Mazda6 Case Study: Data Gathering Is Critical To Your Alignment Diagnosis -

Mazda6 Case Study: Data Gathering Is Critical To Your Alignment Diagnosis

2014-Mazda6-Sport-(19)

 

About a year ago, I got a request from a private vehicle owner to help diagnose a steering problem on a 2010 Mazda6 iSport. Given the power of the Internet, it seems that this person had somehow discovered one of my older columns on alignment problems.

While I’m not fond of dealing with technical ­requests from private individuals, this request was compelling because it was well researched and posed a few serious questions about why several different alignment shops couldn’t or didn’t diagnose the alignment problem on this vehicle. Because this repair might require the services of a shop equipped with a frame alignment bench, I recommended that my reader report the accident to his insurance company at the outset.

According to the owner, the Mazda had skidded on an icy street, struck a curb with the left front wheel, and now the steering was ­pulling to the left, with the steering wheel position changing from center to about 20-30 ­degrees counterclockwise.

According to the owner, the original alignment shop replaced the damaged front wheel and tire and adjusted the front toe angle. The alignment printout indicated that the Mazda had +1 degree camber on the left (driver’s side) and -0.4 degrees on the right (passenger’s side), producing a 1.4-­degree camber “split.” The caster angles were +3.0 and +3.8 degrees, respectively. Total front toe angle was +1.17 degrees.

According to the report above, the steering axis inclination (SAI) apparently wasn’t measured, but the front toe angle, as well as the rear suspension camber, toe and thrust angle, were adjusted to specification. The left front camber adjustment remained the same.

Keep in mind that alignment readings change due to differences in a vehicle’s daily weight distribution, slight differences in machine calibration and how the machine rounds the numbers. Not happy that the steering pull hadn’t been repaired, the Mazda owner solicited an opinion from a second alignment shop.

The second shop recorded essentially the same readings with the addition of an SAI, which was +6.2 degrees left (driver’s side) and +6.6 degrees right. The Included Angle was 7.1 degrees left and 6.3 degrees right, indicating approximately 0.8 degrees more camber on the left side. The rear alignment angles remained essentially the same. I’ll stop here because, for whatever reason, neither shop repaired the problem.

 

THE CUSTOMER INTERVIEW

Since I’m quoting solely from the customer’s point of view, I can only speculate what was said at the service desk of either shop. Did the owner request a routine alignment, or did he communicate a specific complaint? And did he describe the accident in specific terms? If the alignment technician assumed he was doing a routine alignment inspection and all of the readings fell into the “green zone,” he might not have concerned himself with the apparent split between left and right front camber angles. And, because the original camber reading is well within Mazda’s service specifications, he might have given it a pass.

On the other hand, if the owner complained of a steering pull to the left after striking a curb, then the technician should have fully understood the significance of the left/right camber split. Of course, all of us have experienced the owner declining recommended repairs due to budget issues or doubting the shop’s recommendations. So, in any case, my objective isn’t to be critical of any shop, but rather to emphasize the importance of gathering critical information from the customer before starting an alignment.

Looking at the numbers, the Mazda6 front suspension consists of an upper and lower control arm with a short-long-arm (SLA) configuration that’s suspended by a coil-over shock bearing on the lower control arm. The car struck the left-front wheel against the curb hard enough to bend the wheel rim and damage the tire. Obviously, the force from that curb impact was transmitted through the front spindle, through the lower control arm and through the rear control arm mount.

The result was an increase in left camber angle (+1.0 degrees) and a decrease in left side caster angle (+3.0 degrees left compared to +3.6 degrees right), which would suggest that the wheel had been pushed in at the bottom and toward the rear, which is consistent with a wheel skidding into a curb.

The second alignment shows an SAI from +6.2 ­degrees left and +6.6 degrees right, suggesting that the spindle wasn’t bent. Moreover, driving straight ahead with the steering wheel tilting counterclockwise about 20-30 degrees from center would suggest that the steering was correcting for a badly toed-in left-front wheel.

