Subaru requires the use of an on-car brake lathe by its dealers to meet warranty coverage. There are many good reasons why you should use the same equipment.
Brake work is a critical segment of automotive service – for both the shop and the customer. It’s a “bread and butter” portion of the services performed in repair facilities and adds significantly to the bottom line. That’s why it’s important to do each job efficiently and correctly the first time. Comebacks not only cost the shop extra time and money, but can erode customer confidence.
Customers, too, want the job done quickly and properly. They want to know that they are driving a safe vehicle that has been fixed right and that they have received value for what they paid. Returning the vehicle for further repair can be frustrating and time-consuming.
If brake work is not performed correctly, or if improper or inferior parts are used, the chances of the customer returning are greatly increased. These comebacks can severely dig into your overall profit margin.
The selection of proper parts can be easily accomplished by using only Genuine Subaru parts on your customer’s Subaru. However, using the proper equipment and service techniques are also key factors in efficiency, final profit, and reputation.
Lateral Runout: The Profit Killer
Lateral runout, sometimes called axial runout, is the amount of wobble in a brake rotor as it rotates. Runout is the result of the rotor face being out of perpendicular alignment with the hub. If runout is present, the rotor will wobble side-to side during the rotation and contact the pads inconsistently, causing the uneven wear (“thickness variation”) that results in pulsation. It can also cause damage to the caliper and cause excessive pad wear.
Runout can be measured with a dial indicator positioned against the face of the rotor and manually turning the rotor. The dial indicator should be positioned about one inch in from the outer edge of the disc.
Runout is considered to be the main cause of customer complaints. The vibration caused by runout creates brake pedal pulsation, giving the customer a feeling that the vehicle is not braking properly and that stopping is unsafe – both of which are true. These customer complaints result in comebacks, which can easily turn a profitable brake job into a big loss for the shop.
So, not only does runout cause customer complaints, but can also cause the vehicle to return for corrective brake repair much sooner than normal.
After careful consideration and study concerning the problems of lateral runout, Subaru of America chose the use of an on-car brake lathe for performing rotor turning and recommends such a lathe to its dealer network. In fact, this decision was not made recently, but in 1994! Way ahead of the technology curve, Subaru of America learned the value of using an on-car lathe.
The Advantages of Using an On-Car Lathe
There are definite advantages to using an on-car brake lathe. The biggest plus is the virtual elimination of dreaded lateral runout problems. The rotor is cut in place, firmly mounted and in the direction of rotation, thereby almost entirely eliminating runout.
Using an on-car lathe also lessens the labor time – and therefore the cost – of doing a rotor cut. This is especially true with rear rotors and “captive” front-wheel drive rotors that are difficult to remove. Captive front rotors are found on many older Subaru models. Less time spent on a repair also means more profit.
Lastly, the accuracy and efficiency of using an on-car cutter lessens the chance of comebacks. You won’t be doing any complicated disassembly and assembly, where mounting, fitting, tightening and adjustment mistakes can occur.
The use of on-car lathes has become the standard for quality brake work. In fact, the use of on-car lathes is recommended or required by all domestic and most Asian and European vehicle manufacturers.
Using a bench-style lathe requires removing of the rotor from its vehicle mounting and mounting it on the machine’s arbor. Lateral runout must be checked before removing the rotor and corrected for in the cutting procedure. If not considered, the cut may not correct the problem. In fact, it may further the runout deviation, leading to wobble and pedal vibration. Also, if the rotor is not properly mounted on the bench lathe, it may create lateral runout – even if none existed while the rotor was on the vehicle.
Many other factors can lead to poor or inaccurate rotor cutting: damaged or worn lathe components; damaged or worn arbor fittings; dirt or other foreign material on or in the lathe or adapter fittings.
The Two Types of On-Car Lathes
Over the last few decades, two ways to mount on-car lathes have been developed: caliper-mounted and hub-mounted. Of the two, hub-mounted has emerged as the clear industry preference.
