Fitting JCW Suspension to pre-2002 MINIs

[Ian Kuah]

There have been lots of posts about this topic, so it is time to lay the myths to rest once and for all.

The fact is that you can fit the JCW suspension kit to any New MINI from 2001 to the present. However, on cars built before April 2002 you need to use the components that the factory redesigned for the later version.

The parts list consists of the new front strut top mounts, rubber caps for these, various washers and nuts, the spring pan support on which the springs sit and the new anti-roll bar drop links. The total bill for these bits should be around £80.

Major manufacturers have a very high cost base for parts to be developed, tested and homologated, so component change is not someething they take lightly. Sheetmetal is one of the most expensive things to alter as it triggers expensive testing scenarios like crash testing and homologation, so minor facelifts are usually restricted to plastic parts like bumpers and lights.

Thus, when MINI redesigned the front struts to cure the straight running problems that afflicted some early cars, they only changed the top mounts and the anti-roll bar mounting point. There are no changes to the body structure and suspension towers between pre and post April 2002 cars. With the new parts in hand, you can use any aftermarket suspension kit in an older car.

There are a lot of myths floating around dealers, particularly in the USA about this, but JCW told me exactly what hardware was required from my local BMW dealer to fit their suspension kit to my August 2001-build Cooper.

Yesterday, JCW fitted this in two hours at their Works exactly as described.

The JCW kit has the option of three spring rates according to vehicle weight and accessories. I asked for the softest springs to improve the ride over the horrible bouncy factory sport suspension that came with the car. The secondary ride at low speeds is now better while high speed control is much improved.

While they were at it, JCW also fitted Powerflex bushes from their Motorsport catalogue to the rear trailing arms. Lift-off oversteer is now much less pronounced and more progressive.

My car originally came on 15-inch non-runflats as it was a cancelled order. The Pirelli tyres were best described as wooden, squealed like a pig at the slightest provocation and had no grip in the wet. I am currently on 7J x 16-inch Minilites fitted with 205/55R16 Dunlop SP-01 rubber. They are a good all-round tyre, but I am looking to upgrade to Dunlop Sport MAXX soon.

I run 31psi front and 24psi rear as all front-wheel-drive cars are nose heavy. This sharpens the steering and reduces the tendency towards lift-off oversteer.

As an aside, I have just driven a 2006 Mini Cooper with 15-inch runflats. The ride is far, far better than the early cars, but there is still a question over the balance between the front and rear suspension when pushing hard on a bumpy road.

So, fellow MINI enthusiasts, I hope this ends all the speculation about the interchangability of suspension parts for pre- and post 2002 cars.

[nylo]

Very interesting write up, and I'm sure many will find it useful.

Interesting point about the springs, I didn't realise the springs were interchangeable? Or is that just because you had a pre-facelift car?

[Ian Kuah]

The pre-facelift element has nothing to do with the spring rates. It was my choice to go softest to get a good ride on horrid UK roads!

The three JCW springs are soft, medium and hard according to what the customer wants ie road, fast road or track, but also according to the weight of the car. So a Cooper S would use stiffer springs because it has the weight of the supercharger etc in front to carry.

This is normal even for standard manufacturers cars. In the old days, BMW and indeed any other car maker fitted uprated springs if the car had air-con. So if you did an engine swap from four to six-cylinders, or added a turbo with intercooler, you fitted the air-con springs to balance things out.

Today, all cars have air-con standard but there are still variations in weight according to options.

[nylo]

Yeah, I realised it had to do with the spec of your car, but I thought that was the primary (sole?) consideration when the springs were being chosen.

I didn't realise that I could go in and say, I have an S, but I'd like the softest springs please. So this is possible? V Interesting...

When you say you are running the softest springs, are they still harder than the originals?

[Ian Kuah]

Ah, you have just opened a whole new can or worms.

Soft and hard springs are one thing, how they relate to the dampers is another.

As an example, the latest Porsche GT3 runs harder springs than before in poundage terms, but because the PASM active damping is better matched to the springs, the ride is noticeably more supple.

