Of rims, wheels, tyres and TPMS
You've already found your dream rims. And now you might be wondering: Can they simply go on my car? Which tyres should I fit? And what about the Tyre Pressure Monitoring System, or TPMS for short? Don’t worry, we’ll explain what really matters when it comes to rims, wheels, tyres, and TPMS.
First off, are rims and tyres one and the same thing? Not quite. The wheel refers to the entire circular metal structure that connects the car’s hub to the tyre. It consists of multiple parts: The rim, the hub and the spokes, with the rim being the outer edge where the tyre is mounted. In short, the wheel is the complete assembly while the rim is just the outer part of the wheel. So, why does our community not shy away from referring to the wheel as the rim? There is an easy explanation: The rim is the most visible part of the wheel when discussing design and size.
To mount a wheel on your car, the bolt pattern (PCD) must match. This is given as the number of holes and the diameter of the circle in millimetres. The centre of the holes or wheel bolts always lies on this bolt pattern. For example, PCD 5×110 means five wheel nuts or bolts are spaced 110 millimetres apart, measured diagonally. The holes are usually evenly distributed around the circle. There’s also another number, such as, for example, 65.1 – this is the centre bore diameter, meaning the wheel hub flange must match this exactly. Additionally, the offset (ET) must be correct. This refers to the distance from the wheel’s centreline to the inner mounting surface of the rim at the wheel hub.
Every rim also varies in dimension (size). There are often multiple designs and combinations available. Let’s break down the alphanumeric code of a 17-inch rim, like 7.5J×17H2 ET35. Here’s what it means: “7.5” is the nominal width of the rim, measured in inches (1 inch = 25.4 mm) – essentially the width of the cavity between the rim flanges. "J" denotes the rim flange design. The number "17" stands for the rim diameter, again in inches. "H2" indicates the hump design – this prevents the tyre from slipping off the rim during sharp cornering. Finally, as you already know, “ET35” refers to the offset.
Feeling overwhelmed? Don’t worry – we’ll soon get to the good news about how to simplify your choices. But first, let’s tackle the formalities. Without certification, you might be able to physically fit a wheel onto your car, but that doesn’t mean it’s road-legal. At least not for public roads – the law has a say here.
To ensure a wheel meets all requirements – think vehicle weight and load capacity –certification is necessary. These come with their own set of abbreviations.
"VTA" stands for Vehicle Type Approval and guarantees the rim is certified for your vehicle’s load capacity. If your car is in its original condition, a VTA means you don’t need additional type approval. Essentially, if the exact wheel-tyre combination is already listed in your car’s documents, you can fit and drive with VTA-approved wheels without extra paperwork.
Make a note: Since European countries have different regulations, we recommend always carrying the relevant certifications. You can easily download and print them from https://www.aez-wheels.com/DE/tuev and keep them in your glovebox. That way, they’re ready whenever needed.
Now, let’s move on to tyres. A tyre is the part, mainly made of rubber and synthetic materials, which makes contact with the road. It’s filled with air. Modern passenger car tyres are usually tubeless, meaning the combination of tyre, wheel, and valve retains the air.
Tyres are crucial for driving dynamics and safety. The contact patch – the area of each tyre actually touching the road – is usually only about the size of a postcard, yet it manages significant traction, braking, and lateral forces.
We strongly advise against choosing tyres solely based on a flashy tread pattern or the cheapest price. Most of the technology lies in the rubber compound – this applies to summer, winter, and all-season tyres alike. To find out which tyre specifications work with your rims, check with your car manufacturer. When picking a tyre brand and model, the EU tyre label can offer initial guidance. It rates rolling resistance (energy efficiency), wet braking performance, external noise level, and winter suitability – giving you a way to compare options. But be cautious: tyre manufacturers rate their own products. For more reliable advice, consult tyre tests from car clubs or specialist magazines, making sure they cover and have tested the exact tyres you’re considering.
However, the right tyre won’t do much good if the air pressure is wrong. Check it regularly and adjust it to match your car’s load. If your car was registered after 1 November 2014, it must have a Tyre Pressure Monitoring System (TPMS), as this has been mandatory for new cars across Europe since then. As the name suggests, TPMS sensors detect if a tyre’s pressure deviates from a pre-set value.
There are direct and indirect systems: An indirect TPMS usually obtains its information via the ABS sensors. A direct tyre pressure monitoring system works with one sensor per wheel, meaning one for each wheel-tyre combination, and displays the current tyre pressure in the cockpit. The tyre pressure monitoring system is an important tool that allows you to detect if a tyre is losing pressure. This can happen, for example, if the tyre carcass has a damage that is not immediately visible to the naked eye. As such, a TPMS makes a significant contribution to driving safety and should always be checked for proper functioning.
A bonus: TPMS also saves you money. Incorrect tyre pressure increases tyre wear and fuel or electricity consumption. AEZ offers various direct TPMS sensors, but before we get into too many details, let a professional workshop help you choose the right ones.
Finally, let’s revisit the good news about getting it all right. Here’s the key: Our wheels and TPMS sensors are manufactured to the highest quality standards. You can pick your favourite design and colour from our wide range without worry. In doing so, the AEZ 3D configurator is a fantastic tool from the get-go. It contains all the essential technical data — simply enter your car’s details and instantly see a clear list of compatible wheels that would work with your car, including certifications and all vital info.
If your car doesn’t have an indirect TPMS, the configurator will also show suitable sensors. And if you’re still unsure about the technicalities or legal requirements, visiting a specialist workshop is always a safe bet.
