Forza Custom Upgrades: Which Are Best?

There are several ways to upgrade your car in Forza Motorsport and Horizon: auto-upgrade, a downloaded tune with parts installed, and custom upgrade. This article assumes you want to pick and choose your own parts via the custom upgrade process.

One of the great things about Forza is the ability to customize and upgrade. Each upgrade will change your car’s character and it’s potential, which is usually measured by performance index (PI).

But with so many options available, where do you start? Which upgrades in Forza are worth the PI cost?

Let’s do a quick overview of the upgrades along with recommended goals and parts for each type of build.

Upgrade Categories Overview

Choosing the right upgrades is the first step to a good overall build. Here, we’ll introduce you to the main categories and give examples of what each does:

  • Engine and Power: Maximizing horsepower and torque.
  • Platform and Handling: Improving the car’s balance, suspension, and structural rigidity. These will typically unlock a lot of tuning options as well.
  • Drivetrain: Enhancing gear ratios, differential settings, and drivetrain types.
  • Tires and Rims: Selecting the right compound and size to achieve grip or slide as required.
  • Aerodynamics: Using front and rear aerodynamics for downforce and better cornering.
  • Conversions: Changing the heart of your vehicle or its aspiration method.

Build Types Overview

Every race and driving style demands specific car characteristics. Let’s quickly review some of the more common build types and what they generally aim for:

  • Speed: Aim for straight-line velocity.
  • Grip: Maximize traction in corners.
  • Drift: Perfect the art of sliding through bends.
  • Rally/Dirt: Equip your vehicle for unpredictable terrains.
  • Off-road: Be the king of rugged and unbeaten paths.

Upgrade Trade-Offs

Not every upgrade will add more power while reducing weight. Some upgrades are a mixed bag that you need to consider:

  • Add power but also add weight.
  • Boost performance, but make handling trickier.
  • Increase stiffness at the expense of added weight.

It can be hard to keep all these in mind. Given these nuances, let’s roll everything into a handy chart. The matrix below simplifies which upgrades to prioritize for each build type.

Build Matrix

The matrix below will tell you which upgrades are most suited to a type of build.

  • A dark circle (⚫) means this is an efficient use of PI for that build type.
  • A white circle (◯) means this upgrade may be useful for that build but may not be the most PI-efficient option.
  • Empty means you can typically skip that upgrade for a given build.
  • A red x (❌) means this upgrade will hinder your build.

How much you upgrade that part will depend on your PI target. For example, 700 PI may be good with street or sport tires, but 800 will make room for semi-slick compounds, etc.


Upgrades/Build TypesSpeedGripDriftRally/Dirt (Horizon)Off-road (Horizon)
Air Filters and Intakes
Exhaust Systems
Intercoolers and Oil Coolers
Ignition, Fuel System, Pistons/Compression
Sport/Race Suspension
Rally Suspension
Off-road Suspension
Anti-Roll Bars
Chassis Reinforcement/Roll Cage
Weight Reduction
Clutch and Driveline
Tire Compound – Stock to Slick
Tire Compound – Drift
Tire Compound – Rally
Tire Compound – Off-road
Tire Width
Rim Style/Size
Wheel Spacers
Front and Rear Aero
Drivetrain (AWD Conversion)
Forced Induction Conversion
Engine Swaps

Realistic vs. Wild Builds:

Forza offers freedom. Some racers love keeping their cars true to their original spirit, making only minor, realistic changes.

Others prefer to unleash their imagination, transforming a classic sedan into an off-road beast or a supercar into a drift machine.

Both approaches have their place, and you’ll find a lot of our tuning and build examples lean towards realistic setups. But you find your style!

Why Not Max Out Every Build?

Race restrictions and PI (Performance Index) maximums are critical elements of the game.

Over-upgrading can sometimes hinder you from entering specific races or place you in a more challenging bracket. When you’re near the PI limits, look back at our matrix and prioritize.


Customizing in Forza is as much an art as it is a science. The matrix provided will help guide your upgrades, but don’t be afraid to experiment. Every car and every driver is unique. Enjoy the process, refine your approach, and most importantly, have fun racing!

Was this article helpful?