At the moment my car is fitted with 225/45 17 tyres. They have covered a very easy 8000 miles.

Everytime i pass one of those radar speed signs in villages it shows my speed as 28mph while speedo on car shows 31mph. I realise that those signs are not the most accurate in the world but they are consistent. 

I was wondering if I could go one size up to a 225/50 or perhaps a 225/55?

Any thoughts?

Hi Steve,

Personally, I think I'd take the 'safety' margin on the speed. It might be a radar gun one day and the 3mph (10%) buffer might be useful!

Also, taller tyres, while possibly quieter, might soften your handling. Personally, I've always really liked the low profile look (my XF has 255/35x20s)

And, what about wheel arch clearance on full lock?

Unfortunately, not the sort of thing you can have a trial run with.

Cheers,

Jon

Hi Steve, 

I had similar tyres on my X type 2.5AWD. I would keep them as they gave me a very good ride.

Additionally, Jon has made some very good points.

Regards,

Peter.

I've noticed the same disparity in speed readings. I am guessing that the boxes aren't calibrated to the same level of accuracy as a speed camera. Having said that, they usually agreed with my Mazda.