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Tire inflation pressure ?!?

ali_viento

New Member
Joined
Jun 14, 2017
Messages
8
Since the company recommended to set the cold tire inflation pressure to 33 psi for both front/rear then whats you always set and get better result in your experience ?! i replaced the old tires with the new set of 285/60r18 Dunlop AT22 ( factroy recommended ) and try the 4 psi rule like many ppl use on their 4x4 cars but it shows the 33 psi cold tire inflation pressure is high since they came to 35 psi after highway driving test ( about one hour ) but i think any pressure lower than 33 psi can cause heavier steering wheel and poor handling with negative effect on fuel consumption . just please let me know what you think ?!
 
I would view it the other way around.

The higher the "cold" pressure, the less internal friction in the tyre, so the pressure difference between "cold" and "hot" will be less.

Try setting them at 38 psi "cold" and then test them after one hour. I'd be surprised if they register more than 40 psi (an increase of 2 psi).

Personally, on asphalt highway, 40 psi will give you better grip, wear and economy characteristics. JMHO.
 
Yes. If 33 cold gives you 35 hot, then it's too low. Recommend going up to at least 36 cold, for paved roads.
 
Confused , please Correct me if im wrong , its the 4 psi rule that i heard :

A good way of double-checking that your pressures are correct for your application is the 4psi rule, recommended as a good rule-of-thumb for accurate, appropriate tyre pressures.

Check tyres cold and then straight after a decent highway run you should see a 4psi (0.275 bar) increase.
  • If it is less, you have set your cold tyre pressures too high;
  • if it is more, then you have set them too low.
  • Adjust the cold pressures accordingly and check the results when hot again and you should have a 4psi difference.
Then if this is correct then i must reduce the tire pressure instead of increase them , isnt it ? cause its said if the difference less than 4 psi then you set them too high ??!?
 
I can't comment on the 4 psi rule you've quoted, I haven't seen or heard of that before. Maybe I should get out more.

I don't see how there can be a rigid 4 psi rule applicable to all tyres, vehicles and road conditions. The range of tyres, for example, is huge, from Maxxis Trepadors through to 100% road biased low profile high speed tyres.

They all behave differently under the same conditions, so a single rule cannot be applicable, surely. The principle makes sense, but the concept of taking it too literally seems a bit odd to me.

Try some different pressures, and see how it behaves on the highway, then settle on what suits you, your tyres, your cruiser and your driving style, the best.

To hell with some numpty's rules.

JMHO of course, and apologies in advance to the numpty, it wasn't meant in a personal sense... :shifty:

BTW, I've always greased my wheel nuts, so what do I know :icon-rolleyes: :lol:
 
I am wondering if that rule is meant for smaller tyres with lesser rubber on them.
 
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I've never heard of the 4psi rule either but I can't figure it. Going back to our school physics lessons on thermodynamics the pressure of a gas is directly proportional to it's temp when the volume is constant so you wouldn't get differing pressure increases when starting with different pressures...or maybe I'm reading it wrong??
 
I can't comment on the 4 psi rule you've quoted, I haven't seen or heard of that before. Maybe I should get out more.

I don't see how there can be a rigid 4 psi rule applicable to all tyres, vehicles and road conditions. The range of tyres, for example, is huge, from Maxxis Trepadors through to 100% road biased low profile high speed tyres.

They all behave differently under the same conditions, so a single rule cannot be applicable, surely. The principle makes sense, but the concept of taking it too literally seems a bit odd to me.

Try some different pressures, and see how it behaves on the highway, then settle on what suits you, your tyres, your cruiser and your driving style, the best.

To hell with some numpty's rules.

JMHO of course, and apologies in advance to the numpty, it wasn't meant in a personal sense... :shifty:

BTW, I've always greased my wheel nuts, so what do I know :icon-rolleyes: :lol:
Clive , just please let me know your idea with my numbers ?! going higher like 36 that another buddy said ?!
 
I run mine at 38 psi for general use.
Any lower and it feels a bit spongy for the way I tackle the tarmac....
And my brother runs his 33' BF MK2 at 40psi on his patrol ute.....
 
Clive , just please let me know your idea with my numbers ?! going higher like 36 that another buddy said ?!

I tend to work on the end result. I've got excessively wide tyre so nice 10" rims, and I like them to be firm.

Obviously working within the range stated on the tyre wall, where there's often a max pressure stated, I like about 40 psi on asphalt. It delivers less rolling resistance hence I can get close to a reasonable cruising speed and economy.

TBH, I'm more interested in the tyre pressures being even on all 4 corners, more that certain pressures, and my tyres don't appear to leak.

I check them visually every day, and the pressure every 2-3 weeks. It doesn't vary.

In fact, my gauge is measured in Bar, so a psi gauge gives you more (arguably too much) accuracy IMO.

With tyres that perform well down to 10 psi (admittedly not for highway) and my cruising speed as low as 100 km/hr, I don't see the importance of such fine tolerances.

I take your point on the numbers, and the conflict with this so-called 4 psi rule, but I really think you've entangled yourself into a statistical numerical conundrum, as opposed to a sensible and practical solution to what pressures to run at.

Maybe I'm just old-fashioned, but I don't have any issues with overheating, uneven wear, or compromised grip.

Can't help you any more than give my opinion, I'm afraid....
 
I've never heard of the 4psi rule either but I can't figure it. Going back to our school physics lessons on thermodynamics the pressure of a gas is directly proportional to it's temp when the volume is constant so you wouldn't get differing pressure increases when starting with different pressures...or maybe I'm reading it wrong??
The physics is that when the cold press is too low, the tyre heats up too much because of more deforming. When the prss is right (for hy'way), the tyre doesn't deform that much, and the temp doesn't increase much.
 
Today i just set the cold inflation pressure to 36 psi and then drove for about 30-45 mins ( about 35 km ) at highway and when check the hot pressure , 2 tires comes to 40 psi and the 2 other comes to 41 psi then it seems the cold pressure is correct right now . Thanks everybody
 
I run at 40psi with 275/75x16 BFG's on my 100 series when running on the highway.
Below this the tyres seem to drag I feel a slighly higher pressure helps for even tyre wear and better fuel economy, off road obviously would benifit from being lower.
My tyres have worn very evenly over 40,000 miles and still have plenty of tread on them.
To get the best on/off road performance I believe a mid range pressure is quoted by tyre manufacturers but obviously changing the pressure to suit the terrain should give benifit, higher for road and lower for mud/ trail.
 
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