Aerodynamic balance is one of the more easily overlooked measurables when it comes to setting up a car for the track. Determining when a handling malady should be resolved with aero or chassis changes is the first step, as we addressed previously.
A front aerodynamic aid such as a splitter, air dam, or chin spoiler is one of the most accessible and functional pieces of kit a DIYer can do in their garage. Visually unobtrusive, these devices serve a number of purposes, and can ultimately benefit handling, front end grip, cooling, and economy.
For project Gruppe R, our 2013 Golf R, we already had extensive aero at the rear in the form of a dual plane spoiler and fender flares, and at the front with our widened rally/DTM-style fenders. Having raised the ride height slightly for clearance on gravel roads, we introduced a large gap under the front lip of the car, allowing more air to get under the chassis.
After listening to Chris Meeke’s sage advice on the importance of a front lip, we decided to create our own solution. To combat the threat of front end lift at speed, we opted to fabricate our own flexible air dam.
Navigating Industrial Materials
Gathering the materials for a job like this is super simple, but requires thinking a little outside the automotive box. Sourcing the actual material for the air dam lead us to a number of different resources. While deep pocketed motorsports programs may turn to custom-molded composites for their light weight and rigidity, they are expensive, require significant mold tooling, and in the case of rally – are consumables, as rocks and ruts erode their effectiveness.
Landscaping planter edging, found at any local hardware store is a popular go-to for many undertaking this job. The durable plastic, flexible nature, UV resistance, and cheap price tag make this stuff a favorite.
Due to the complex shape of the Golf R’s chin, we decided the edging would be too inflexible to curve around tight radius bends – that added to the projection that we will be scraping the chin over obstacles daily, meant we needed something a little different.
To cut two inches off our conveyor belt we marked a line on a piece of masking tape.
Fabric-reinforced conveyor belt webbing is option number two. We wanted our air dam to be flexible over bumps in the road, but remain rigid in the flow of air. We found Grainger to be one of the easier-to-navigate sources of rubber conveyor belt. After putting in our parameters for thickness, color, material, and price we were presented with a few options.
Our conveyor belt measured six inches wide and 1/4-inch thick, and is constructed of three plys of rubber separated by two fabric plys. This stuff is relatively heavy and very robust, certainly enough to stand up to our application.
We decided four inches would provide the depth we were looking for without sacrificing too much approach angle. Using a razor blade we took two inches off the belt.
We marked the rivet intervals at about six inches.
To mark our holes, we applied some blue painter’s tape and measured even intervals. Using a 15/64-inch drill bit we drilled our holes in both the rubber belt and the bumper.
Using a 15/64-inch drill bit we placed our rivet holes.
Nuts and bolts are, of course, one option for attaching your air dam to the chin of your car, but they are heavy and require generous access to the backside. Pop-rivets are the preferred fastener for a situation like this.
We backed every rivet with an aluminum washer.
We decided to use 3/16-inch aluminum rivets to distribute the load and affix the rubber to the bumper. We spaced the rivets about six inches apart, and were careful to use a backing washer on both sides where the rivet sandwiches material – on the belt, and inside the bumper.
Squeezing everything together while holding the washer on the backside was the most challenging part, however our Golf made this job exceptionally difficult because the front bumper is not open at the bottom and needs to be pulled away from the car for access.
With the holes already drilled in the bumper, we match-drilled the belt as we went to ensure everything would line up.
This job took one person a couple of hours to layout and complete carefully. The end result is functional and durable. We can count on reduced front-end lift with the limited ground effect gap, and more air striking the air dam will be forced up into the cooling, or around the flanks of the car.
The new air dam conforms to the curves of the Golf R bumper.
Upon first test drive with the new device, the primary difference we noticed was reduced steering wheel vibration. What previously felt like slightly out of balance wheels and tires is now almost imperceptible. This calmed feedback is augmented by an overall settled feeling in the handling. Turn-in at speeds in excess of 70 mph is less dramatic, as the inside corner of the car does not catch the wind like a kite and upset the weight balance.