ADUK Archive

I bought a Vaxhall insinga and was surprised the manual lists comfort and eco tyre pressures which are vastly different.
This lead me to wonder, which I should use

What is the effect in handling when over inflating tyres? And life of tyres?

Over inflation reduces grip and shortens the life of tyres, by causing rapid wear in a narrow central band.

It may be that the tyre/wheel combination has a degree of tolerance that has been identified by the manufacturer under testing, allowing essentially a range of acceptable pressure so I'd be surprised if staying within that band would cause gross wear.

As to handling - you'd probably need to test it it out, but I would expect that the range of pressures in a significant deterioration in handling under normal driving, but I suspect it would become evidence is pushing towards the limits of the vehicle.

mawallace wrote:I bought a Vaxhall insinga and was surprised the manual lists comfort and eco tyre pressures which are vastly different.

To clarify, are these different pressures to be used with the same type of tyre, or is there one set of pressures to be used in low rolling-resistance "eco" tyres, and another set to be used in conventional tyres?

David

B, it says

Comfort and then listgs the lower pressures

Then it says economy pressures, so it is for the same tyres, as far as I can see

Most unusual. I would have thought that if the pressures differ vastly, it would relate to different tyres as the sidewall profile would bulge on the comfort setting causing weakening of the sidewall, and the tread would show excessive wear on the eco setting.

fungus wrote:Most unusual. I would have thought that if the pressures differ vastly, it would relate to different tyres as the sidewall profile would bulge on the comfort setting causing weakening of the sidewall, and the tread would show excessive wear on the eco setting.

What does the OP mean by "vastly"?

Front Rear
Comfort with up to 3 people 32 29

ECO with up to 3 people 39 38

With full load Engine 32 39

The ECO figures seems to be significantly increasing the pressure - I don't think I have even seen such a high typre pressure being recommended for a mainstream car.

It has long been know that increasing pressures up to the laden max slightly decreases fuel consumption due to an decrease in . The impact of wear AIUI is not noticeable under conservative driving - but more spirited shall we say driving would see increased tyre wear and poorer handling. To be fair if you are concerned with ECO driving you are probably going to be conservative.

I have an old AA maintenance book that contained a section on saving fuel that suggested doing something like this during the summer to save fuel (specifically inflating the tires to the max load pressures), but personally I'd not be happy taking the pressures up that high at the front, especially not in winter as grip has to be compromised IMO.

This feels to me as something done to "tweak" the MPG figures downwards to meet the every stricter EU demands cut cut fuel consumption and CO2 emissions, even at the cost of safety and maintenance costs!

Personally if I was considering using it - I'd be asking the manufacturer for a copy of the testing data, and confirmation that these pressures were safety tested in a cold climate during winter!

Ok - I would describe that as a significant difference rather than a vast one.

The higher pressures are similar to those recommended for my car on full load (and also for sustained speeds of 100+ )

I guess modern cars have a fairly wide envelope in terms of suitable pressures for normal driving.

Just double checked, they are 2 different models ecoflex and comfort which explains the differences, same as my corsa Eco has 39 front always thought it was high, but different tyres to the other models as well

mawallace wrote:Front Rear
Comfort with up to 3 people 32 29

ECO with up to 3 people 39 38

With full load Engine 32 39

I think that sort of thing is becoming more normal. A couple of reps from a tyre company gave a talk to my IAM group recently and they mentioned that car manufacturers are starting to do this. I'm sure I've seen similar in one or two new car handbooks too. I was expecting you to have a difference more than 5, less than 10 - that seems to be how these eco numbers work.

You can feel when a tyre is under-inflated and over-reliant on the sidewall -- you get a particular shimmy as you cross whitelines (particularly in the wet when the tyre loads and unloads quickly). It's harder to detect an overinflated tyre but you have a reduced contact patch and reduced grip.

In the trade-off between burning hydrocarbons and beating out metal panels, my eco-driving is to have as much available grip in the car, even if that means a little more rolling resistance. 18 all round.

7db wrote:In the trade-off between burning hydrocarbons and beating out metal panels, my eco-driving is to have as much available grip in the car, even if that means a little more rolling resistance. 18 all round.

Should be the only concern, for who knows when that grip might be needed.
Perhaps manufacturers get EU bonus points for this sort of stuff. It's just having to follow the current, missguided, concerns.
In other words, PR.