I checked my tyre pressures yesterday . Each read 1.9 bar , but the pressure on the petrol cap label stated that they should each be 2.2

Have I therefore been running around on under inflated tyres or is this part of the running in process ?

Many thanks in advance for the advice, as always much appreciated.

YetiRob

Hi!

As far as I know underinflated tyres is not part of the run-in process, so you should raise the pressure to avoid excess wear of the tires. If you are willing to sacrifice some comfort you can have higher pressures (closer to the ones stated for fully loaded car) if you like as this will improve the fuel consumption. I read somewhere that running with overinflated tyres does not harm anything (apart from some impact on the comfort), whereas underinflated will increase fuel consumption and heavily decrease the handling! Of course yoy should never inflate the tires over the tyre specifications!

I'm running with around 2.5 bar in all tires, and I am quite happy with it.

Edited 11 August, 201015 yr by the_raz

I tried the Eco settings as they call them on my last car for a while, set to the mfrs levels. I managed a marginal improvement on economy, 1-2mpg, but my tyres wore badly down the centre due to the over inflation. The tyre fitter looked at me as though I was stupid when I explained why the tyres were inflated to that level and since then I have kept them to the standard pressures.

Incidentally, if you do these eco settings you also tend to get a little more road noise and the ride is firmer and bumpier. For me the extra you gain in mpg is not worth it but that is a personal decision and others may be happy to go along with it.

As to why your tyres reduced a little I think they all do that to an extent. The good sign is they are doing it consistently as that is important in good grip, 4 consistent tyres levels. Ideally they are at the right pressure but that means you just have to check them every 1-2 weeks.

Hi!

As far as I know underinflated tyres is not part of the run-in process, so you should raise the pressure to avoid excess wear of the tires. If you are willing to sacrifice some comfort you can have higher pressures (closer to the ones stated for fully loaded car) if you like as this will improve the fuel consumption. I read somewhere that running with overinflated tyres does not harm anything (apart from some impact on the comfort), whereas underinflated will increase fuel consumption and heavily decrease the handling! Of course yoy should never inflate the tires over the tyre specifications!

I'm running with around 2.5 bar in all tires, and I am quite happy with it.

Running on under inflated tyres is dangerous in the extreme. The tyres can overheat and strip treads or even get stripped off the wheel when cornering sharply. Even if that doesn't happen, then the outside shoulders of the tyres will wear away quickly. With higher pressures and light loads, you may find that your tyres will wear in a band around the centre . Also if the pressures are too high for the load you are carrying, you are reducing the contact area with the road and this could cause problems with grip in wet weather. It is best to use the recommended pressures or only small variations. eg. My own Superb's recommended pressures convert to 30.5 lbs sq inch front and 34lbs sq inch rear. I have experimented a bit and now run at 32 front and 33 rear. 32 front stiffens up the front and makes it more responsive without reducing grip too much or making the ride too sharp. 33 rear reduces the tendency for the rear end to bounce with lighter loads.

Hi,

daft as it may sound how did you check your pressures; most accurate method is to use a 'pencil gauge'. Also remember seasons and weather will effect the pressure and you will get a slight loss over time anyway. Hence why checking your tyres on a regular basis is a must and that includes a visual inspection for damage and for the 'full works' removing stones etc. from the tread if you really like getting carried away.

Regard tyres both under inflation and excessive over inflation can seriously effect the safe handling of a vehicle and premature tyre wear. Under-inflated usually leads to more shoulder wear on the tyre, whereas overinflated affects the centreline of the tyre.

Some manufactures such as Vauxhall now give three levels of tyre pressures, normal light load, heavy load/high speed and economy running (a higher tyre pressure can improve fuel consumption). I personally tend to stick with the light load pressure unless I'm planning a long motorway run where an increase in pressure is desirable due to the speed and heat build-up.

As I previously mentioned an increase in pressure will save fuel but there can be a trade off against grip particularly in wet of slippery conditions.

Regards,

TP

Thx to all .

I have increased the pressures to the suggested level. So I'll see how they go.

YR

I personally tend to stick with the light load pressure unless I'm planning a long motorway run where an increase in pressure is desirable due to the speed and heat build-up.

Hi Tim,

I used to do that, but here is another logical position:

As the speed builds, the tyres warm up and hence the pressures also increase. It is quite likely that this effect takes care of the desire to run higher pressures at speed to reduce warm-up and decrease rolling resistance. If it suddenly starts to rain, the water will cool the tyres and they should return to near normal temperatures and pressure - all by their little lonesome selves.

I have stopped increasing the tyre pressure for high speed. I suppose this idea really came from the old cross-ply (=pre-radial) tyres, which really got hot at speed.

Just t'inken'...........................

Hi Tim,

I used to do that, but here is another logical position:

As the speed builds, the tyres warm up and hence the pressures also increase. It is quite likely that this effect takes care of the desire to run higher pressures at speed to reduce warm-up and decrease rolling resistance. If it suddenly starts to rain, the water will cool the tyres and they should return to near normal temperatures and pressure - all by their little lonesome selves.

I have stopped increasing the tyre pressure for high speed. I suppose this idea really came from the old cross-ply (=pre-radial) tyres, which really got hot at speed.

Just t'inken'...........................

For continuous maximum legal speeds in this country (say up to 80 mph), I don't think it is necessary to increase tyre pressures unless you are carrying heavier loads. If however you were running on the continent at speeds that are sometimes permitted there and for a period of time, then I think it is still a good idea to use higher pressures in order to restrict heat buildup.

For continuous maximum legal speeds in this country (say up to 80 mph), I don't think it is necessary to increase tyre pressures unless you are carrying heavier loads. If however you were running on the continent at speeds that are sometimes permitted there and for a period of time, then I think it is still a good idea to use higher pressures in order to restrict heat buildup.

You mean exceeding the Uk limit by just a little? :wonder:

I did a very subjective test on my last long trip in Germany - 100 mph where possible - and felt the tires on each stop, as I usually do. There was not any noticeable temperature difference with the standard pressure of 2.2 bar all around as I normally use or by adding another 0.2 bar, which I used to do.

Load dependent higher pressures are a different question - they should be followed, no doubt about that. I usually do not carry anywhere near the maximum loads, so do not feel the need for anything more than the 2.2 bar.

With modern radial tyres, I doubt there is any significant diffeence in rolling resistance with the 0.2 bar pressure difference. With the old crossply, there was a big difference.

The Autoclubs like ADAC, FDM and maybe AA and RAC as well still do recommend the practice of extra pressure for prolonged HS driving. I am just wondering if there is any real need, because they do not explain there reasoning behind it. The car manufacturers do not make this recconmendation - only list the load dependent reccommendations.

Edited 11 August, 201015 yr by Agerbundsen