This page aims to provide a full methodology for how vehicle testing is carried out by Broughy1322 in GTA 5, in order to find the top speeds for each vehicle that are used in his videos and on this website. Start with this video for frequently asked questions.
Written by: Broughy1322
The highest constant speed a vehicle can achieve after acceleration has stopped determines its top speed and its place within testing video lists.
Speed = Distance ÷ Time
Five testing runs were done with each car, keeping as straight a line as possible with minimal controller input between the two checkpoints. The section of road that was used for this was chosen due to it being one of the most flat, straight, and smooth sections of regular road surface in the game with a long run up. All of this ensures the cars are going at their actual top speed throughout the course of travelling between the two checkpoints, which is the only point at which measurements are taken such that acceleration is not considered.
The footage for all five runs was then added into video editing software and analysis was carried out to find, to the frame (1/60th of a second), how long each car took to hit the second checkpoint after hitting the first for each run. The maximum variance in all results for any car was 4 frames (which leads to a maximum standard deviation of 0.25 mph), but the majority were identical. All of these times were then averaged to get a single value for time taken to traverse the distance for each car.
These times and distances were plugged into the standard equation to find the speed of each car, and that value was then rounded to the nearest 0.25 mph. This level of accuracy was chosen because it's what I feel comfortable with reporting, given the variability in testing error, taking averages, distance covered, and frame rate considerations. To attempt to be any more accurate than that is an exercise in futility using this method and would only serve to report what could be incorrect conclusions.
One thing to point out is that there are a lot of variables when it comes to top speed in GTA Online which could lead to different (higher and lower) top speeds in various circumstances. However before all of that can be addressed I first need to inform that all non-digital in-game speedometers and other forms of speed measurements such as manu stats either don't work or at the very least are inaccurate (see here for more details). So if you're basing your own observations on those metrics you will most likely be getting incorrect results.
This testing has been done to minimise variables as much as possible and make it repeatable/verifiable. Anybody should be able to repeat this testing on the same piece of road and find the same results. However individuals may find different results to this if they're testing in a different way, such as going uphill or downhill, taking advantage of kerb boosting), racing against others online (never an accurate determinant due to connectivity and variation in driving), using mods or single player abilities, and even using the left stick too much to correct the steering whilst trying to keep in a straight line. Even different road surfaces can have an effect (see here for more details). I am simply reporting the actual top speeds of these cars when fully upgraded, on a flat regular road with no external factors and identical testing methods. I also test on the Expanded & Enhanced edition of the game where fps has no impact on performance.
So with that all being said, my vehicle testing should be taken as a guideline. The testing is very accurate for this piece if road and similar pieces of road without any extra refinements. At the very least you should be able to use this testing to help narrow your field of view for your own personal testing. I would always recommend testing a variety of cars yourself and take into account what kind of tracks you're racing on, what is better for you and your skill level, and even your budget. My testing is meant to guide you, not tell you exactly what to use in every situation.
If you do find the my testing helpful, my videos entertaining, or want to be kept up to date on any car performance changes as GTA Online develops please do subscribe to my channel as that will be the first place for any news. You can also directly support the creation of more testing videos and continued testing for this site in a number of ways shown here. Finally, for a comprehensive spreadsheet on GTA 5 vehicle performance & info that I continue to maintain despite the existence of this website, click here.