Ok, few moments to play with numbers here, (bet Im close when the actual results are known.)
this is based on
180 ft total skid
asphalt road surface, (guess on my part)
assumption that only back wheel was skidding on the bike.
now, had the bike actually stopped at the end of that 180ft without hitting the car,
we take the numbers.
Where "S" will equal speed.
C will equal a constant of 30 (just works that way in the equation,, sorta like pie is 3.14)
D will equal distance of the skid
F will be the drag factor of the road
N will be braking efficency based an the assumption of a 70% braking. (100 % would have had the front wheel skidding also.)
so, we take the Square Root of C*D*F*N to get S (S was the speed)
30*180*.75*.70 = 2835
Square Root of 2835 = 53.24
so, based on that, I get 53.24 mph pre braking speed ,, IF the bike would have stopped on its own at the end of the 180 ft. but, it didnt, it had enough speed to hit the car hard enough to create the damage, and to tragically end the lives of the two on the bike.
I just did the same thing, based on the motorcycle braking site just posted.
D=1/2 A t^2
d=180
a=-.46g
t=4.89sec
v=t*a = 72feet per second deceleration under braking (48mph)
so speed was reduced at least 48mph before impact.