Front Wheel Pull Where It Fits In

By: Anthony Analetto
Originally Published in AutoLaundry Magazine

Is it better for the conveyor to pull the front wheel of the car through the conveyor, or load it first and push from the back wheel? There are strong advocates for both approaches and I don’t want to start trouble by saying one is better than the other. Rather, several factors have changed in car washing that warrant an open mind to select either option under the right set of conditions. In today’s real estate market, many operators are trying to get more cleaning on a smaller property. In other areas, operators are trying to fit more equipment into shorter tunnels to eliminate prepping and labor expense. Most discussions often center upon application technologies, chemistry, wash materials, and hybrid combinations of friction and high pressure cleaning. Today, I want to talk about something even more fundamental, the conveyor itself.

The History

I’m not a car wash historian, but I can still recall some of the first conveyors used in the car wash industry. They’re easy to recall because only last year I was involved in a remodel that replaced an old hook and chain model still in use. For anyone not familiar with the technology, it’s exactly how it sounds; a hook was placed on the front bumper and connected to a moving chain that dragged the car through the wash. The next models I can remember were the all roller up double chain conveyors that caught the front wheel and pulled the car through the wash. These were particularly dangerous in that it was not uncommon for cars to jump the conveyor. Often, the electric drive would allow the conveyor to continue for several feet after the stop button was pushed making the problem even worse. Fortunately, these technologies are a distant memory for most of us. The advents of the over/under, roller-on-demand conveyor and computer controlled automatic roller up systems available have changed everything. Today, it’s expected that a conveyor will bring a car safely through the wash. Most considerations when evaluating different brands relate to durability, lifespan, reliability, and ease of maintenance. The one choice that remains is not actually about the conveyor itself, but rather how it is configured. Do you want it to push the rear wheel or pull the front? This is a debate that I anticipate will become more heated in the next couple of years.

Conveyor Technology 101

Some of you may have chuckled while remembering the old hook and chain conveyors, but there was valid logic to them. By pulling the front of the bumper the car went straight through the tunnel no matter what. As soon as you push or pull the wheel on one side of the vehicle, you now have to deal with differing tire width, alignment, and concrete pitting issues that try to pull wheels out of the conveyor. Even in the last few years, conveyor widths have increased several inches to accommodate wider tires. Now, the 12 inch wide conveyors that will fit the P265 tires on a Chevy Silverado Truck unavoidably leave the P195 tires on a new Chevy Cobalt with more space than desired. The last reality is that the chain pulls the center of the roller down the conveyor leaving the potential for it to angle slightly with smaller tire sizes that can track the car to the outside rail, increasing the potential to jump. Unfortunately there is no such thing as a free lunch. Using two chains to pull both sides of the roller introduces the fact that metal stretches unevenly and more often than not, without constant maintenance, the roller will only find itself on a permanent angle disrupting every vehicles track. Wide conveyor belts that move the entire vehicle in a parked state through the tunnel solve the problem, but unfortunately create several new ones. With the wheel no longer rolling, you loose the ability to bring all parts of the wheel and tire outside the fender and past CTAs, brushes, and dressing applicators. It’s difficult enough to clean wheels online when you can roll them by low profile cleaning actions. Getting automated equipment under the fender to clean is impossible. That leaves us with the over/under roller-on-demand single chain conveyor as the leading contender for car washing – at least for now! Now back to the question at hand; is it better to pull the front wheel or push the back.

Rear Wheel Push

Pushing a car from the back wheel didn’t exist before the introduction of roller-on-demand conveyors. Before it, attendants drove on between rollers and jumped out before it grabbed the front wheel. The ability to fire a roller on demand allowed an operator to drive the car completely onto the conveyor and fire a roller to push it through. This was not a trivial change. Completely loading the car improved safety at the wash. Operators no longer needed attendants skilled enough to time loading between rollers. Employees at a full serve are forced to carefully and accurately load the vehicles completely before getting out.

To understand the last advantage of pushing the rear wheel, I’ve included several diagrams. Ideally, the tire will ride against the inside rail of the conveyor, with an outside rail, usually covered in plastic, in place as a precaution to keep a wandering car on track. Pushing the rear driver’s side wheel naturally guides the car towards the outside rail which is easier to control. Elevating the conveyor by 1 1/2in at a very slight incline towards the exit keeps the car rolling smoothly with slight pressure against the inside rail, securely against the roller.

The cost for the increased safety of the rear wheel push configuration is the 18 feet of additional conveyor length it requires. For years, many full serve washes manually prepped or vacuumed cars in the first 18 feet anyway. The additional expense for a longer conveyor was easily offset by the increased safety. That has changed. Most express-exterior and flex-serve locations have eliminated prep labor and are eager to get back those 18 feet, more often because of high land and building cost than the additional conveyor expense. Simultaneously, many full-serve locations are hungry to switch to automated equipment to replace manual prep. Changing to front wheel pull would give back 18 feet of conveyor for wash equipment to substitute labor without any major construction. Although I’m still a strong proponent for pushing the rear wheel, I have to admit, the value of those 18 feet warrant some serious consideration.

Front Wheel Pull

Pulling the front wheel does give you back 18 feet on your tunnel, but it’s not without drawbacks. First, the car pulls toward the inside rail. Although this is where you want it to be, inconsistencies in vehicle alignment and floor abnormalities on the passenger side wheel can exaggerate the track to the point a car may climb out of the conveyor. To counteract this, the conveyor is installed approximately 1 inch below the floor surface to lessen the pull towards the inside rail. Inherently, issues happen when controlling the track across varying tire sizes and wheel alignment conditions. Installing either smooth stainless steel slip plates down the passenger side of the conveyor, or ridged steel rails, help eliminate the problem of the floor or poor alignment destroying a straight track. One of those methods should be incorporated with any front-wheel pull installation as a precaution to avoid costly mishaps.

Summary

When space permits, I personally believe rear wheel push delivers straighter tracking. With that said, the number one priority of a car wash is to deliver a clean, dry, shiny car. If push comes to shove, front-wheel pull can be done safely with careful installation and supplemental aids to track the passenger wheel straight through the tunnel. If unanticipated zoning changes on a new site reduce the available land to build a conveyor long enough to process the projected car count, front wheel pull is a viable option. For existing locations looking to add equipment to either eliminate prep labor or increase throughput, converting to front wheel pull can be like adding an 18 foot tunnel extension. Needless to say, I expect changes in technology, land prices, and the desire to put conveyorized washes on smaller footprints, to bring this debate to the forefront of industry discussions.