over-inflated tyres

andyrules

Hi

REcently I had 2 new tyres fitted at a small local tyre specialist. I asked them to ensure all the tyres were at the correct pressure as one had been swapped from front to back.

Yesterday I went to check them all and discovered that they were all set at 37 as against the 32/30 as recommended in the handbook. I rang to ask if there was a reason and what should I put them at, and they said definitely follow the handbook spec, and couldn't really explain why they were above this.

My concern is that I thought it was important to ensure you have the correct pressure for safe driving, or is this not so? Also, would there be any damage or extra wear on the tyres - I've been on a few longish journeys and drive around town a lot.

Thank you

malamute

Tyre pressure



Correct tyre pressure can help to extend the life of your tyre, improve vehicle safety and maintain fuel efficiency. Pressure is measured by calculating the amount of air that has been pumped into the inner lining of your tyre in pounds force(PSI) or BAR pressure.
The manufacturer of your vehicle specifies the suitable pressure, and it is your responsibility to make sure that the pressure is checked and corrected on a regular basis, at least every couple of weeks.

Maintaining correct Tyre Pressures

There are three main reasons why maintaining the right tyre pressure is important. The first is safety. Tyres that are under inflated can overheat; and over inflated tyres can lead to poor vehicle handling on the road.
The second reason is economy. Over or under inflated tyres suffer more damage than those with the correct pressure and need to be replaced more regularly. Vehicles with under-inflated tyres have increased rolling resistance that require more fuel to maintain the same speed.
The third reason for maintaining the correct tyre pressure is the environment. Correct tyre pressures help to maintain optimum fuel efficiency. This can equate to lower Co2 emissions coming from your vehicle than those with incorrect tyre pressures and that has to be good for the environment.
To search for the recommended tyre pressure for your vehicle please Click Here.
Click here to see an example of a correctly inflated tyre.
It's important to check tyre pressure regularly. It's not always apparent that air is being lost, but it generally escapes at the rate of up to two pounds of air every month. More air is usually lost during warm weather, so more regular checks are needed when temperatures rise.
Look for the tyre pressure recommended for your vehicle in your vehicle hand book or within the technical information usually found on the inside of your vehicle's front right hand door or fuel tank flap.
Always check the tyre pressure with a tyre pressure gauge when your tyres are cold. Finally, if you are using your vehicle to carry additional load or weight, always consult your vehicle handbook for the correct loaded tyre pressure.

fender

They do not sound to be vastly over inflated. In any case, tires can be inflated above the recommended level if you are carrying a heavy load and the level you mention suggests they may have been inflated for load carrying.

Given the short time they were more inflated, I very much doubt there will be any damage or bad effects.

MrsTinks

Also bear in mind that SOME garage tyre doofers are less than accurate because people use them on tyres that they are not suited for... like lorry ones (seen it... ) and it can shag the calibration.
So best bet is to have them tested with a good quality meter when your tyres are cold.
It could also be the garage who fitted them had a calibration problem with their machine that day...

seftonsun

It is actually illegal to have your tyres over or under inflated. Not likely to be a problem for everyday motoring except for reasons in post above, but if you are in a serious accident and the police examine your vehicle they will check the tyres and the pressures in them. You could well then find that if the pressures were too high or low that it was classed as being contributory to the accident and cause you many problems.

Worth checking tyres regularly.

custardy

as said ,how are you checking the pressures?
petrol station gauges can vary wildly and TBh 5psi over a relativly short period isnt too much of a worry

anewman

I remember reading a website saying overinflation can be good. Think it was this page but too tired to read through at moment sorry

http://www.carbibles.com/tyre_bible_pg2.html

I don't recommend over inflation though as someone above says agains the law etc.

philhuff

Over inflation (to a degree) can be beneficial. It can improve initial turn in and actually improve economy, although to balance that you could be reducing maximum grip and increasing wear slightly.

Under inflation can cause increased fuel consumption, more air pollution, shorter tyre life and greater risk of tyre failure. Over inflation may cause reduced comfort, less grip, greater risk of impact tyre damage and reduced stability in braking and cornering.

The recommended tyre pressures are just that - recommendations. Use that as a starting point, and go from there. For all we know, you might be carrying four adults and some luggage around all day, in which case increased tyre pressures are a very good thing. Conversely, you might head out over muddy fields on a daily basis, where lower pressures would be preferable.

