The tyres currently fitted are 225/45ZR17 (91Y) but when I put the reg into BlackCircles it comes up with 235/50R19 V 99. Does this mean a previous owner has changed the wheels, or is the database just a bit dodgy?

Their database will be incorrect. That sizes isn’t correct for an Octavia. When I put my reg in, it calls up 225/35/19 (I think). My actual tyre spec is 225/40/18. They do say to always double check before buying 👍🏻

Yes, I've just tried Halfords and they got the size right. Slightly higher load rating but that's no bad thing.

Also worth reading the label inside the fuel filler flap as that lists the OE tyre sizes.

Edited 17 June, 20232 yr by PetrolDave

On my car that just has tyre pressures, not sizes.

6 minutes ago, wiggers said:

On my car that just has tyre pressures, not sizes.

Strange, on both the Octavia 3s I've owned it shows tyre sizes as well as pressures?

Yeah. Because usually there is a range of fitments possible between 16 and 19" often with different pressure requirements. 

Also remember since the mk3 Octavia was built, tyre manufacturers have generally introduced new summer tyres with formulations that are more summer biased so as not to overlap with their new all season (all year) tyres.

 

So unless you change to winter tyres November-April, go for all seasons as you will find latest summer tyres tend to have grip that falls off rapidly below +10c in wet (and we get cold rain in UK), are often skittish by +5c, and completely useless and will leave you stranded on rare days of snow.  Modern summer tyres are often also poor on damp salted roads at low temperatures.

 

Many tyre websites now allow you to choose season, so just filter on all season.

 

Blackcircles gives the right tyre size for my registration, but worth double checking.