Tyre Pressures

[Mick F]

This is in Tea Shop because it's about cars!

We know that (same sized) bike tyres need different pressures because of carcass make-up.

If you read your car handbook, it will tell you the pressure requirements front and rear with respect to loaded/unloaded, and different tyre sizes depending on vehicle spec.

What happens if you change your tyres from the original spec?
Say your car came with Conti tyres, and you eventually change them for Firestone, or Dunlop, or Michelin or Yokohama, let alone cheap budget tyres?

These tyres are all very different, so maybe then need different pressures?
Don't get me onto the subject of the accuracy and precision of tyre pressure gauges.

[mjr]

If you read your car handbook, it will tell you the pressure requirements front and rear with respect to loaded/unloaded, and different tyre sizes depending on vehicle spec.

What happens if you change your tyres from the original spec?

My current car's handbook gives different pressure ranges for different tyre specs, as well as loaded/unloaded and they are ranges not single values, so probably it varies by manufacturer too. Maybe if the car is less refined, you won't feel enough difference to matter or they don't expect most drivers of such cars to do more than occasionally aim at a rough number with imprecise kit?

[NATURAL ANKLING]

Hi,
I find that you have to see how the tyres wear, and adjust the pressures to give even wear.

But how many of you actually rotate your tyres anymore to correct front asymmetric wear with front wear drive.

Surprised you worry that much Mick F as you swap your car often
Your not swapping tyres when old ones are still useful are you...................

[Mick F]

Swap our car often?
We sold our Clio after 17years of ownership only last September having traded in our 2nd car a month previously - Fiat500 - owned for four years - and bought a Yaris Hybrid.

New tyres on the Yaris last month. They kept the old ones, though it costs them to dispose. I took a trailer-load from them a few years ago for free in an effort to build a wall that we could fill with soil and grow flowers and strawberries ............. but it never got off the ground.

[fausto copy]

Probably the best way is to look on the website of the individual tyre manufacturer.
They often give specific requirements for tyre sizes etc.

With motorhomes the converter usually states the maximum pressure allowed for a specific tyre.
However, the best way is to weigh the vehicle, obtain accurate axle weights and refer to the website for accurate pressures.
For instance, when we picked up our new 'van we were told to inflate to 80 lbs.
Having visited a weigh bridge (for the very modest fee of £10) we are now running at 48 lbs front and 58 lbs rear.
And what a difference the ride is.

I suspect you could do the same with car tyres too.

[Mick F]

What an excellent idea.

All we have in our handbook for the Yaris is this, and it doesn't tell you the axle weight, only the total weight. I would imagine this is the same for most cars.

May have to do research, not just for the axle weights, but the tyre websites too.
Sounds like a happy hour Googling.

[Mick F]

I'm finding conflicting information. I'm not surprised in the slightest!

First, is the info in the handbook, and second, the info from https://www.puretyre.co.uk/search-resul ... 195/50R16/
I'm actually prepared to believe Pure Tyres as when we replaced our tyres they were all worn on the outsides signifying long-term under-inflation.

Can't find any axle weights yet.

[geocycle]

On a related point we have a tyre warning light that comes on if the tyre loses pressure. How does this work? It seems very sensitive ie topped up last week to 32 psi, indicator light came on when on M6 so stopped and checked at services and all tyres were above 30 psi. Given these were different gauges with error margins I'm very surprised I got a warning.

[fausto copy]

To find an accurate axle weight, you really need to get the vehicle weighed.
Your local weigh bridge would accommodate you for a small fee.
Weigh the whole vehicle first to establish total vehicle weight, then drive slightly off leaving one axle on the weigh bridge.
Obtain that reading for that axle weight and simply deduct that number from the total weight for the other axle weight.

I don't suppose there's that much difference weight wise from an unloaded or loaded car, but if you weigh the car with the normal load, then you'd be able to obtain the appropriate tyre pressures for general usage.

With our motorhome. we weighed it with the normal two occupants, half a tank of fuel, 20 litres of freshwater on board, and all the kit we normally take when travelling, including the two bikes.

[NATURAL ANKLING]

Hi,
Tyre pressures will be there abouts, keep an eye on front wear, depends how and where you drive......................oh gov are to ban hybrids that won't go 50 miles on the battery

[Mick F]

Still searching for definitive info.
I don't have confidence that Toyota's info is correct.

I still believe that tyre pressures won't be the same for different tyre manufacturers' tyres. They're bound to have different attributes and make-up, so therefore pressure requirements will be different.



BTW, our car will do about 2miles constant speed on the flat, but could be much further if there's braking or downhills involved because the battery get charged by re-gen. Driving back home from the west, the car goes into electric drive at the top of Southover and stays in electric all the way home .............. and we still get home with a full battery. Three miles of electric and finishing with a full battery thanks to gravity.

[RickH]

... oh gov are to ban hybrids that won't go 50 miles on the battery

There is an unconfirmed rumour about hybrids. AFAIK there is nothing official. Also, whatever is decided, it is currently intended as a ban on sales of new vehicles. There may be separate, complete bans of use of internal combustion powered vehicles in cities.

[cjchambers]

My car has two tyre pressures listed in the manual - 'Comfort' and 'Eco' (latter about 5psi higher than the former, if I recall correctly). After a few months of ownership I pumped them up to 'Eco' - no change to the fuel economy but it now steers much better.

To my mind, they are either overinflated at the 'Eco' pressure or underinflated at the 'Comfort' pressure. I will be keeping a close eye on the wear pattern

On a related point we have a tyre warning light that comes on if the tyre loses pressure. How does this work? It seems very sensitive ie topped up last week to 32 psi, indicator light came on when on M6 so stopped and checked at services and all tyres were above 30 psi. Given these were different gauges with error margins I'm very surprised I got a warning.

Tyre pressure monitoring system (TPMS) is now compulsory on all new cars in the EU and USA. In the traditional setup, the valve stem has a pressure sensor at its base and a radio which transmits the pressure information to the car. They have an embedded battery which obviously has a limited lifespan which is a pity because they're not cheap.

The newer setups use the wheel speed sensor (which all cars have for their ABS/ESP anyway) to sense the slight change in wheel speed when the tyre is underinflated. Much better system, I would imagine.

[NATURAL ANKLING]

Hi,
I see ratio is height 50% on your 16" tyres.
What the comfort like?
All these suv's with low profile tyres............ours feels like a go cart.......rock hard suspension.......but I like it like that

Is that 2 miles on battery? The battery weighs 1/4" of a ton? Or is that another model...................

[philvantwo]

What about in the hot weather though, what happens to tyre pressures then? Oh and what's happening with Mick F's old tyres in his back garden? Have the neighbours complained yet?