Why do dealers always over-inflate my tyres?

Thanks Brad

I've always let the pressure back down to 30 PSI as it seemed a reasonable compromise, but I used to have a niggling doubt that I was making a mistake. I tried to run the Prado a couple of times with 40 PSI, but the ride was really rough and uncomfortable even on smooth asphalt.

Steve

I run my Oz made bridgestone A/T duellers 265/75/16 40 f 42 r anywhere, have done for 6 years will do until they stop making them.
Never had a problem and I work them hard.

You guys using figures around 40 psi may as well go back to using cross ply tyres !

i also have the ozzy made brigdgestone and am on my second set after getting around the 100,000k mark i only run 32 psi front and back for unloaded around town and 33psi loaded with ct on all long distant travels and have never had any probs i have a GQ patrol. Col

I was always of the opinion that car manufacturers specify low pressures on tyre placards in order to give a smoother ride for the occupants.

Remarkable how Original Equipment tyres are always shot after about 20,000km as they like to supply as cheap a tyre as possible and as I said are usually soft compound and at low pressure to give the best ride.

Even on a Prado the original tyres are totally geared to comfort. Toyota know full well that 80% of Prados will spend their life on the bitumen and that anyone whi is half serious about 4wding will upgrade the tyres about 4 nanoseconds after delivery of the vehicle. Helps sell the vehicle during test drives as well. Most customers will buy the soft riding quiet vehicle.

Cheers
Muddy

The asphalt or graded gravel roads is where my Prado spends most of it's time. Towing my caravan or my boat or driving to fishing spots on beaches or bush walking spots in the Flinders Ranges. I hate 4 wheel driving :-)

Steve

Hi Hero, And tell me then, who was it that taught the driver training organisations what is the 'proper' tyre pressure? Go to three different organisations and you will get three different views. Rural or outback travellers will prefer a different pressure to black top travellers. Do you know what pressure an F1 race car or a Baha rally car or an overloaded rural delivery van. Totally different pressures for totally different jobs.

The proper pressure is that which does the job 1, safely and 2, comfortably and it must be in that order, you can fit in best mileage before running out of tread after comfort.

The training organisations will base their view on what is logical for the scenario. For example drive a Prado through a tarmac slalom at 60-70km/h on 26psi, and then again at 34-36psi, you dont need to be real bright to notice that the higher inflated tyres are supporting and directing the vehicle cleaner and than the low inflation tyre. Kiwi Kia, as I stated "the tyre should be inflated in accordance with load and driving conditions" of coarse each tyre has its own requirements, An F1 car or Baja Rally car does not come equipped with a tyre inflation placard. My point being that usually the placard recommendation is unsafe for day to day driving but coincidentally suitable for slow offroad or sand only.

Hero, you state:

"My point being that usually the placard recommendation is unsafe for day to day driving but coincidentally suitable for slow offroad or sand only".

That is absolute drivel !! You expect me to believe that with all the specialist test tracks, years of development and the litigious nature of the American market that Toyota etc. put tyre inflation placards on their vehicles that state an unsafe tyre pressure, rubbish !

Hence why this topic is one of the most sensitive and widely opinionated. There are those of us that have our own opinions via realworld experiences and others that do what the book says.
Naturally there are always going to be exceptions to any rule, but you will find regardless of what the manufacturer states that the majority of the population would agree and run higher pressures to that on a placard.

Can I ask, do you drive daily on the placard recommendation?

Yes I do (or close to it, say +2 psi). Pajero and Kia's, 100 series camper.
I have only had one puncture when off road and that was a puncture in a tube and not in the case. I didn't even get a puncture on the GRR (reduced pressure) or any of El Questros rocky tracks. I think that a lot of people just do not understand what a modern tyre is designed to do. The pressure that some people use in radial tyres should only be used in cross-ply tyres. Radials are supposed to be baggy and are very hard to handle without power steering. People who put oversize tyres on a vehicle sometimes find that the have to increase tyre pressure just to get the vehicle to handle in a reasonable fashion but this increased tyre size and pressure is not vehicle OME. Vehicle manufactures spend an incredible amount of time matching various tyres to their vehicles. Several European car makers and most Japanese makers bring their pre-release vehicles down to New Zealand for winter testing including the choice of tyres. The vehicles are thrashed around a special test track 24 hrs a day changing tyre brands regularly till they get the best combination for the suspensions. If you have ever watched tv shots of the international Hill Climb near Queenstown you will have seen the area near where the tests are conducted. Saw a vehicle a few years ago that had been flown down to Auckland from Japan on a 747 freighter, trucked all the way down to Queenstown (Cardrona) and then 'stared' in a couple of minutes filming for a tv commercial before it rolled and was written off ! Hell, I could have made bucks on a photo of that :-)) The choice of OME brand and tread type on vehicles are of course a compromise for noise, comfort etc.... but not handling and safety ! The tyre pressures are arrived at for the best handling characteristics of the suspension (which includes brakes). Millions of dollars go into tyre research and the manufactures do know what they are doing - end of story.

Not sure that I would be comfortable running my LC 100 at 220kpa with a few people in it. I understand what the placard says, but realistically, 32psi in a cruiser around a corner doesnt sound safe.

Max,
I have an 80 series as well and run 32 front and 33 back. Makes for a comfortable ride and seems to comply to the 4psi rule after about 20min's driving. I also run BFG A/T's and they now have 70k on them and still have 9mm of tread left.

I have tried 36front and 40 rear, but unless there is a constant load in the car it just makes it uncomfortable and rough.

I also remeber reading in 4x4 monthly about pressures where a tyre expert stated that any pressure below 30 psi should only be used off road and at low speeds, never on bitumen.

Rob

I have tried that in the Prado (95 series). It suggests around 32-34psi on bitumen. That gives a comfortable ride with reasonable steering response, but I must say that I get a lot better fuel economy at around 37. Personally I find the car handles in a pretty sluggish way under 32 psi on bitumen.