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Tyre pressures and Motorway speeds - brum

Many years ago it seemed the advice was to pump up tyres an extra so many psi if you were going on a long high speed journey. Not sure why.

My Superb has a tyre pressure label in the fuel flap that states 32psi as minimum, an "eco"/passengers with luggage setting of 36 psi and a higher pressure still if fully laden to the gunnels. All pressures to be checked when tyres are cold of course

What comments on whether sustained high speed (read 70 mph motorways) merit an elevated (cold) pressure and by how much. Particularly if just with driver only and no heavy luggage.

Tyre pressures and Motorway speeds - Xileno

I've never bothered adjusting for motorway use, only the number of passengers or luggage advice in the handbook. Usually something like 1 to 3 passengers, or 3 + luggage.

Tyre pressures and Motorway speeds - Andrew-T

I've never bothered adjusting for motorway use, only the number of passengers or luggage advice in the handbook. Usually something like 1 to 3 passengers, or 3 + luggage.

The main effect of adding passengers and/or luggage is to increase load on the rear wheels, the front load is pretty much the same. So it's the rear tyres that need boosting.

Tyre pressures and Motorway speeds - Engineer Andy

I've never bothered adjusting for motorway use, only the number of passengers or luggage advice in the handbook. Usually something like 1 to 3 passengers, or 3 + luggage.

The main effect of adding passengers and/or luggage is to increase load on the rear wheels, the front load is pretty much the same. So it's the rear tyres that need boosting.

Indeed - my cars says 32 all around for normal use with up to 2 passenegers, with (if I recall correctly) a max. of about 45-46 psi when full with passengers and boot load.

When I go on holiday (just me) but have a (heavy) full boot load, I will up the fronts to 33 and the rears to 35-36 psi for the journey there and back.

A lot of this is as much about personal preference for the feel of the car when driving as it is safety and the balance between handling and comfort.

Add to that that it's always a good idea to keep an eye on the tyre depths across the width of each tyre, and to slightly modify the tyre pressures to keep the wear as even as possible across the width of each tyre.

As John Cadogan says, it's also far better to 'over' inflate tyres (obviously not above the maximum recommended) than to significantly underinflate, as the latter (not really an issue on safety for <10% down) will mean lower mpg, higher wear generally and a greater risk of catastrophic tyre failures at high speed.

Tyre pressures and Motorway speeds - _

I think with modern cars, everything is calculated for optimum usage.

Us 2 adults plus 1 dog and shopping.

Since my high speed days of doing London-Geneva are over, I leave tyres at what Kia suggest for my car.

In the good old days I would check tyre pressures each way before that trip, since having tyre pressure monitors I use those and if near a mates place let his apprentice check and give a tip.

Only check levels monthly now.

What does t'internet say?

Edited by _ORB_ on 27/03/2021 at 13:41

Tyre pressures and Motorway speeds - John F

Hardly worth bothering about for a mere 70mph. Over sixty years ago, In the handbook for my father's Rover 105S, there was the following advice........For sustained speeds above 90mph inflate tyres by an extra 4 psi. Heigh ho - such is progress....

Tyre pressures and Motorway speeds - RT

For most modern cars, sustained high speed means flat out on the unrestricted Autobahn - I treat 70 mph on UK motorways as normal so only increase pressures for load or towing.

Tyre pressures and Motorway speeds - brum

What does t'internet say?

Ok, you asked, so I googled......

It seems that www.etrto.org/Home is the organisation that is all expert in tyres

And somewhere they say that you should add 1.5psi for every 10kph inncrease over normal speeds.

By normal speed they mean 160-190kph depending on the speed rating of the tyre.

So for all UK law abiding citizens, no pressure adjustment is required.

Some further explanation here

www.tyreleader.co.uk/tyres-advices/adjust-tyre-pre...d

Tyre pressures and Motorway speeds - Terry W

I have never adjusted tyre pressures to reflect changing loads or speeds.

