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# Tyre pressure measurement

edited 22 September 2022 at 8:53PM in Motoring
55 replies 1.7K views

## Replies

• Forumite
7.6K Posts
Forumite
"pounds per square inch."

Being pedantic, it's pounds(lb)f/sq.in.
That was used, pre SI units, to differentiate between force and mass, mass = pounds(lb).
Whereas SI mass = kg, force = Newtons.

Alternatively pedantic (or pedantically alternative?), in pre-SI (Imperial) units, pound = force, slug = mass. A slug would have a mass of about 32.2 pounds, if one were to accept the alternative view that mass is measured in pounds.

Confused? You will be.

Even more alternatively, we have poundal = force, and pound = mass.

At school in the 60s, I was taught Newton's laws in metric units in the Physics class, and in Imperial in Engineering. This didn't help dispel the notion that science subjects were difficult.

And if you tell that to kids today ...
• Forumite
4.6K Posts
Forumite
chrisw said:
sheramber said:
For many years fabric was sold in inches width but meter lenghths.

So bought x meters of 36 inch wide material.
Timber is still sold like that. So you buy 1.8 metres of 4"x2".
I think you'll find that it's actually 100mmx50mm but they put a label on it with the nearest Imp. sizes for those who might be confused and prefer such things. Now if we look at 8'x'4' sheets of plywood ...........
• edited 25 September 2022 at 10:11PM
Forumite
19.6K Posts
Forumite
edited 25 September 2022 at 10:11PM
Car_54 said:
"pounds per square inch."

Being pedantic, it's pounds(lb)f/sq.in.
That was used, pre SI units, to differentiate between force and mass, mass = pounds(lb).
Whereas SI mass = kg, force = Newtons.

Alternatively pedantic (or pedantically alternative?), in pre-SI (Imperial) units, pound = force, slug = mass. A slug would have a mass of about 32.2 pounds, if one were to accept the alternative view that mass is measured in pounds.

Confused? You will be.

Even more alternatively, we have poundal = force, and pound = mass.

At school in the 60s, I was taught Newton's laws in metric units in the Physics class, and in Imperial in Engineering. This didn't help dispel the notion that science subjects were difficult.

And if you tell that to kids today ...
It's not much different today! We use miles to measure driving distances, we use litres when we fill cars with petrol, but fuel efficiency is always quoted in miles per gallon, or km/litre! Not miles/litre which are the measures we actually use!
It's part of this ridiculous half way house the UK has been stuck in for last 50 years. In the 70's the govt decided to go metric, we were only ever taught metric in school (late 70's/early 80's), things started changing eg using litres instead of gallons, using 100 pence in a pound instead of 12p in a shilling and 20 shillings in a pound etc, but they never completed the job, the govt kept caving into the "can't cope with change" brigade half way through the job, so we still use miles, pints, feet, pounds, stones etc in some contexts but metres, litres, kg etc in other contexts.
You buy pints of beer in the pub but litres of orange juice, coke etc in the supermarket. You think of your weight in stones and pounds but your baggage weight when you go on holiday in kg. Tyre measurements are even more ridiculous - the width is in mm, the diameter is in inches!

7K Posts
No wonder kids today (OK, those under 50) are useless at mental arithmetic. Look at all the units we oldies had to work with!

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• Forumite
2.5K Posts
Forumite
shiraz99 said:
Iceweasel said:
Are we now metric - we've been metric since 1972. No school in UK has taught in Imperial since then.
Yet we still measure distance in miles not km.
Because that is the legal unit for distance/speed on the road.  Draught beer can only be legally sold
zagfles said:
Car_54 said:
"pounds per square inch."

Being pedantic, it's pounds(lb)f/sq.in.
That was used, pre SI units, to differentiate between force and mass, mass = pounds(lb).
Whereas SI mass = kg, force = Newtons.

Alternatively pedantic (or pedantically alternative?), in pre-SI (Imperial) units, pound = force, slug = mass. A slug would have a mass of about 32.2 pounds, if one were to accept the alternative view that mass is measured in pounds.

Confused? You will be.

Even more alternatively, we have poundal = force, and pound = mass.

At school in the 60s, I was taught Newton's laws in metric units in the Physics class, and in Imperial in Engineering. This didn't help dispel the notion that science subjects were difficult.

And if you tell that to kids today ...
It's not much different today! We use miles to measure driving distances, we use litres when we fill cars with petrol, but fuel efficiency is always quoted in miles per gallon, or km/litre! Not miles/litre which are the measures we actually use!
It's part of this ridiculous half way house the UK has been stuck in for last 50 years. In the 70's the govt decided to go metric, we were only ever taught metric in school (late 70's/early 80's), things started changing eg using litres instead of gallons, using 100 pence in a pound instead of 12p in a shilling and 20 shillings in a pound etc, but they never completed the job, the govt kept caving into the "can't cope with change" brigade half way through the job, so we still use miles, pints, feet, pounds, stones etc in some contexts but metres, litres, kg etc in other contexts.
You buy pints of beer in the pub but litres of orange juice, coke etc in the supermarket. You think of your weight in stones and pounds but your baggage weight when you go on holiday in kg. Tyre measurements are even more ridiculous - the width is in mm, the diameter is in inches!