Caliper-mounted lathes, while the earliest arrivals, did not have the ability to fully, precisely and automatically eliminate lateral runout. The quality of the cut was dependent upon the technician precisely mounting the lathe, measuring and adjusting before, during and after the cut. Quite often, another cut was required – and sometimes a third pass. The result could be wasted time and excess removal of rotor material – shortening the useful life of the rotor.
Hub-mounted lathes are fitted to the installed rotor, thereby aligning the axis of the lathe cutter with the axis of the hub.
No U.S. auto manufacturers recommend caliper-mounted lathes for vehicle warranty service. Only a few European companies still use them.
While on-car lathes may intially cost a bit more than bench models and the learning curve to setting up the cutting procedure may take a bit more time, the overall results and the virtual elimination of runout problems make the choice much easier.
The Pro-Cut International PFM 9.0 On-Car Brake Lathe
Pro-Cut International’s PFM 9.0 on-car brake lathe is required equipment for Subaru dealers for performing warranty service.
As early as 1994, Subaru of America realized the need to eliminate lateral runout, which leads to rotor thickness variation, resulting in brake pedal pulsation. The vast majority of comebacks are because of runout problems. SOA issued a directive stating that an on-car lathe must be used when performing warranty work for brake judder. The lathe required under that directive was the Pro-Cut unit.
Subaru dealers took to the lathe so well that in 2003 SOA lowered the flat rate time allowances for warranty work. The move illustrated the shorter times necessary for set-up, calibration, measurement and use for an on-car lathe.
The current Pro-Cut lathe can perform runout compensation in under a minute after mounting the adapter and drive unit to the hub. When the start switch is flipped on, the unit’s computer system automatically begins to adjust the cutting head perpendicular to the rotor’s axis of rotation. The one-pass finish cut can remove up to .020 in. per side. The lathe features a computer to reduce runout to less than 0.002” as measured on the rotor.
Once a technician is trained to use the lathe and is familiar with its operation, it takes less than 10 minutes to set up and complete the cutting procedure.
The following steps are used to complete the machining procedure:
- Mount the adapter: (two minutes) The first step is to choose the proper adapter, mount it and tighten the nuts.
- Set up the lathe: (two minutes)
- Mount the lathe to the adapter. The lathe is mounted to a trolley to facilitate ease of movement.
- Position the lathe for cutting.
- Adjust for lateral runout: (one minute) Pressing the start button for two seconds activates the runout measurement/adjustment process. This takes between 10 and 60 seconds, depending in the severity of the runout.
- Make the cut: (four minutes)
- Set the cut depth.
- Engage automatic feed. The machine will shut off when the cutting procedure is finished.
The question is: Should you stick with the old bench lathe you’ve been using for years, or step up to the latest technology offered by an on-car brake lathe? If you are experiencing comebacks due to lateral runout problems and pulsation and want to improve profits by performing brake rotor turning in less time, the answer is clear.
For more information on the Pro-Cut PFM9.0 (SOA Part Number 38-PFM90.4), contact your local Subaru N.E.W. Horizons Dealer or visit the Subaru Special Tools website at .
Additional On-Car Brake Lathe Choice Coming Soon
Subaru of America will soon offer an additional on-car brake lathe to its dealers as required equipment for warranty repairs. The Hunter OCL400 will also be available to independent repair facilities.
The OCL400’s ServoDrive system enables the technician to vary the spindle speed and rotational torque of the lathe while in operation. This allows the technician to adjust speeds “on the fly” without compromising the final surface finish.
The ACT (Anti-Chatter Technology) feature minimizes machining problems by virtually eliminating chatter. The ACT feature oscillates the speed of the lathe while machining the rotor to prevent the buildup of vibration (chatter) that can occur on any fixed-speed lathe.
The Pro-Comp computerized compensation system adjusts for lateral runout with the push of a button and a simple single-point adjustment.
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