Why are Tyre sizes a mixture of Inches and mm

[CrusaderPhil]

Why are Tyre sizes a mixture of Inches and millimetres

[Guest]

Wheels are imperial, tyres tread are metric, the middle number is a percentage just to upset things

[CrusaderPhil]

Wheels are imperial, tyres tread are metric, the middle number is a percentage just to upset things

 

That does not answer Why?

[fq-craigus]

Accepted units are combined because it's what people are used to and universally approved and used

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[onesea]

So the world can blame the English......

You can be sure the americans will be blaming us for the metric and the europeans for the imperial..

[Guest]

Wheels are imperial, tyres tread are metric, the middle number is a percentage just to upset things

 

That does not answer Why?

Trying to change the wheel system was attempted in the 80's but it didn't happen. Not only would all wheels become a different size but tyres would all have to be changed. Then 2 systems would have to be running as 99% of tyres run the current system, for instance 17" wheels would become 438.1mm which isn't a metric size, just a conversion so would become 440mm to most of us on here im sure mm is

The same could be asked why do we buy petrol in ltrs and then worry about our miles per gallon

[CrusaderPhil]

So the world can blame the English......

You can be sure the americans will be blaming us for the metric and the europeans for the imperial..

 

I think I agree with this one.

[Via]

Never understood why the need to pick one or another both have their advantages.

Always use inches for larger measurements or when accuracy is not that important and metric for smaller accurate measurements and a lot of times in same project. Think that's greatest thing about being British we just use whatever suits the situation, metric is great for accuracy and conformity (1000ml of water takes up 1000mm cubed space and weighs 1000g but beer comes in a pint glass!)

[Mr Fro]

https://m.youtube.com/watch?v=pikrntjcbyw

[TimR]

Wheels are imperial, tyres tread are metric, the middle number is a percentage just to upset things

 

That does not answer Why?

Trying to change the wheel system was attempted in the 80's but it didn't happen. Not only would all wheels become a different size but tyres would all have to be changed. Then 2 systems would have to be running as 99% of tyres run the current system, for instance 17" wheels would become 438.1mm which isn't a metric size, just a conversion so would become 440mm to most of us on here im sure mm is

The same could be asked why do we buy petrol in ltrs and then worry about our miles per gallon

 

And to throw in that we all buy a petrol can commonly referred to as a gallon can which holds 5l ...

BUT a uk gallon is 4.54 litres ...

[Guest]

And to throw in that we all buy a petrol can commonly referred to as a gallon can which holds 5l ...

BUT a uk gallon is 4.54 litres ...

although you can get 6 1/2ltrs in them

[CrusaderPhil]

And to throw in that we all buy a petrol can commonly referred to as a gallon can which holds 5l ...

BUT a uk gallon is 4.54 litres ...

although you can get 6 1/2ltrs in them

 

Not the ones I have on the bike crash bars, they only hold 2.5 galls

[CrusaderPhil]

And to throw in that we all buy a petrol can commonly referred to as a gallon can which holds 5l ...

BUT a uk gallon is 4.54 litres ...

although you can get 6 1/2ltrs in them

 

Not the ones I have on the bike crash bars, they only hold 2.5 litrs

[Tigcraft]

So all in all we still don't know about tyres!!?

[CrusaderPhil]

So all in all we still don't know about tyres!!?

 

No, nobody seems to know, so we will just have to live with it.

[Tigcraft]

Heard a similar question and explanation about LHD and RHD. It was interesting and one was to do with being right handed in javelling!!

[Tigcraft]

Heard a similar question and explanation about LHD and RHD. It was interesting and one was to do with being right handed in javelling!!

Whoops meant to say jousting!!

[RantMachine]

We should probably through off road tyre sizes into the mix, just to make things extra confusing

[Hoggs]

So all in all we still don't know about tyres!!?

 

They're black and round and stop you riding around on the rims

[CrusaderPhil]

So all in all we still don't know about tyres!!?

 

They're black and round and stop you riding around on the rims

 

They way my tyres operate I be safer on the rims LOL!

[Tigcraft]

So all in all we still don't know about tyres!!?

 

They're black and round and stop you riding around on the rims

 

They way my tyres operate I be safer on the rims LOL!

Keep thinking that one day I'll make use of those crap space savers nobody ever wears out and stick some on a bike to enter 'the dark side' as it's done in the US

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[someone]

metric is great for accuracy and conformity (1000ml of water takes up 1000mm cubed space and weighs 1000g but beer comes in a pint glass!)

 

Roughly accurate, at least. It is only 1000ml of pure water at 3.98°C at the mean atmospheric pressure at the latitude of Paris that is exactly 1000mm³, of course.

 

So all in all we still don't know about tyres!!?

 

Tyre sizes are not a mixture of metric and imperial, though, are they? Wheel sizes are in inches, so the tyre sizes obviously have to reference this, but as far as I know the tyre itself is then sized in either in one system or the other. Certainly for my bike I only know of two different formats for the tyre sizes, one in inches and the other in millimetres.

Changing systems for something like wheel sizes though would mean starting over from scratch. All new wheels would be incompatible with old ones, which means you cannot simply reuse old vehicle designs with a few upgraded components, and everything else that depends on them would need changing.

So when you have an established standard like this, changing to a different system simple for the sake of the unit is never worth the hassle and cost.

With something like tyres though there will be slight differences between one brand and another of the same size that you can easily just convert the measurement unit and round it off as they seemingly do not require such accuracy.

[CrusaderPhil]

metric is great for accuracy and conformity (1000ml of water takes up 1000mm cubed space and weighs 1000g but beer comes in a pint glass!)

 

Roughly accurate, at least. It is only 1000ml of pure water at 3.98°C at the mean atmospheric pressure at the latitude of Paris that is exactly 1000mm³, of course.

 

So all in all we still don't know about tyres!!?

 

Tyre sizes are not a mixture of metric and imperial, though, are they? Wheel sizes are in inches, so the tyre sizes obviously have to reference this, but as far as I know the tyre itself is then sized in either in one system or the other. Certainly for my bike I only know of two different formats for the tyre sizes, one in inches and the other in millimetres.

Changing systems for something like wheel sizes though would mean starting over from scratch. All new wheels would be incompatible with old ones, which means you cannot simply reuse old vehicle designs with a few upgraded components, and everything else that depends on them would need changing.

So when you have an established standard like this, changing to a different system simple for the sake of the unit is never worth the hassle and cost.

With something like tyres though there will be slight differences between one brand and another of the same size that you can easily just convert the measurement unit and round it off as they seemingly do not require such accuracy.

 

They are a mixture, 160/60 R17 is 160mm width 60% of 160mm is the profile and R17 is a rim diameter of 17", so a mixture

[someone]

They are a mixture, 160/60 R17 is 160mm width 60% of 160mm is the profile and R17 is a rim diameter of 17", so a mixture

 

That is my point, though. Wheels are sized in inches and obviously a tyre has to say what size wheel it fits, the 17. But the tyre size itself, as in the profile of the particular tyre for a 17" rim, is only metric: 160mm, and 60% of 160mm.

[CrusaderPhil]

They are a mixture, 160/60 R17 is 160mm width 60% of 160mm is the profile and R17 is a rim diameter of 17", so a mixture

 

That is my point, though. Wheels are sized in inches and obviously a tyre has to say what size wheel it fits, the 17. But the tyre size itself, as in the profile of the particular tyre for a 17" rim, is only metric: 160mm, and 60% of 160mm.

 

OK so why are the rims in inches when everything else on the bike is metric