Some of what I am going to say here may contradict what you may believe, so if you choose to believe it, feel free to continue on. Otherwise, you might want to click off.
Warning: Long post.
Now I know a lot of people are going to be up saying that the Adder is a great car for racing because it's the fastest car in the game, and that it's based off the Bugatti. Thing is, the Adder isn't a very good car for racing. It lacks the two things which matter most in racing; Traction, and Acceleration. In case you don't know, the Adder has a pretty bad case of understeer, and acceleration which is only better than the Bullet. According to Broughy1322's testing, (while not universal, it does provide an idea as to which vehicles are quicker than others) the Adder is the nineth fastest Super in the game around a circuit when fully upgraded, and is notably behind any of the other competitive cars. Indeed, a fully upgraded Adder is on the same pace as a stock T20. The Adder's top speed only matters on two circumstances: When Catchup is turned off, and on very long, highway races. Otherwise, you're better off with pretty much any other Super.
Yes, even the Infernus.
And the Cheetah.
And the Vacca.
Another common misconception is that the Carbonizzare is a competitive car and good for racing. This has never been true. It may seem like the Carbonizzare is good because it has handling that favors racing, but in actuality, it's pretty decently off the pace. The Carbonizzare lacks any amount of, shall I say, oomph, which while it doesn't matter much with the help of catchup-slipstream, it is a major problem in pacemaking or when catchup and slipstream are not available for some reason. Cars can catch up to your lower top speed and be on your hind quicker than cars such as the Massacro, or to a lesser extent, the Jester Racecar. Noticed why Carbonizzare leads don't seem to last as long as Massacro leads? That's why.
The Elegy seems to ride in a similar boat, but that car has brilliant speed carry which keeps it from becoming another Carbonizzare. Enough so that on some tracks, the Elegy RH8 is quicker than Jester and Massacro racecars.
If you want a car that handles similarly to the Carbonizzare but is on the pace, my suggestions are the Feltzer and Elegy. Both rely heavily on speed carry and getting good runs out of corners, but are both very quick cars nonetheless. They also feel similar enough to the Carbonizzare that someone would be able to adjust easier than to the distinctively different Massacro or Jester.
I have a good idea as to why people consider the Monroe to be a good Sports Classic to race. Again, I'm about to break your hopes and dreams and tell you why it's not such a good racing Sports Classic. The Monroe, while it has decent acceleration and top speed for a Sports Classic, has unfavorable handling. It understeers to such a point it feels faster than it actually is. While that understeery attitude may be good when cruising around the city, when you don't want to spin out, you want cars which oversteer because they can be controlled for some pretty quick lap times. Hence, why the Monroe is off the pace; while it's an easier Sports Classic to use, it's slower around a track.
Ultimately, the Stirling GT from IGG pt. 1 completely demolishes every other Sports Classic, including the Monroe, because of how brilliantly it handles. Still, though, the Stirling's top speed issues mean the Z-type is still a good choice... on tracks with loads of straights.
Here comes a fun one. The wheel option in Los Santos Customs? They are not all actually equal. Any of the "high end" style rims (High Ends, Sports, SUVs) will have a tendancy to spin out when going over curbs, and as such, oftentimes aren't the best type for thoroughbred race cars. If you pick the "low end" rims though, which have more sidewall, this spin out issue over curbs is nowhere near as noticeable (Off-roads especially, which make going over curbs rediculiously effortless). It doesn't take long to figure it out, just put on some cheap Tuners or Muscles onto a car with High ends on, and note the difference when going over curbs. I garuntee you'll notice in the first minute.
So yes, your pink dollar rims with whitewall are actually better on your Adder than High Ends. But still get those things off your car, that's a sign of bad taste. :P
Quite table for good and bad rims:
|"Bad" Choices||"Good" Choices||"Best" Choice|
Believe it or not, the Z-type is the literal fastest car in the game. If you want to be in a car and want to go as fast as you can, then this is the car to pick, not the Adder. I bring the following video evidence to prove that the Z-type is faster than the Adder:
(skipped to the gameplay, prior 14 minutes of the video isn't relative)
I'll explain why briefly. While the Adder has a higher maximum velocity stat and engine power value, the Z-type has incredibly low drag. The Adder, on the other hand, has a fairly average drag stat: lots of cars across all classes have that. Just because the Z-type has low drag, it is faster than the Adder. Barely. It comes out to a 0.4 mph difference in the Z-type's favor at the end, which makes practically no difference. Why people might say that the Adder is still quicker is because of the Adder's acceleration, which is still much better than the Z-type. If you take a long straight, you can remove the difference in acceleration by having cars reach their ATS (actual top speed, how fast cars go without the help of Boosts or slipstream or the negative effects of Catchup).
Simply put, they are absolute liars. Doesn't matter if it's SSASA or Legendary Motorsport (LM is especially known for inflating the crap out of their Supers and Sports), but those little bars don't tell you the whole story about how fast a car actually is, or how quickly accelerating it is, or how efficently is corners, or anything like that. This is a copy of the handling.dat files from GTA V, only adjusted for ease of reading. Does it look like a single little bar can decide what each of these do? The Adder, again, can be emphasized strongly here, as on the website, the Adder has a top speed of 250 mph, but in the files, it has a maximum velocity of 160 mph. Add in that maximum velocity is never reached during normal gameplay, the Adder is MUCH slower than the stated top speed of 250 mph (more around half that).
The bar values in Los Santos Customs are decided on single values out of that table. Do they have any relevance if these values are really high, but everything else for that car is very low?
Another note about stats, the value upgraded in LSC (what your EMS, Turbo, and Transmission upgrades apply to) is your car's Driving Force value. Now that value affects two things; acceleration and top speed. The top speed part is notable, as while the little bar does not increase for these performance parts. However, it does nonetheless affect top speed. Because more power is applied to your car's wheels, it reaches a higher top speed than before. It doesn't have a higher maximum velocity stat (what "Top Speed" actually refers to), but improves top speed in other ways.
This also explains a couple other notables. While the Jester is implied to be faster than the Massacro according to the stats, the Massacro has a higher top speed than the Jester. That's just one of them, there are bound to be much more.