LFI Engineering Guide · Combined-Load FEA
A wheel does not only carry weight. It also sees torque, side load, tyre pressure, brake load, spoke twist, and repeated road stress. That is where simple radial-load screenshots start to fall short.
A radial-load-only simulation is a decent first check. It shows whether the wheel can carry vertical vehicle weight. But a real wheel is not sitting on a test bench with one clean downward force. The tire contact patch twists the barrel, acceleration and braking pull through the spokes, cornering pushes the wheel sideways, and tyre pressure is always acting inside the rim.
Radial load is the baseline.
Useful, but it mainly answers one question: can the wheel carry vertical weight?
Torque changes the story.
Once drive and braking force enter the model, the spokes twist and the root areas start showing their real stress path.
Good FEA improves the wheel.
The point is not a prettier screenshot. The point is catching the weak geometry while there is still time to fix it.
| Simulation type | What it shows | What it can miss | Takeaway |
|---|---|---|---|
| Radial load only | Vertical load from vehicle weight. | Torque transfer, spoke twist, braking force, lateral load, tyre pressure. | Good baseline, not a full story. |
| Torque load | Rotational force through hub, spokes, and barrel. | Needs realistic direction and support logic. | Reveals angular spoke deformation. |
| Lateral load | Side load from cornering and tire grip. | Does not show acceleration or braking by itself. | Important for high-grip use. |
| Tyre pressure | Constant internal pressure acting on the rim barrel. | Usually not dominant by itself. | Adds realism around the barrel and transition zones. |
| Combined load | Radial, torque, lateral, and tyre pressure reviewed together. | More complex to set up and interpret. | Much closer to real force transfer. |
This is the comparison that matters. Same wheel geometry, same material basis, same sample threshold — only the load case changes. The radial-only case looks fine. The combined-load case exposes the spoke-root groove.
| Review stage | Max stress | Result | What it means |
|---|---|---|---|
| Radial load only | 57.3 MPa | Pass | Basic vertical-load check looks acceptable. |
| Combined load | 167.1 MPa | Fail | Angular spoke deformation exposes stress concentration at the spoke-root groove. |
| Revised groove design | Below target | Pass for production | The geometry was cleaned up before machining. |
This is where combined-load FEA earns its keep. The design did not fail because the material was weak; it failed because a local geometry feature concentrated stress in the wrong place. Once the groove was removed, the stress path cleaned up and the design could move forward.
FEA should never be sold as a magic guarantee. But when a real crack appears in the same zone predicted by the model, the simulation becomes a useful engineering explanation instead of a decorative screenshot.
The crack runs across the spoke-root transition where the narrow spoke meets the thicker root area.
This view follows the spoke edge / transition region, consistent with a structural stress path.
The simulation highlights the same spoke-root / barrel transition zone under combined load.
The predicted high-stress region appears around the same spoke-root transition where the crack was observed.
A FEA result is meaningless if the material is guessed. LFI ties the model to the intended forged alloy and heat-treatment condition. In the sample CSF1 V3 report, the material basis is 6061-T6 aluminum with a conservative design stress threshold based on one-third of yield strength.
| Sample input | Value | Why it matters |
|---|---|---|
| Material | 6061-T6 aluminum | Sets the alloy and heat-treatment basis. |
| Operating air pressure | 2.0 bar / 200 kPa | Represents tyre pressure acting on the barrel and seat areas. |
| Young’s modulus | 69 GPa | Defines elastic stiffness and deformation behaviour. |
| Yield strength | 313 MPa | Reference point for plastic deformation risk. |
| Design stress threshold | 104 MPa / 1⁄3 yield | Creates a conservative target for reviewed load cases. |
| Tensile strength / elongation | 330 MPa / 12% | Adds strength and ductility context for the material condition. |
EV load targets, hub-centric geometry, brake clearance, and forged-wheel planning for Model Y builds.
High-torque S58 fitment, xDrive rolling diameter, M brake clearance, and M-platform load planning.
Performance SUV forged-wheel planning around chassis load, large brakes, wide tires, and drag-pack logic.
The article is written from LFI’s forged wheel engineering workflow. These external references give readers broader context for finite element analysis, aftermarket wheel testing, JWL / VIA testing language, and 6061-T6 aluminum material inputs.
| Reference | Why it matters | Link |
|---|---|---|
| Autodesk Fusion Simulation overview | General FEA reference explaining simulation as a validation tool for predicting how a design reacts to forces, heat, vibration, and other conditions. | Open Autodesk simulation overview |
| Autodesk FEA assumptions reference | Useful context for why geometry, materials, meshing, loads, constraints, and physics assumptions matter when interpreting FEA output. | Open FEA assumptions reference |
| SAE J2530 aftermarket wheels | Aftermarket wheel reference covering performance requirements, sampling, certification requirements, test procedures, and marking requirements. | Open SAE J2530 |
| JWTC VIA / JWL testing Q&A | Japan Light Alloy Automotive Wheel Testing Council reference for JWL / JWL-T impact-test judgement, crack language, and test-air-pressure context. | Open JWTC testing Q&A |
| JAWA light alloy wheel quality certification | Japanese light-alloy wheel quality reference connecting JWL compliance, third-party testing, and ongoing quality maintenance. | Open JAWA quality reference |
| MatWeb 6061-T6 / 6061-T651 aluminum | Specific 6061-T6 / 6061-T651 material-property reference for strength, workability, corrosion resistance, and alloy behaviour. | Open MatWeb 6061-T6 reference |
| AZoM 6061 aluminum alloy | Material reference for 6061 aluminum mechanical properties including tensile strength, yield strength, fatigue strength, modulus, elongation, and hardness. | Open AZoM 6061 reference |
No. It is useful as a baseline vertical-load check. The problem is treating it as a complete simulation of real driving.
Yes. That is exactly what the sample review shows: 57.3 MPa under radial load and 167.1 MPa once torque, lateral load, and tyre pressure were added.
Because the load path changes. Torque and side force twist the spoke structure and can expose stress concentration around spoke roots, hub transitions, and barrel junctions.
Tyre pressure is not usually the biggest load, but it is always present. Including it helps represent the barrel as a pressurised structure while other vehicle loads are acting on the wheel.
No. FEA is a design and review tool. Fatigue testing, impact testing, production QC, material control, and real-world use still matter.
They are transition zones where force moves between hub, spokes, and barrel. Under torque and lateral load, these areas often show the stress that radial-only analysis can understate.
Sometimes. If the geometry and case details are available, a reconstructed model can help show whether the predicted high-stress zone matches the actual crack location.
Yes. EVs are especially relevant because they combine high vehicle weight, instant torque, regenerative braking, high tire load, and heavy daily use.
Send LFI your vehicle, wheel size target, brake package, tire plan, use case, and fitment goals. For EVs, track cars, heavy SUVs, and high-torque builds, the engineering work should happen before the CNC program starts.