tokyo-wangan-racing/tools/diag_wheelroot.luau

--[[
	diag_wheelroot.luau -- two suspected bugs in the shell wheel re-hang
	(CarManager ~line 585-641).

	(1) ROOT CHOICE. Line 589 picks
	        root = w:IsA("BasePart") and w or w:FindFirstChildWhichIsA("BasePart", true)
	    For a wheel group that is a Model, FindFirstChildWhichIsA returns an
	    ARBITRARY first BasePart -- a rotor, caliper or hub, not necessarily
	    the tyre. Line 621 then does delta = phys.Position - root.Position and
	    shifts the whole group, making THAT part concentric with the axle. If
	    root is not the tyre centre, the visible tyre is displaced by the
	    root-to-tyre offset. User reports rx7_fc wheels "sticking out from the
	    side of the car", which is this signature.

	(2) SURVIVING OUTSIDE WELDS. Line 605 only scans shell:GetDescendants()
	    for welds to cut. Any weld parented OUTSIDE the shell (on the model,
	    on body, etc.) that ties a wheel part to the bodywork survives, which
	    would rigidly glue the wheel to the chassis and pin the knuckle --
	    the measured steering lock.

	Reports, per wheel group: which part was chosen as root, how far that root
	sits from the group's true centre, and any surviving weld from the group
	to a part outside it.
]]

local ServerScriptService = game:GetService("ServerScriptService")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RunService = game:GetService("RunService")

local out = {}
local function log(...)
	local parts = {}
	for i = 1, select("#", ...) do
		parts[#parts + 1] = tostring((select(i, ...)))
	end
	table.insert(out, table.concat(parts, " "))
end

local Shared = ReplicatedStorage:FindFirstChild("Shared")
local Cars = require(Shared.Cars)
local Chassis = require(Shared.Chassis)
local orig = ServerScriptService:FindFirstChild("Server", true):FindFirstChild("CarManager")
local cm = orig:Clone()
cm.Parent = orig.Parent
local CarManager = require(cm)

-- ---------------------------------------------------------------- template
log("=== TEMPLATE wheel groups: what does line 589 pick as root? ===")
log(string.format("%-12s %-5s %-16s %8s %8s", "car", "grp", "root picked", "off|X|", "nParts"))
for _, t in ipairs(ReplicatedStorage.CarModels:GetChildren()) do
	local wg = t:FindFirstChild("Wheels")
	if wg then
		for _, w in ipairs(wg:GetChildren()) do
			local root = w:IsA("BasePart") and w or w:FindFirstChildWhichIsA("BasePart", true)
			-- true centre of the group = AABB centre of all its parts
			local lo = Vector3.new(math.huge, math.huge, math.huge)
			local hi = -lo
			local n = 0
			if w:IsA("BasePart") then
				lo, hi, n = w.Position, w.Position, 1
			end
			for _, d in ipairs(w:GetDescendants()) do
				if d:IsA("BasePart") then
					lo = Vector3.new(
						math.min(lo.X, d.Position.X),
						math.min(lo.Y, d.Position.Y),
						math.min(lo.Z, d.Position.Z)
					)
					hi = Vector3.new(
						math.max(hi.X, d.Position.X),
						math.max(hi.Y, d.Position.Y),
						math.max(hi.Z, d.Position.Z)
					)
					n += 1
				end
			end
			if root and n > 0 then
				local centre = (lo + hi) / 2
				local off = root.Position - centre
				log(string.format("%-12s %-5s %-16s %8.3f %8d", t.Name, w.Name, root.Name, math.abs(off.X), n))
			end
		end
	end
end

-- ---------------------------------------------------------------- built
log("")
log("=== BUILT cars: tyre alignment + surviving outside welds ===")
log("tyreErrX = how far the widest shell wheel part sits from its physics")
log("cylinder along the car's lateral axis. Should be ~0 on every corner.")
log("")
log(string.format("%-12s %-5s %9s   %s", "car", "grp", "tyreErrX", "welds tying group to OUTSIDE"))

for _, t in ipairs(ReplicatedStorage.CarModels:GetChildren()) do
	local car = Cars.Get(t.Name)
	if car then
		local m = CarManager._buildForDiag(car, Chassis.tuningFor(car))
		m.Parent = workspace
		m:PivotTo(CFrame.new(0, 5010, 0))
		for _ = 1, 4 do
			RunService.Heartbeat:Wait()
		end
		local body = m.PrimaryPart
		local shell = m:FindFirstChild("Shell")
		local wg = shell and shell:FindFirstChild("Wheels")
		if wg then
			local inv = body.CFrame:Inverse()
			for _, w in ipairs(wg:GetChildren()) do
				local phys = m:FindFirstChild("Wheel_" .. w.Name:upper())
				local group, inGroup = {}, {}
				if w:IsA("BasePart") then
					group[1], inGroup[w] = w, true
				end
				for _, d in ipairs(w:GetDescendants()) do
					if d:IsA("BasePart") then
						group[#group + 1] = d
						inGroup[d] = true
					end
				end
				if phys and #group > 0 then
					-- widest part = the tyre; compare its |X| to the cylinder's
					local physX = (inv * phys.Position).X
					local best, bestW = nil, -1
					for _, p in ipairs(group) do
						local vol = p.Size.X * p.Size.Y * p.Size.Z
						if vol > bestW then
							best, bestW = p, vol
						end
					end
					local errX = (inv * best.Position).X - physX

					-- any weld from this group to something outside it,
					-- searched across the WHOLE model, not just the shell
					local bad = {}
					for _, c in ipairs(m:GetDescendants()) do
						if c:IsA("WeldConstraint") or c:IsA("Weld") then
							local a, b = c.Part0, c.Part1
							local aIn = a ~= nil and inGroup[a] or false
							local bIn = b ~= nil and inGroup[b] or false
							if (aIn or bIn) and not (aIn and bIn) then
								local other = aIn and b or a
								local oname = other and other.Name or "nil"
								-- weld to its own physics cylinder is CORRECT
								if oname ~= ("Wheel_" .. w.Name:upper()) then
									bad[#bad + 1] = oname .. "(" .. c.Parent.Name .. ")"
								end
							end
						end
					end
					log(
						string.format(
							"%-12s %-5s %9.3f   %s",
							t.Name,
							w.Name,
							errX,
							#bad > 0 and table.concat(bad, ", ") or "-none-"
						)
					)
				end
			end
		end
		m:Destroy()
	end
end

cm:Destroy()
return table.concat(out, "\n")