Winter tyre pressures

[Ootohere]

^^^^ Nail on the head.

There are lots of ambient temperatures (Air & Ground temps) between November & April in the UK, even hot sunny days.

Then also adjust the tyre pressures to suit the load being carried during the time tyres are fitted, so that is all year round..

(Do checks & reset TPMS as well.)

[ejstubbs]

Both the Michelin and Nokian pages linked to above, imply the "extra 0.2bar" people talk about is only needed if you're setting the pressures when the car is in a warmer environment (eg a warm garage) than it's going to be used in.

So if you're checking/setting pressures outside in typical ambient usage temps, and the tyres are cold, then normal pressures should be used as far as I can see.

 

I agree, and that's what I'm planning to do in future.

 

I wonder if there's a hidden cultural component behind this advice: countries where people typically do use winter tyres - especially those where it is legally required - tend to be a lot more prone to extended sub-zero temperatures during the winter, so it's more common for people to keep their cars in garages.  Perhaps.

Edited 9 November, 2016 by ejstubbs

[Wardy]

Looks good Clive. I should have just put my set of 17" Yeti winters in the boot when I brought it up to you

 

Will be up for sale shortly...

[Clive]

Looks good Clive. I should have just put my set of 17" Yeti winters in the boot when I brought it up to you

 

Yeah but me being a tight Yorkshireman I'd have expected them thrown in with the price of the car mate , so it's as well I didn't know about them at the time 

[Wardy]

Yep - and that's why I didn't mention them

[Clive]

Yep - and that's why I didn't mention them

 

:p  :moon:

[Llanigraham]

I agree, and that's what I'm planning to do in future.

 

I wonder if there's a hidden cultural component behind this advice: countries where people typically do use winter tyres - especially those where it is legally required - tend to be a lot more prone to extended sub-zero temperatures during the winter, so it's more common for people to keep their cars in garages.  Perhaps.

 

Brother-in-law lived in Switzerland and certainly their apartments all had heated underground parking areas. Some of them even had tyre storage areas!

[mumpsim]

I suggest that the reason for using a bit more pressure in winter is that a bit more pressure makes for a significant increase in tyre temperature, and a higher tyre temperature makes for a significant increase in grip. Even though winter tyres are meant to work in low temperatures, these principles still apply, since there is no getting away from the pressure-temperature law of gas physics.

 

Here is a discussion of the matter as it affects racing tyres. But again, the principles are the same for road tyres, even though effects may be less dramatic. http://www.tal-ko.com/getting-the-best-from-your-tyres

[Ootohere]

When those that let tyre pressures down to get out of certain situations like no traction leave the pressures low is when tyre can get too hot.

Even in low temperatures.

Then over inflating tyres in winter is not something advised to improve traction or safety.

[longedge]

The idea of increasing tyre pressure to raise the tyre temperature seems counter-intuitive to me. A softer tyre flexes more doesn't it and I would've thought that additional flexing would cause the tyre to heat up. So I can add that to the list of examples where my thought processes apprarently lead me to the wrong conclusion :notme:

[Llanigraham]

Quite, especially when the linked article is about highly specialised KART racing tyres.

[ejstubbs]

Indeed.  Cunning tweaks that people apply when they're trying to achieve fractional extensions to the performance envelope for a few laps on a racing circuit have vanishingly little relevance to good practice for day-to-day driving on public roads.

[mumpsim]

Indeed.  Cunning tweaks that people apply when they're trying to achieve fractional extensions to the performance envelope for a few laps on a racing circuit have vanishingly little relevance to good practice for day-to-day driving on public roads.

And yet ten per cent more or ten per cent less inflation pressure has a very large effect on the way any car handles, even day-to-day on public roads.  If you are not interested in understanding all the various factors that contribute to that big change, fine, just move on. Tyres are just boring black round things, aren't they?

Edited 10 December, 2016 by mumpsim

[Ootohere]

Some people give lots of thought, have pressure gauges and temperature gauges and monitor road and ambient temps, and even tracks if on track. Winter tyres and performance and behaviour is well documented. Driving black top or black ice is and tyres or snow ice slush covered being something many drivers do year after year.

Edited 10 December, 2016 by Offski

[fatzy]

I agree, and that's what I'm planning to do in future.

I wonder if there's a hidden cultural component behind this advice: countries where people typically do use winter tyres - especially those where it is legally required - tend to be a lot more prone to extended sub-zero temperatures during the winter, so it's more common for people to keep their cars in garages. Perhaps.

Yes, you are partly right.

By experience people are lazy, and do not check tyre pressures often. When putting on the winter tyres in October/November the temperatures is normally much higher than later in the winter season. A temperature drop of 20 deg. do have an impact on the pressure, and is not uncommon.

In addition, the air tend to seep out over time. Air escapes through the rubber.

Last, the economic/environmental aspect. Slightly overinflated tyres saves fuel, which is very important for some (like the eco setting). It does not have big impact in traction or wear.

All above factors gives an overall advise: a slightly higher pressure than strickly necessary is better than risking that many people drive around with underinflated tyre pressures, and all in all: underinflated tyres have more negative effects than overinflating.

