Hi all,

I have a 1986 HiAce with Dunlop 185/70R14 LT light truck tyres. This is my first van or light truck; I'm generally accustomed to owning cars.

Looked in the manual and on the tyre sidewalls for the correct pressure; the manual and the sidewalls specify 450kPa cold. This converts to 65psi in the old money.

Sounded high to me, in bicycle tyre territory, so I consulted a mecho at a petrol station who advised no more than 40psi. I put 40psi in all 4 and went merrily on my way.

About a week later, while blasting down the curvy mountainside on the Great Western Hwy (M4) from the Blue Mountains at about 100km/h, the ENTIRE tread surface peeled off the left rear tyre, leaving only the casing and steel belts, which thankfully remained inflated.

I got it stopped safely but the hunk of tread did at least a couple of rotations before coming off completely and did some serious damage, badly flogging the fender support crossmember just behind the left rear wheel in the process.

The van was unladen except for one very surprised driver- me. These tyres were in visually good nick with ample tread remaining but as they were fitted when I bought the van about a year ago, I don't know how many k's were on them.

I've since been running the tyres at more car-like pressures, 32-34psi and checking them frequently.

What do you think, defective tyre? Wrong pressure?

Thanks much,

Brian
Blue Mtns NSW

Hi Brian,

65 PSI is WAY TOO HIGH!

I'm running 205/70R/15 commercial mud and snow tyres (bought them for a job in the snow last year and still running on them sadly) and for day to day driving I run 40 PSI - increasing to 45 if I have a load on, which is rare.

At 65 PSI you risk damaging the tyre due to over-inflation or worse, having it blow out on you at the worst possible moment.

If the tread has peeled off the casing then what you have there are retreads - which are inherently dangerous on a light vehicle.

Not so bad for trucks where if you lose one tyre you aren't going to have a major on your hands, but not ideal for vans and cars. I would NEVER run retreads - see too many cases of them coming unstuck and at 100 km/hr on the open road the last thing you need is to lose a tyre.

Cheers.

I just bought a 1994 Hiace Camper. The genuine manual states the pressures to be set to 47 front & 65 rear. (PSI)

So it seems 65 probably is not too high at all. This would be assuming you have good tyres and not retreads!!

I would highly recommend using what the manufacturer recommends.

I've been a mechanic for 20 years ( bikes not cars ) and have found this to be best practice. (IMG:style_emoticons/default/s12.gif)

I too, thought the pressures sounded very high. My van seems fine at those settings

YIKES!!

No one needs to be running 65 PSI in their tyres unless they are carrying gold bullion in their van!

I have a Hiace Jumbo 4X4 - the biggest Hiace they made, and I only run 45 PSI in my 6 PLY commercial tyres which are 205/70R/15.

A tyre that is overinflated will wear just as badly as one that is underinflated - not only that, it's dangerous as you have so much less tyre in contact with the road.

Hiace4x4,

I am very interested in how you came to your decision on what is correct for tyre pressures.

Can you tell me why 45psi is correct for us? I am sure your van is fine at 45psi, why wouldn't it be.

Don't get me wrong, I am all ears here, just curious why 65 is incorrect and 45 is correct.

cheers

I thought normally, two pressure setting would be labled when there was a reason to lower if unlaiden? I have seent his plenty of times on vehicles & bikes

Hi Dom,

Yes, I understand your comments.

My pressures are based on manufacturer's recommendations for the size and rating of tyre that I
am running at the moment - which is a fairly common size to be running on a Hiace.

If the owner's manual is recommending 65PSI for a loaded vehicle then they must be specifying some
substantially larger tyres.
I wouldn't even consider putting 65 into my tyres. That's a lot of air.

Personally I would ignore what the owner's book says and base your pressures on what the tyre manufacturer
recommends.
After all, they made the tyre, they know what pressures are suitable for it.

I must apologise for my double post as well! I didn't realise I'd already posted in this thread.

The tires that came with my van are all season 205/70/R15. I had to pump them up to 45psi otherwise the tires look shagging. The ride was smooth but the steering was not too precise when it was windy.

Since the tire were quite worn, I got a set of light truck 215/75/R15. The pressure I put in was 40psi. Although the tires look full, but not too full - The ride was hard. So I will let some air out to may be 36.

In the owner's manual, although it does not mention what the proper tire pressure should be, it does depict what the tires should look like when the tires are over-inflated/under-inflated/properly inflated.

Based on this experience, I suspect the proper tire pressure is related to the load, the tire size and the type of tires.

My van's tyres are 205/85R16 size and by the book I should use unloaded 3,0 bar front and 3,5 bar rear.
But I have faced the best solution and handling using 3,5 bar in both ends.
Right now Hiace wears Continental M+S winter tyres with spikes but after changing to those from
Michelin summer tyres I noticed the looser structure on winter ones. So I use 0,3 bar more on those.


But that 450 kpa so 4,5 bars.... It's possible to use if needed by the cargo with you. The tire should
last the usage if it's printed on side.
I haven't used to so high pressures on automobiles but I think i got around that in my bike's tyres.