Best size tyres for a Mk3 on 15's?

[thai-wronghorse]

Ok cool, Il certainly bare it in mind for when the gearbox eventually comes out which probably won't be until after the new year realistically speaking.
I'm sure you've told me before but 3.94 is the standard O2A FD ratio isn't it and 4.2 was taken from a Passat box of some nature?
Apart from the narrower footprint and extra compliance were there any other pros or cons for this tyre choice, how was the speedo effected before and after the swap as from the what i've read on the tyre calculator it's very marginal yet you say the bigger FD is required?

[Ess_Three]

I'm sure you've told me before but 3.94 is the standard O2A FD ratio isn't it and 4.2 was taken from a Passat box of some nature?

3.68 is standard ABF.
3.3 standard VR6.
3.94 is available in the odd Passat 'box...and 4.2s like hens teeth!

That's twice I've changed the FD.

Apart from the narrower footprint and extra compliance were there any other pros or cons for this tyre choice, how was the speedo effected before and after the swap as from the what i've read on the tyre calculator it's very marginal yet you say the bigger FD is required?

Mainly, it was a change to a size I could get decent trackday rubber in.

Speedo has virtually no error now - according to the GPS it's spot on.
There is a noticable chance in MPH/1000 RPM changing the FD...and a noticable difference in true speed  vs indicated speed changing the tyre size.

215/40/16s were right at the bottom end of the standard wheel gearing...whereas 195/50/16 are right up at the top.
As an example, 195/50/16 gives the same overall gearing in top on a 4.2 FD as 215/40/16 did on a 3.94 FD...but the ratios have changed too - it's now approx 20 MPH/1000RPM in 6th, vs the same in 5th before.