Help needed with tyre sizes

[rowdy]

I have got my lad a 125 to ride while he waits for his car test.
It is of the finest Chinese quality, and has the original Chinese? tyres still on it, that are losing pressure.
They are a strange mix of sizes being a 90/90 18 rear and a 2.75 18 front, which I’m guessing is a metric rear and imperial front.

I’ve found some metzelers on offer online, but they are in imperial so 2.75 18 front is ok but I don’t know what size rear to get, they do a 3.00 18 as well the tyres being listed as suitable for front and rear.

So do I go 2.75 front and rear or 2.75 front and 3.00 rear?

[Seeker]

So do I go 2.75 front and rear or 2.75 front and 3.00 rear?

2.75 front and 3.00 rear would work according to Avon's tyre chart:

https://www.avontyres.com/en-gb/tyre-care/technical/tyre-size-information/

a 90/90 is equivalent to a 3.00 or 3.25.

Have you done the spit test on the valve to make sure it's not leaking?

[rowdy]

Thanks for that. No I haven’t but they are dubious quality tyres that I suspect have been on the bike since new (2016) so would rather replace them anyway.