Fastest Cars and Bikes of each class.

Best vehicles:
Class A Car - Velocita for $649,900 - Purchase at Kennedy Town Docks
Class B Car - Terre GT for $280,100 - Purchase at (Northeast North Point) Top Glamour Imports
Class C Car - Enterprise for $198,000 - Purchase at Central Impound Yard
Class D Car - Bismarck for $390,000 - Purchase at (Northeast North Point) Top Glamour Imports
Class A Bike - 1100 NA-R for $150,000 - Purchase at Kennedy Town Docks
Class B Bike - GX300 for $38,000 - Purchase at (South) North Point Chop Shop
(If you have the Wheels of Fury DLC pack then use that for the Class A Car races)


I got this info from the GAMEFAQS Message bord from the user [VividAxis] all cred to him

Cars:
Name / Class / Price / Location
Velocita / A / 649,900 / L4
Etalon / A / 620,300 / L4
Tuono / A / 605,000 / L4
Wangan GSX / A / 550,500 / L4
Blast / A / 420,000 / L4
Panzer / A / 360,000 / L4

860 MHC / B / 462,000 / L1
SES / B / 405,000 / L1
Terre GT / B / 280,100 / L1
Drifter GT / B / 210,000 / L3
Executive / B / 210,000 / L1
Hassha / B / 153,000 / L3
Taikai / B / 125,000 / L3
Neo V / B / 63,200 / L2

Enterprise / C / 198,000 / L3
Odaiko / C / 160,000 / L3
Kyou Kan / C / 85,000 / L2
Prime / C / 73,200 / L2
Sparc / C / 55,000 / L2
Bisai / C / 29,000 / L2

Bismarck / D / 390,000 / L1
Ridge Sport / D / 270,000 / L3


Bikes:
Name / Class / Price / Location
1100 NA-R / A / 150,000 / L4
Drag 979 / A / 92,700 / L1
CS 750 R / A / 69,300 / L1

GX300 / B / 38,000 / L2


Locations:
L1 - (Northeast North Point) Top Glamour Imports
L2 - (South) North Point Chop Shop
L3 -Central Impound Yard
L4 - Kennedy Town Docks

i got the real speed chart from http://www.ign.com/wikis/sleeping-dogs/Speed_Chart

I got all the car location info from the GAMEFAQS Message bord from the user [VividAxis] cred to him
heres a link http://www.gamefaqs.com/boards/981377-sleeping-dogs/66222547
Give him much love