I have just gone to check the tyre pressures on the V70 and see the normal settings for front and rear which work out at 2.2 BAR front (32 psi), and 2.1 BAR rear (about 30 / 31 psi), but also a column for 'ECO' which dictates 2.6 BAR front and rear (38 psi).
I understand of course that the 'eco' levels probably mean less rolling resistance and so better fuel economy, but would that not mean less grip, and probably not be a sensible level to have the tyres pumped up to in the winter? 38 psi for a car tyre does seem rather high....
I have never seen the choice before and wonder what the forum think.
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It is a trifle odd. Anyone who competes or goes to track days will be familiar with running the tyres are higher pressures to counter sidewall flex and wearing out the edges. But usually, running a higher pressure on the road will lead to tyres with the middle worn out.
So ECO mode probably will save on the petrol bill, but increase the tyre bill, plus the car will have less grip.
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The Insignia runs at "Eco" pressures of 41 psi and apart from a slightly firmer and noisier ride there appears to be no difference in grip or handling. Not that a car that size "handles" anyway...
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38psi is not that high. 'Fully laden' pressure for the rears on the Octavia is 44psi, which my Halfords pump struggles to reach.
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Is there no explanation of the column title?
What is the title of the first column?
I'd be wondering whether the columns referred either to different models, or different tyre fitments.
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While googling came across a previous discussion here from 4 years ago, including contributions from Number_Crruncher:
www.car4play.com/forum/post/index.htm?t=1030
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Sounds like the full load figures have been renamed Eco pressures, more greenwash.
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My Jetta Sports 170 has Continental Sports tyres, which have a tyre pressure requirement of 33 psi all round for normal use.
I keep them at 36 psi throughout the year and tyre wear has been very even and remarkably low. I've only had to replace two of the tyres on one occasion in the past four years, the front pair, which had covered 30k and still passed the MOT about six weeks before.
I had bought a new pair after being advised of a pending price increase, so eventually decided to have them fitted as the tyre fitting firm concerned had kindly stored them for me for a little while.
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Presumably it's the excessive pressure that helped your car limp through it's emissions test for those awesome but unachievable CO2 figures, and the 'comfort' level is what the dealers are advised to inflate to for servicing.
As pressure goes up the tyre footprint size (and tendency to aquaplane) comes down - each square cm however carries more weight so overall grip isn't usually much different.
Put my old Swift up to the ECO pressures (~41fr 38rear) and saw no change in MPG and a touch more noise compared to comfort (~36/33).
Kept at comfort after that.
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>>Is there no explanation of the column title?
>>What is the title of the first column?
The title is actually 'ECO pressure' alongside other columns for tyre size, speed, Load (1-3 persons) and Max load.
On closer inspection the ECO option only appears to be applicable to the 16 and 18" wheel sizes, whereas mine is on 17's, but the recommended pressures for mine are already pretty high as 39 to 42 psi depending on load.
Lygonos; fascinating info about pressure v. footprint. Never really thought about that before. I guess by the same token the higher the pressure the lower the footprint size, the lower the grip, but I guess we are talking tiny percentage points.
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>> Lygonos; fascinating info about pressure v. footprint. Never really thought about that before. I guess
>> by the same token the higher the pressure the lower the footprint size, the lower
>> the grip, but I guess we are talking tiny percentage points.
A I think Lygonos implied, the basic formula for friction (grip) is the coefficient of friction between the two materials x the weight - i.e. independent of the contact area.
Tyres on roads are more complicated than that of course, but I suppose it will work within limits, other things being more or less equal.
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Question re: Tyre pressures - 'Eco' v. normal - Slidingpillar
