Motoring Discussion > Tyre pressures and fuel economy Miscellaneous
Thread Author: BobbyG Replies: 11
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New Thu 28 Jul 11 09:31 
 Tyre pressures and fuel economy - BobbyG
Checked the Beetle's tyre pressures last night and was surprised to see that the recommendation for the "light load" was 1.9 (or 28psi) all round. This for a heavy, diesel engined car.

Can't remember the last time I had a car where the tyre pressures were in the 20's although my memory is maybe playing tricks.

However was wondering, many of the new fuel efficient eco bluemotion thingy type cars have narrower wheels and tyres to improve fuel economy. I assume that less tyre surface on road equals less friction.

So if I upped the tyre pressures to the "heavier load" setting, could I achieve better mpg as this presumably would mean less contact surface? I realise this might affect handling slightly but as it is my missus' car and she is not exactly a rally driver, I don't think she would run the risk of exceeding the grip levels.

Thoughts?
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New Thu 28 Jul 11 09:40 
 Tyre pressures and fuel economy - bathtub tom
I think you'll find it makes very little, if any, difference.

It seems that this is a result of tyres becoming wider and with lower profiles.

However, if you were running around on 155/13s..............
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New Thu 28 Jul 11 10:15 
 Tyre pressures and fuel economy - idle_chatterer
I used to run my 170PD A4 at the 'higher load' setting in an attempt to get reasonable economy out of it in my mostly motorway usage (it didn't work). all it did was mean that the centre section of the tyres wore out more quickly. IIRC they were 235/45 R17s.
Last edited by: idle_chatterer on Thu 28 Jul 11 at 10:15
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New Thu 28 Jul 11 14:54 
 Tyre pressures and fuel economy - -
Wouldn't raising the pressures decrease the footprint, in which case whether driven saint like or not there could there be less grip in the Heaven forbid event of a panic wet stop?

As a rule i always run my tyres at the lowest normal setting unless i'm loading up or going long distance high speed.

4psi in MB land difference.
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New Thu 28 Jul 11 15:21 
 Tyre pressures and fuel economy - Armel Coussine
I always run mine at the higher settings. Makes very little difference to ride comfort except through potholes and does make a small, but measurable, difference in fuel consumption. Most of all it makes the car feel more like, well, a car.

Vehicles vary quite a lot in this area though.
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New Thu 28 Jul 11 16:33 
 Tyre pressures and fuel economy - Lygonos
Increasing pressures by 20% (say 30 to 36) will bring around 2% benefit in fuel economy - so small you'll prob not even notice it. Conversely you'll use about 1% more fuel for every 10% lower pressure.

Too high a pressure may reduce grip in some circumstances but will likely reduce the risk of aquaplaning (note this is NOT the same as non-aquaplaning wet grip).

Depending upon the tyre/car/suspension, running at 'non-standard' pressures can do all sorts of wacky things to treadwear rates.
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New Thu 28 Jul 11 17:17 
 Tyre pressures and fuel economy - Stuu
My Ignis is very sensitive to tyre pressures, anything more than a couple of psi out and it tramlines horribly so I keep on top of them.

I experimented with putting another 3 psi in each tyre over and above the heavy load settings ( always have these as I use it to carry loads ) and it made about 2-3 mpg difference but with the ride so hard anyway, I didnt continue with it, my spine cant take it!

On the Charade higher tyre pressures made some decent gains, around the 5 mpg mark, but then it had pretty small low resistance tyres.
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New Thu 28 Jul 11 17:26 
 Tyre pressures and fuel economy - Lygonos
You'll find the Ignis quite sensitive to different types of tyre too.

If you keep it long enough to need new tyres ;-)

Apart from the Panda 100hp and some Twingo variants are there any other bargain basement (under 10 grand after discount) warm hatches out there these days?
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New Thu 28 Jul 11 17:29 
 Tyre pressures and fuel economy - Stuu
They are all too heavy these days Lyg.

Panda 100hp is dog slow, as was the Sport Ka. They have just discontinued the Suzuki Swift Sport which I fancy a go in one day.

Id say the sporty Twingo models are the best bet, I look at them whever I see one, they look sweet as a nut.
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New Thu 28 Jul 11 17:33 
 Tyre pressures and fuel economy - Lygonos
Looking at the usual discount brokers none have the Panda 100HP available - presume there's no stock with the new Panda due in a few months.

There must be a market for a 'modern-day' 106 Rallye, Saxo VTR, Ignis Sport.

I think the cheapest 'low weight' sporty variants are Clio Cups at north of 15 grand.
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New Thu 28 Jul 11 17:49 
 Tyre pressures and fuel economy - Stuu
>>I think the cheapest 'low weight' sporty variants are Clio Cups at north of 15 grand.<<

Of course its worth considering that cars in general cost more than they did so perhaps its now impossible.

The do a Twingo Gordini tce 100 for £11,600 ( maybe less with disc ), its prob as cheap as warm hatch thrills get these days.
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New Thu 28 Jul 11 17:33 
 Tyre pressures and fuel economy - RattleandSmoke
The 100hp is now discontinued, and they are quite fast if you drive it like an Italian, they have 6 gears to help with that too. My main problem with the 100HP is the ride.

Somebody on the Panda forums changed his 100 HP to a 1.2 Euro 5 Mylife and prefered as although slower and not as well equipped it was a lot more comfortable.

Edit the 100HP was discontinued because it would have been too much effor tot make it comply with Euro 5 considering how few of them sell and the range is being replaced early next year.

Last edited by: RattleandSmoke on Thu 28 Jul 11 at 17:34
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