But I suspect there are theoretically good arguments for doing so:

  • flexing of the tyre as it rotates creates heat. Higher pressure = less flexing = less heat = less tyre wear = reduced risk of "catastrophic" failure
  • reduced fuel consumption as less energy is wasted in tyre flexing and reduced rolling resistance

However most tyres are likely to be rated at 120-150 mph. 70 mph is hardly putting them under great stress. And as even fairly modest family hatches weigh in at 1200-1500kg, the weight of an extra one or two people (+5-10%) is hardly likely to materially change handling or tyre characteristics!

Tyre pressures and Motorway speeds - skidpan

My Superb has a tyre pressure label in the fuel flap that states 32psi as minimum, an "eco"/passengers with luggage setting of 36 psi and a higher pressure still if fully laden to the gunnels. All pressures to be checked when tyres are cold of course

Have run both Superb's between the min and Eco for most of the year but put them up to Eco when we go to Scotland with a higher load.

Tyre pressures and Motorway speeds - Sofa Spud

We have a small hatchback at the moment and I usually keep the tyre pressures at half-way between the maximum and minimum recommended. It works OK for me and all 4 tyres, which are now quite old, are worn evenly across the treads.

Edited by Sofa Spud on 28/03/2021 at 14:29

Tyre pressures and Motorway speeds - thecloser

On the subject of tyre pressures, if I inflate my tyres to the recommended pressure (32psi) how long should that pressure be maintained before needing to be topped up given that the car is doing about 200 miles per week with 50 of those being motorway and the balance urban travel on uncongested roads?

Tyre pressures and Motorway speeds - Engineer Andy

On the subject of tyre pressures, if I inflate my tyres to the recommended pressure (32psi) how long should that pressure be maintained before needing to be topped up given that the car is doing about 200 miles per week with 50 of those being motorway and the balance urban travel on uncongested roads?

It really depends upon the car, what combo of wheels and tyres and the age/condition of all three, as well as usage pattern. Older wheels will likely lead to small tyre leaks due to corrosion/misshapen rims, even when running new tyres. Having the proper sealant (or a bit more) used when fitting can help reduce leaks when tyres are fitted on older wheels.

Play it by ear, really - check them weekly (when cold, before use [they will result in higher readings if left in direct sunlight), then if they don't drop, leave it for half a week more and then do so again, until they do drop, then monitor and pump back up to the recommended level that often.

For your usage (about average), I'd say 1-2 weeks between checks will be fine, assuming the wheels and tyres are in reasonable condition and your driving pattern isn't made up of lots of high speed turns on twisty roads.

I'm currently only using my car once every 1-2 weeks (about 25 miles round trip) for shopping and can get away with a check once a month, needing pump the tyres up slightly every couple of months, but then both tyres and wheels are still quite new (I had them replaced 3 years ago and have only covered around 6k miles in that time).

On the old (12yo) rims and 6yo tyres, I was having to check them weekly (using it for about the same mileage as you) as the corroded alloys were starting to engender small leaks around the tyre sidewalls. I forgot to check them for a month and 3 had dropped from 32psi to 28 and the worst affected one had dropped to about 24psi.

Underinflated tyres can be dangerous, as they are more susceptible to blowouts, which obviously isn't good at high speed. better to check more often than not - it only takes a couple of minutes, so keep the tyre pump in the boot and pressure gauage handy.

Tyre pressures and Motorway speeds - thecloser

Engineer Andy, very many thanks for your comprehensive answer to my tyre pressure query and apologies for the delay in replying. I have not visited the site for several days. Your reply gave me just the information that I was looking for. I have asked tyre fitters the same question and have never received received a definitive answer. I couldn't agree more with your final sentence.

Tyre pressures and Motorway speeds - Smileyman

I've only bothered when going on very long journeys with passengers and luggage, mind you, I'm not sure about the impact of very hot or very cold weather on the guidance!