Based on the age and mileage, a better suspect is a tire pull. The car is too new for a problem with any brake system part to be a suspect, unless an improper brake job has already been performed. Control arm bushings used to last the life of the vehicle but to meet the demand for a softer ride, most manufacturers are using softer rubber compounds that deteriorate quickly. Now worn bushings are real common, but not at such a low mileage.
Almost all front-wheel-drive cars use a split-diagonal brake hydraulic system that puts one front wheel and the opposite rear wheel on one system. If you ever had the luxury of driving an old, heavy, rear-wheel-drive car with one front brake disabled, you will know that applying only the other working front brake will tear the steering wheel out of your hand. How hard the steering wheel pulls to that side is directly proportional to how hard the brakes are applied, and it is totally impossible to adjust and control accurately where the car goes. Why then does not a front-wheel-drive car veer to one side when there is a leak in one of the hydraulic systems? It is because the engineers have modified a non-adjustable alignment angle called "scrub radius". Chrysler had that so well-perfected that if there's a failure in half of the system, the only way you will know is the red "Brake" warning light will turn on. For most other brands, all you might see is a slight wiggle in the steering wheel when the brakes are applied, but the car will still stop in a straight line.
That story refers to a total failure of one front brake. Now it is easy to understand why a sticking caliper or a restricted rubber flex hose will not result in a brake pull to one side. It is also important to understand these are generalizations, and there are always exceptions, but there are better suspects to start with.
The mileage listed is right around when the original tires are about worn out or new tires were recently installed. Both are right in the typical time frames of where a tire can develop a pull. That is not to say it has a broken belt, although that is a common cause too of a pull. The rolling resistance and directional stability between the two tires can change. There are two ways to identify that. For any vehicle, switch the two tires side-to-side. If the pull goes the other way, it's a tire problem. If the pull stays the same, it still could be a tire problem, but you would have to switch them front-to-rear to know for sure. For front-wheel-drive cars, the forces acting on the tires includes that from acceleration as well as from braking. A pull to the left, for example, while braking, will usually also cause a pull to the right when accelerating.
Understand too that anything that allows the alignment to change between braking and accelerating can cause a pull. That is where worn control arm bushings are good suspects, but as I mentioned, the mileage is too low to look at those first. Related to that, some cars are rather forgiving if "camber" is not equal on both sides. Camber is the main alignment angle that affects pulling to one side. Some car models will pull to one side when camber is unequal by as little as a few hundredths of a degree. (Alignment computers can measure to one one hundredth of a degree). Some models will not have a noticeable pull with a really big difference side-to-side, however, that difference can be exaggerated during braking from the additional weight that transfers to the front, and the additional force that tugs on the tire tread. A brake pull can be caused by an alignment problem that doesn't cause an apparent pull while cruising at a steady speed.
Anyone who ever owned a late 1980's Ford Escort or Tempo knows all about pulls caused by worn steering system parts too. It was real common for outer tie rod ends to separate after as little as 15,000 miles. While driving those cars onto a drive-on hoist, it was common to see the left wheel turn to the right when accelerating, and to the left when braking or just letting off the gas. The wheel did the same thing when driving down the road. That would also cause a pull that changed direction between braking and accelerating, but because this was so common, both outer tie rod ends usually wore out at the same rate, and it was possible for the two pulls to offset each other. The car would follow the tire with the most weight on it, and that changed depending on the slant and bumps in the road. There could be no pull one time when the brakes were applied, and an unexpected horrendous pull the next time.
One often-overlooked clue to a brake pull is to observe what the steering wheel does. When something in the suspension or steering systems changes and causes a pull, you have counteract that by turning the steering wheel the other way. With unequal front braking forces, you may need to hold the steering wheel straight while braking lightly, but the straight steering wheel will match stopping in a straight line. With worn control arm bushings, a brake pull to the left will be met with a steering wheel that shifts to the right on its own. What the steering wheel does depends on whether the steering linkage is in front of or behind the centers of the wheels. With a tire pull, during braking the steering wheel will stay straight. It is only the driver having to turn the steering wheel the other way that keeps the car going straight. You have to observe what happens at the instant the brakes are applied, and ignore what you need to do after that.
Saturday, February 4th, 2017 AT 3:25 PM
