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DRIVING/TOWING - TOWING

'BRUSH' STONE GUARD
An alternative to mud-flaps and trailer-mounted stone deflectors.

 

There are several ways of keeping tyre-driven stones off your caravan, camper trailer or boat trailer, including rubber mud-flaps, mesh panels between tow vehicle and trailer, and deflector guards on the front of trailers. An alternative is the brush-type stone deflector that we bought to test.

 

No protection device is perfect and none suits all tow vehicles and trailers.

Rubber mud-flaps offer good flying-stone protection, but need to be full vehicle width, not just the  narrow, legal-size flaps that come with utes and tray bodies. Full-width mud-flaps need to be stiff or heavy, so that they don’t ‘sail’ in the slipstream, lifting well clear of the road and letting stones fly past.

Fitting rigid or heavy mud-flaps can be a problem for some vehicle installations. Also, many users complain about increased fuel consumption when using full-width, ground-hugging mud-flaps.

Mesh panels, like the Stone Stompers we’ve tested, offer excellent stone protection for trailer fronts, but still allow stones to impact components underneath the trailer, so they need additional protection.

Most camper trailers and some caravans come with deflector guards on their drawbars. Ideally, these are fitted with loose, tightly-woven mesh, to absorb the energy from impacting stones. Tight mesh may look neater, but makes the stones bounce, like a ball off a tennis racket and they can break tow vehicle back windows and chip paint.

Deflector guards need to be angled forward at their top edges, so that stones are directed downward.

 

Brush guards

‘Brush’ guards are derived from industrial sweepers that keep streets and factory floors clean. The most common automotive use for industrial brush strips is as spray suppressors on heavy truck and trailer mudguards. The bristles help condense blinding spray from tyres into large droplets that fall to the ground.

Their use as stone guards is becoming increasingly popular, because they cover the same area as a full-width mud-flap, but with less wind resistance and less tendency to ‘sail’ in the wind. They’re particularly popular in the USA, where towing speeds up to 80mph (130km/h) are permitted in some States. 

However, some US makers supply brush guards with reinforcing bars, to improve high-speed anti-sail performance.

We checked out several Australian brush guard suppliers before buying from Industrial Brushware Pty Ltd. We chose this company’s StoneGuard Brush two-metre strip, with 400mm-long bristles, mounted in an h- section aluminium extrusion. Some competitor strips don’t come pre-mounted into an extrusion.

We picked up ours for under $200.

The bunches of bristles were 800mm long, wrapped over an aluminium rod ‘core’ and clamped in place by a soft aluminium cover that’s pressed into the h-section extrusion. The soft aluminium cover strip was simply crimped over at each extremity, to retain the bristles.

We shortened our two-metre strip to the LandCruiser’s tray width of 1850mm and crimped the cut end, to stop the bristles ‘escping’. We offered it up, above the towbar and then cut out the centre 100mm section of bristles, to let the strip drop over the tow hitch and tongue.

To make it quick and easy to attach and remove, we used two available holes in the rear cross member (it’s not advisable to make unnecessary holes in chassis components) and locked a pair of 13mm stainless steel studs in place. 

Holes drilled in the h-section extrusion let the strip fit over the studs and it was secured in place by a couple of Nylock nuts. That arrangement means we can fit and remove the brush guard by simply undoing two nuts.

We decided that a pair of studs was ample, because the mid-section of the StoneGuard Brush strip sits on top of the towbar tongue receiver, so the bar supports it at its centre of gravity.

 

On and off road results

The LandCruiser ute exhaust pipe lined up right where we wanted to install the StoneGuard strip, but we didn’t want to go to the trouble of re-routing the pipe, or putting an extension on it.

We knew there might be an issue with exhaust pipe heat affecting the bristles, but we weren’t sure what the effect would be or its target area.

We reasoned that the exhaust gas heat would melt the bristles at one point, so we went for a drive to find out. Sure enough, a section of the bristles melted, leaving a gap in the protection ‘shield’. We trimmed off the affected bristles and worked out a way to plug that gap; at least partially.

The 150mm section that we’d cut off the original two-metre length was the answer.

It was simply matter of drilling a hole in the middle of that 150mm aluminium h-section and bolting it through the exhaust pipe rear mounting bracket.

That put the short section further forward than the main strip and higher from the ground, but did a reasonable job of plugging the ‘gap’.

Thus set up we did an 800-km on and off road test, pulling our Hobie Mirage Trimaran behind the LandCruiser ute.

For the first time on any towing trip we didn’t find any small stones inside the boat and there was also no sign of chip damage to the leading edges of the fibreglass hull and floats.

The bristles proved to be easily deformed by off-road obstacles, such as rocks and ruts, but returned to their original shape instantly. In addition, they didn’t get trapped under the rear tyres when reversing, as long mudflaps can do.

So far, so good.

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