Tyre pressure & MPG

biko

Just as a discussion as I've read a few threads elsewhere but not on boards.

As you increase tyre pressure you decrease footprint and therefore resistance thus getting better fuel economy.
I'm currently running on 30 PSI all around and have been thinking of putting the tyres on 36 all around, does anyone have info on whether this will significantly decrease fuel consumption on motorway driving?

Yes, I know that one should use recommended pressure and that higher pressure will mean less road contact and also greater risk of car loosing grip in rain etc.

omb0wyn5ehpij9

biko wrote: »

Just as a discussion as I've read a few threads elsewhere but not on boards.

As you increase tyre pressure you decrease footprint and therefore resistance thus getting better fuel economy.
I'm currently running on 30 PSI all around and have been thinking of putting the tyres on 36 all around, does anyone have info on whether this will significantly decrease fuel consumption on motorway driving?

Yes, I know that one should use recommended pressure and that higher pressure will mean less road contact and also greater risk of car loosing grip in rain etc.

A difference of 6psi will make very little difference on your fuel consumption unfortunatly!

biko

Do you have stats for this or is this in your experience?

I'm more interested in the discussion than actually going ahead with this. I think some BMW models (I've a 320i) can be pushed over 40 PSI with the risks that entails.
I drive mostly city so won't really benefit much from higher pressure.

Btw, very hot weather will expand the air in the tyres so driving long and fast on a scorching day with already high pressure mightn't be a great idea.

omb0wyn5ehpij9

biko wrote: »

Do you have stats for this or is this in your experience?

It's from my own experience. I have never noticed a difference at all. Apart from when I had a slow puncture and the fuel consumption went up for obvious reasons!

CiniO

It will make a difference.
Hard to say how much of a difference. Depends a lot on a car, tyres, tyre size, etc...

But remember that by increasing tyre pressure you will cause more stress to the suspension, causing it to wear more quickly.
All shocks, joints, bushings, etc will shorten it's life.

shedweller

I have looked but there is no definitive answer. It's small to be honest. But your tyres will last far longer as they will wear more evenly.
Here's a graph showing rolling resistance vs pressure:

It looks more dramatic than it is.
As for grip, well, that debate has been going for some years now but i have yet to see conclusive proof (ie: graphs, youtube videos etc) that it is affected negatively.
So pump up all you want.
As for heat generated, don't worry. They don't get as hot when pumped up more due to less flex in the tyre. Mine have been high for years without any ill effects at all. Even helps avoid pothole damage!

biko

An interesting look at pressure and resistance, although not much there is a difference.

https://www.youtube.com/watch?v=61X-UoIt_64

shedweller

Small difference alright but it makes a difference on the road at speed.
Anyhoo, here's a link that appears to have a load of info:http://www.retread.org/Inflation/
And a prius forum where they tend to be majorly geeky with such things!
http://priuschat.com/forums/gen-iii-2010-prius-technical-discussion/66000-tire-pressure-mpg-tests-tire-inflation.html

-Chris-

Increasing pressure will also promote uneven wear on the tyres, wearing them prematurely. It's possible that the money you save on fuel will be countered by the cost of replacing your tyres more regularly.

shedweller

-Chris- wrote: »

Increasing pressure will also promote uneven wear on the tyres, wearing them prematurely. It's possible that the money you save on fuel will be countered by the cost of replacing your tyres more regularly.

Without malice i must really disagree with you on that. The tyres i put 100,000km on had 4mm tread left on them when i retired the car and it was even wear too, despite being at 40 psi for their whole life.
If overinflated from new, they will wear more in the middle, but run them in for a while, say 1000km and you can then inflate them to whatever you wish. There will be no excessive centre wear.

biko

I've just put my brand new Uniroyal RainExperts up to 40 PSI (max on tyre is 51). I'm always noting my MPGs when I fill up so will see if it changes anything or if handling in rain changes.

Front right tyre after increasing to 40PSI, tyres has about 200 miles on it