What is wrong with Bike Covers?

We understand you want to keep your bike in good condition and partially hidden from prying eyes during travel, but RockyMounts cannot recommend the use of bike covers during transit on the roof or hitch and it voids the warranty on the rack. We are not alone, most rack companies dictate the same.

Hitch- Covers pose two problems during transit.

-Wind Drag. Depending on the vehicle, your bike is broadside to the wind. There are significant wind forces in this case as the air travels over the car and hits the bicycle. Bikes are fairly porous and wind can pass through the wheels and frame. When a bike cover is used, this wind force grows by a factor of minimum 10x. Remember when you put your arm out the window or sunroof going 75mph? That is a lot of force, now multiply that force on your hand by about 80 and that is the wind force on your bike and rack compared to your hand. These forces will eventually cause the rack to fail, not a matter of if, just when.  

On some vans and SUVS, the bike has less wind load than a sedan as it does get some “draft”, but there is no way to quantify your vehicle and the additional wind loads placed on the rack.  

-Tail Light/License Plate Obstruction. These bags could lead you to getting pulled over as the cover will block more of your turn signals, brake lights and license plate.

Roof- When we started producing roof racks in the nineties, a customer lost a bike, we were disappointed and dug into the problem. Upon further inspection, we learned the bike had a “bike bra” and was pulled out of the mounting position. Why? Bikes are fairly “porous” and there is ample area for wind forces to get through the frame, wheels and components. A bike cover or bike bra negates this and turns your bike into a giant sail. A side wind in this case puts over 10X the force on the rack vs no bike cover. We have all been in side winds driving and riding, now imagine how large a force is acting on your bike and rack. Best bet, wipe the bugs off and deal with the elements, better than picking your bike up off the highway. The companies that make the covers do not make bike racks, so it is not their problem, so they are happy to sell you one, avoid.