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 |   |   |  2015 VW GTI Coilover & Control Arm Install - Update 4
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2015 VW GTI Coilover & Control Arm Install - Update 4

Better living through geometry

Dec 15, 2015

When last we left our intrepid project, we had just installed H&R Sport Springs and antiroll bars in an effort to sharpen the already impressive handling of our '15 Performance Package VW GTI. While I was mostly satisfied with the improvement in looks and handling, I thought the factory damping rates weren't as well matched to the springs as they could be, and I found the ride height to be just slightly too low for my daily driving (apparently I've gotten old). I kicked around the idea of swapping out the factory shocks and struts for aftermarket units, but after looking at the cost of quality dampers, plus the cost of the springs already on the car, I decided that what most enthusiasts would likely do is pony up slightly more money and buy coilovers in the first place. Yes, in the real world the cost of springs was already spent, but let's pretend I hadn't bought them yet—learn from my mistake. Also, new shocks and struts wouldn't have changed the ride height.

2015 vw gti coilover control arm install lower strut Photo 2/11   |   2015 Vw Gti Coilover Control Arm Install Lower Strut

If you only want to spend the money on springs, roughly $250, then that is a pretty good deal for slightly stiffer rates. Let's be honest, 99 percent of you are buying them just for the lower ride height, so you'll be happy stopping there. If you want increased damping rates, which you will need to see bigger performance gains, then you're looking at $650-$800 for shocks and struts in addition to the springs, which gets you in the ballpark of the $1,200 you would spend on the coilovers. The coilovers give you not only perfectly matched damping and spring rates, but ride height and corner weighting adjustment as well. So really put some thought into it in the beginning and decide what your goals are down the road, performance or mostly just lowered ride height.

We went back to Auto Union Tuning in Huntington Beach, California, for the coilover install. It was essentially the same process as the sport spring install, but it required some adjustment at the end. We decided on a ride height slightly higher than the springs, to allow for more suspension articulation to soak up bumps on the rougher roads and tracks in our area. We would all like to be able to drive on nothing but FIA-approved circuits, but that just isn't reality, and our local tracks are probably rougher than some of the roads our readers use on a daily basis.

2015 vw gti coilover control arm install factory upper trut mount Photo 3/11   |   The coilover kit reuses the factory upper strut mount. An impact wrench definitely makes the process easier, but isn't necessary. This is a job that can be done in your garage with handtools.
2015 vw gti coilover control arm install factory hr coilover Photo 4/11   |   The new H&R Coilovers. Ride height is adjusted with the spring collars' position on the threaded boy of the strut using the supplied wrenches.

Our initial impression of the coilovers, along with the antiroll bars we had previously installed, is all positive. On the street, the increased damping rates make the ride better than with just the springs. The extra rate is now more controlled and there is considerably less oscillation. When the suspension is loaded up in turns, even large bumps won't upset the chassis; give some credit to the additional ride height as well. You might think cars look cool slammed on the ground, but it really is more about style than performance.

2015 vw gti coilover control arm install hr coilover Photo 5/11   |   2015 Vw Gti Coilover Control Arm Install Hr Coilover

When talking to engineers about the latest models from companies like Porsche, AMG, and BMW Motorsports, one thing that keeps coming up is how much work they have been putting into bushing design recently. Keeping your geometry fixed while the suspension is loaded is key to optimum performance. BMW has even gone as far as mounting some of its subframes rigidly to the body of the car without using bushings at all. Soft rubber mounts and bushings absorb vibration and noise, but they do so by deflecting. It might be good for comfort, but you're giving away handling.

Australian-based SuperPro has been honing the craft of polyurethane bushing design and manufacturing for three decades. Starting with the MK5 Golf platform, it took things a step further with not only performance-enhancing bushings, but entirely new front control arms. I decided to try out a set of the Supaloy arms, which include Duraball bearing in the rear position and a poly bushing in the front position. The Duraball is a monoball bearing mounted inside a poly bushing. It gives some vibration absorption while eliminating most of the factory deflection. If you search online, you can find videos shot from underneath the car, showing the amount of movement in the factory bushings, and it's shocking.

2015 vw gti coilover control arm install ball joint mount Photo 6/11   |   With the pivot points lined up, it's easy to see the offset in the ball joint mounts of the black factory arm and silver Supaloy arm.

