OK
![Very Happy :D](./images/smilies/icon_biggrin.gif)
. In the UK it is a bit of a mix/mess Some clubs run 13.5 as "compatible" some don't. The national body ducked the subject last winter. Recently our club - which considers 13.5 not to be compatible with 27T - has been testing 17.5s. These clearly are very close to 27T. Considered view after 2 months is that they are equal but an expert/well tuned 27T would have the edge.
If you are running on tight circuit then a good 27T will give a 13.5 a run but on a wide open circuit, long straight or 2, the 27T will get hammered.
All other things being equal
LRP/Nosram/Novak/Speed Passion seem to be the leaders here in the UK. I would suggest you buy a brand that has a distributer in Denmark so your shop has support. I know people here are buying direct from the States but clearly from reports these things can go bang and it is easier to get your money back from someone in your country!!