Tyre pressure

NeilW · Member

Tyre pressure

yobarr · Guru

NeilW wrote:
Hi all, this is my first post so forgive me if this has been covered before, We have recently purchased a 93 Mazda T3500, and was wondering what tyre pressures to use. Front and duels on the rear?

Hi Neil.....Can you advise what size tyres you have? I seem to remember that those vehicles had 16 wheels? GVM is around 4500kg but we need to know what weight your vehicle is in order to give a helpful response.Cheers

Aus-Kiwi · Guru

Is there no tyre label inside door frame ??

Tony Bev · Guru

Welcome to the forum, NeilW

I can not answer your question, as I do not have your type of vehicle

As a rule of thumb, the maximum pressure will be on the side of your tyre, which may not be the vehicle manufactures pressure, which is usually somewhere on a small plate, on your vehicle

In my opinion

Never go above the pressure which is stamped on the side of the tyre
Set the pressure which is on the tyre, then go for a run, or short road trip
If you think that the ride is a bit hard, then let about 5 PSI out, and then go for another road trip, until you find a ride you are comfortable with

The trade off is that a high pressure will give better fuel economy

Less pressure will give less fuel economy, but a smoother ride

Too low or high pressures, will destroy the tyres

As yobarr has already said, if you give him the manufacture and size (every number you can see on the tyre), he can then probably give you a specific pressure to use

Hope that this rule of thumb info, is useful to you

-- Edited by Tony Bev on Tuesday 23rd of July 2019 12:54:40 AM

Mr Fuse · Veteran Member

Tony Bev wrote:
In my opinion
Never go above the pressure which is stamped on the side of the tyre
Set the pressure which is on the tyre, then go for a run, or short road trip
If you think that the ride is a bit hard, then let about 5 PSI out, and then go for another road trip, until you find a ride you are comfortable with

Sorry Tony but while point 1 is obviously correct but point 2 is seriously bad advise. First off, never run a tyre at maximum rated pressure. During use the tyre will heat up and the pressure will increase, taking it beyond its rating. Plus, excessive inflation results in stiffening of the tyre and thereby reduces the flex required to make a tyre work properly. The difference is most often noticed only in a catastrophic fashion.

Assuming the tyre is suitable for the vehicle (if not, why are they on it?) it's extremely unlikely that normal pressures should be more than about 80% of the tyre's maximum. Usually it's very much lower than that. Start with the manufacturer's recommendation for the load you expect to carry. From there make only small adjustments as you feel are necessary, bearing in mind that both over and under inflating will result in reduced performance and lower tyre life. The only time I'd suggest anything different is when lowering pressures when leaving the bitumen, which is probably not something you'll do too often with a vehicle of that weight.

denmonkey · Senior Member

pretty sure the rate tire pressure marked on the side also says max cold tire pressure .

So it already takes into account the expansion when the tire warms up.

sorry about the size, got it direct from the web biggrin

With that in mind, I'd say Tony's advice is a good place to start.

Peter_n_Margaret · Guru

To establish the appropriate tyre pressure you need to know the tyre specifications and the actual load that each tyre carries.
Without that information, you can only guess.
The tyre placard on the vehicle will only be appropriate if the vehicle is fully loaded to its legal maximum.
Cheers,
Peter

Mr Fuse · Veteran Member

denmonkey wrote:
With that in mind, I'd say Tony's advice is a good place to start.

Really? Good advise based on what information? Even without more specific information, the fact that you can rarely means that you should.

Still, if you lot want to run your tyres at maximum pressure you go for it. I'll stick to using appropriate pressures and I will always advise the same to anyone who asks.

Aus-Kiwi · Guru

I look at the way the tyres look on the ground . 16 medium trucks are from 60 lb
. Drive for a while . Check tyres heat . If hot add more pressure .,

Jaahn · Guru

NeilW wrote:
Hi all, this is my first post so forgive me if this has been covered before, We have recently purchased a 93 Mazda T3500, and was wondering what tyre pressures to use. Front and duels on the rear?

