Best rim size and lowering kit/coilovers

[kaanage]

40 series rubber isn't the issue, it's the width factory that generates the profile height. If you have a 205 width tyre then 40 series rubber will give you a sidewall height of 80mm. On a Porsche type tyre, 40 series rubber will give you a sidewall height of 130mm. It's all relative and down to the person. My GTI has 40 series boots on 215mm tyres and it's not the tyres that give it a stuff ride, but will I get the same tyres when I replace them? Nope, I'm going wider so this will also increase the sidewall height.

But due to the nature of tyre construction, width and enclosed air volume, ride/compliance will correlate most closely to profile series rather than the absolute height of the sidewalls.

[Stevie G]

Ok, now i have come across this website, where i calculate the difference in tyre size and so on
http://www.1010tires.com/tiresizecalculator

with my tire size of 185x60x15 being replaced by a 205x45x17 it will be Speedometer Difference: 2.192% too slow and Diameter Difference: 2.15%

I am going to fit my polo with cross polo wheels with this tyre. not going to drop the car at this stage.
what do you guys think?

[kaanage]

You forgot the .asp at the end of your link - that is my favorite tyre calculator since it lets you compare multiple options.

I think not dropping the car is a good move since the Cross is raised 15mm vs your Polo so it presumably runs longer, softer springs to do this which keeps the compliance in the overall suspension.

That said, you can get the Comfortline models here with a Sports Pack which drops the car by 15mm with shorter, firmer spring and gets you 17" Boavista rims (I think also with 215/40R17 tyres) so it all depends on what you can live with - there's another thread here where someone complained about the harshness of their Polo with the Sports Pack and then someone else posted that they thought that their Polo with Sports Pack rode just fine.

As you stated earlier, you can always drop it later.