Should i change my tyres?

benham3160

skiddlydiddly wrote: »

It doesn't sound that high for the fronts but I generally have the rear 2-3psi lower on my cars as the majority of the weight is over the front wheels.

"Weight" doesn't affect pressure in a container of a fixed volume. You may have more air particules, but that doesn't always correlate to pressure.

Steering is generally the reason the front and rear wheels are set differently......

Sorry to be a smart !!!!.

Regards,
Andy

ailuro2

Just checked my '03 Mondeo last night, for 16" tyres it is 33 on front and 30 on rear, so it sounds about right that the 17s would be 35...

hubby has the car or I'd nip out and check it... the info is inside the petrol filler flap.;)

If you think you've been running on a partiall inflated tyre I'd take it in and get it checked out, it may have internal damage.

I get free tyres via work and have taken a few slow punctures in, only for them to find a nail and a handful or rubber where it's worn inside through running flat even for a short period of time.

Better safe than sorry,imho.

anewman

An alarm with a tilt sensor would go off if someone let your tyres down

keith1950

Hi , it could be a small nail or screw in the tyre and it only deflates when you come to rest with the nail at the bottom ( between the tyre and the road ), in any other position there is no leak.

skiddlydiddly

benham3160 wrote: »

"Weight" doesn't affect pressure in a container of a fixed volume. You may have more air particules, but that doesn't always correlate to pressure.

Steering is generally the reason the front and rear wheels are set differently......

Sorry to be a smart !!!!.

Regards,
Andy

Well I don't know about that, but then why do commercial vehicles have such high tyre pressures eg 60 psi on vehicles not much heavier than some cars but built to carry say 1-1.5 tons of load.

anewman

benham3160 wrote: »

"Weight" doesn't affect pressure in a container of a fixed volume. You may have more air particules, but that doesn't always correlate to pressure.

Steering is generally the reason the front and rear wheels are set differently......

More weight flattens the tyres however making more area contact with the road. This is why pressures can be higher up front, particularly on cars with heavy engines. It's all about the amount of tyre in contact with the road.

You will notice most recommended tyre pressures are based on load in the car, with different figures for a full laden car to one with only 2 passengers and an empty boot.

skiddlydiddly

Yes thats how I see it too.It doesn't seem to me that a tyre is a container of fixed volume as being made of rubber it will have a certain amount of stretch in it which will increase as you pump more air into it ie increase the pressure.

anewman

skiddlydiddly wrote: »

Yes thats how I see it too.It doesn't seem to me that a tyre is a container of fixed volume as being made of rubber it will have a certain amount of stretch in it which will increase as you pump more air into it ie increase the pressure.

This effect can be seen on a not fully inflated football. If you push on top (apply weight) the ball flattens out and more of the ball touches the ground. The more weight you apply, the more the ball's shape changes and area is in contact with the ground.

skiddlydiddly

And I would imagine it also increases the pressure inside the ball.

benham3160

skiddlydiddly wrote: »

Well I don't know about that, but then why do commercial vehicles have such high tyre pressures eg 60 psi on vehicles not much heavier than some cars but built to carry say 1-1.5 tons of load.

Why do some pushbikes have tyres inflated to 120psi?!

Regards,
Andy