency stop and the ABS kicked in really early and I travelled  way further than I thought  I should have and nearly collided with the other vehicle.
After this I did some more testing (emergency stops) at those pressures after checking on line and with my hand book and I wasn't happy with the grip or noise so I lowered to 34psi front 32 psi rear (I only drive myself in the car and don't carry any weight) I must say the noise has lowered to a more comfortable level and the grip is way better than before on stopping, cornering is also fine. The wet grip is excellent with the esp "on" as well, so maybe those Hancook tyres are not so bad after-all, Anyway I have settled on the above psi as a good compromise on those tyres on the i30 diesel.

[tla]

42psi (or even higher) is the pressure that was delivered to the dealer.  The dealer should have dropped it down to a more reasonable level before delivering it to you.

Mine came with pressures at around 45psi.  It felt like Fred Flintstone's granite-tyres. They're now at 38 front, 35 rear.

[Surferdude]

I think Baradeur is right. I have an i30 Diesel 1.6, and it came with 42psi in the Hancook tyres when supplied new, and I'm convinced this is way too much pressure.
After quite a bit of driving It seemed really noisy and bumpy especially on motorway trips, I'd heard this was mainly due to the Hancook tyres and assumed they were just rubbish. I had to do an emergency stop and the ABS kicked in really early and I travelled  way further than I thought  I should have and nearly collided with the other vehicle.
After this I did some more testing (emergency stops) at those pressures after checking on line and with my hand book and I wasn't happy with the grip or noise so I lowered to 34psi front 32 psi rear (I only drive myself in the car and don't carry any weight) I must say the noise has lowered to a more comfortable level and the grip is way better than before on stopping, cornering is also fine. The wet grip is excellent with the esp "on" as well, so maybe those Hancook tyres are not so bad after-all, Anyway I have settled on the above psi as a good compromise on those tyres on the i30 diesel.

Baradeur is partly correct. 42 is at the very upper level of what is acceptable but then, 34 is at the very bottom of acceptable. Given others' issues on here with tyre wear on their diesels, I'd suggest that tla is pretty much spot on with 38 / 35

Sorry, I meant to clarify the "partly correct" comment. he says, Car and tyre manufacturers spend millions on research.  Do you really think they do not know what they are doing?
The point here is that car and tyre manufacturers, despite all their millions spent on research, DO NOT AGREE on the optimum pressure. Which is why we're having this discussion.

[Asterix]

Hi

I have 2,5 bar / 36 psi in both front and rear tyres (15") all the time except when towing the caravan, than I increase rear to 40-42 psi.

We are 4 people in the car every day when driving to work, so most of my driving is with approx. 250 kgs extra weight.

[druggist]

Just home from doing a defensive driving course with my wife, through Driver Dynamics http://www.driverdynamics.com/

Great day and we both had a great refresher on the joys of ABS and ESP.

They were adamant that cars should be running at least 40psi for maximum grip, and also for best sidewall heat dispersion in the tyre.

BTW I wish this forum used Australian and not US spelling in it's spell checker.

[Surferdude]

Just home from doing a defensive driving course with my wife, through Driver Dynamics http://www.driverdynamics.com/

Great day and we both had a great refresher on the joys of ABS and ESP.

They were adamant that cars should be running at least 40psi for maximum grip, and also for best firewall heat dispersion in the tyre.

BTW I wish this forum used Australian and not US spelling in it's spell checker.

Did you mean "sidewall"?

[Shambles]

BTW I wish this forum used Australian and not US spelling in it's spell checker.

I'll look into it, cobba

[asathorny]

Just home from doing a defensive driving course with my wife, through Driver Dynamics http://www.driverdynamics.com/

Great day and we both had a great refresher on the joys of ABS and ESP.

They were adamant that cars should be running at least 40psi for maximum grip, and also for best sidewall heat dispersion in the tyre.

BTW I wish this forum used Australian and not US spelling in it's spell checker.

I think you meant to say *ENGLISH*  ......   and I agree with you   

[druggist]

BTW I wish this forum used Australian and not US spelling in it's spell checker.

I'll look into it, cobba

Rippa Mate Beaudddddy

[bryanj86]

I pump my tyres front and back 38PSI COLD.  Hard ride but much better for wear as all i do is highway driving...

[Bitsumishi]

I'm running 34psi all round, but will try 36psi and see how it goes.

I did notice the car handled better with the extra 2psi which kinda surprised me!

[snakoil]

The quality of the roads in Europa must be quite better than ours
I had my tires at 35psi and could not stand it, was thinking of changing the car as this was too harsh for all the bumps we have in the pavement.
Dropped it to 30psi and I can at least tolerate the suspension now. 
This car is still more harsh than all the others I've owned before and weirdly it has the bigger wheel/fender gap I ever owned.

[Bitsumishi]

Keep in mind Hyundai customised the suspension for Australian conditions, so maybe more air pressure suits us more than you. Believe me, our roads aren't too great either

[kabukiman]

I checked my tyres today to see what pressure was in them.
I was surprised to see they were at 37psi. The sticker in the
door trim says 32 for 17" wheels. I know some people on here
are using 34 - 36psi. What pressures are people using and what
psi would be the maximum you would put in safely.

for my 205/55s on 16"s hyundai told me 35psi

the door says 32 but it does on nearly every new car.  it will differ where you buy and drive your car.

35 has always worked for me on every car, except my old peugeot, I used to use 39 psi

[komaterpillar]

18 inch wheels with 225/40 18 tyres

37 psi in the front and 34 psi in the rear (cold)

[Talking Hoarse]

Interesting feedback thanks.  I reckon manufacturers tyre pressure settings are compromise between handling /economy (ie hard) and comfort (ie soft).  I prefer to err toewards the former.  I think my 205/55x16 shod i30 seems about right with 38psi in the backs, 36 in front.  Odd that I prefer fronts slightly softer - many posters have the fronts slightly harder than the backs.
Also .... very early days (daze?) yet and I will likely develop this furter on another more appropriate thread, but there has been a lot of banter about tyre noise of standard fit Hankook's fitted to the i30 - which I reckon is already quite a noisy car.  Mine has just had a new steering column fitted to resolve the knocking noises, and I think it is now much quieter reavelling on motorway.  If my memory serves me  correctly the bush where the column passes through the bulkhead now has a great piece of (maybe) soundproofing around it, maybe makes the difference.

[Dazzler]

That is interesting about the extra soundproofing ED