We choose the rims ourselves

The rims in the car are a bit like a man’s shoes. It is often through their prism that the whole is judged. Well-chosen rims are not only the proper functioning of the chassis or braking system, which also translates into safety. These are nice aesthetic impressions, thanks to which even older models become younger and “ordinary” ones become more prestigious or take on a “sports claw”. We advise on what to remember when choosing rims for our car.

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The easiest way to choose the right rims is to contact the store or authorized service of the brand we have, where we can get professional advice regarding the rims you are looking for. However, this is not always the case. It is good to have the right knowledge in this topic, when we want to install rims from another car, or used / regenerated rims or unusual rims, the parameters of which will not necessarily correspond to those recommended by the manufacturer of our model.

Knowledge of the basic parameters of the rims and compliance with them ensures the proper functioning of the most important components in the car, although it must also be remembered that there are some deviations that we can do without compromising the handling.

Rim diameter and width

RIM Width & Diameter
RIM Width & Diameter

These are two basic parameters that are most often taken into account when choosing the right rim. Importantly, however, there is quite a lot of room for maneuver. For example, in many smaller cars it will be possible to mount rims with a diameter of 14 to even 16 inches, although each selection should be preceded by even a momentary analysis of the benefits and disadvantages of such a solution.

When using a smaller rim diameter than recommended by the manufacturer, a problem may arise with the brake discs and calipers, which may be too large for some rims (on smaller rims they may simply not fit). It is worth remembering that even within the same model, e.g. in richer equipment versions or with more powerful engines, brake calipers of various sizes may occur.

On the other hand, increasing the diameter may result in the tire not fitting in the wheel arch after it has been fitted. Most often, increasing the rim is accompanied by a reduction in the tire profile to keep the wheel diameter at a similar level. The lower tire profile may look more impressive, but you have to reckon with poorer ride comfort, especially on inferior roads, and a greater risk of damage to the rims. A lower profile can also lead to faster wear of suspension components and chassis components.

The choice of specific rim size involves subsequent tire selection. For example, a 7J / 15 rim means a 15-inch diameter and 7-inch width. A bit like a tire, but, interestingly, as long as the rim diameter directly determines the diameter of the tire (in the case of 15-inch rims, we have 15-inch tires), with the width of the rim the matter is a little different. Well, with the assumed rim width, you can choose several tire widths – e.g. for a 7-inch rim, you can choose a tire with a width from 185 to even 225 mm. The situation is similar in the opposite direction. If we choose the rims for the tires we already have, then we also have some freedom of choice. For example, a tire with a width of 215 mm can be mounted on a rim size 6.5 to 8.5 inches.

Rims offset

While the diameter of the rim leaves quite a lot of choice, we have less freedom with the width of the rim with which the so-called wheel offset factor (referred to as ET or offset). The ET coefficient in short means the distance between the mounting plane of the rim to the hub and its axis of symmetry. It can be positive or negative, which results in a smaller and larger track width, respectively. Let us remember that car manufacturers allow a wheel track change of about 2 percent, without affecting the driving parameters or the chassis components. Therefore, in a car with a track width of e.g. 150 cm, you can use a wheel offset factor that is even 15 mm smaller than the factory one (e.g. instead of 45 you can use a wheel with ET 30).

The choice of rim in accordance with this factor will guarantee that the wheel will fit in the wheel arch, will not rub against the elements of the suspension, braking or steering system, or the fender and will not finally protrude beyond the outline of the car, which is prohibited by applicable law in our country . Wrong selection of this parameter will contribute to faster wear of the tire and even rims, and in extreme cases even worse control over the car, e.g. when cornering (although there are known cases of increasing the track width in motor sports, just to improve stability). Let’s remember, however, that these undesirable effects may not be noticeable immediately, but only when the load is heavier or the wheels turn strongly.

Number of bolts and hole spacing

On the other hand, there is no further room for maneuver, which is important when choosing rims. For example, the notation 5×112 means that the rim has 5 mounting holes, and the diameter of the circle on which these holes are located is 112 mm. Both the number of holes for mounting bolts and their spacing must perfectly match those given by the manufacturer. Otherwise, even with a slight deviation (talking about the spacing of the holes), it may turn out that the rim will simply not fit. And even if we somehow manage to put it on, there is a very high risk that it will fall off at some point.

The diameter of the central hole

An often overlooked parameter, which, however, is also important in terms of the correct assembly of the rim is the diameter of the central hole. It should be remembered that differences between the central hole and the diameter of the hub flange may prevent the assembly of such a rim, and after mounting without perfect fitting (only using screws only), there may be noticeable vibration and vibration when driving at higher speeds.

After checking all the important parameters, you can finally proceed to search for the appropriate rim design, including to the number, shape and thickness of the arms. Although decisive here will be the tastes of the car owner, let’s remember that a large number of arms / spokes can significantly hinder keeping them clean. In addition, rims with thin shoulders are much less durable and may not be suitable for heavier SUVs or a large limousine.

Although the final decision will belong to us, it is not always worth insisting on getting your way. If you choose the right rims, please refer to the car manufacturer’s and rim’s details. It doesn’t hurt to ask an experienced salesman or service technician for advice.

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