Over/under inflation certainly isn't illegal. If it was, then I could well be legal on my driveway, but illegal by the time I've done 400 miles down the motorway at 70mph. Yes, incorrect pressures can be a contributing factor to an accident, but so can sneezing, and that wasn't illegal last time I checked.

Of course, over/under inflation can increase wear, and lead to an illegal tyre far quicker than otherwise, but that's not to say the inflation itself is illegal.

andyrules

Interesting responses, thanks to all.

I checked them a couple of weeks after the garage as I was planning a journey, and used the pressure gauge at Sainsburys. Tyres would have been fairly cold as I drove directly there. Must admit, i do vary these, depends on which petrol station i'm nearest to.

At the time of the fitting, no-one asked if the car was going to be fully laden, and I was alone with an empty car at the time, so if this was their reasoning then it was an unjustified assumption.

seftonsun makes a worrying point, which is why I was so concerned that the garage in question were so blase about it. I agree philhuff, sneezing is dangerous whilst driving, but there's little you or I can do about that - but I believe you can and should get your tyres safe -and as the experts seem to offer little useful advice then I came on here for your knowledge!

Seems it's probably good to stick with the same gauge? It's a difficult one, suppose you change them according to needs at time. I am a bit paranoid about road safety, and always think that there's only your tyres between you and the road, if you see what I mean.

custardy

i keep a gauge in the car so i can use that to check v garage psi readings

mrbadexample

philhuff wrote: »

Over/under inflation certainly isn't illegal.

Uh-oh! Yes it is:

Condition And Maintenance Of Tyres

Regulation 27(1)(a) to (h) Road Vehicles (Construction and Use) Regulations 1986

A wheeled motor vehicle or trailer fitted with a pneumatic tyre shall not be used on a road, if :-

• (a) the tyre is unsuitable having regard to the use to which the vehicle is being put or to the types of tyres fitted to its other wheels, except where a temporary use spare tyre is fitted to a passenger vehicle with up to 8 passenger seats driven at not more than 50 m.p.h.,

• (b) the tyre is not so inflated as to make it fit for the use to which the vehicle is being put,

• (c) the tyre has a cut in excess of 25 mm or 10% of the section width of the tyre, whichever is the greater, measured in any direction on the outside of the tyre and deep enough to reach the ply or cord,

• (d) the tyre has any lump, bulge or tear caused by separation or partial failure of its structure,

• (e) the tyre has any of the ply or cord exposed,

• (f) the base of any groove which showed in the original tread pattern of the tyre is not clearly visible,

• (h) the tyre is not maintained in such condition as to be fit for the use to which the vehicle or trailer is being put or has a defect which might in any way cause damage to the surface of the road or damage to persons on or in the vehicle or to other persons using the road.

except (none of these exceptions apply to (h)) :-

• • an agricultural motor vehicle that is not driven at more than 20 m.p.h.,

• • an agricultural trailer,

• • an agricultural trailed appliance, or

• • a broken down vehicle or a vehicle proceeding to a place where it is to be broken up, being drawn, in either case, by a motor vehicle at a speed not exceeding 20 m.p.h.,

• • in respect of (c), (d) or (e), if the wheel and tyre are designed to run flat and the tyre is marked as such,

• • in respect of (f) only, :-

• - a three-wheeled motor cycle unladen weight not exceeding 102 kg and maximum speed 12 m.p.h.,

• - a pedestrian-controlled works truck, and

• - passenger vehicles other than motor cycles constructed or adapted to carry no more than 8 seated passengers in addition to the driver,

• - goods vehicles with a maximum gross weight which does not exceed 3500 kg, and

• - light trailers, not being goods vehicles, first used on or after 3rd January 1933.

Having said that, I've never known anyone being prosecuted for over-inflated tyres (probably because they don't look flat, and as a result may not actually be checked).

Seriously under-inflated tyres are dangerous and prosecution action is common. As to what "seriously" is defined as, well that's ultimately for the courts to decide.

MBE :cool:

And OP - I wouldn't worry about 5psi over for a short term. As has been mentioned, if the car is heavily laden, an increase from the normal pressure is recommended.