GT V8 original tyre size

[1340fxd]

My MGB GT V8 original handbook states the tyre size to be 175HR x 14 - no mention of an aspect ratio to determine tyre diameter. The car has 185/70R 14 fitted. Does anyone know the original tyre aspect ratio or diameter / circumference please so I can work out of the tyres fitted have the same gearing and speedometer reading please?

[Paul Scott]

This Might help

https://www.mgb-register.org/moss-tech-tyre-guide/

Regards
Paul

[Bumpa]

The original size tyres, 175 x 14, will be full profile, which means they have the tallest side walls at about 82% of the width. So they would be classed as 175/82 (or 80 is close enough) x 14. There are dozens of tyre comparison sites out there, eg, https://tiresize.com/tyre-size-calculator/. Using that comparator shows that your 185/70 x 14 tyres are slightly smaller in circumference than the originals and will cause your speedo to over-read by about 4%. Whether you can actually buy the original size now I don't know.

[Gareth]

The original size tyres, 175 x 14, will be full profile, which means they have the tallest side walls at about 82% of the width. So they would be classed as 175/82 (or 80 is close enough) x 14. There are dozens of tyre comparison sites out there, eg, https://tiresize.com/tyre-size-calculator/. Using that comparator shows that your 185/70 x 14 tyres are slightly smaller in circumference than the originals and will cause your speedo to over-read by about 4%. Whether you can actually buy the original size now I don't know.

Even Halfords are saying this is an available size (175/80 R14), so any tyre specialist should have a better choice

[Bumpa]

That's good that those tyres are still available. I said I didn't know because I don't need that size. My car runs on 195/65 x 15.