"Steering wheel! Hey!!"
I have noticed the exact same thing. Tried tt on pad and it's a different game all together. Played F1 2016 on a pad for a month, from then I've been using a wheel. Now I compared in tt and I was within 0,1 seconds straight away without assists on the pad.
A game of this type (ie not a sim) shouldn't inherently be easier depending on your equipment imo. In esscence - Why should a setup for a particular track be changed according to wheel or pad? I have massive loss of mid corner front end grip on a wheel but not with the pad? Car won't stop as fast no matter what I try.
Something is odd. Either it's in the game or my equipment. But what do I change and why? AND how come other people find the same problem and don't have the same issue with F1 2018?