Wheel-Size.com - Entries for the category Wheel Terminology Explained

Offset

info@wheel-size.com (admin) — Wed, 21 Feb 2018 10:37:58 +0000

Offset is the location of the flat mountin surface of a wheel relative to the wheel's centerline. Negative offset means that the mounting surface is toward the center of the car, postive offset means that it's toward the ouside of the car, or the wheel is "pulled in" toward the center. Offset affects many things other than just whether the wheel has the appearance of "sticking out" past the fender. The wrong offset can causerubbing problems when the suspension is compressed of the wheel is turned. Offset affects the steering geometry's scrub radius, possibly leading to problems with torque steer or self-centering characteristics.

Offset also affects the suspension's motion ratio, which directly determines the effective spring and damper rates. Potentially, in a very heavily loaded vehicle, or with extreme changes in offset, wheel bearing life can be affected, but this is more often talked about by truck people than by small car enthusiasts. It is very, very important that the proper offset wheel be used.

While not directly a matter of offset, brake caliper clearance is a related issue. If you have, or plan t have big brakes on your car, be sure that you wheels that you are going to use, will fit over the calliper. Spacers are available to solve the problem if they don't, but it is best to get a wheel with enough dish to met your offset specs and still fit your brakes. Consulting the wheel and brake manufacturers ahead of time is wise. Many aftermarket brake companies even have templates of their brakes available that you can easily check against any wheel.

An average deviation of 5 mm is acceptable.

A positive (+) offset is when the mounting surface is shifted from the centerline toward the front or outside of the wheel.
A negative (-) offset is when the mounting surface is toward the back or brake side of the wheel's centerline.
A zero offset is when the mounting surface is in the plane of the centerline.

Negative offsets are considered aggressive, since the mounting surface of the wheel will "hit the hub of your car much quicker, hence the wheel will stick out more."

Centre Bore

info@wheel-size.com (admin) — Wed, 21 Feb 2018 10:37:58 +0000

For most road wheels, the weight of the car is transmitted from the spigot, (the bit the centre of the wheel that protrudes from the hub), to the centre hole in the wheel. The job of the wheel studs or wheel bolts is to hold the wheel in place over the spigot. It is therefore very important that the centre bore of the wheel matches the spigot size of the car's hub.

It is possible to use spigot rings to adapt the size of the centre bore, and spigot rings are available in all the useful sizes from places like eBay. Of course this only works if the wheels have a larger centre bore than the car's spigot ring. If the wheel's centre bore is too small, then the only way they could be made to fit would be if they were machined, (ie bored out), which is so costly it makes it pretty much impractical.

Bolt Pattern/Pitch Circle Diameter (PCD)

info@wheel-size.com (admin) — Wed, 21 Feb 2018 10:37:58 +0000

A wheel's PCD is usually displayed after the number of studs, separated by a slash. Hence a 'pcd' of 5/120 means that the wheel has five studs, and a pitch circle diameter of 120mm. A 'pcd' of 4/114.3 means the wheel is four stud with a pitch circle diameter of 114.3mm.

Measuring the PCD of a 5 stud wheel is a tricky business. It is much easier to determine the PCD by checking the manufacturers' original specifications or by checking our PCD reference guide for each model. It is possible to roughly measure the PCD of a 4 stud wheel, as the pitch circle diameter is the same as the distance between two opposite bolt centres.

Different cars have different PCDs, but often similar cars within the same manufacturers group have the same PCD. Many of the VW Golf-sized cars in the VAG range have the same PCD and other wheel dimensions, meaning that wheels are often interchangeable between these cars.

The PCD has to do with the sizing of the diameter of a circle that the lug holes create. The center of every bolt/lug lies on the circumference of a circle that they create. PCD is usually measured in millimeters (mm).

For example, the 5x114.3 (or 5x4.5 in inches) PCD that our 3G TLs use means that there are 5 lug holes, with a pitch circle diameter of 114.3mm or 4.5in.

What are hub centric rings?

alexander.zagvozdin@gmail.com (Alexander) — Wed, 21 Feb 2018 10:37:58 +0000

Before we begin, you should know that hub centric rings may also be called either..

center rings
centre rings
centric rings
centering rings
spigot rings (in the UK mostly)
hub rings
fitment rings
wheel fitment rings
and so on

These are different names for the same thing, in most cases. We'll decide to use the name hub centric rings to describe them in the text/information below.

Example of plastic hub centric rings in the colour red.

Example of plastic hub centric rings in the colour white.

So, shall we solve this "mystery" about hub centric rings, what are they and what are they used for?

Hub centric rings are wheel fitment rings for vehicles and should be used if the center bore of the wheel (the big hole in the middle of the rim) is larger than the center bore of the car's wheel hub (the round offset in the middle of the hub). The hub centric rings will then fill the space required to make a perfect fit, simple as that basically = they convert the rim center bore to a smaller and precise measurement which matches the wheel hub. Notice that this mainly complies with aftermarket wheels or wheels used from other car makes, since OEM wheels usually fits without any rings.

The center bore of a alloy wheel.

