A few questions about car classes

Can anyone explain the recommended car class system for specific challenges? For example I had a challenge that required me to use a certain car with a certain class and ended up completing it with a slightly different class number car. I can’t remember specifics but it was something like “use a Ferrari class S1900” and I completed it with a Ferrari S1850. How much difference is allowed?

Second somewhat odd question. I have a car that is class B850 (stock) and changed the tuning to A800 for a challenge, after which I reverted everything to default but the class was slightly different than it was by 1 (B851). Just curious as to why that is.

Sorry for the noob questions, this is my first Forza game.

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Class restrictions for events, such as S1 900, are shorthand: “Must be currently S1 class, up to a maximum PI of 900.” This allows players more options in choosing cars so that they can go with a stock setup like that 850 and still have a competitive race. You could pick a car as low as 801 in an S1 event.

Ideally returning a car to its stock settings should result in the PI returning to the same PI as stock, but a switch from 850 to 851 when restoring stock parts and settings may indicate that the car was actually rated around 850.5 or so and it rounded differently. It’s possible there is a part change for that particular car, and you could potentially find it by taking note of all the parts before resetting the car and then note all the parts after. If it’s something you’d like to see addressed, submit a ticket about it via the pinned message in the Support subforum.

Always nice to see new players! I’ll be happy to answer any other gameplay questions you have while I work on writing up FAQs that explain various menu and feature topics.

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The 1 PI change: Not sure if it’s related to this or not (may not have carried over) but there was apeculiarity sometimes in FH4 where, if you installed a tune, it would be listed as 1 PI over…so an A800 tune would become an S1801 tune…you’d then need to reapply the tune to get it back to A800 (usually it added 5KG or something to the weight). Of course, not entirely sure how you’d reapply the default tune again having already applied it once

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Thanks for the help guys, I really appreciate it.

On the subject of the class change I had the numbers wrong but the odd 1 number difference still persists. It even shows the original class number as well as the new one simultaneously sometimes (see pic).

Also what does PI mean?


PI is Performance Index, which is derived from running each car on a virtual track. PI numbers are further grouped into performance classes: D, C, B, A and so on. Although PI will be changed by upgrading parts, it may not provide a perfect comparison about whether cars with the same PI will perform equally even on the same track. PI should be treated as a guideline, particularly since changing tuning settings on the same car can have significant impact on its performance.


A few remarks from me:

The PI classes normaly span 100 Pi-points. So S1-900 is anything from 801 to 900.
If you race against ai, they will scale to your actual PI rating.
So if you enter a S1 race with a 850PI car, you will face opponents ranging roughly from 845 to 855. Most tuners will therefor try to reach exactly 900, cause then you will face opponents from 895 to 900. This gives you a slight advantage.
For anything else than racing against ai its even more important to max the PI, for example for PR stunts. I think there is a weekly danger sign this week for a jump in a A-class muscle car. Obviously this will be much easier in A800 car than a A701.

Also, the PI rating describes the all over performance. Roughly: Speed, acceleration, handling and braking. Setting the ballance between these with a certain PI target value and a task is the most important part of upgrading/tuning. E.g. for jumping far you don’t need good brakes, but for racing on short tracks you do.

Oh, and that 1 PI difference is imho a rounding error. Just yesterday I had a car build to b700, switched to the rims selection to see if I can shave of another kg and there it showed A701. Switched back to engine and it shows b700 again.

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FH4 was like that, FH5 is more like…

Most tuners will therefore try to reach exactly 900, cause then you will face opponents from 900 to 905 if you go above Highly Skilled.

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Cheers guys, ya’ll have been super helpful.

Personally I won’t be delving into the tuning/upgrade aspects of the game myself, I mostly play solo anyway and I’m usually pretty happy with the stock versions of cars. I’m also beyond clueless when it comes to that kind of thing but the info’s good to know nonetheless.