Tyre measurements in Metric AND Imperial WHY???

[~SlideWays~]

This really bugs me.

Why on earth are tyre sizes measured in metric and imperial at the same time?

ie width in mm (metric) and wheel size in inches (imperial)?

Its just weird!

Someone please explain this so I can sleep at night.

[CaM]

no idea.
although if it helps you sleep easier.... some euro stz have metric rims. goodbye to $500+ per tyre when they're worn out

[fivebob]

Because wheel sizes came in inches long before tyres were marketed in metric (and most tyres were 100% profile so all you need to know was the width)

Only metric wheel I can think of were early '80s Ferrari 308, and it a major PITA to get tyres for them.

[CaM]

ferarri, mg metros, a handful of bmws, some pugs etc etc etc

[Leon]

Imperial, Metric, and then a %.

I agree, what's up with that?

[Steve123]

Same reason Holdens have metric and imperial bolts. So do other cars.

[THA SHZ]

ferarri, mg metros, a handful of bmws, some pugs etc etc etc

ur talkin bout tyres not rims like fivebob was mentioning
and as was said wheels were measured in inches since pretty much day dot .
metric tyres came in as of the japanese and etc of us who dont measure in the old school ways , usa still use alot of imperial tyres especially in 4wd tyres

[fivebob]

Same reason Holdens have metric and imperial bolts. So do other cars.

Yep almost every Japanese car would have a minimum of six imperial bolts. Want to guess which ones ??

[AE82 FXGT]

I have found my car to have all metric bolts so far....
What six imperial ones are there?

[Ae92typeX]

Yep almost every Japanese car would have a minimum of six imperial bolts. Want to guess which ones ??

Im going to lay awake all night thinking about every car Ive taken apart now...
was thinking ball joints, but no, not brake bleed nipples.argh...brain time for bed.

[fivebob]

Answer will be posted tomorrow, but I'll give you a hint, size is 9/16UNF

*Edit I also said at least six, could be a lot more, but certainly less than 30, in cars anyway

[Malcolm]

I've come across imperial bolts mostly in seat belt ancorages....I guess there's 3 of them per seat, right?

[Ae92typeX]

meh...bet I just jammed a 14mm on it...
Im thinking in the brake/suspension or head/crank
but thats a broad guess.
going to bed to lay awake thinking...

[Ae92typeX]

I've come across imperial bolts mostly in seat belt ancorages....I guess there's 3 of them per seat, right?

thats it! I remember putting some japper seatbelts in the mini and using the bolts that came with them.
...but they wernt all 9/16 size, some were bigger...is there more?

[fivebob]

I've come across imperial bolts mostly in seat belt ancorages....I guess there's 3 of them per seat, right?

Yep, that's the ones, Nearly all cars have 9/16UNF seatbelt anchorages, there are some wog European ones that use a 14mm bolt, but all Japanese ones I've seen have them, and that's a few thousand from when I was involved in complicancing industry.

[fivebob]

I remember putting some japper seatbelts in the mini and using the bolts that came with them.
...but they wernt all 9/16 size, some were bigger...is there more?

Not that I can recall, at least not the anchorage bolts as I think that's an ISO standard (though I may be wrong, it's been 12 years since I last fitted seatbelts)

[fivebob]

Just checked the standards, and it's a minimum 7/16"UNF not 9/16", doh. Must've been confused the the bolt head size... it's been a long time

[TrouserFxGt]

This really bugs me.

Why on earth are tyre sizes measured in metric and imperial at the same time?

ie width in mm (metric) and wheel size in inches (imperial)?

Its just weird!

Someone please explain this so I can sleep at night.

I certainly wouldn't want to go to a tyre shop and ask for 33.02cm tyres for my starlet or 43.18 cm for the corolla. A bit of a mouthfull.

[~SlideWays~]

This really bugs me.

Why on earth are tyre sizes measured in metric and imperial at the same time?

ie width in mm (metric) and wheel size in inches (imperial)?

Its just weird!

Someone please explain this so I can sleep at night.

I certainly wouldn't want to go to a tyre shop and ask for 33.02cm tyres for my starlet or 43.18 cm for the corolla. A bit of a mouthfull.

Yeah but it makes about as much sense as having a speedo read in Km and the trip metre in Miles.

Well it looks like its a case of old and new integrated together and its just too hard to change the international standard.

Its still strange though. I thought it was worth finding out...i will sleep now.

[barryogen]

This really bugs me.

Why on earth are tyre sizes measured in metric and imperial at the same time?

ie width in mm (metric) and wheel size in inches (imperial)?

Its just weird!

Someone please explain this so I can sleep at night.

I certainly wouldn't want to go to a tyre shop and ask for 33.02cm tyres for my starlet or 43.18 cm for the corolla. A bit of a mouthfull.

you wouldn't... you'ld ask for 33 or 43cm tyres, theyre would be suficient stretch in them for that. also it would probably be in mm