It works out about 9% fella. Yes they are open, but I only bought a CWP set, so kept my LSD.

Recalibration is only 50 quid, and it will prob be marginal from factory, so worth getting done. Who runs std wheel and tyre combos these days also!

I run a wheel and tyre profile with a greter rolling radius, so smaller difference on mine, but worth it seeing as motorists are the chosen means of revenue generation, and most of us drive these things to enjoy, that extra bit of accuracy is well worth it!

I stand corrected on the early cars having LSD's. Another Ford cost saving measure :-(