- Drilling: Web of longitudinal member only. Minimum 20% of frame height from top/bottom edges. 50mm min spacing between holes. Deburr, ream, cavity-seal every hole.
- Welding: Plug welds on the vertical webs of the frame side member only. No welding on structural pillars, axles, bending radii, or airbag zones.
- Bolting: All attachments to longitudinal and transverse members require INEOS approval and OEM-approved brackets.
- Production holes: Not approved for body mounting — even if they line up perfectly, do not use them.
- Wheelbase: Cannot be changed under any circumstances.
INEOS published a Body Builder Guide covering every permitted and forbidden modification to the Grenadier ladder frame. These are the rules — drawn from that document.
The community found the original Body Builder Guide PDF in 2024. Forum member K2grenadier on The Grenadier Forum posted it and noted: "I found this document from Ineos. They call it a body builder guide." It immediately became the authoritative reference for anyone doing structural builds. What follows is a technical digest of the frame section.
The No-Weld Zone Is Larger Than You Think
Welding on the Grenadier frame is restricted to one specific scenario: plug welds on the vertical webs of the frame side member. That's it. Everything else is off-limits.
No welding on the crash-relevant structural pillars. No welding on the main frame rails. No welding on the axles. No welding anywhere near the bending radii where stress concentrates during a collision or off-road impact. The airbag and driver-assistance system zones are also completely protected — INEOS treats these as safety-critical and will not permit modification.
This isn't conservative engineering for its own sake. The Grenadier frame went through finite element analysis to map where energy must travel during an impact. Welding outside the approved zones alters the stiffness and energy dissipation path of the entire structure. You may not see the failure for thousands of kilometers — and then you will.
Permitted Welding
- Plug welds only — vertical webs of the frame side member
- Spacer bushes must be welded to the member first (load distribution)
- Bracket bolts to the spacer bushes — not directly to the weld
Drilling: The 20% Offset Rule
You can drill holes in the web of the longitudinal member. That is your primary option for attaching custom equipment. But there are hard constraints that must be followed.
Position Requirements
Y-direction (vertical): Every hole must be positioned at least 20% of the frame height from the top edge and at least 20% from the bottom edge. This preserves the top and bottom flanges, which carry most of the bending load. The middle 60% of the web height is your drilling zone.
X-direction (horizontal): Holes must be spaced a minimum of 50mm apart from each other. Clustering holes creates stress concentration that the original frame design did not account for.
Absolute No-Drill Zones
Even if you're in the permitted web area, certain locations remain off-limits:
- A and B pillars — completely forbidden
- Upper and lower chords of the frame side member
- Load application points (spring brackets and structural attachment points)
Post-Drill Process
The INEOS guide is explicit about what happens after you drill. The process is as important as the hole location:
| Parameter | Requirement | Status |
|---|---|---|
| Permitted zone | Web of longitudinal member only | Defined |
| Y-direction offset | Minimum 20% of frame height from top/bottom edges | Required |
| X-direction spacing | Minimum 50mm between holes | Required |
| A/B pillars | No drilling permitted | Forbidden |
| Upper/lower chords | No drilling permitted | Forbidden |
| Load application points | No drilling permitted | Forbidden |
| Post-drill: deburring | Deburr all edges | Mandatory |
| Post-drill: reaming | Ream to final diameter | Mandatory |
| Post-drill: chip removal | Remove all chips from inside frame immediately | Mandatory |
| Post-drill: sealing | Apply cavity sealant to prevent corrosion | Mandatory |
Those Existing Production Holes? Do Not Use Them
This is the mistake that catches most builders. The Grenadier frame has holes from the production process. They're convenient, they're already there, and your custom bracket might line up with them perfectly.
INEOS is explicit: production holes are not suitable for body mounting.
These holes exist to serve manufacturing purposes and were never validated for aftermarket attachment loads. The load paths, stress distribution, and fatigue behavior at these holes were never engineered for the kind of repeated loading that body-mounted equipment creates. Do not use them.
Welding Brackets to the Longitudinal Member
If you need to attach a bracket using plug welds on the longitudinal member, there's a required intermediate step: weld spacer bushes to the member itself first.
The spacer bush distributes the load from the weld over a larger area and prevents the weld itself from becoming a hard stress concentration point. Once the spacer bushes are in place, the bracket bolts to them — not to the frame directly, and not to the weld bead.
This sequence matters. Skipping the spacer bushes and welding the bracket directly creates exactly the kind of point loading that the frame section was not designed to handle.
Wheelbase Is Untouchable
The guide is unambiguous: do not change the wheelbase under any circumstances.
Wheelbase changes cascade through the entire vehicle. Weight distribution shifts. Suspension geometry changes. Brake balance changes. And critically, the ESP calibration — which was mapped at the factory for the specific wheelbase — is no longer valid. INEOS will not certify a modified wheelbase, full stop.
What DVA Accessories Mount Without Violating These Rules
DVA: Engineered for the Grenadier's Mounting System
The right answer to the frame modification question is to use accessories that attach to existing OEM-approved points — no new drilling, no welding, no production hole abuse. DVA Mechanics designs Grenadier accessories specifically around the factory mounting system.
- Front Bumper (3-Light Bar) — Bolts to the factory front crossmember attachment points. No frame drilling required. Engineered to mate with the Grenadier's OEM front structure.
- Rear 2" Hitch Receiver — Heavy-duty towing upgrade that uses the factory rear frame attachment provisions. Fits within OEM load specifications.
- Side Steps (Set of 2) — Mount to the existing rocker body attachment points. No new holes in the frame web required.
For the full range of Grenadier-specific accessories built around the OEM mounting system: DVA Grenadier Collection →
The Approval Requirement
All attachment of additional equipment to longitudinal and transverse members requires INEOS approval, and must use brackets with plug welding per the Body Builder Guide process. This applies even if you've followed every drilling rule correctly.
The review process exists because structural modifications can create failure modes that are not visible from the outside and may not manifest for thousands of kilometers. If you're planning anything structural — body mounts, custom bumper brackets, frame-mounted rack systems — contact INEOS through their Body Builder program before proceeding.
The frame is the foundation. Everything else depends on it being right.
