Because the braking effort is shared by the other axle if the brakes are any good or if they're not it may jump out of the rollers. Putting the transfer box in neutral would fix that but AFAIK there's no provision for that and what they're actually supposed to do when only 2 rollers are available is use a decelerometer. I'm only repeating what MOT testers have told me over the years BTW.Chris said:Why Jon? They drive it onto driven rollers, out of gear and then press the brakes.
The effectiveness of the brakes and controlability of the vehicle in a low traction braking situation has been compromised if ABS is disabled?Chris said:but for the sake of sense, does it need to be?