Here’s a very interesting and worthwhile video from Vorshlag discussing the challenges of producing an adjustable upper strut mount for the Focus RS – but also the need for more negative camber for tracking the RS.
Like all FWD cars, or FWD-based AWD cars, the Focus RS has a very poor front-to-rear weight balance. It’s the inherent result of starting with an drivetrain where the majority of weight is ahead of the front wheels: 59% in the case of the Focus RS. There isn’t any practical way of designing a FWD-based car around this issue, so it’s endemic to all manufacturers (and, yes, even the Imprezza WRX/STi which because of it’s well-forward engine location and a drivetrain design that results in crippling understeer on the track). It’s the nature of the beast; all of these types of cars are inherently camber-limited, but suspension tuning can help mitigate some of the weight imbalance. And in the case of the RS, the torque-proportioning differential can help mitigate a lot of the weight issue as well by shifting torque not only to the rear but also (critical difference) to the outside wheel in a turn (we’ve said it before, this intriguing differential changes everything in this market: we explain it by saying that “the differential is the differentiator”). So a suspension tune with better damping and spring rates is going to help the RS realize it’s full potential.
The video also discusses what the market usually wants for a new-to-market car like the RS: an adjustable camber plate for use with the stock springs and struts as a cost-effective way to start the process of suspension tuning. Unfortunately, the very wide spring design of the Focus wouldn’t allow for enough movement to get a meaningful camber change, so the stock strut and spring couldn’t be used.
Here’s what that front strut looks like from underneath: there is not enough room between the side of the spring and the side of the strut tower to allow the movement that a camber plate would need to provide to meaningfully change camber:
That means that the only possible approach would be to design a strut, spring, and camber plate as a unit. A systematic approach always yields better results anyway, and with a wide range of narrower springs available as well as several choices in strut manufacturer and adjustability, a complete system can be designed. Here is an example from another car that shows something along the lines of what Vorshlag is looking to build (springs not shown, but their outer diameter is the same as the back/blue spring perch shown):
The video also shows several interesting parts of the RS that we haven’t seen clearly before. First is the factory strut. Note that Vorshlag weighs everything; measurement is the first step in a professional engineering methodology and optimization is then second. The Focus RS adjustable strut weighs 16.9 pounds.
Next is the factory upper mount. 3 bolts, pressed steel. And as was said it has zero adjustability from the factory – although it does provide a useful (but not enough) 1.1 degree negative camber.
The upper strut mount is covered completely by the factory strut tower brace – which the windshield wiper motor (silver) also mounts to. A very efficient design by Ford (and we love the opposed-sweep of these wipers from Ford of Europe) but this would cover up an adjustable upper mount. And two plastic covers over all of this would also hide the adjustable mount. This has to be taken into consideration in the design of a strut replacement as well.
And here’s that strut tower brace out of the car: 7.5 pounds.
On top of all of this is the rain tray, which captures water from the windshield and drains it off to the sides. That needs to be retained, although perhaps cut on the sides to expose the intended adjustable upper strut mount. This also has another plastic cover over it.
So there it is, with Vorshlag taking a methodical and professional engineering approach to the design of a replacement strut system. These folks are clearly the pros, and very clearly it will be done right. That’s the reputation they already have from their work on the current and last-gen Mustang as well as more recent work on BMWs. All developed with extensive track testing. Their eventual products for the Focus RS will be the best on the market.
More Focus RS imagery: DrivingEnthusiast.net Ford ST, RS, Cosworth Pinterest Board (512 pins).