Edited 10 December, 2016 by fatzy

[ejstubbs]

And yet ten per cent more or ten per cent less inflation pressure has a very large effect on the way any car handles, even day-to-day on public roads.  If you are not interested in understanding all the various factors that contribute to that big change, fine, just move on. Tyres are just boring black round things, aren't they?

 

Read my post again: I didn't say or even imply any of those things you're suggesting.  Please don't put words in to my mouth and then use them as a excuse to be rude and dismissive.

Edited 10 December, 2016 by ejstubbs

[Llanigraham]

And yet ten per cent more or ten per cent less inflation pressure has a very large effect on the way any car handles, even day-to-day on public roads.  If you are not interested in understanding all the various factors that contribute to that big change, fine, just move on. (1) Tyres are just boring black round things, aren't they? (2)

 

1/ This is a discussion forum, people discuss things. Please don't tell us what to do.

 

2/ Oh dear!! Do some research, please.

[Breezy_Pete]

I suggest that the reason for using a bit more pressure in winter is that a bit more pressure makes for a significant increase in tyre temperature, and a higher tyre temperature makes for a significant increase in grip. Even though winter tyres are meant to work in low temperatures, these principles still apply, since there is no getting away from the pressure-temperature law of gas physics.

 

Here is a discussion of the matter as it affects racing tyres. But again, the principles are the same for road tyres, even though effects may be less dramatic. http://www.tal-ko.com/getting-the-best-from-your-tyres

 

Seems to be some confusion in your head about pressure-temperature law of gas physics. Do you think that increasing the pressure in your tyres makes them get hotter, and stay hotter indefinitely? 

[Breezy_Pete]

The idea of increasing tyre pressure to raise the tyre temperature seems counter-intuitive to me. A softer tyre flexes more doesn't it and I would've thought that additional flexing would cause the tyre to heat up. So I can add that to the list of examples where my thought processes apprarently lead me to the wrong conclusion :notme:

I don't think you reached any wrong conclusion. Your intuition seems spot on.

[Ootohere]

[g6zru]

Oh no, not another "mine is bigger/better than yours" discussion?

 

Fred

[coldplug]

More pressure in tyre = less heating during driving.

 

However, when you inflating the tyre, the more you increase pressure, temperature will increase with it also. It comes from pressure law that states that pressure divided by temperature equals constant value. So, when you inflate tyre, it warms up. But, it will eventually cool down right to the environment temperature after you stop inflating it, as fast as in several hours, if vehicle is not moving and is in shade, you will not be able to detect any temperature difference from air within the tyre and outside of it, regardless of how much you inflated it.

 

Now when vehicle starts to move, tyres are going to warm up because of different reasons. One of reason is friction between tyre surface and road that creates heat. That isn't dependent on tyre pressure much, if at all. But there is another factor that warms tyre up. It is tyre flexion that revs around tyre and creates friction forces within rubber itself. Now, the LESS pressure in tyre is, flexion will be bigger and friction forces between molecules of rubber will increase, so the heat produced will increase also. This means that less pressure in tyre leads to more heating during driving, especially on highway speeds. And vice versa.

 

For example, this is the only reason why offroad drivers stop the vehicle and reinflate tyres after airing them down for offroad, after they come back to the road. If they are not able to reinflate tyres for some reason, they must drive very slowly on road in order to not overheat and damage the tyres.

[Breezy_Pete]

More pressure in tyre = less heating during driving.

 

However, when you inflating the tyre, the more you increase pressure, temperature will increase with it also. It comes from pressure law that states that pressure divided by temperature equals constant value. So, when you inflate tyre, it warms up. But, it will eventually cool down right to the environment temperature after you stop inflating it, as fast as in several hours, if vehicle is not moving and is in shade, you will not be able to detect any temperature difference from air within the tyre and outside of it, regardless of how much you inflated it.

 

Now when vehicle starts to move, tyres are going to warm up because of different reasons. One of reason is friction between tyre surface and road that creates heat. That isn't dependent on tyre pressure much, if at all. But there is another factor that warms tyre up. It is tyre flexion that revs around tyre and creates friction forces within rubber itself. Now, the LESS pressure in tyre is, flexion will be bigger and friction forces between molecules of rubber will increase, so the heat produced will increase also. This means that less pressure in tyre leads to more heating during driving, especially on highway speeds. And vice versa.

 

For example, this is the only reason why offroad drivers stop the vehicle and reinflate tyres after airing them down for offroad, after they come back to the road. If they are not able to reinflate tyres for some reason, they must drive very slowly on road in order to not overheat and damage the tyres.

 

Almost correct. It's only a constant value if the quantity of substance in the 'system' remains the same.  When we pump up a tyre, we add air, so the quantity in the system goes up in direction proportion to the pressure increase; so no temperature change.  PV=nRT,  n= amount of gas.

 

Everything else you write looks correct.

[coldplug]

Wino, probably yes. I just wake up and don't function at full speed yet :coffee: