Forza Horizon 5 Cars Guide: How to Build and Tune for Optimal Road Race Performance

Forza Horizon 5 is the latest edition of the series to grace our screens. For new players, building and tuning cars can be a daunting prospect, especially when you aren’t sure what half of the options for tuning do.

Building or upgrading a car in Forza Horizon 5 gives anyone the opportunity to create a vehicle that gets to the top of their desired performance index (PI) class whether it be from D through to S2. When you’re in the upgrades window, you’ll see your car’s PI if you look at the top left of the screen. Here’s how the PI classes work:

Keep these numbers in mind when you decide what class to make your car, additionally, you can’t race an X class car online or in rivals so don’t worry too much about those.

Now that you know your maximum PI for the vehicle you want to upgrade, let’s jump into all the different parts you can add on to your car.

When you first open the custom upgrade window, you’ll see several options, these being: conversion, aero, tires and rims, drivetrain, platform and handling, and engine. You may notice that those options have been listed back to front and that’s for a good reason. Many options can be taxing on your PI budget and it’s better to have those on your car before you start using up the PI you have left over on engine upgrades.

Conversions give you the option to change the drivetrain of a car, utilise engine swaps, change the aspiration of the engine and change the body kit.

The stock engine will usually do the trick, however, changing your engine is necessary if you want to move into a higher PI class or you need more power and have the PI to spare. Engine swaps can also decrease PI, meaning you have the option to drop some cars into a PI class below its stock.

Drivetrain swaps allow you to change which wheels get power from the engine. Typically, a RWD car will get the option to switch to AWD, a FWD car will typically get the option to swap to AWD or RWD and AWD will always get the option to switch to either RWD or FWD.

Most of the time it’s best to leave the cars with their stock drivetrain, but you’ll find out what manufacturers might need to be changed with trial and error. For example, Mercedes-AMG vehicles are mainly RWD, however, they can slide a lot, so it could be worth changing the drivetrain to an AWD.

It’s always best to try to meet your power goals with natural aspiration, however, if you’re still lacking power and have the PI to spare then you should consider it.

Body kits are available on some cars, they increase the track width of the car in turn increasing the handling, you can install this if you’d like, but keep in mind you probably won’t be able to install a front aero upgrade.

Aero is one of the many ways the car obtains grip while on the track, its most effective through corners, additionally, too much aero will create drag and slow the car down on the straights.

Front aero is important for higher class cars (A class and up), you could test the car without it first and if you’re struggling for grip or having some corner entry understeer you might need to add it on. Alternatively, you can add it from the start, the choice is up to you.

Sometimes rear wings can lower your PI, if it does, add it on, you’ll get some added aero and you’ll be able to free up some extra PI to spend elsewhere. Like the front aero upgrade, rear wings are very good for higher class cars and help with grip while driving at a high speed. The rear wing also helps with rear grip when getting the power down on corner exit so it’s definitely something to consider adding on.

Sometimes you’ll have multiple options when adding on a rear wing but be careful because some are non-adjustable upgrades. Additionally, there are more non-adjustable add-ons such as side skirts, rear bumpers etc. sometimes these will decrease your PI, giving you the option to put an additional upgrade elsewhere.

This is the first section that is extremely important, setting your wheels up properly can add a large amount of grip and can cut your lap times down significantly.

There are four types of tire compounds for road races, these being: street, sport, semi-slick and slick. Sometimes you won’t see all the options because the car’s stock tires might be better than one or two of the possible upgrades. For an AWD car, the stock tires work quite well but go for one above the stock if you want to upgrade. For RWD and FWD cars it’s advisable that you go for the tire compound one above the stock to give yourself some extra grip. Additionally, slick tires aren’t really worth it when racing online but are the best choice if you want to take the car into rivals.

Widening your front tire width is very beneficial and will increase grip through corners, it’s a good idea to add this on if you’re struggling with some understeer, however, this can be very costly and might take a chunk out of your budget.

Usually increasing the rear tire width will increase your PI but on some occasions it’s a free upgrade or may even decrease your PI, in that case add it on for some more grip. On a RWD car, it’s worth adding this on as it will drastically improve rear grip.

Rims will either be heavier, lighter or the same weight as the stock rims. Heavier rims will drop your PI, lighter will increase it and rims with the same weight are basically a free rim swap. These can be utilised at the end of your build to reach your final PI.

Larger rims are normally a cheap upgrade and will make the car feel more responsive.

Another cheap way to increase handling and grip, on RWD it might help to leave front spacing alone and maximise the space on the rear, which will increase the rear grip and stability.

The drivetrain affects transmission, driveline, and differentials, you can also upgrade the clutch which can drop the shifting time between gears.

If you’re using manual without clutch or automatic settings this can be useful. Additionally, its useful in older cars where you need to decrease the time between shifts.

Putting in a sport transmission allows you to adjust the final drive while tuning, however, if you want extra gears or want to tweak individual gears add on a race transmission.

This allows you to drop some weight off the car while costing minimal PI. It’s another upgrade that can be used towards the end of your build when you’re trying to get your final PI.

A differential gives added power to the cars outside tire when cornering to maintain grip through the corner. Adding one on here will give you the option to adjust your differential settings when tuning which are pretty important. The sport differential is almost worthless so in this case go for the race differential as we’re building a track car.

This section is another important one and gives several upgrades that are a must when tuning a car.

It’s always best to take the race brakes when building a car, it’s costly and will take a chunk out of your PI budget but you’ll unlock brake tuning and get better braking performance.

Race suspension is the best here too, it’ll give a massive boost to handling and also unlocks tuning for springs, dampers, and alignment.

These are also known as ARBs, they normally don’t cost anything, but on some occasions can cost a couple PI. They also unlock the ability to tune ARBs which is very important.

This can normally be kept stock; you shouldn’t add a full roll cage unless it’s absolutely necessary as it adds a lot of weight and the handling benefits aren’t that noticeable. If you want to add a roll cage, the general rule is, put on one level of upgrade for each PI class you move through.

This is very expensive to add on and forces you to make a major decision. Do you want more power or less weight? For this game it’s always best to min/max your decision as adding a little power and dropping a little weight won’t really reward you. If you decide to have minimal weight and have the budget to do it, drop the weight as much as possible or skip this part and just build up the car’s power instead. Keep in mind, power is normally best for online racing.

If you have everything you want from the other upgrade options and have PI to spare, this is where you can use it. Since the engine is a large section, it’ll broken down with first things to upgrade down to the last.

·         Intake and exhaust are extremely valuable, they’re cheap and give a nice little boost to your car’s power.

·         Oil and cooling are solid upgrades, they’re cheap because they add weight but also add some decent power. Additionally, you could add an intercooler if you have a supercharger or turbo in the car.

·         If the car is supercharged then upgrade it now if you have the budget, however, it’s best to leave turbo upgrades till last.

·         Fuel system, ignition and compression are also very good, and you should add these if you have the budget.

·         Displacement is one of those things that doesn’t do much and can be left till last.

·         Camshafts are great if you want to increase your red line but are expensive at this point in your build and might put you over your budget.

·         A flywheel is great for getting to your final PI, it also drops a little weight for you as well. 

Tuning a car is a great way to add that personal touch to your car. It also allows you to create a tune that suits your own driving style rather than having to adapt to a tune that’s already been created. Something important to note when you’re tuning a car; RWD cars are going to oversteer while AWD and FWD cars are going to understeer.

The general rule is higher tire pressures will increase responsiveness but are more likely to break traction while lower tire pressures do the opposite. Having a higher front tire pressure is generally preferred, try to keep the pressures between 30-34 PSI as well.

Quick gear tuning: In this example you can see the stock gearing doesn’t cover the whole graph meaning the car isn’t reaching its top potential. A quick fix is to either lengthen or shorten the final drive so that it covers the whole graph, like in the example shown.

Individual gear tuning: Once again we can start with the untuned gears. Making the first three gears a little longer can help a lot, the longer gears mean it’ll take more revs to shift up but also means you’ll have more traction and minimise wheel spin when accelerating out of a corner or on a race start. The final gears you can make shorter and relatively even as you reach your top speed and have full traction. Here’s the stock gear tune compared to individually tuned gears.

The alignment determines the tires position when driving.

Camber: Camber determines the tires horizontal position when looking at the car head on. Negative camber means the top of the tires are leaning in towards the car while positive camber means the opposite. The default camber values are usually a little too high, so to start drop them down a few notches.

Toe: Toe is the tires vertical position when looking at the car from above, toe-in will point the fronts of the tires towards the car, while toe-out will point them away. Toe-out produces more oversteer and responsiveness while toe-in increases understeer and stability, however, adjust this in minimal increments as the toe values are extremely powerful. For AWD and FWD start with 0.1 degree or front toe-in, for RWD cars start with 0.1 degrees of rear toe-out.

Caster angle: the caster angle adjusts the vertical angle of the suspension when looking at the side of the car. Having a higher/positive caster angle means the suspension is pointing towards the back of the car, while a negative angle is pointing towards the front of the car. Additionally, the caster angle works as “dynamic camber”, this means it will add more camber in corners and has no effect on straight. Try to keep the caster angle between 4-7 degrees, six is a good start for a track car.

