Q I lowered my Mini Cooper SPi on Hi-Los, but it wasn’t quite enough to suit the 10-inch wheels I’ve fitted. So I’ve now had them machined down even more so I can lower it further, creating the look I was after. But I’ve noticed it’s sitting on the front bump stops. Can I trim them down? Should I remove them or will it fail the MoT test? Matt Bell A Do not remove the bump stops. If you do this then there is nothing to stop the top arm/ball joint from crashing in to the subframe tower. Such metalto-metal contact will cause two major problems – an instantaneous increase of the spring rate (literally eliminating suspension movement) and the real possibility of breaking the swivel pin off or out of its retaining cup. The consequences of either are every bit as you can imagine. It’s better to cut the bump stops down a little at a time until there is around a quarter inch gap between the bump stop and top arm with the car sitting on level ground.
However, be very aware that once the top arm does connect with the cut down bump stop when cornering hard/violently, the suspension rate will still increase massively and you will be left with just the give in the tyres as your suspension medium. This is something the dampers can not control, so severe hopping/bouncing may occur at the least, and loss of control of the car the worst. The dampers may also bottom out if you go too low, depending on the type you have fitted.
Also, running so low can cause problems at the rear, with your brake pipe unions hitting the bodywork and the potential for the brake pipes to be crushed. The solution here is to fit longer braided flexible hoses that bypass the union on the radius arms and go direct to wheel cylinder. There’s a lot to consider here, so it may be best to just raise the car a little and play it safe!
Never remove bump stops.