Hi Neil smile

Here are some tire pressures from a Toyota SWB bus manual. They would be a good starting point as it would be very similar to your Mazda and the same weight. Note the tires are specified as light truck 10ply rating, min.

tires 6.50R16 10PRLT front 73-80 PSI (500-550) rear 51-62 PSI (350-425)

tires 7.00R16 10PRLT front 58-69 PSI (400-475) rear 44-47 PSI (300-325)

Cheers Jaahn

-- Edited by Jaahn on Wednesday 24th of July 2019 10:48:18 AM

denmonkey · Senior Member

Mr Fuse wrote:
denmonkey wrote:
With that in mind, I'd say Tony's advice is a good place to start.

Really? Good advise based on what information? Even without more specific information, the fact that you can rarely means that you should.
Still, if you lot want to run your tyres at maximum pressure you go for it. I'll stick to using appropriate pressures and I will always advise the same to anyone who asks.

Based on the fact that he said refer to the details marked on the tire itself. Surely that is going to be a better starting than any guess work provided without knowing the specs of the item in question.

Tony also suggested reducing the pressure and taking it for a run. Both of these points seem reasonable to me .

He went on to point out that too hard or too soft can have their impacts etc. no issue there.

Me personally, I asked the guy who installed my new tires not long ago.

He said to run them somewhere between 40-45. I checked them when i got home and they were on 36. So I'm afraid you can't even trust the guys who do them for a living to get it right.

During use the tyre will heat up and the pressure will increase, taking it beyond its rating. Plus, excessive inflation results in stiffening of the tyre and thereby reduces the flex required to make a tyre work properly. The difference is most often noticed only in a catastrophic fashion.

No one suggested inflating the tire over its rating or excessive inflation as a starting point. In fact Tony said

Never go above the pressure which is stamped on the side of the tyre

I don't think many run their tires on full pressure as marked on the sidewall of the tire and I think most know that this could most likely result in uneven wearing of the tire.

That said, as I posted above, often it will be marked with 'cold' pressure. I'd suggest it would be unlikely manufacturers would be placing a suggested max pressure on the tire which results in failure in a 'catastrophic fashion' . If they did, I reckon a recall would happen pretty bloody quick.

Good advise based on what information

well, based on the manufacturers ratings stamped right on the wheel and of course just based on my general opinion.

Hope that helps, if you have any other questions, let me know.

cheers

oh and welcome to the Club Neil. Did you end up with something you were happy with as far as tire pressures go ?

blaze · Guru

well said den monkey, seems to me mr fuse knows a lot about every thing. Been some good advice in this thread. I run my coaster at 70psi and that seem to be what they run all the commuter bus at
cheers
blaze

Mr Fuse · Veteran Member

blaze wrote:
well said den monkey, seems to me mr fuse knows a lot about every thing. Been some good advice in this thread. I run my coaster at 70psi and that seem to be what they run all the commuter bus at
cheers
blaze

Not everything but I do have considerable experience in quite a few areas. There are many more areas where I know little or nothing. Because I only post where I do have knowledge I can certainly see that I may appear to be just another know-it-all smart-arse but that's normal on fora for many people, including other posters on this question. Still, if jumping to conclusions is your preferred form of exercise just go for it.

denmonkey · Senior Member

Mr Fuse, it's not the information that you provide, nor the fact that your opinion differs to others. Many of us disagree with each others on quite a number of things but most don't take it personal.
it's probably more about the last comments you throw at the end of each post that seems to needle others.

e.g
Still, if you lot want to run your tyres at maximum pressure you go for it. I'll stick to using appropriate pressures and I will always advise the same to anyone who asks.
Still, if jumping to conclusions is your preferred form of exercise just go for it.

I think you see where I'm coming from.

If you just shared what you knew and allowed others to do the same, I'm sure you'd find others more responsive to listening to what you have to say .

cheers Brett

blaze · Guru

denmonkey wrote:
Mr Fuse, it's not the information that you provide, nor the fact that your opinion differs to others. Many of us disagree with each others on quite a number of things but most don't take it personal.
it's probably more about the last comments you throw at the end of each post that seems to needle others.

e.g
Still, if you lot want to run your tyres at maximum pressure you go for it. I'll stick to using appropriate pressures and I will always advise the same to anyone who asks.
Still, if jumping to conclusions is your preferred form of exercise just go for it.

