Wheel and Tyre Fitment: Centre Bore
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Centre Bore
03.44
| 00:00 | In a previous module we looked at the centre bore of the wheel and some considerations it presents. |
| 00:06 | In this module we'll bring all that together for a clear and comprehensive view. |
| 00:11 | Most hubs, be it on the driven axle or not, will have a snub or spigot for a hub centric fit of the factory wheels. |
| 00:18 | Some will also have features like dust caps to seal the opening to the greased wheel bearing, keeping grease in and dirt out. |
| 00:26 | If we're fitting different sets of wheels to our vehicle, the centre bore, being the centre hole in the middle of the hub, needs to be at least as big as the spigot, otherwise the wheel won't be able to sit flush with the mounting surface. |
| 00:40 | While lug centric only wheels are out there, they tend to be rarer and they aren't really ideal for performance applications. |
| 00:48 | Mostly we want to retain the hub centric fit, as this is stronger and limits vibration, with better alignment compared to the centring of the wheel on the lugs alone. |
| 00:58 | While some aftermarket wheels are made specifically for certain car models, so will have the correct centre bore size, more commonly the manufacturer will use a relatively large size to ensure that can be mounted to the widest range of vehicles. |
| 01:14 | So, if the centre bore of the wheel is bigger than the hub spigot, then we can use a hub centric ring or spigot ring to take up this gap and provide this alignment. |
| 01:24 | We cover this in more detail in the mounting module so check back if you need a refresher but put simply, they're available in plastic and aluminium. |
| 01:33 | Plastic is usually the cheaper option and works great for most applications, while preventing any corrosion causing the wheel to stick in place. |
| 01:43 | Aluminium is necessary where extreme temperatures of the hub from the brakes can damage the plastic ring, like in endurance racing for example. |
| 01:51 | These can cause the wheel to stick on from corrosion with contact of dissimilar metals, but a small amount of anti seize helps here and it tends not to be an issue for racecars where the wheels are removed often. |
| 02:05 | Centre bore measurements are usually expressed in millimetres and are generally in the range of 50-80mm for performance applications but can be up to 120 or more for larger vehicles. |
| 02:17 | So, for example if our wheel had a centre bore of 73.1, but the hub spigot outer diameter was 67.1, we need a ring with a 67.1 inner diameter and a 73.1 outer diameter. |
| 02:33 | Clearly, the size of the centre bore possible on a wheel will depend on the PCD among other things, as this will limit the amount of space available. |
| 02:42 | The last thing to note is really just an aesthetic feature. |
| 02:46 | Most wheels will come with a centre cap, which should attach to the centre bore in some way or another. |
| 02:52 | While centre caps can prevent dust from entering the centre bore, they aren't often used in motorsport, as they're generally just an unnecessary feature that'll get in the way and have the tendency to get lost. |
| 03:04 | Chances are you'll want them on your street car though, but there's not too much to consider here, as they'll come with your wheels and won't cause any issues unless a part of the hub protrudes very far out the centre bore. |
| 03:16 | To summarise the main points here, the centre bore is a hole in the centre of the wheel. |
| 03:21 | This needs to fit over the spigot of the hub in order for the wheel to be mounted. |
| 03:26 | While some wheels will have the correct size centre bore, more commonly it'll be oversized to accommodate a wider range of vehicles. |
| 03:34 | In this case we need to use a hub centric ring to take up this gap and provide proper hub centric alignment. |
