The frame is where theory meets reality. INEOS has drawn a very specific line between what you can modify and what you absolutely cannot touch. Understand this boundary, and you'll save yourself months of rework. Cross it, and you're starting over.
The No-Weld Zone Is Larger Than You Think
Welding on the Grenadier frame is restricted to one place: the vertical webs of the frame side member, using plug welds only. That's it. Everything else is off-limits. No welding on the crash-relevant structural pillars, no welding on the main frame itself, no welding on the axles, and no welding anywhere near the bending radii where stress concentrates. The airbag and assistance system zones are also completely protected.
This isn't conservative engineering. This is the result of finite element analysis showing where the energy has to go when things go wrong. When you weld outside those approved zones, you're changing the stiffness and energy dissipation characteristics of the entire structure.
Drilling: The 20% Offset Rule
You can drill holes in the web of the longitudinal member. That's your primary option for attaching custom equipment. But there are constraints.
First, observe the 20% frame height offset in the y-direction. This isn't a guideline — it's a minimum. The hole must be positioned at least 20% of the frame height away from the top and bottom edges. Second, space holes a minimum of 50mm apart (x-direction). Anything closer and you're creating stress concentration that the original design didn't account for.
The A and B pillars are completely off-limits for drilling. The upper and lower chords of the frame side member are also forbidden. The load application points — your spring brackets and other critical attachment points — cannot be drilled. If it carries a structural load in the original design, you don't drill it.
After you drill, the process matters as much as the hole location. Deburr every edge. Ream all holes to final size. Remove all chips from inside the frame immediately. Apply cavity sealant to prevent corrosion.
Drilling Parameters
- Permitted zone: Web of longitudinal member only
- Y-offset: Minimum 20% of frame height from top/bottom edges
- X-spacing: Minimum 50mm between holes
- Post-drill: Deburr → ream → remove chips → cavity sealant
- Welding: Plug welds only, vertical webs of frame side member
Those Existing Production Holes? Don't Use Them
This catches people. There are holes in the frame from production. You see them, they're convenient, and your custom bracket lines up perfectly. Do not use them. The guide is explicit: INEOS specifies that production holes are not suitable for body mounting. These holes serve manufacturing purposes and were not validated for aftermarket attachment loads.
Welding on the Longitudinal Member Requires Preparation
If you need to attach a bracket using plug welds on the longitudinal member, you must first weld spacer bushes to the member itself. This distributes the load from the weld over a larger area and prevents the weld from acting as a hard point that concentrates stress. The bracket then bolts to the spacer bushes.
Wheelbase Is Sacred
Do not change the wheelbase under any circumstances. The wheelbase affects weight distribution, suspension geometry, brake balance, and ESP calibration. Change it, and you've redesigned the truck from the ground up. INEOS won't certify it.
The Approval Question
All attachment of additional equipment to longitudinal and transverse members requires approval and must use brackets with plug welding. If you're planning something structural, contact INEOS now. The review process exists because you cannot see inside the frame to verify that your installation won't create a failure mode that shows up only after thousands of kilometers.
The frame is the foundation. Get it wrong, and nothing else matters.