that has nothing to do with the shadow split i think. If not mistaken, (slightly fuzzy subject for me) the shadow split controls the amount of (correct/static/dynamic) shadows it will show under the AI/other players cars. So if you max it it will show shadows under all cars even hen further way rather then modding it out.
Seeing that one hill climb there is only one car ont he track it can't really be that setting i think.
Agree , on hill limb if you want to keep a good frame rate you got to reduce the shadows. I'm playing on triple screen at 5760x1080(+bezel) with a gtx770 I'm able to run pretty much everything at max on most track, getting high 50+ To 70Fps, but forget it on hill climb it sometimes drops in the high 30's