Draught beer can only be legally sold in pints (or sub divisions of pints) and distances/speeds on roads can only legally use miles.  Everything else has to use metric units. People may use other units of measure informally but they are not the official units.

Tyre dimensions use mixed units for historical reasons that the tyre manufacturers agreed to do.

• edited 26 September 2022 at 9:29AM
Forumite
19.6K Posts
Forumite
edited 26 September 2022 at 9:29AM
wongataa said:
shiraz99 said:
Iceweasel said:
Are we now metric - we've been metric since 1972. No school in UK has taught in Imperial since then.
Yet we still measure distance in miles not km.
Because that is the legal unit for distance/speed on the road.  Draught beer can only be legally sold
zagfles said:
Car_54 said:
"pounds per square inch."

Being pedantic, it's pounds(lb)f/sq.in.
That was used, pre SI units, to differentiate between force and mass, mass = pounds(lb).
Whereas SI mass = kg, force = Newtons.

Alternatively pedantic (or pedantically alternative?), in pre-SI (Imperial) units, pound = force, slug = mass. A slug would have a mass of about 32.2 pounds, if one were to accept the alternative view that mass is measured in pounds.

Confused? You will be.

Even more alternatively, we have poundal = force, and pound = mass.

At school in the 60s, I was taught Newton's laws in metric units in the Physics class, and in Imperial in Engineering. This didn't help dispel the notion that science subjects were difficult.

And if you tell that to kids today ...
It's not much different today! We use miles to measure driving distances, we use litres when we fill cars with petrol, but fuel efficiency is always quoted in miles per gallon, or km/litre! Not miles/litre which are the measures we actually use!
It's part of this ridiculous half way house the UK has been stuck in for last 50 years. In the 70's the govt decided to go metric, we were only ever taught metric in school (late 70's/early 80's), things started changing eg using litres instead of gallons, using 100 pence in a pound instead of 12p in a shilling and 20 shillings in a pound etc, but they never completed the job, the govt kept caving into the "can't cope with change" brigade half way through the job, so we still use miles, pints, feet, pounds, stones etc in some contexts but metres, litres, kg etc in other contexts.
You buy pints of beer in the pub but litres of orange juice, coke etc in the supermarket. You think of your weight in stones and pounds but your baggage weight when you go on holiday in kg. Tyre measurements are even more ridiculous - the width is in mm, the diameter is in inches!

Draught beer can only be legally sold in pints (or sub divisions of pints) and distances/speeds on roads can only legally use miles.  Everything else has to use metric units. People may use other units of measure informally but they are not the official units.

Tyre dimensions use mixed units for historical reasons that the tyre manufacturers agreed to do.

Exactly, this ridiculous half way house situation. Ireland managed to cope with switching from miles to km.
What are the official units for measuring fuel efficiency? I always see mpg quoted everywhere. So manufacturers are still using miles per gallon, even though litres are supposedly the official units. What's mpg supposed to mean to anyone who's never bought fuel in gallons? I have but long enough ago to have forgotten the meaning of a gallon (and even further confused by a US gallon being different, if they ever look up conversion)

• Forumite
4.6K Posts
Forumite
The first thing I do in any/every car I drive is change all the units to Metric - it's very easy.

As for fuel consumption - I find that litres/100km is so much more sensible than miles/gallon.

This half-way house system we have in the UK is nonsense.

I remember back in the 70's when we started to change, there were those who said it would be difficult for 'the old folks' and perhaps it would be better to wait until they had died off.

I think they were trying to be funny - at least I hope so.
7K Posts
I hear Liz is going to convert us to driving on the right. Gradually though, trucks first.

I’m a Forum Ambassador and I support the Forum Team on the In My Home MoneySaving, Energy and Techie Stuff boards. If you need any help on these boards, do let me know. Please note that Ambassadors are not moderators. Any posts you spot in breach of the Forum Rules should be reported via the report button, or by emailing [email protected].

All views are my own and not the official line of MoneySavingExpert.

• Forumite
3.2K Posts
Forumite
Iceweasel said:

This half-way house system we have in the UK is nonsense.

I rather like the half way house system we have tbh. It feels comfortable and doesn't conform to either the US or Europe.
• Forumite
12.5K Posts
Forumite
Iceweasel said:

As for fuel consumption - I find that litres/100km is so much more sensible than miles/gallon.

I don't really.

Always known that more miles/gallon is better so it is counter-intuitive to me to talk about litres/100km or kWh/mile where less is better.