I too have noticed the exact same thing. I will build/tune a car then go and do multiple laps in time trial, till the things running perfect. As soon as I go online and try to race, the things usually an undriveable pig that spits me into a wall or off track almost immediately. I am trialling with all aides off, usually the same tyres, ss, so everythings the same as it has been for the last 2 hrs, but go online, totally different handling vehicle. I am finding this incredibly frustrating. I am glad that someone else has noticed this annomally, because I started to think it was just me, destined to be a non online racer. Can't really work out how/why this would be so.