Hi I'm looking for advice on best size tyre for 13 inch bbs mesh on 40 mm lowered front and back pics be great of setups and sizes on 13 inch wheels and 40 mm suspension drop thanks 

I used a mixture of tyres on my mk2 bv, rubbing on the rear is your main enemy due to the flat arches, so you will need to measure the clearance you have either side of your wheels, depending on the width and offset of the wheels the clearance can be altered by using spacers or changing to a higher offset wheel. You should be fairly safe with sizes like 155/70 and 165/65. Hope this helps.

40mm drop at the back...

some breadvan pictures in the FAQ.

 

I needed 5mm spacers to clear the wider springs after lowering 40mm with 165/65/r13 on ET38 offset Hockenheims.

 

Some people Dremel the breadvan arch lips away or fold them inwards.

https://www.clubpolo.co.uk/topic/118967-mk1mk2mk2f-various-amounts-of-lows-and-wheels/?do=findComment&comment=1422583