You completed a lap of Chicago - Wabash Run driving the Ford Mustang Mach 1 in less than 60 seconds.
This is a rather difficult achievement, but with patience and the proper racing line it is possible. First, you'll want to create a Custom Event with the following settings:
Race Type: Race
Vehicle Tier: Tier One
Rounds: 1 Round
AI Drivers: Very Easy
Grid Order (Advanced Options): Random
Flashbacks (Advanced Options): Unlimited
Track Selection: Chicago - Wabash Run - Day - 5 Laps
Vehicle: Ford Mustang Mach 1 Twister Special
During lap 1, your goal is to cleanly gain the lead and set yourself up for a good lap. You'll be going for the achievement during laps 2, 3 and 4. If you don't have the achievement by the beginning of lap 5, it is advised that you restart the event as AI cars will get in the way during this lap.
The goal is to get a lap time of 59.99 or lower, in this stock car. There are various ways of approaching this, but keeping to the racing line and controlling your drifts is essential. The best line through corners is to approach from the outside wall, steer into the inside apex of the turn, and then keep speed through the corners to the opposite side wall again. This line will allow you to maintain the best speed through corners and minimize unnecessary drifting. You will need to drift, but the goal is too not drift too much. Drift to slow yourself down, and to get yourself through the corner, but straighten out as soon as you have enough track to do so. The most important turn of the entire track is the large downhill hairpin before the long straight. Make sure to get maximum speed through this corner and come out of it with a high top speed to shave off a good amount of seconds.
Also, keep in mind that you have unlimited flashbacks. If you are having a really good lap, feel free to spam those flashbacks and make sure you get every corner perfect.
Note: It is possible to do this achievement online using a fully upgraded car.
This is a little tricky to do because you have to basically take every corner as fast as you can and you can't really use the brakes at all. The video below shows the the driving line I took and finished with a time for 58.8 seconds. My advice would be for you to take a few practice runs on the track first to get to know the corners and how fast you can take them, then go for the under 60 seconds time. I did this in time attack, but it can also be done in a race.
did it on a private match offline, 5 laps, very easy opponent difficulty, and unlimited rewinds. the first 3 to 4 laps i would try and get the fastest lap times i could getting approx 1:00:xxx last lap or two i would perfect every corner by rewinding slow process but works if your really struggling like i did hope this helps