22 replies to this topic

[Wrenchpuller]

Hi Crazy,
As said at least 3 times above I am NOT fitting "coil-overs" I am replacing the Moulton springs with coils. The insuirance company does not have concerns, as long as the suspension kit is designed for the car. Yes I do know that "coil-overs" transfer the weight load to the shock mount. Please forgive me, but I have been a mechanic since 1963 and worked on Minis when they were new cars.
Cheers Ric

[tiger99]

As bmcecosse stated, the design of the Mini was based on progressive rate springs. Replacing them with coils may be ok for track use, but never, ever on the road. The short suspension arms mean that the vertical travel is severely limited, and for that to work acceptably, you need a springing medium which is fairly soft with only the driver on board, but rapidly becomes stiffer as the load increases. If you use coils, even those purporting to be progressive rate, you do not get a sufficient rate of increase of spring rate with deflection. Either the coils will be far too hard with only the driver on board, so the car will jump about all over the place, or if they are softer, it will be on the bump stops with a larger load.

[Cooperman]

Actually, on the back it would be possible to replace the rubber cone springs with quite long rising-rate coils and short trumpets, but the limitation is on the front. It would, one might guess, be possible to use a very short trumpet on the front to allow for a longer spring. The alternative on the front could be to massively re-inforce the inner wing by making up the sort of strut support structure as used on Fords with McPherson suspension, then making up a strut/coil-over unit with a very long rising-rate spring. But, even after doing all that,the original rubber cone springs would probably still be better on a road car.

For track use it's an entirely different matter as high-single-rate coils will work well and can be changed for different circuits if necessary.

[mike.]

Plenty of people have used coil spring conversions on the road with success. It apparently makes the ride much more supple and rides over bumps better; more like a modern car.

The trade off is the car needs to be raised to give enough travel for the springs to work properly, and the car will roll more as well.

I've seen a diagram somewhere recommending how much to raise the height by for each type of coil spring. I seem to remember it was something like 60-80mm travel needed for the road springs and 30-40 for the race ones.

Then an antiroll bar can be fitted to counteract the body roll - They did this in a miniworld/minimagazine feature after fitting the spring conversion.

Edited by mike., 02 June 2012 - 11:52 PM.

[tiger99]

No! That is wrong. The problem is that you CAN NOT COMPENSATE FOR LOAD VARIATIONS in a road car, by fiddling with ride height. It may give you more travel, indeed it is the ONLY way of getting the extra travel you need with coils, but it is downright dangerous because the geometry will be very wrong at both extremes, and there is a grave danger of bump stop failure, followed by ball joint fracture, if you fully load the car. The Mini was designed with a certain specific amount of suspension travel, and between these limits, and slightly beyond, to the designed safety margin, is all that you can safely use.

And, if you need to add anti-roll bars it is because the coils have massively degraded the handling.

Using coils on a road car is just plain stupid. It gains nothing at all, and loses much.

[JustSteve]

Hi WrenchPuller,

Ignore them. Ofcourse the coils are not an equal trade off to the rubber cones- that's why you would change! I'm sure you've already done research and made your mind up on them. As you say, youre a competant mechanic so aren't just splashing your cash like most teenagers because they 'look good'

Many people have used them, and prefer them. There are also a few different types to use.

It's your car, do what you want


..As for the 'access hole', I wouldn't bother. Seems a shame to cut up your shell to save a few minutes.

[mike.]

No! That is wrong. The problem is that you CAN NOT COMPENSATE FOR LOAD VARIATIONS in a road car, by fiddling with ride height. It may give you more travel, indeed it is the ONLY way of getting the extra travel you need with coils, but it is downright dangerous because the geometry will be very wrong at both extremes, and there is a grave danger of bump stop failure, followed by ball joint fracture, if you fully load the car. The Mini was designed with a certain specific amount of suspension travel, and between these limits, and slightly beyond, to the designed safety margin, is all that you can safely use.

And, if you need to add anti-roll bars it is because the coils have massively degraded the handling.

Using coils on a road car is just plain stupid. It gains nothing at all, and loses much.

I'm going off what the manufactures say, so its not me thats wrong. Also, the ride height may not necessarily need to be raised more than the suspension was designed for, just raised more than the car might have been with it collapsed cones fitted. It says 82mm is the guide height needed between wheel and rear arch - So 3 and a bit inches, which isn't far off what a minis rear ride height is as standard anyway. I think what the manufacturers are saying is, you can't fit coil springs and still run the car very low like you can with rubber cones.

I understand what your saying, I personally wouldn't fit them for the same reasons but; how can so many people of used them without problem and say the ride quality is vastly improved?

[bmcecosse]

Ah right - I saw 'coilovers' mentioned somewhere and just skimmed the other posts. I still think it's a rubbish idea for a road car - but each to their own!