As automotive experts that we Italians are, we should not even pause to explain what the convergence of a vehicle is; however, many of us often confuse it with balancing, or just don’t know how to give it a meaning, although it is now a common term.
Let’s clarify the two concepts: convergence is a predefined angle, established by the manufacturer in the design phase of the vehicle, which determines the geometric attitude of the vehicle together with the incidence and the camber. We would be inclined to think that the wheels of the same axle of a car are perfectly parallel to each other, but in reality it is not: there is an angle of inclination, even if minimal.
L ‘ balancing is instead the operation that accomplishes the tire and that allows the tire and the respective rim on which it is mounted, to have a distribution as uniform as possible loads during the rolling, and then in running conditions: plus the set tire-rim is uniform with weights and loads well distributed in all its parts, the lower the vibrations and the wear of the tread, which will always be uniform, ensuring maximum travel comfort and maximum safety and grip.
Convergence: why is it necessary?
Now let’s go back to our convergence: what is the reason why the manufacturers create this infamous lean angle to the wheels of the vehicles? We all know that tires are made of rubber: this makes them subject, depending on the loads, speed and different forces to which they are subjected, to modify their shape, their contact surface with the ground and consequently their grip. under different circumstances. It’s not all; the suspensions are also organs specifically designed and manufactured to dampen any vibration and jolt of the vehicle on bumps in the best possible way.
To give a better idea of how a tire behaves depending on the forces to which it is subjected, we invite you to take a sponge, place it on a table and exert a certain weight on it: the shape of the sponge will gradually change. , going to widen and increasing its surface in contact with the top; if, on the other hand, you try to pull it (once anchored in some way to the surface on which it is positioned), the same sponge will decrease its footprint on the surface, increasing its height instead.
This occurs in the same way on our tires : when braking, for example, the wheels (especially the front ones) undergo a strong transfer of load with consequent crushing; the opposite phenomenon will occur in the case of a sudden acceleration. Precisely to compensate for the continuous stresses, with consequent alterations of the shape and the coefficient of adhesion of these elastic components, in order to optimize consumption, comfort and road holding, the manufacturers conceive the vehicles by equipping them with a certain degree of convergence to the wheels.
Convergence in layman’s terms
Having understood the reason why this solution is adopted, we can simply say that the toe-in is the difference created between the wheels of the same axle , by measuring the distance from the front and rear limits of the vehicle’s rims . In technical jargon, we speak of positive toe (“toe in”) when the wheels are closer in their front limit, while we speak of negative toe-in (“toe out”), when they are closer to the rear. The difference between one distance and another is usually expressed in millimeters or, less frequently, in degrees.
When a check is advisable
If you touch a pavement abruptly when you park your car, or hit a hole in the road surface while traveling at high speed, it is advisable to have the vehicle checked to ensure that it has maintained the correct attitude.
Some symptoms of an imperfect balance are: vehicle running straight despite the steering wheel turned slightly to the right or left, steering “laziness” to go straight back after a turn, different force required to turn the steering wheel from one side to the other, vehicle that “pulls” (ie tends to go when you let go of the steering wheel) to the right or left.
The aforementioned symptoms are not always to be attributed to an incorrect convergence, but to prevent worse problems, it is always advisable to contact a workshop to identify and promptly resolve the cause.
Abnormal tire wear can help us understand what the problem is: if the inflation pressure is correct, a worn out tread will mean excessive toe, vice versa it will be evidence of a so-called “divergence”, with the vehicle’s wheels tending to open in the direction of travel.
Front-wheel drive cars usually adjust with the convergence at 0, or slightly diverging, in order to counteract the tendency to “close” which then occurs while driving.
On many vehicles equipped with McPherson type suspensions, the toe-in of the front axle is the only setting that can be registered in the set-up, as camber and caster are invariable. The adjustment is carried out by acting on the steering rods which are adjusted in length thanks to the thread on the wheel side. The tie rod is screwed to bring the wheel closer and unscrewed to move it away, so as to obtain the desired adjustment.
The operation, which can be carried out in about 30 minutes, on many modern cars equipped with “multi-link” suspension is also possible on the rear axle, in case of anomalies in the set-up or heterogeneous wear of the tires.
Now that we have finally shed light on all (or almost all) of the questions, let’s answer the question that the most practical of you will have asked: how much does it cost?
While balancing is in fact usually carried out, both in the case of repair or replacement of even the single tire, convergence instead has additional costs to be incurred, usually on the order of € 50/60; this leads many people to request it in conjunction with the assembly of a new set of tires, to restore the correct set-up to the vehicle once the new “shoes” have been worn, guaranteeing uniform wear of the treads for the future and the restoration of the best conditions driving safety of the vehicle. Other times, the operation is necessary after major maintenance involving the transmission and steering components.
Keeping in mind the importance of the correct maintenance of a vehicle, especially in adverse weather conditions, with funds at the limit of adhesion or in the case in which emergency maneuvers must be carried out, it is always advisable not to skimp on the maintenance operations to be carried out. A well-balanced and equipped vehicle will easily overcome high risk situations and will be more easily managed in all circumstances; saving on your safety and that of those around you, you could take great risks.
Is it really worth it?