Tank Chassis broken with new update

The new update that came out broke all tank chassis cars in some ways. If you don’t know what tank chassis cars are, they are the old way of making cars in roblox. While it may not seem like a big deal, it is. There’s this thing called ‘‘ro-racing’’ which is basically some leagues where drivers race. Most leagues use a tank chassis car, and while ro-racing isn’t the biggest thing on roblox it is definitely a large scale (some of the biggest leagues have over 5000+ users on their groups and discords) Which is why this is incredibly alarming. So, what happens to the cars? Well, first of all, the steering sometimes just locks. In roblox properties, this basically can just mean that even if you aren’t pressing any steering key: (ex. a, d) the steer basically sets the value to 1, however it is only temporary but still enough to be a big nuisance. There’s also a thing called vision lag that basically, with cars they aren’t synced perfectly in everyone’s screen, which can cause a lot of confusion if the cars are collidable. There are scripts for this issue already which only work with tank chassis cars. This new update makes it so that sometimes the scripts break. Other reports include (i haven’t experienced these yet but a lot of people say they happened): Brakes sometimes made the cars stop working, sometimes the cars change in mass, etc. I hope this gets fixed soon!
by the way, if your car’s have motors, hinges, and use scripts to move and you say they dont have any of these issues they are NOT tank-chassis. Those are normal chassis cars.


Why not just upgrade the chassis to fit with the times?

I see you didn’t read my post well.
The new chassis cars don’t work well with vision lag scripts, and the handling is very awful for leagues, and a lot of other issues that while they don’t really matter in a casual game, for ro-racing leagues the new chassis cars are very unconventional.


Are these “Tank Chassis” people talking about the absolutely old classic way of making cars, something like this?

If so, I assume that it might be an internal engine issue due to the recent changes with some ManualSurfaceJointInstances being deprecated.

A fix would be to make a new chassis system that works with constraints. This is not hard to do at all.
Even I have made a vehicle system with constraints and I’m a builder.

Gather whatever developers your community has, and work on a universal chassis system the whole community could use. This would be beneficial to everyone involved.

As for the “vision lag scripts”, I guess they sort of minimize the difference between the players position on their screen compared to where other players see them? If so, a similar effect can be made with a constraint chassis by just sending a message to the server with the players position, current ping, current turning angle, speed, and front facing vector.

With these parameters, you can algorithmically predict where the player should be after a short period of time, and display this position to other players.

Latency and client visual position differences have been discussed a lot on game developer forums, you can look for them yourself, I linked a decent one below.


Basically its a shit ton of prediction.

TLDR: switch to constraints

I hope this helped.

Good luck.

You see, there are other chassis systems on roblox: ex. A-Chassis, J-Chassis, etc. but none of them work as well as tankchassis. Making a new chassis to work similar is actually way harder than you believe, still, thanks for the input.

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but none of them work as well as tankchassis

is this just an assumption or are there objective parameters you are considering when deciding which works better? If you have a system to compare them, you can certainly make a constrain chassis that behaves similar to how the tank chassis does, although of course it will take time and dedication to achieve this.

I understand your whole community is built around it, but look at it like this, you are building your whole community around a method that dates back to the time when roblox “studio” looked like this

If you don’t want that to change, that’s up to you, but I think you should at least try to create a more modern and resilient system to use for your races. If you don’t want to dedicate the time and effort towards that then reconsider how important the league actually is to you.

Roblox itself has posted a tutorial on how to make a simple car with constraints in a detailed tutorial you can find here

For now, you could try enabling custom physics properties for the wheels and raising the friction and friction weight.

This isnt just one league. I see you’re being kind of ignorant to the original post, also this isn’t just some leagues. SO many games still use tank chassis car and the games would probably break if they tried changing. I don’t think you understand how big of a problem this is. Also the new constraints chassis would be awful for racing. Its not bad to have scripts, i really support it but having to base the whole car around scripts would be downright awful, and the tankchassis cars steer WAY better than them most of the time. The only good think is that they semi-simulate some suspension.

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I can definitely confirm this, the tank chassis at random times just stops receiving steering inputs and instead just goes back and forth between 1 and 0 or -1 and zero and the rate of less than 0.5 seconds normally. I will send a video when I can.

Yep I hope this is fixed. Many leagues are affected and theres really no other better chassis for ro racing.

This is what that looks like:
download (1)


Yessir! If someone is a regular PLEASE put this in engine bugs.

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I forgot to say, but the problem isnt that you cant just make cars like this new anymore. The problem is that it just locks the steering sometimes. Also, a hella lot of games still use the system. Its not as horribly outdated. as you think. This is a tank chassis league. These cars can actually be way better than you may think they are: RSCRA D1 | Daytona 500 @ Daytona International Speedway | S2 Full Race Replay - YouTube

This is expected behavior, VehicleSeat.Steer value is either 1 (right), 0 (straight), or -1 (left).

VehicleSeat.SteerFloat is identical to VehicleSeat.Steer unless specifically set to a float value through a script

VehicleSeat.Throttle and ThrottleFloat behaves similarly.

After a bit more searching I found that these classes have been deprecated:
RotateP (that is used by SurfaceType SteppingMotor)
RotateV (that is used by SurfaceType Motor)
Rotate (that is used by SurfaceType Hinge)

You can find the whole difference log created by @Maximum_ADHD here: https://maximumadhd.github.io/Roblox-API-History.html#516

This is most likely either the root cause or closely related to what’s causing the issues for you.

You could try to get someone to make a post in engine bugs but issues with deprecated classes usually don’t get fixed because they are deprecated, but I believe it is worth giving it a shot.

Otherwise, I still HEAVILY recommend creating a custom chassis for the racing league. Of course it won’t be an easy task, but it will be worth it in the long term. If you don’t know where to start or if you get stuck anywhere along the way, you can ask for help in #help-and-feedback:scripting-support or in any reputable development related discord servers.

These have been this way for years. Once again, this is mostly not the problem.

It hasn’t been this way for years. The change happened on the 4th of march of this year (roughly 14 days ago, same day that you made your post)

Here’s the release notes Release Notes for 516

when i watch an video or something the A-Chassis do like you say (steering lock) but i have the environment becomes a little grayer as if the graphics had been removed from my game. I also have the sounds of the car playing by itself and when I jump out of the car, everything stops but when I go back up, the speedometer shows “nan”. This bug sometimes happens in other games