BUMP STOPS

Mini Magazine - - Tech -

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.

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