Suspension Brakes 3rd Gen Most liked posts in thread: JCW Pro coilover unboxing

Here goes. I'll try to make my nomenclature easy to understand by starting with some definitions.


*Static ride height: The position the suspension sits when the car is parked. For this car, I'm using the centerline of the axle to the apex of the wheel arch trim directly vertical from the centerline of the axle.

*Droop: The amount the wheel sags or extends [e.g. when the tire falls into a pothole] compared to the static ride height. This will show more tire gap between the tire and the fender arch

*Compression: The amount the wheel pushes into the body's wheel housing [e.g. when you run over a bump]. This will show less tire gap between the tire and the fender arch

*Bumpstop: A carefully design micro-cellular foam piece that helps exponentially cushion the damper during large compression actions [e.g. a very large speed bump or too many fat American's climbing aboard]. The bumpstop usually compresses to between 1/3 to 1/4 it's normal height when the weight of the car is on it, depending on stiffness and design. Keep in mind that when the bumpstop is compressing the added spring rate exponentially approaches infinity. The bigger the bump, the harder the shock transferred into the cabin. The goal for bumpstop design is two-fold; to not allow the damper to bottom-out its internal bits, and to absorb enough force such that the largest intended impact does not exceed the point of the bumpstops compression curve where it approaches infinity. Sounds simple, right?

*Motion ratio: The difference in stroke between how far the damper moves and how far the tire moves. Thankfully for the MINI, the damper motion ratios are basically 1:1, so they're not of concern. The rear spring on the MINI does have a motion ratio other than 1:1, but that's not something we'll touch on here.


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Stock Sport Suspension:

Droop @ 17.375" front and 16.5" rear
Ride Height @ 14.75" front and 14.375" rear
Free Compression @ 13.75" front and 13.125" rear
Bumpstop Compression @ 11.875" front and 11.625" rear

Put into a different context:
Total Possible Stroke is 5.5" front and 4.875" rear.
From Ride Height to full Droop is 2.625" front and 2.125" rear
From Ride Height to first bumpstop contact, or "free compression travel" is 1.0" front and 1.25" rear.
Full bumpstop compression adds another 1.875" front and 1.5" rear of compression travel, but it won't be comfortable.

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JCW Accessory suspension kit by KW

Droop @ 16.625" front and 15.625" rear
Ride Height to be determined, however 13.5"-13.875" front and 13.25"-13.5" rear appears to be design breadth
Free Compression @ 12.5" front and 12.0" rear
Bumpstop Compression @ 11.0" front and 10.75" rear

Put into a different context:
Total Possible Stroke is 5.625" front and 4.875" rear.
Full bumpstop compression adds another 1.5" front and 1.25" rear of compression travel, but it won't be comfortable.


What can we learn from these numbers? Put it into a very simple statement, the JCW coilovers offer the ability to lower the ride height 1.25" front and 1.125" rear with zero compromise to compression ride comfort versus the OEM Sport Suspension. The bumpstops are shorter and thus more progressive, yet I'd wager the difference in very large bumps will feel basically the same. The total stroke of the JCW setup is actually slightly more in front and identical in rear, and the design intent is to locate the ride height between 7/8" and 1.25" lower than stock without any noteworthy compromise in ride comfort.

It'll be a few days before I'll be able to give quality feedback on the final ride height and dynamic behavior, but rest assured I'll update this thread when I do!

Cheers,
Ryan

 

Here's how I set the car up tonight:

The "axle center to wheel arch apex" ride height is set for 13.6" front and 13.2" rear, the same chassis rake as stock, but 1.1" lower than stock. I haven't yet analyzed the roll centers, so this might not be ideal for handling, just FYI.

JCW Pro coilovers installed by Ryephile, on Flickr

JCW Pro coilovers installed by Ryephile, on Flickr

JCW Pro coilovers installed by Ryephile, on Flickr

JCW Pro coilovers installed by Ryephile, on Flickr


And here's how the spring collars look. In front there are 25 threads of useful adjustment available. I set the collars so there are 10 threads visible below the collar, or 0.75" of exposed thread. In the back, it's "full down", with 0 threads visible.

JCW Pro coilovers installed by Ryephile, on Flickr

JCW Pro coilovers installed by Ryephile, on Flickr


How does it ride and handle? Well, I drove it a whopping 2 miles through my neighborhood tonight, so my impressions are minimal. :arf: The ride feels pretty much the same, maybe 20% firmer due to stronger damping. The stock Sport Suspension IMO was lusciously soft and didn't seem fitting for a MINI, even a grown-up refined MINI-BMW like the F56. These JCW Pro coilovers aren't a drastic change, but they're a small step in the right direction. I'm not sure if my mother would even notice the change from inside the cabin.

I will be driving the car tomorrow, so I'll try to provide more thorough feedback then. First impressions are good; the ride quality isn't ruined at least, and the car looks a whole lot better not sitting on the factory lift-kit.

 

Yes, most likely.

It'll take me longer than just throwing them on because I'll be doing a complete stroke and bumpstop analysis on both the stock and this JCW Pro setup. I'll also try to get some bumpsteer measurements in too if there's time.

 

Ok I got the analysis done and the coilovers installed, but I haven't had time to drive it yet and the ride height still has to be sorted out.

Pictures first. Here are the rear SS [black] and JCW [red] springs. The JCW spring wire is much thicker, but there are also more turns and thus longer wire length, so the final spring rate might be similar.
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr

One of each disassembled rear dampers, SS on left, JCW on right. Note the much different bumpstop size.
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr

One of each assembled rear dampers, SS on left, JCW on right. The mounting surfaces of the top-moutns are lined up; note the JCW is shorter overall.
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr

Front spring comparison, JCW [red] on left, SS [black] on right. Even though the JCW is wound shorter, it still has approximately 4 turns total. The JCW wire is about the same thickness, but the coil turn diameter is generally less, meaning a shorter overall wire length which means a stiffer spring. This is all assuming the wire alloy is similar, which is very well may not be.
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr

Front strut comparison. JCW [stainless] on left, SS [black] on right. SS bumpstop not shown here, but it's much bigger than the JCW bumpstop. Of note is the SS damper has surplus damper shaft, meaning at maximum possible stroke there's still some chrome damper shaft outside the body. This is important later on with the stroke analysis.
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr


Here's a picture of the stock SS front strut installed in the car w/out the spring. This allows me to measure axle location at full droop, at first bumpstop contact [which I also call "free compression stroke", and compressing the bumpstop until the car lifts off its respective corner jackstand, putting the corner weight of the car into compressing the bumpstop. This demonstrates an approximation of full travel in a static situation, however dynamically [e.g. slamming into a speed bump] the bumpstop would compress slightly further, as indicated by it's typically unpublished rate vs. travel graph.

I did these measurements on one side of the front and rear.
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr

Here is a picture of a partially assembled JCW front strut, after doing stroke measurements.
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr

...and finally something installed in the car!
OEM Sport vs JCW accessory suspension by Ryephile, on Flickr

numbers to follow