Articles from Renkaankierrätys magazine
Get your toe straight
The correct toe or tracking keeps the car stable, spares the tyres and saves fuel. If you can detect the problem with the naked eye, it is time to get a set of new tyres.
Toe. A familiar word that puzzles in an automotive context. Surely it means those ten little digits in your feet. Or does it maybe refer to toeing the line? The answer in this context is a no both times.
In reality, toe or tracking in relation to cars refers to the angle of the front tyres to the geometric centreline of the vehicle. The correct angle balances the car. The idea has really sunk in with car enthusiasts, but for many of us ordinary car drivers, the significance of toe is alien. For us, it is often enough when there is petrol in the tank and the scenery changes.
“Toe is always adjusted at an authorized repair centre. The procedures are not complicated, but it is seldom documented or explained to the customer. It would be important to give the customer instructions to avoid the same mistakes,” says Matti Morri, Manager of Nokian Tyres Technical Customer Service.
Ari Tuononen (D.Sc (Tech), Department of Engineering Design and Production Vehicle Engineering, Aalto University) assumes that for new cars, toe is normally always adjusted in connection to any repairs.
"However, we also have many older cars on the roads, for which you can replace, for example, the track rod yourself, and thus, the car’s toe is unlikely to be checked," he notes.
When you get deeper into the psyche of toe, you will undoubtedly also encounter the concepts caster angle and camber angle. However, Tuononen believes that for a driver, it is enough to talk about toe or tracking.
Typical misalignment problems are a result of hitting the curb or a pot hole with force. Control arms have become lighter, and the general shift is towards lighter cars. It is in many ways a good thing, but it also makes cars somewhat more fragile. On the other hand, parts become worn in old cars, thus, changing toe.
Modern bushings, in other words the rubber bushing between the control arm and the anchor bolt, are perfectly optimized. It also makes them sensitive.
“They have different properties for different directions, and major problems may occur if they become worn,” Tuononen says.
In principle, zero toe is when the wheels are parallel to each other, in other words, all wheels point to the same direction in relation to the direction of travel. However, in practice, a number of complicated adjustments with the structure are carried out at the car factory to ensure optimal toe when driving.
These days, the wheel is quite loosely attached to the body, and the new style wheel mountings are more sensitive than the old style ones. Toe as a whole is quite a complicated package, and thus, it is always important to have it properly checked after impact. Toe misalignment is a treacherous problem to have. You can drive the car without any issues, and the problem may not show up in day-to-day driving. Most common signs of problems with alignment are uneven wear of the tyres or the car pulling to one side.
In case of toe in, the outside shoulder of the tyre shows wear. And in case of toe out, the inside shoulder of the tyre shows wear. When there are clear signs of uneven wear, the observation is irreversibly late.
“That means that the car has been driven for a long time with toe alignment problems, and the tyres will undoubted have to be replaces,” Tuononen adds.
The effects of wear are emphasized in modern premium tyres. They are so called inside-outside tyres.
“They cannot be turned around on the rim. In such a case, the only alternative is to buy completely new tyres,” Morri says.
Even a small change to the ideal alignment shortens the lifespan of tyres by up to one tenth. Furthermore, the unstable driving also puts a strain on the axels, bearings and mountings. Toe misalignment also creates side force which means there is a small rear facing component causing resistance. The resulting longitudinal force must be reversed and that means increase in fuel consumption.
According to Morri, problems with toe normally reveal themselves in the spring. In the winter, the surface has natural slip, and a softer surface forgives more than a hard road surface which also creates more friction. Wear caused by toe misalignment is also dependent on tyre types.
“Winter tyres are often different size from summer tyres, and particularly low-profile tyres may increase the likelihood for problems. Higher aspect ratio and softer compound mix are more forgiving," Tuononen says.
Tyres, axels and fuel can be bought with money but human lives cannot. Although in normal driving situation the defects in the car can be compensated with easy and defensive driving, in unexpected extreme situations, the technology has to obey the driver seamlessly.
“The reasons behind the changes in toe should always be checked. For example, a broken bushing may be dangerous in a lane change or breaking situation,” Tuononen says.
Morri also points out that significant toe out problem may cause a surprising change in the direction of travel when hitting an edge of a rut on a road.
“Tyre wear also means reduced wet weather and aquaplaning properties," Morri continues.
When changing your tyres, it is a good idea to check if they are evenly worn. However, if the damage is recent, it is hard to see the wear with the naked eye. It is always good to trust an experienced repair centre or an established tyre store for investigation and repairs.
Renkaankierrätys 1/2014
Text: Juho Paavola