Although the JCW springs are stiffer than the standard ones, the dampers work much better with them as a partner and so the secondary ride is superior. To qualify that, the valving of the dampers is critical, and many aftermarket suspensions, especially from German tuners, are too hard for UK roads.

Suspension works in two modes - bounce and rebound. Ideally springs work in bounce, with the dampers or shock absorbers working in rebound to pull things back together. However, there is a tendency for some manufacturers to use the dampers as springs as well and this results in the suspension being too hard in bounce mode.

Part of this problem is valving. If a dampers valving can crack open with low vertical force, it will work very well on short, sharp bumps at low speeds, helping to round off bumps. This is known as the secondary ride. The stock MINI dampers from the 2001-2002 period (Sport and Sport Plus suspensions) were too stiff in this respect and simply reinforced the stiff springs in bounce mode.

The valving in the JCW dampers is set to crack open with fairly low inputs and this results in a more comfortable secondary ride. Over bigger bumps at speed, the primary ride, or the suspensions ability to control the car in high speed over longer wave undulations, is also better because the damping is tauter.

The three JCW springs fall within the performance envelope of the dampers, but the softest does of course have a better low speed ride.

It is a given that rally preparation experts often do road cars better than race preparation companies because race tracks are generally smooth and rally stages are not.

Always remember that to deploy power, a car has to ride bumps and not bounce off them. Ultimately, the matching of springs and dampers is as much an art as it is a science.

Incidentally, I am a professional motoring writer with race experience.

[nylo]

So that all adds up to why many people on here, and especially on NAM I have noticed, all have good things to say about the JCW suspension's secondary ride.

So is it possible then to request the different spring possibilities when you're speccing them? Or is it as a rule, soft for ONEs and Coopers and stiffer for Ss, purely because of the weight thing ?(bearing in mind that mine has a sunroof too, which all adds to the overall weight).

I do a lot of my driving (my daily commute) on back roads which are humpy and bumpy, and would not want the ride to be much harsher than it is at the moment (I'm on SS+), so to be able to spec the springs to suit my needs would be a distinct advantage

Basically, the JCW springs and dampers are better suited to each other than the OEM springs and dampers are, is that about the height of it?

[Ian Kuah]

The JCW kit is a more sharply focused product than the standard suspension, but as it has to be sold through BMW MINI dealers with a full warranty, it has fewer compromises than aftermarket equivalents. The JCW kit is made by Delphin, who make the OE suspension for MINI.

One of the things I like is that the ride height is only 10mm lower. There are too many speed bumps and bumps on our crappy roads to drive a racecar low MINI around here! In any case, you need spring travel to achieve a comfortable ride.

While your dealer will check your chassis number and recommend that you use the requisite springs, this does not mean that you have to, but of course the springs are calibrated for your vehicle weight and will produce the best results.

Don't forget that if you increase vehicle weight, the effect is to soften the springs and vice versa. Taking 50kg out of your car has a similar effect to fitting stiffer springs.

Your sunroof puts about 20kg of extra weight in the centre of the car, which is neither here nor there in weight distribution terms, although this extra weight high up raises your cars centre of gravity and roll centre.

The S has the weight of the supercharger, intercooler etc in the nose and so needs stiffer front springs to compensate. It is as much a case of weight distribution as weight per se, but of course you have to have all four springs from the same category for balance.

What you say about springs on the One, Cooper and Cooper S is not strictly true. There are other differences. The One does not have a rear anti-roll bar and if you want to fit the JCW suspension, you need a rear anti-roll bar. Buying and fitting this is not cheap.
Some early Coopers also did not have a rear bar.

JCW sell an uprated anti-roll bar kit as well if the suspension alone is not enough for a hard-core driver.

Beyond that, the basic One does have a softer suspension, the Cooper comes with Sport suspension with Sport Plus as a no-cost option, and the S has Sport Plus standard. Originally, the Chilli Pack gave you Sport Plus, but so many owners complained about the hard ride that BMW withdrew it in 2003, making it a no-cost option instead.