49 minutes ago, farty said:

You did not read my post carefully.  I'm on about the SIZE designation 225/40YR18.  I asked why this number has a Y in the middle.  The previous explanation covered a Z.

This is a presentation issue on the website, having filtered to correct size 225/40 R18, they are including the 92Y.  As already discussed the letters are max speed.   The 92 is a load weight rating. (92 is 630kg), so no wheel should carry more than that fully loaded (might be easier to think of it as 1260kg max per axle).  
 

Table of weights here

https://www.ctyres.co.uk/general/load-index

 

Edited 29 November, 20205 yr by SurreyJohn

Is it still the case that the speed rating is the 10 minutes a tyre can last without it self destructing, so 11 minutes on a Y at the rated max might get interesting (not on a Superb obv.)

On 29/11/2020 at 23:59, NJRJ said:

Is it still the case that the speed rating is the 10 minutes a tyre can last without it self destructing, so 11 minutes on a Y at the rated max might get interesting (not on a Superb obv.)

I'd have to use premium diesel to get my Superb elegance estate up to 186 MPH :-)

I have V rated winter tyres on to slip along at 70 mph when weather conditions allows and the Max speed is only 93 mph anyway.