Yep, my 'ice' comment was perhaps a little lazy and generic. Your description is more appropriate.
Being forced to play with a controller probably didn't help, as I've been using a FFB wheel since FM2. Having said that, I could switch to the controller in 2/3/4 with no real adjustment problems. FM5 just felt really slippery, even using the same GT cars in the same stock setups and race tunes from previous Forzas and on the same tracks. It felt like a completely different game, and not (for me) in a good way. I found it pretty frustrating, to be honest. I much, much prefer the more predictable grip levels in pCARS where you can drive pretty hard up to the limit, but push beyond that and you get punished, badly. By many accounts this mimics actual on-track racing experience pretty well.