I thought I’d throw this up there, as reviews for this coilover setup are few and far in between.
Stats:
KW Street Comfort Coilovers
Spring rate - 458lbs/in f, 240lbs/in r
Rebound adjustable short stroke dampers.
Stainless steel front damper body, painted steel rear body.
Progressive springs
Factoring in the motion ratio, the wheel rates end up being approx 195lbs/in front and rear. Looking at another car of similar curbweight and weight distribution (conveniently the Mustang Boss 302), the wheel rates on that car are 130lbs/in f, 154lbs/in r. These are mildly firmer than an OE Boss setup, but the rates are definitely very street oriented. So consider this a “suspension lite” or mild suspension setup. Very suitable for street use as the name suggests (duh!). Despite that, it is noticeably different from stock and the cornering limis have changed for the better.
For those looking for a compliant ride with the ability to both set ride height and elevate the handling limits, this is a decent choice. From a ride quality perspective, the KW’s are improved over stock. The compression is much softer on these shocks than the OE setup, allowing the suspension to go through a lot of travel really quickly (more on this later). As well, there is rebound adjustment for performance tuning–16 clicks of it. Despite being so soft, the rebound adjustment has enough range to make a distinct change in handling characteristics – one can easily set it up for street cruising vs more focused track work. I like to think of this as the equivalent to the hottest suspension the factory would spec on a car – it is tuned enough to make a quality difference in both ride and handling (which sometimes does not go hand in hand).
In stock form, the car will push at the limit – on or off throttle. Even in situations where one is very aggressive with lifting the throttle, the car will not rotate in stock form. At best, it will reduce the amount of push and tuck in mildly. With the KW’s, the front end bite is improved in these scenarios. There is an increase in both steering response and the ability of the car to change direction on corner entry (if the throttle is lifted). The most dramatic positive change however, is stability. The car can now carve out corners at much higher velocities before and be significantly more composed. Yes, it’s awd and yes, the pushy nature of the stock car makes it very composed to begin with. However, throw elevation changes, off camber corners and undulations into the mix, and you will notice that even the out of box understeery setup will be unsettled – this is not due to handling balance. This is due to the tuning of the OE shocks. There simply was not enough rebound control in the stock setup for those sorts of situations. The car would spring back from a loaded state too quickly causing an undesired change in the balance of the car.
With the KW’s rebound set appropriately, body control is greatly improved and as a result, the stability is elevated. This sort of thing does a lot for driver confidence, as you can imagine. And with confidence comes consistency. So this is all good news.
On power, the car is the same as ever. Sport diff vectors the power to the outside rear wheel and the car will rotate in the middle/end of the corner.
NOTE: all of this feedback was done with the Eurocode swaybars (32f, 25.5r) set to full stiff. I explain why I set them this way in this sway bar review. If I did not have the sway bars, my feedback may have differed. The roll stiffness–especially up front has been reduced from stock. All else being equal, this actually results in a reduction in turn-in/steering response. The sways, rebound settings, alignment and reduced droop and my general setup would have accounted for much of this.
What is not so great about the KW’s is the lack of compression stiffness–the front shocks especially. Even holding them in my hand and pushing on them, I can tell that the compression setting on the front shocks are VERY soft. Even softer than stock. This combined with a softer progressive spring leads to blowing through travel really quickly. The only good news here is that the KW has a shortened shock body, so you have similar suspension travel levels as stock despite the car having a reduction in ride height. I have bottomed out on these KW’s a number of times by simply hitting some larger cracks in the ground. None of these types of hits would have affected the stock suspension (or even my old PSS9’s for that matter), but the KW’s gladly ate up all the available travel (note: my car is lower than I’d like. If it was raised 15mm or so, this will not be as much of an issue)
The other thing about these is that the base rebound settings are very soft. If the shocks are set to the KW recommended settings, the car will float around like a boat. It’s much too soft for any form of performance driving. Body control becomes very bad, and the car will continue to bob up and down after going through some bumps at speed. In the end, I set the fronts to 5 from max stiff and rears 1 from max stiff. This gave back the body control I wanted. With the current setup, it works very well on the street and for aggressive driving. TBD on the track performance though. I will follow up with updates after my next track outing. FWIW, you can definitely not put stiffer springs on the KW street comfort coilovers due to the lack of available rebound stiffness–so do not think about it. At near max settings, the rebound is a good match for the springs, though honestly i could do with more rebound for track use.
That said, I do like these coilovers. They were what I was looking for - a proper suspension setup that would retain OE levels of suspension travel but improve body control and offer a degree of adjustment for fine tuning handling traits of the car. These would be great for the occasional track enthusiast or for those running less grippy tires (read: Michelin PSS). FWIW, I am using Dunlop Z2’s, and the grip that these tires generate are definitely enough to put the car on the bump stops in some corners on the track–especially if one did not change the sway bars. With less track oriented tires, this becomes less of an issue, and actually, the suspension becomes better matched. You do want some body roll and you do want some body motion. Having a fully rigid setup is not going to do anyone any good–especially for a street car at factory weight with gobs of suspension travel. Having that body motion allows for more progressive behavior of the car and improved composition at the limit.
With the shocks setup appropriately, and the ride height not done too low (IMO my car is done too low), this is a great setup – even for the track. It is a viable improvement over stock and I would take these over the KW HAS or KW V1 solution any day.
Keep the ride height up to retain bump travel and also reduce droop for better response. Having the roll center higher with these softish springs doesn’t hurt either. It is a competent streetable setup, with 75% of the focus on the street and 25% on the track…which arguably, is what the S4 was intended for.
For the record, my alignment settings are as follows:
Toe: 0f, 2.7mm r (total)
Camber: -3f, -2r
Caster: stock
Ride height: 13.5inches hub to fender