I need help with a wheel model instance error.

[MtsMatheus]

Hello everyone,

I’m trying to convert a standalone truck mod from 4x2 to 6x2, but I’m running into an issue that I can’t solve.

Here’s what I did:

The original mod is a 4x2 (standalone).
I removed the original chassis and imported a 6x2 chassis (initially I tried to extend the original chassis).
I adapted the chassis to fit my model (adjusted length and position).
I used the original wheel locators from SCS 6x2 chassis (version 1.58):

wheel_f_0 / wheel_f_1
wheel_r_2_1 / wheel_r_3_1
wheel_r_0_1 / wheel_r_1_1

All locators are inside the correct part ("chassis") and assigned to a variant (chs_6x2).
The entire structure is inside the truck root.
I also updated the DEF file (powered_axle and liftable_axle correctly set for 6x2).

However, in-game I get the following errors:

"wheel model instance 4 is missing for chassis..."
"wheel model instance 5 is missing for chassis..."
"incorrect r-wheel definition..."

(All of them point to the same truck.pmd file from the mod.)

From what I understand, this means the game is not recognizing the third axle (tag lift), even though the locators are present.

Important notes:

The model visually has the third axle (functional), but the game does not seem to create wheel instances 4 and 5.

So my questions are:

Is there any specific part of the internal chassis structure that must be preserved for the third axle to work correctly?

Are there additional steps required beyond locators + DEF to properly register a 6x2 setup?

I’m new to this, so I may have made some mistakes. Any guidance or tips would be greatly appreciated.
I’m available to provide my DEF file and the mod itself if needed.

Thanks in advance!

[MtsMatheus]

[RESOLVED]

Hello everyone,

I am posting the solution to my problem in case someone else encounters the same issue when converting a 4x2 chassis to 6x2 in a standalone mod.

The problem was in:

/def/vehicle/truck_dealer/scania/scania_6.sii

and the missing definitions in "vehicle_wheel_accessory" and "accessories[]:"

Explanation:

For a 6x2 chassis, the game expects "two sets of rear axle wheels":

Main rear axle (default)
Tag/lift axle (extra axle)

I only had definitions for one rear axle:

scania6.rtire
scania6.rdisc
scania6.rhub
scania6.rnuts

Therefore, even though the third axle existed in the model, the game "had no wheel definitions for it", which caused:

-> Missing wheel instances (4 and 5)
-> Incorrect rear wheel definition

My solution was:

I added a second set of rear wheel accessories in "accessories[]:"

accessories[]: .scania6.rtire2
accessories[]: .scania6.rdisc2
accessories[]: .scania6.rhub2
accessories[]: .scania6.rnuts2

Then, I created corresponding entries in "vehicle_wheel_accessory"
with: offset: 2

Example:

vehicle_wheel_accessory : .scania6.rtire2 {

offset: 2

data_path: "/def/vehicle/r_tire/315_80.sii"
}

Without this, the game will NOT create wheels for that axle.

After adding the second rear wheel definitions with the correct offset:

No more errors in the log and wheel instances 4 and 5 are created correctly.
The 6x2 chassis works as expected.

I hope this helps someone!

[Digital X]

Seems like you're missing some accessory info, you'll need to add some parts to the truck's .sii file.

Let's say this is for a quick job, you need to assign the correct tyre, hub etc.

Go to: def/vehicle/truck_company, or truck_desktop whichever you have made, do you have definitions made for both the front and rear tyres, wheels?

Should look like this:

Front:

vehicle_wheel_accessory : .mercedes1632.6x6h.f_tire {
offset: 0
data_path: "/def/vehicle/f_tire/ng1632.sii"
}

(fnuts, fhub etc below)

Rear:

vehicle_wheel_accessory : .mercedes1632.6x6h.r_tire {
offset: 0
data_path: "/def/vehicle/r_tire/ng1632.sii"
}

vehicle_wheel_accessory : .mercedes1632.6x6h.r_tire2 {
offset: 2
data_path: "/def/vehicle/r_tire/ng1632.sii"
}

(rnuts, rhub etc between)