Four SKUs. That's It.

INEOS approved exactly four tyre options for the Grenadier at launch. Not four brands with multiple models each — four specific stock-keeping units, validated through the vehicle's complete type-approval testing program. Every system on the vehicle — ABS calibration, ESP tuning, speedometer accuracy, traction control algorithms, and even the gear ratio calculations for the transfer case — was validated against these specific tyres.

Running unapproved tyres does not merely void a warranty line item. It changes how every electronic safety system on the vehicle behaves.

The Approved List

Wheel	Tyre	Size	Load/Speed
17" Steel	BFGoodrich All-Terrain T/A KO2	LT265/70R17	121/118S
17" Alloy or Steel	Bridgestone Dueler All-Terrain	265/70R17 XL	116S
18" Steel	BFGoodrich All-Terrain T/A KO2	LT255/70R18	117/114S
18" Alloy	Bridgestone Dueler All-Terrain	255/70R18 XL	116S

What Happens When You Run Unapproved Tyres

ESP and Traction Control

The Grenadier's ESP system uses wheel speed sensors to detect loss of traction and yaw rate divergence. These sensors are calibrated to a specific tyre rolling circumference. Change the tyre diameter — even by 3% — and the ESP's calculations of vehicle speed, wheel slip percentage, and yaw rate all shift. The system may intervene too early, too late, or with incorrect force distribution.

Speedometer Accuracy

The speedometer reads based on wheel rotational speed multiplied by the factory-programmed tyre circumference. A 265/70R17 BFG KO2 has an overall diameter of approximately 805 mm. Fitting a 315/70R17 (a common upsizing choice) increases the diameter to approximately 874 mm — an 8.6% increase. Your speedometer will read 100 km/h when you are actually doing 108.6 km/h. That is enough to trigger speed cameras, mis-calculate fuel economy readings, and cause odometer errors that affect service interval tracking.

ABS Performance

ABS modulation frequency and pressure profiles are tuned for a specific tyre contact patch, tread compound, and sidewall stiffness. Different tyres have different grip characteristics, and the ABS needs to know what "locked wheel" and "optimal slip" look like for the specific rubber on the vehicle. Running a tyre with significantly different grip characteristics can result in longer braking distances even with ABS active.

The Upsizing Temptation

The Grenadier community has an active contingent of owners fitting 33" and 35" tyres, often combined with suspension lifts. The engineering arguments for and against are well-documented:

Arguments For Upsizing

• Increased ground clearance (the only way to achieve it on a solid-axle vehicle)
• Larger contact patch for soft-terrain flotation
• More aggressive tread patterns for mud and rock
• Improved departure and approach angles (marginally)

Arguments Against

• ESP, ABS, and traction control miscalibration
• Speedometer error (typically 5–9% under-reading)
• Increased unsprung weight → worse ride, more stress on wheel bearings and CV joints
• Reduced steering lock in some cases (rubbing at full turn)
• Potential warranty implications on drivetrain components
• Higher centre of gravity (see our article on the 30% rule)

Tyre Pressure: The Variable Most Owners Ignore

Tyre pressure matters more than tyre brand for day-to-day driving. The Grenadier's TPMS (tyre pressure monitoring system) is set for the factory tyre specifications. INEOS publishes pressure recommendations based on load condition:

Condition	Front (bar)	Rear (bar)
Normal load (highway)	2.5	2.5
Full load (highway)	2.7	3.0
Off-road (soft terrain)	1.6–2.0	1.6–2.0
Off-road (rocky terrain)	1.8–2.2	1.8–2.2

These pressures are validated for the approved tyre sidewall stiffness and load ratings. Running different tyres at the same pressures may result in different load-carrying capacity, different deflection characteristics, and different heat build-up profiles.

The Practical Approach

If You Stay Factory

The BFGoodrich KO2 is the better all-round choice for owners who venture off-road regularly. It has a more aggressive tread pattern, better sidewall puncture resistance (LT rating), and better mud/rock performance than the Bridgestone. The Bridgestone offers a quieter highway ride and marginally better fuel economy.

If You Want to Change

Stay within the factory diameter range (±3%) to minimise electronic system impact. Match the load index and speed rating to the original specification. Have the speedometer recalibrated by a dealer if you change by more than 2% in diameter. And accept that any ESP, ABS, or traction control warranty claim on unapproved tyres will be an uphill battle.

The Bottom Line

INEOS did not restrict the tyre list to four SKUs to limit owner choice — they did it because validating each tyre through the full electronic calibration process is expensive and time-consuming. The four approved options cover the two most common use cases: highway-biased touring (Bridgestone) and off-road-biased adventure (BFGoodrich). For most owners, one of these four will be the right tyre. For owners who want something different, go in with eyes open about what you are trading away.