Since the left tie rod apparently remained straight, it would tend to toe the wheel in, producing the +1.17 degree total toe angle now being displayed on the ­machine. Of course, the original printout indicates that the left and right toe angles were split from side-to-side, but I’m speculating those were measured with the steering wheel not centered.

Alignment-Readings_Feb_6_2013
Initial Alignment Report: Camber angle pulls the steering toward the side with the most positive reading. The above camber angles indicate and confirm that the Mazda did indeed pull toward the left.

 

RECOMMENDATIONS AND THE REPAIR

I responded to the help request only by properly qualifying my comments. Clearly, I’m not the person operating the alignment machine and I’m certainly not looking at the actual vehicle. So I’m speculating on the possible damages based on several alignment reports and upon the customer’s account of what happened. But I think it’s safe to say that the initial inspection should center on the rear mounting point of the lower control arm. It could be that only the control arm is bent or it’s possible that the frame mount is bent as well.

The other issue was collateral damage. The customer complained of an intermittently hard brake pedal and brake pull. Here again, I’m not in a position to analyze why the brakes would react in such a fashion. A steel brake line could, for example, have been pinched, or the rubber brake line, caliper guides and other ­related hardware could have been damaged. All of this requires a ­visual inspection by a qualified brake technician. Other collateral damage came up after the customer had the lower left-front control arm replaced, but we’ll leave that to the last paragraph.

After the left-front lower control arm was replaced, the driver’s-side alignment angles were restored to -0.07 degrees camber and +3.3 degrees caster. The camber and caster angles aren’t perfect, so they suggest that some damage still ­remained at the left-rear lower control arm mounting point at the frame. On the other hand, a slight camber/caster split generally won’t produce a steering pull on a front-wheel-drive vehicle.

After the final repair and alignment, the reader ­reported that the steering wheel felt “stiff” and wouldn’t fully return after cornering. Given the ­direction of impact, it’s entirely possible that the steering rack gear was slightly bent. Here is another reason to keep an open estimate when diagnosing and repairing collision damage. In many cases, this type of concealed damage won’t be apparent until the vehicle is driven on a daily basis.

Alignment-Readings_May_6_2013
Final Alignment Report: The final alignment report indicates that the lower control arm replacement essentially brought the driver’s-side camber and caster angles into specification and remedied the left-front steering wheel pull.

 

Afterthoughts: When I began aligning vehicles in 1968, I used ­mechanical gauges that came with a card overlay to indicate desired settings. I soon discovered that all of the cards in my file didn’t produce the desired ­results. So, I began recording alignment-in readings and alignment-out readings, along with mileage. It didn’t take long to compile a paper database that I could use to fine-tune the alignment settings to my customers’ driving habits.

Three years ago at a trade show, a representative from a major alignment manufacturer demonstrated his latest machine and explained all of the latest additions, including automatic run-out compensation and a full video for each vehicle application explaining adjustment points and tools required. So, I’ll be the first to say that this type of machine is needed to not only ­enhance productivity and create a nearly perfect wheel alignment, but also to re-learn steering wheel centering and other safety-related sensor ­inputs as well.

 

But, the principles I used in 1968 still apply to ­modern wheel alignments:

  1. Accurately determine the reason the customer wants his/her wheels aligned.
  2. Accurately analyze the significance of the alignment data.
  3. When dealing with collision damage, understand the angles of impact and the related ­damages that might result.
  4. Remind the customer that he might want to notify his insurance company when collision damage is evident.
  5. Learn to fine-tune alignments to correct for unusual vehicle loading patterns, highly cambered road surfaces and other variations in the ­vehicle’s driving environment.

Based on my experience, following these suggestions will help provide a wheel alignment that will meet or exceed your customers’ expectations.

 

Courtesy ImportCar.

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