I think you see where I'm coming from.

If you just shared what you knew and allowed others to do the same, I'm sure you'd find others more responsive to listening to what you have to say .

cheers Brett

yes to the above, I just couldn't put in words, so didnt

cheers

blaze

oldbloke · Guru

Aus-Kiwi wrote:
Is there no tyre label inside door frame ??

Lol. Or the glove box or owners manual.

Or drop onto the local tyre fitter.

JayDee · Guru

We just had Bob Jane reversethe Front and Rear tyres.on our cruiser.the 4 tyres have 40 incl. the spare.

Seemed to handle the road very well. I will now RTFM to check if 40 is correct

Jay&Dee

Peter_n_Margaret · Guru

The tyre placard (if it has one) and the owners manual or the local grease monkey will have no idea what the axles of this 26 year old motorhome weighs and the likelihood of the current tyres being exactly the same specification as they were 26 years ago is almost zero, so that information will not be correct or even useful.
Weigh each axle separately and give us the current complete tyre information and a sensible calculation of appropriate pressure can be made.
It is important to get it right from both a safety point of view and for best economics.
Cheers,
Peter

Aus-Kiwi · Guru

The placard should have axle weights to tyre size etc . Yes along time ago . But still gives you an idea .

Peter_n_Margaret · Guru

Aus-Kiwi wrote:
The placard should have axle weights to tyre size etc . Yes along time ago . But still gives you an idea .

When the placard was produced this vehicle was a cab chassis. The only weight known then was the GVM and it may not even have specified the split from front to rear.

And as I suggested, it is likely that the tyres have quite a different specification now, even if they are the same size which they may not be.

Guesses on top of guesses.

Cheers,

Peter

Aus-Kiwi · Guru

Agree but how far off would pressures be though ? Starting point if you have to ask .

Peter_n_Margaret · Guru

Aus-Kiwi wrote:
Agree but how far off would pressures be though ? Starting point if you have to ask .

They could be out a long way - enough to either risk tyre failure or to increase wear rate and reduce braking and handling.

Why guess?

Getting the pressures correct is easy once you have the tyre specifications and the actual loads carried.

There is no way that I would make a guess which could then either create a safety issue or cost the OP money - someone else can guess if they like, but not me.

Cheers,

Peter

Aus-Kiwi · Guru

Thats why you start with what the manufacturer recommends or the tyre place you bought them from ? In my case I run the rears 20 lb under MAX ( 70lb) with no issues . Gives better ride. 6.5 ton., 225 X 19.5 They are not trucks anymore so weight
Stays much the same .
.

Jaahn · Guru

Jaahn wrote:
NeilW wrote:
Hi all, this is my first post so forgive me if this has been covered before, We have recently purchased a 93 Mazda T3500, and was wondering what tyre pressures to use. Front and duels on the rear?
Hi Neil
Here are some tire pressures from a Toyota SWB bus manual. They would be a good starting point as it would be very similar to your Mazda and the same weight. Note the tires are specified as light truck 10ply rating, min.
tires 6.50R16 10PRLT front 73-80 PSI (500-550) rear 51-62 PSI (350-425)
tires 7.00R16 10PRLT front 58-69 PSI (400-475) rear 44-47 PSI (300-325)
Cheers Jaahn

_________________________________________________________________________________________________________________________________

Hi smile

I was astonished that this simple request is still attracting replies that do not actually have any real answers. Just "experts" discussing their point of view on a correct answer. As no one else had given a real answer I attempted to give what I thought was some real pressures for a very similar bus from the same years. I would think that was good if I was asking.

However this just seemed to spur replies that were not very useful, again!! This thread now runs to 22 answers most not very useful to Steve IMHO. He has not chosen to reply either which possibly says something about the replies. It starts to be like the battery threads that go on and on and on and .................... till most are p*ssed off and go away. hmm

Give it a break from the replies unless you have something useful to say IMHO. disbelief

Jaahn

denmonkey · Senior Member

Yes Dad