Mazda3/Axela — Rear wheel alignment specification — Negative Camber & Toe-in
There are some common problems raised many times among Mazda communities as such whether there is an issue related to the rear wheel alignment and excessive tyre wear in Mazda3/Axela vehicles.
These issues can easily be sorted out by studying the technical specifications of the particular vehicles.
However many of the people who’re using these vehicles, even those who repair them, especially those who’re working in wheel alignment service centers, do not seem to have a real understanding of these facts.
This is an explanatory article on the issue. Before proceeding it would be important to have a basic understanding of the angles used in wheel alignment.
The primary angles considered in the wheel alignment specifications of a vehicle are called Camber, Castor and Toe.
Camber is the angle which the vertical axis of the wheel makes with the vertical axis of the vehicle. This camber angle has a great influence on the response and stability (cornering performance) of the vehicles. There are 3 ways the camber angle can exist.
1. Positive Camber
The Camber would be called positive when the top of the wheels lean outwards. Positive Camber is generally used in off-road vehicles. This is because, it improves the steering response and decreases the steering efforts required for turning the vehicle. Positive Camber is also provided in load carrying vehicles. This is because the heavy load on these vehicles cause outward leaning wheels to straighten up, improving the vehicle stability.
2. Zero Camber
The vehicle is said to have zero Camber when the wheels stand perfectly straight on the ground.
3. Negative Camber
Negative Camber is encountered when the top of the wheels lean inwards. Providing Negative Camber improves the cornering performance. When the vehicle turns on a corner, it performs a circular motion. Hence, it experiences equal and opposite centripetal & centrifugal forces. The centripetal force is experienced in the form of friction on tyres. The centrifugal force experienced by the car tries to throw it away from the turning center.
Toe is the side-to-side difference in distance between the front and rear of the wheels/tyres. If the distance is closer at the front, it’s called toe-in. If the difference is closer at the rear, it’s called toe-out.
Now when it comes to Mazda3 / Axela cars, we know that these cars are generally designed to give some great sporty handling features.
The suspension systems used in these vehicles have a MacPherson Struts type suspension system at the front and a multi-link independent suspension system at the rear (Ford designed “E-Link” suspension system).
The wheel alignment specification has a negative camber angle at the front and a much greater negative camber angle at the rear with a toe-in.
In fact, this suspension system design itself, the rear negative camber and toe-in greatly contribute in giving that fun-to drive sporty feeling when driving these Mazdas.
The special advantages of having such a negative camber angle and a toe-in is that the increase of stability and control when cornering.
When taking a bend, the wheel at the outer side of the bend is in good contact with the road surface due to the negative camber. This wheel position can be seen in vehicles like BMW, which are famous for their driving dynamics, as well as in many sports / race cars. (Actually, this rear wheel negative camber of Mazda3 / Axela vehicles can be seen by looking closely at the vehicle.)
While this type of negative camber and toe-in setups giving these advantages, the major inherent disadvantage is the comparably quicker wear in tyre inside edges.
The rear wheel alignment spec has a significantly larger negative camber than the front wheel alignment camber of these models. The rear suspension system has an adjustment for wheel alignment. But this adjusting cam bolt is mainly for adjusting the toe.
There is no dedicated adjustment for the camber in this design. The adjusting cam bolt for the toe, only slightly adjusts the camber accordingly when adjusting the toe. According to the design specification, it is acceptable for the rear wheels to have a negative camber angle over a broad range.
Accordingly, the toe should be adjusted properly with the adjusting cam bolt and the camber should be checked accordingly to ensure that a correct wheel alignment has been performed.
Therefore, it is clear to you that you cannot make a dedicated adjustment to the camber here. Otherwise, if you want to change the camber adjustable range and keep the negative camber at a minimum, or even to make it zero or positive, you have to modify the suspension system with an aftermarket camber adjusting kit.
Now this story only applies when all parts of the suspension system are in good condition.
The problem arises when some parts of the rear suspension system of these vehicles wear out or break over time.
As mentioned earlier, these vehicles have a relatively sophisticated multi-link independent suspension system that allows them to move more arms and linkages. The number of bushings associated with these parts is also high. Weaknesses, especially in the case of parts such as stabilizer bar links, trailing arms / lateral arms bushings attached to the suspension system, have a major impact on wheel alignment specification. In such cases, no matter how many wheel alignments are done, it may not be possible to get the specified values and the alignment will continue to be out of specification and a large amount of wear in tire inner edge may have to be paid for.
When performing wheel alignment on these vehicles, it is essential to accurately identify whether there is such a situation in the rear suspension system. If such a situation exists, the relevant parts must be replaced and the suspension system to be restored to its original condition before performing the alignment. After that the rear wheel alignment specification has to be adjusted so that the negative camber & toe-in come to the relevant correct ranges.
Attempts to adjust the wheel alignment without properly identifying the service and repair requirements of the rear suspension system mentioned above will not be successful. The rear wheel negative camber as well as the toe falling in out of spec will result in excessive tyre inner edge wear eventually. Those who do not know exactly what is happening here might say that there is a problem with setting the correct rear wheel alignment of these vehicles that results this unavoidable excessive tyre inner edge wear.
Also, unnecessary repairs and modifications to the wheel alignment adjustment mechanism, which are intended to use as remedial actions for the alignment problem could cause damage to those parts.
Now you have the answers to the problems about the rear wheel negative camber angle, toe-in and excessive wear of the tire inside edge of these vehicles. It is important to keep in mind that the rear suspension system design and the manufacturer specified wheel alignment setting itself has a fairly large negative camber angle and toe-in. But when performing a wheel alignment service, it is mandatory to properly identify whether there is any abnormal condition or a fault in the suspension system or the alignment mechanism. It is also important to get the wheels rotated correctly to minimize abnormal wear of the tyres.
