Suspension - Dangers to consider when altering ride height
I have been fielding a lot of questions re raising and lowering Minis, mainly from our foreign brethren. The increase in exported Minis to farther shores has revitalized interest in our precious Mini, indeed some new owners have rarely seen one of them and are delighted by it's 'cutesy' character, unbelievable road-holding and the discovery of the plethora of (relatively) cheap, readily available spares and accessories. One of the first 'tuning tweaks' applied is dumping the car in the weeds.
The Internet has also played its part in increasing interest in the Mini. It also provides near-direct links from the beginner ('newbie') or first time owner with those who have extensive knowledge and experience in dealing with our favourite little car. The down side to this is that the associated chat or message boards where information is sought is also frequented by those of the 'a little knowledge is dangerous' brigade. Now I'm not belittling their attempts and desire to help others, it's just that some of the answers are far from correct, and support information dangerously lacking. And this whole business of raising and lowering the Mini is just one such abused subject.
The crux of the problem is the suggestion that fitting Hi-Los (or some such) will afford you the convenience of winching the ride height up when carrying a larger than normal load (say four full sized humans) then dumping it to the floor for track days to 'maximise handling'. This simply isn't so for two very important reasons - and many smaller but still significant ones. Just to get those grey cells activated, I'm only going to cover those two important items.
One. Raising and lowering the ride height can dramatically alter front suspension geometry - including tracking. When setting up a car's suspension geometry, the very first parameter you set is the ride height simply because as the car moves up and down, the suspension moves through different sections of the arcs they describe. Each suspension component describes a different arc on a different radius - the interaction of all dictates what attitude the wheels develop. So raising/lowering the car will change camber, caster and track on the front. Consequently this winching up and dumping should most definitely not be done without checking/re-setting all the front-end geometry. If you want to do this road/track day malarkey, set the geometry at 'road' use height, then lower the car to your 'track day' height and check what's happened to the front-end geometry. In particular the tracking. If changes need to be made, either set the car up before you go, or take some equipment with you to do it at the track. There are some very cheap and simple to use tools on the market to facilitate this. The good news is raising and lowering the rear doesn't change the geometry at all.
Two. Dampers. Not all dampers are capable of dealing with radical changes in ride height. Many are aware of the various dampers available for lowered ride height cars, although there seems to be a general vagueness (even from the damper manufacturers) about when the lowered damper is needed since referring to a difference from 'standard' ride height generally means very little. And the fact the 'short' dampers are 3/4-inch shorter doesn't help either. What you need to know is will the damper work OK on your car. Since the main details of whether they will or not is the distance between the top and bottom damper mounting points, how far apart/close together they get in operation and the open/closed distance between the mounting points on the damper, some critical measuring is needed. So why don't the manufacturers give you the specific information you need? Suffice to say - unless you take the necessary steps of measuring the differences you may well end up scrapping them. Perhaps it's time I dug out my data on this and submitted it for your delectation.