ARBs are what tie the front and rear suspension together, they play a major role in managing mid corner understeer and oversteer. A softer front ARB will produce more oversteer while a softer rear will produce more understeer. The opposite will occur when the ARBs are stiffer. On a AWD or FWD car, aim for around halfway between the default and softest value on the front and halfway between the default and stiffest value on the rear. For RWD leave the values as is and adjust after initial testing.

The springs control the car’s weight under acceleration, braking and through corners. Lowering the front spring stiffness will increase oversteer while lowering the rear will increase understeer.

Spring tuning: For an AWD or FWD car, decrease the front spring a little to give the car more oversteer. For RWD cars its best to adjust as needed, but you might end up softening the rear spring to promote more understeer.

Ride height: The ride height is the car’s gap between it and the ground and also determines its centre of gravity. Lowering the car gives more control through corners, but lowering it too much can cause it to bottom out and lose traction. Start with a ride height of one to two notches off the bottom and adjust from there.

This determines how soft or stiff the suspension is over the car when driving over bumps or uneven surfaces. Rebound stiffness determines how much the suspension will extend, while bump stiffness determines how much the suspension will compress. Leave the rebound stiffness as the default for now. Since the drive physics have changed for Horizon 5, the bump stiffness varies between cars, but start with a value around half of my rebound stiffness. So, in this example, the default front rebound stiffness is 10.8 so the front bump is 5.4. The rear rebound is 12.8 so the rear bump is 6.4. Again, this is something that we’ll play around with again.

Aero is a beautiful thing and allows the car to have more grip. Front aero gives the car more grip on corner entry while rear aero gives more grip on corner exit when you’re trying to get the power down. For this it's best to leave it stock until testing and then increase or decrease from there.

When it comes to brakes, everyone's preferences are different. If you’ve never played with the brake settings, leave it as default to start. I prefer the balance to be 55% and a brake pressure of 105%. Also remember that the brake balance is flipped in this game, so if you move the balance above 50% and to the front like I have, it will actually give more braking power to the rear and vice versa when moving it to the other side.

Known as diffs for short, give added power to the cars outside tire when cornering, to maintain grip through the corner. AWD has a front, rear, and centre diff while RWD and FWD only have a rear or front diff.

The base benchmark to aim for when tuning diffs is pretty standard throughout. On the front differential start with 15% acceleration and 0% deceleration the front diff. Start with 80% on the rear acceleration and 0% on the deceleration. Finally, a good starting centre balance is around 70%. You might have to play with these a bit to find the sweet spot.

It’s obvious a base tune won’t be perfect and there’s troubleshoots and solutions for a lot of problems.

This is where a lot of problems will occur when testing a tune. Understeer can occur in three ways, those being: corner entry understeer, mid corner understeer and corner exit understeer, while oversteer will occur on corner exit.

Entry understeer: Entry understeer is when the car feels like it doesn’t want to turn into the corner.

·         Increase or decrease tire pressure for peak grip depending on the PSI you set.

·         Decrease front springs or ARBs

·         Increase rear toe-out

·         Increase front downforce

·         Decrease rear deceleration differential (more than likely already 0%)

·         Increase front bump stiffness

·         Decrease front rebound stiffness

Mid Corner: Mid corner understeer happens when the car wants to straighten as you hit the apex of a corner.

·         Increase rear ARBs or spring rate

·         Increase front downforce

·         Increase rear rebound or bump stiffness

·         Increase/decrease tire pressure, camber or caster angle

Exit understeer: Corner exit understeer happens as you get back on the throttle and feels like there is resistance against your steering input, it may also feel like the car is going to drift off the track.

·         Increase the rear bias on the centre differential

·         Increase rear acceleration lock

·         Decrease front acceleration differential

Oversteer: This will happen when you apply the throttle on corner exit and the car wants to turn too much.

·         Lower rear acceleration differential

·         Increase front bias on centre differential

·         Soften rear ARBs

·         Increase rear aero

·         If these don’t help you can try doing some opposites of the understeer troubleshoots.

·         Increase toe-out

·         Lower tyre pressures

·         Increase front ARB stiffness

·         Increase rear aero

·         Increase rear deceleration differential

·         Reduce front camber

·         Increase caster angle (will also give more camber in corners)

·         Increase front aero

·         Stiffen front suspension

·         Adjust the final gear more to the speed side

·         Lower front and rear aero

·         Lower toe 

·         Increase first and second gear ratio towards speed

·         Lower rear tire pressure

·         Lower rear camber

Learning how to tune a road race car may be the hardest thing to do in Forza Horizon 5, but, with everything you’ve just learned, you’re well on your way to becoming a building and tuning master. Finally, stay tuned for the other building and tuning guides so you’ll be prepared for anything the world of Forza Horizon 5 throws at you.