Am I running the wrong size tyres?

[mullermn]

The tyres on my mk7 PP GTI are nearing replacement so I’ve been looking for some quotes. After checking the size that the tyre sites are automatically suggesting versus what’s on the car I’ve realised that mine are ‘wrong’. I didn’t deliberately choose them to be wrong, so either it was a mistake in ordering on my part or the guy that fitted them out the wrong ones on (it was Costco, for the record).

Anyway, the tyre sites say 225/40 R18, but what I have on the car are 225/45 R18, on standard Austins. They’ve been on there for a few years and haven’t caused any problem, but now that I come to reorder I notice that my size is more expensive than the standard size.

So my question is, what benefit/drawback have I been getting without realising it? I need to decide if the price premium is worth it to stay with the size I have or whether to move back to factory specs.

Thanks

[Andy198]

Have a look at this website: https://www.willtheyfit.com and put the existing tyre/wheel sizes in - I think they're 7.5J width and 51 offset as standard but might be wrong.

Your speedo is 'out' as the circumference is bigger on the higher profile tyre that you've been using, so you're out by about 2mph at 60mph but nothing that would cause any major issues. If you're replacing tyres anyway, its probably best to put the standard size back on, just in case of any Insurance modification issues but that's highly unlikely.

[Guzzle]

https://www.willtheyfit.com/index.php?width=225&aspect=40&diameter=18&wheelwidth=7.5&offset=51&width2=225&aspect2=45&wheel_size=18&wheel_width=7-5&offset2=51

You'll have had a slightly softer / wallowy ride (assuming same tyre pressures), your speedo will have been under reading slightly and your alloys will have been less prone to kerbing. You'll also have a smaller arch gap.

Strictly speaking, changing tyre sizes is a deviation from manufacturers standard spec so you may want to have a think about whether or not your insurance company needs to know.

[mullermn]

Thanks. I hadn’t thought of the potential insurance implication so I’m glad I asked.