I am not saying that it is or is not an issue. I would be cautious about doing it as there is a lack of definitive answers out there and it would differ from vehicle to vehicle, mod to mod.Has Jaguar Land Rover Limited published any warnings to support this? I would need to see concrete, reliable data before regarding this as a serious problem.
Maybe you should read this and see if you think that your vehicle will still meet the safety standards. http://www.fujitsu.com/downloads/MICRO/fma/marcom/convergence/data/papers/2010-01-2342.pdf
It appears that some manufacturers take it seriously and Procomp actually put their mods through the proper test procedure to make sure the vehicle was still compliant. Maybe Johnson Rods can show their data when they put their mods through the required tests.
Maybe this article from "pickup trucks" in the US will add some light.
As America’s most customized vehicles, pickup trucks are often fitted with specialized aftermarket equipment. However, when an owner alters a vehicle’s wheels, tires, suspension, steering or anything that affects the center of gravity, the stability system could be compromised. This could theoretically include putting a roof rack with a spare tire on top, adding larger tires or an off-road suspension, or even changing to a different-size steering wheel.
Adding complexity: pickup truck stability control systems require special calibration settings that can exceed that of cars and crossovers because most trucks are rear-wheel drive and ESC response has to account for when a truck is hauling a load over those wheels in the cargo box and when it’s empty.
So far, nobody really knows exactly which alterations can be tolerated without compromising a stability system, but it’s clear the arrival of these systems will be a game-changing event for both owners and the aftermarket.
To get a sense of what would happen if modifications were indiscriminately made to a new pickup with stability control, we asked GM’s full-size truck vehicle line director Mike Tulumello.
“Systems integrated to compliance [with mandatory stability control] could be harder to monkey with,“ Tulumello said.
He explained that the electronic systems are so interwoven, it’s hard not to affect some aspect of stability control when you change the handling charateristics of the truck by adding or replacing driveline or suspension hardware.
“Everything has to talk,” Tulumello said. “It’s all integrated. They’re not independent systems.”
Customizing a pickup truck could be risky, he said, “depending on how you do it. More and more, as you alter center of gravity, you’ll get yaw sensors that predict rollover and you’ll get false airbag deployments, things like that.”
Nick Cappa, spokesman for Chrysler, agreed that modifications could be problematic.
“Engineers design, test and optimize performance on factory tires and suspension,” he said. “Modifications, tampering with safety devices and the installation of some aftermarket parts can create unforeseen issues with stability and safety systems.”
The widespread use of stability control technology has prompted manufacturers of suspensions, wheels and tires to begin to study stability systems and what can be done to allow owners to continue to confidently install specialty equipment.
Legally, should an accident occur, the aftermarket parts manufacturer and installer could be targeted, whether the accident was caused by the alterations or not. Once the safety equipment becomes government-mandated, altering a vehicle’s dynamics might even be considered tampering -- a federal offense. The worst-case concern is that aftermarket modifications for pickup trucks could be legislated out of existence.