I had purchased a set of KW competition coilovers a while back, and went with H&R springs of my own specification.
This setup did not work well and was disappointing. The rear shocks squeaked quite loudly into the cabin, and the fronts caused a lot of creaking noises and bottomed out hard over medium bumps.
All these problems made my remove the shocks, and convert my KW V2s to use the H&R springs. This worked ok, but could definitely feel this setup was very underdamped for the stiffer springs. The lack of compression damping was very evident, and really made the car compress too much over bumps, with the weight transitions very slow. Over rough roads this really caused the rear end to feel way too soft and bounce a lot.
After the last track day and drive days it was finally time to revisit the KW competition shocks and develop the setup more so it could work.
1. Squeaky rear shocks
This problem is mainly due to the top mount of the KW competition shocks. They are solid ball joints which transmit the high frequency noise into the chassis. I removed these and installed my old Dinan upper shock mounts which are rubber. These do not fit because the KWs are 14mm thread and the Dinan holes are only 12mm. I bored out the holes to 14mm on my lathe, simple change.
2. Rear bump stops disintegrated
The rear foam bump stops had fallen apart, causing the rear to also bottom out and crash over bumps. I purchased a set of Powerflex BS015 bump stops. The powerflex ones are 20mm internal diameter, while the shock shaft of the KWs are 22mm. The polyurethane stretches easily over the 2mm difference and result in a nice fit.
3. Fronts harsh and creaking, and ride height was quite low.
The KW fronts come with their own camber plates which are pillowball mounts. I reverted to stock top mounts with Dinan camber plates. Not as sexy piece of hardware but the stock top mounts perform nicely for a street car. The stock top mounts result in a much higher ride height.
4. Suspect the spring was bottoming out before the bump stop was engaged.
I had around 15mm of preload on the front spring which can result in the springs bottoming out before the bump stop is engaged. This is probably the thing that requires the most thought in rectifying.
The KW competition upper spring perch tapers downwards, which is bad for my setup. I went with a turner motorsport piece which has a flatter design, so I can mount the lower perch higher up.
I also inserted a 12mm stainless steel spacer block underneath the spring perch, which mounts the top perch higher on the shock spindle. This allows me to raise the lower perch without increasing spring preload.
These changes are critical due to the fact the KW competition shocks actually have more travel than stock. Its also fortunate the spindle where the top mount and spring perch mount is actually longer than a standard spindle, so I can put spacers in there without running out of thread on the top nut.
It has taken me a while but have finally got all the parts into the car. The front ride height was achieved with 7mm of front spring preload. From my calculations this is enough to hit the bump stop before bottoming out the spring. I still need to drive the car on rough roads to test but looks promising so far.
The damping is much improved, doesn't over compress over bumps and feels more composed. Extremely happy with the setup.
I will dial in some extra front damping but overall the car is massively improved. The ride comfort is excellent.
I will also need to do additional investigation to prevent the rear wheels from contacting the fuel filler neck. The bump travel is controlled by the shock and increasing shock travel on a 1 series can easily result in rubbing the fuel filler neck on large bumps. This will involve using a longer bump stop and swapping out the Dinan upper shock mount with one with standard dimensions (like the Monroe).
Current setup:
Front:
- KW Competition, single way adjustment (slow compression and rebound)
- Spring: H&R RF200050 (200mm length, 50N/mm, 60mm ID)
- Dinan camber plate with stock top mounts
- 12mm spindle spacer
- Swift thrust sheet
Rear:
- KW Competition, two way adjustment (slow compression and rebound )
- Spring: H&R part number R25100600 (10" length, 600lbs/in, 2.5" ID) Metric: (254mm length, 105N/mm, 63.5mm ID)
- Dinan upper shock mount
- HDPE bump stop spacer
- Powerflex BS015 bump stop
- MCA 2.5" rubber lower spring perch