This page aims to document all upgrades to cars in GTA 5 that have a tangible impact on performance and should be used by every player. This video is also an option for a more simplified explanation with visual aids.
Written by: Broughy1322
These apply to all cars that have them and should be upgraded to the maximum level possible.
Even if the stat bars are already full in Los Santos Customs you’ll still gain a benefit from maxing out these upgrades. Those bars should not be trusted, as shown here and here.
Not all cars in GTA have a spoiler modification, but those that do will receive an increase in grip when any non-stock spoiler option is chosen, resulting in higher cornering speeds. To clarify, “non-stock” means any spoiler that isn’t the top option in the spoilers category list. All spoilers below the option at the top of the list will give the same increase in grip - larger spoilers aren’t any better than smaller spoilers in this respect. Some cars like the T20 and Furia have active spoilers which give the increase in grip by default, however if they are broken mid-race the car will experience grip loss until fixed as shown here. Spoilers also have no effect on top speed as shown here.
Some high performance cars have a downforce multiplier. The higher the car’s downforce value, the better cornering ability it has when travelling at high speed. After many changes by Rockstar over the years, spoilers are now required for these cars and will still improve cornering speeds, but to a lesser extent than if they were added to a non-downforce car. For more background on how downforce and spoiler work in detail, see here.
For cars that don’t have a spoiler category in Los Santos Customs, it’s possible that they receive an increase in grip from other modifications. Keep an eye out for the traction bar increasing when upgrading to identify these parts, or look for the "Adds traction like a spoiler" category in the performance section of the vehicle's page on this site (like with the Dubsta for example).
Any car that has the tyres_can _clip handling flag in the data (but doesn't also have the fix_old_bugs advanced flag) will be smoother over kerbs and bumps in the road when they have off-road wheels applied, making them much more stable. A lesser benefit will be experienced with other wheels depending on the size of the tyre sidewall. Because off-road wheels have the biggest sidewall, they give the biggest benefit. More details here.
You can find which cars benefit from this by checking to see if the vehicle has the "Off-road wheels better" improvement in the performance section of a vehicle's page on this site (like with the Osiris for example). For these cars any wheel from the Off-Road category will improve bump absorption, with wheels from the Tuner and Muscle category also helping but to a lesser extent. Some of these cars do however get a bigger kerb boost from wheels with less sidewall, such as High Ends, while sacrificing stability.
In general suspension options don’t impact car performance. A car will be no quicker or slower by running the lowest suspension vs the highest for example. However some cars introduced from 2019 onward have the reduce_body_roll_with_suspension_mods advanced flag which actually increases the amount of traction they have when lower suspension is applied (most notably cars in the Tuners class, but also things like the Asbo).
You can find which cars benefit from this by checking to see if the vehicle has the "Lower suspension better" improvement in the performance section of a vehice's page on this site (like with the Vectre for example). For these cars the lowest suspension upgrade is the best option and often that involves having cars with extreme negative camber, where the bottom of the wheels tilt outwards. Any car that has suspension induced camber but doesn't have the aforementioned attribute will either handle worse with it or it has a negligible effect.
For the vast majority of cars the maximum brake option is usually the best unless there's a specific preference to have something less from a setup perspective. Higher levels increase braking force, resulting in better stopping ability. However a small number of cars have the abs_alt_std and abs_alt_option model flags which cause them to lock up more easily under braking. Applying the maximum brak upgrade to these cars further exacerbates this issue.
You can find which cars are affected by this by checking to see if the vehicle has the "Stock brakes better" improvement in the performance section of a vehice's page on this site (like with the Yosemite for example). For these cars having stock brakes is better as it allows the driver to easier find the window of brake pressure required to not lock the brakes.
Hao's Special Works was introduced with, and is only available on, the expanded and enhanced version of the game for PS5 and Xbox Series X|S. A small number of cars have access to a special modification in the Los Santos Car Meet which gives them significantly higher straight line speeds, as well as access to higher levels of Brakes, Engine, Transmission, and Turbo/Mode upgrades. Since HSW upgrades can be enabled or disabled on the fly in races, they're treated as separate cars entirely on this site with lap times and top speeds reported for HSW and non-HSW versions of a car.
A small number of cars have a variety of extra boosts. Open Wheel cars have KERS, which regenerates slowly when off the throttle and quickly when braking. Arena vehicles like the ZR380 can have nitrous boost upgrades and special vehicles like the Scramjet have rocket boosts by default. Most boosts are most effective when activated at low speed and are fully depleted, though open wheel cars can benefit from utilising KERS to raise their relatively poor default top speeds.
All armour upgrades have zero impact on performance in terms of vehicle speed, but will help with avoiding damage. 100% armour is the best option as it will offer the most protection when your car is involved in crashes and collisions. A damaged car will impact performance negatively and make you slower, so it’s a good idea to protect against it as much as possible.
All other modification options not otherwise mentioned here (such as bumpers, sides skirts, etc) have no tangible impact on performance. Carbon parts aren’t lighter, and other body modifications don’t add grip like spoilers do.
However almost every GTA car modification has a very nuanced and almost imperceptible impact on the way a car feels by changing where the car’s centre of mass is located. The vast majority of people won’t be able to notice this aspect and is something that’s only really applicable to the quickest racers to finely tune the way their cars behave.
While these changes won’t improve the outright speed of a certain car, they can be used to good effect to allow drivers to make cars drive closer to how they prefer, enabling the theoretical maximum of the car to be achieved more consistently. All of this falls under car setups and more information can be read on this page.
With the Tuners update in summer 2021, 17 cars were introduced that had the ability to apply Low Grip tyres at the Los Santos Car Meet. With the 2022 Criminal Enterprises DLC, all cars gained the ability to add these tyres. They make cars have much less traction and therefore improve their drifting ability, but they will always be slower for lap time and racing. They initially made cars have higher top speeds, but this was later fixed in a patch. They do however remain a source of buggy behaviour.
Open Wheel cars in GTA have high levels of downforce (explained above) but don’t get the usual benefit from spoilers in the traditional sense. Instead, the front and rear wing upgrades actively change the downforce values on the cars. This means that it’s possible to set up all open wheels cars to have high or low levels of downforce.
Naturally there are a huge number of options in this regard, with each front and rear wing modification increasing or decreasing the downforce value of the car by different amounts. This can result in the same cars performing very differently with different mods applied.
You can find the exact effect of every front and rear wing option for every Open Wheel car by checking the Open Wheel Wings section of the main spreadsheet, linked here. In general the further down the list you go the more downforce is applied, but there are exceptions.