The factory arm is stamped steel with rubber bushings, so the shiny alloy SuperPro pieces add countless bling points that, likely, no one will ever see. They are presumably more rigid, but I wasn't willing to bend one up to find out. On earlier applications, like MK5 and MK6, I am told they offer a substantial weight savings. On the MK7, which VW put on a preproduction diet, the final assembly with bushings saves about 6 ounces per side. While we were doing it, we also replaced the rear toe-link bushings to keep the rear tires pointed in the right direction during cornering. SuperPro offers a full set of bushings for the rear, but we decided to not do everything all at once.

2015 vw gti coilover control arm install superpro supaloy arm Photo 7/11   |   The stamped steel factory control arm on the left compared to the new SuperPro Supaloy arm on the right. So pretty for something that will never be seen.

The new control arms are designed to move the lower ball joint forward, adding additional caster to the front end. Caster is the angle at which the steering axis of the front wheel sits, relative to straight up and down. Camber, on the other hand, measures that angle as the top of the tire tips in or out from the centerline of the car and is usually visible. Caster measures the angle of the steering axis as it tilts front to back in relation to the car. It is only visible with the front tire turned considerably, but can make a big difference in performance and feel. As you tip the top of the steering axis toward the rear of the car, the point at which the axis intercepts the ground moves forward of the tire's contact patch. That trailing distance results in a self-straightening effect as the tire is pulled behind the center point of the steering axis. This isn't the only effect, however. Since the steering axis is tilted, as you turn the wheel, it adds negative camber angle the more the wheel is turned.

2015 vw gti coilover control arm install control arm bushing Photo 8/11   |   2015 Vw Gti Coilover Control Arm Install Control Arm Bushing
2015 vw gti coilover control arm install control arm bushing Photo 9/11   |   You can clearly see the voids in the rubber making the factory bushing even softer; the SuperPro bushing is solid and stiffer material.

What does it all mean? The decreased deflection alone means bumps won't cause the tires to steer around and get knocked out of line. It also adds more precision and feel to the front end. With the stock rubber bushings, your initial steering inputs are all being used up just to load up the bushings. On-center feel is better and that initial turn of the steering wheel is immediately translated to the front tires and what they are doing is immediately translated back to your hands. Mid-corner on slightly rough surfaces, the steering wheel no longer has that bounce between feel and nothingness you normally get while the rubber is cycling between loaded and unloaded. As another bonus, it has gotten rid of some of the wheelhop inherent in hard launches from a stop.

2015 vw gti coilover control arm install wheel fitment Photo 10/11   |   Using the lower ball joint mount to increase caster results in the wheel sitting slightly more forward than it did from the factory. Aggressive wheel fitments might require some fender "adjustments."

As good as the GTI is compared to other hot-hatches, I now find myself comparing it to rear-wheel drive cars in terms of steering feel and reaction. I expected the stiffer bushings to transmit considerably more noise and vibration into the car, but that just isn't the case. Our Bridgestone RE-71R tires are loud-ish over some surfaces, and that has become a little more noticeable with the stiffer bushings. The cost of the arms is relatively high, right around $1,000, although we've seen them online as low as $900.

I would recommend these arms to anyone looking to maximize the handling and driving experience of the car, but you will really have to be able to drive the car to notice. If you aren't taking the car to the track or on canyon runs, you probably won't appreciate them and might be better off just getting the bushings.

2015 vw gti coilover control arm install wheel aligning Photo 11/11   |   As with any suspension work, the guys at AU Tuning finished the job on the alignment rack.

Spoiler Alert

As this issue was going to press, we had just installed a Corsa cat-back exhaust system, Unitronic Stage 1 engine and DSG flash, and new engine mounts from SuperPro. They had just been installed hours ago, so it's too early for any real impressions. Watch for a more in-depth evaluation in the next issue, and with any luck, we'll have gotten our GTI out to the test track for actual performance numbers.


Camarill, CA 93012
Bellingham, WA 98226
Tire Rack
South Bend, IN 46628
Corsa Performance Exhaust
Berea, OH 44017
Auto Union Tuning
Huntington Beach, CA 92649
SuperPro Suspension
Michael Febbo
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