Tyre pressue vs fuel economy

I believe upping the pressure does help.

Every little bit helps said the monkey as he P'd in the river.

Taking off my roof rack improved my economy by about 2 litres per 100.

Pooley

Good reminder. I'll check my pressures tomorrow morning before we head off to the big smoke.

Higher tyre pressures definately help with fuel consumption, but don't get carried away.

I made the mistake of thinking high pressures were good, especially on the bitumen. On the last trip up the coast I was running about 45psi and it was great. I shot up the expressway to Newcastle and could see the difference on the fuel gauge.

North of Hexham the traffic was crawling and we decided to go up Buckets Way. With a little bit of rain about and the patched and quite rough road surface I found the car was bouncing and skipping all over the road. It was quite scary so I stopped and pressured down. 40psi on the warm tyres felt a lot better.

When I did a cold tyre pressure check they were at 36psi and have remained there ever since.

I am using a little more fuel but what price safety?

Duncs

Speaking of pressures, I note the recommended tyre pressures in my Patrol are 29 front and 36 rear.

I know that 3 litre is a "lightweight" engine but that seems a little odd to me, especially when the car is empty...

I was told with a car that for every 3 psi above 30psi, up to about 40psi, it gives a 2% improvement in less rolling resistance created by the flexing of the side walls. Most tyres, unless LT, have a maximum pressure of 40 psi.
With the experimentation I have done over the years, it seems about right.

Hi, Just a point , I ride a mountain bike about town and when the tyres are pumped up hard ( not the best ride ) , it is amazing the difference in rolling ease .
You tend not to notice the slight reduction in pressure , same in the 4x4 , but it definately affects the freedom of rolling and the steering as well.
Cheers Des.

Hi Greenant
We have a Nissan wagon and i just run 35psi front and back regardless of ct and weight, maybe i could let the front down a little probably down to 30, we have 10 ply rated tyres and if you had them at 45 it would not be comfortable.
I have never checked the difference in fuel consumption between pressures i find this interesting as i set them to a practical or comfortable pressure.

Mattie

Hi Guys.

Just an observation but looks as though most run higher pressures in the rear than the front. Put my hilux loaded up as for a trip the other week over a weigh bridge and the front was 100 kilos heavier than the rear.

Cheers Graeme

Hi All

from what I have been told by the tyre experts (manufacturers) once the pressure is correct for the weight being carried and the speed you are traveling then you will only gain about 2 percent in reduced rolling rsistance.

This may be because making the tyre stand up more makes the gearing higher (fractionally) so the engine is pushing harder.

Of course if this puts you into a better part of your torque band you could be gaining bith ways.

Of course driving steadily and anticipating so you don't need to brake and accelerate as much can make up to 10% difference, at least thats what I notice when the wife (she of the lead foot) gets behind the wheel.

regards

A

One further issue, The higher the tyre pressures, the harder it is in your suspension, Shocks springs & bushes. I now go for a slightly lower pressure and look to see a slight 'bag' in the tyres, but still over 30 psi

Dunedigger

It is all about finding that perfect balance for your particular set-up. After trying a few different pressures you will find a point where they tyres are not so soft that the vehicle squirms around and not so hard that it rides like a pogo stick.

As Duncs pointed out above - the higher the pressure the less rubber you have on the road.

Like walking on the ball of your foot a rounder harder tyre with high pressure has less of a footprint than a softer lower pressure tyre that has a greater flat spot at the bottom. This leads to extra rolling resistance as the softer tyre has to flex more every time it rotates. The flexing takes more energy to push along increasing fuel consumption as well as creating heat in the tyre which causes the rubber to wear more and shortens tyre life.

I run my tyres on the Prado at 40psi which seems to give a good ride (firm without squirming) while keeping heat buildup to a minimum. At this pressre there still seems to be a good flat section of rubber in contact with the road.

To go for better fuel economy then definately go a bit harder to reduce that rolling resistance to a minimum but just don't go so high as to make the ride too bouncy which may indicate that there is not enough of a contact patch on the road to be safe. Too high a pressure is also evident when the centre of the tread starts to wear out before the edges.

Have fun.
Muddy