A wheel hub from a car.

Hub centric rings mounted directly to the wheel center bore

Hub centric rings mounted directly to the wheel hub

And now you think, why not just fit the wheel without any rings and fasten it with the wheel bolts or lug nuts (whichever are used) when it's "kind of" centric? Well, you could do that, but most cars and wheels of today are designed to be "hub centric", which means they are meant to be mounted only if the rim center bore has the same diameter as the wheel hub.

A hub centric design may also mean that there's a gap around the wheel bolts, etc. The wheel bolts or lug nuts of a hub centric wheel can have a flange that is either coned or flat or rounded, while a lug centric design (the wheel is centered by the lug holes) often has a coned flange regarding the wheel fasteners (bolts or nuts).

So, even if you may fasten the wheel just fine when the car is jacked up (when it comes to hub centric), it will put a lot of stress to the wheel bolts/lug nuts and probably make the vehicle wobble/shake during some, if not all, speeds. This is because a hub centric wheel is held in place (centric) by the wheel hub, while the wheel bolts or lug nuts mainly "clamps" the wheel together with the hub. The wheel hub (not the bolts) should take most of the force put vertically on the wheel.

Hub centric design (newer BMW) - Steel wheel mounted to wheel hub, hub centric rings wasn't required in this case as the diameter was the same

Lug centric design (older VW Beetle) - Steel wheel mounted to wheel hub, no hub centric rings needed because of the older lug centric design

When the wheel bolts or lug nuts are put up for stress, it doesn't only mean the ride will be uncomfortable, but also a safety hazard! Our recommendation is to always use hub centric rings! They are pretty cheap to buy, so that's no excuse if any..

Other things which are good to know about:

Hub centric rings are often made of either plastic or aluminum. Plastic rings (a mix of polycarbonate and ABS-plastic or just polycarbonate or just ABS) are the most recommended to use, since they won't corrode against the metal of either the rim or the hub. If aluminum rings are to be used, be sure to put a thin coat of copper paste or similar grease before mounting them, or you may find it hard to remove them in the future!

Heads up! Remember that plastic rings are made of just plastic, which means they can melt if the temperature gets to high, in example during a "burnout" or something like that, if you race the car at the track! In that case, aluminum rings are a better choice.

Also worth mentioning is that hub centric rings are mostly used with aluminum rims (or other alloy wheels), they aren't that common with steel rims, but if there's a gap and hub centric rings can be used, then make sure to use them! Otherwise buy some steel rims with the correct center bore as the car.

P.S. If the rim center bore where to be smaller though, than the hub center bore, you'll need to machine the rim center bore to a larger size, which is recommended to be done at a workshop.

So, this article has now "come to an end" so to speak, hope you've enjoyed reading it and escpecially learned something about hub centric rings. Spread the knowledge for a safer road ahead!

Best regards,
Bolt-pattern.com @ Wheel-size.com

Link to author:
http://www.bolt-pattern.com/

Bolt pattern in metric or inches

alexander.zagvozdin@gmail.com (Alexander) — Wed, 21 Feb 2018 10:37:58 +0000

The metric unit is the most common one and is today used by both vehicle- and wheel manufacturers, although some may also provide the measurement written in inches. The units in inches is otherwise mainly used in the USA when talking about classic cars, but also regarding newer vehicles and such. You may say that tradition lives on, but one also has to remember that the unit in inches was used for a long time which many got used to, and that USA of course uses inches otherwise as well.

By the way, the units in inches was developed by the SAE (Society of Automotive Engineers), but they too are using the metric units today, officialy.

So, does all of this mean that a bolt pattern in metric is different than a bolt pattern in inches? No! The only thing that differs is the units, provided that the measurement is the same of course.

Look at it like this, 1 inch is equal to 25.4 millimeters, and with that knowledge on your hands you can easily calculate between one another.

For example, a bolt pattern in metric, let's say 5x114.3, is equal to 5x4.5 in inches, because 114.3 divided with 25.4 = 4.5, easy, don't you agree? In the same way we may calculate the following bolt pattern in inches, 5x5, to metric, which will be 5 times 25.4 = 127 (bolt pattern = 5x127).

Vernier caliper set on 25.4 mm which equals to 1 inch.

Bolt pattern conversion chart between metric and inches:

Here's a bolt pattern conversion table below, from metric to inches and vice versa, to make it a little easier and faster to convert to either unit. The most popular measurements (bolt patterns) are included in the list, but if some are missing, you should now know how to convert is yourself with your smartphone calculator or similar (if you've read above)

Bolt pattern in metric	Bolt pattern in inches (SAE)
3-lug bolt patterns
3 x 98 mm	3 x 3.86"
3 x 100 mm	3 x 3.94"
3 x 112 mm	3 x 4.41"
3 x 150 mm	3 x 5.91"
3 x 160 mm	3 x 6.3"
4-lug bolt patterns
4 x 95.2 mm	4 x 3.75"
4 x 98 mm	4 x 3.86"
4 x 100 mm	4 x 3.94"
4 x 101.6 mm	4 x 4"
4 x 108 mm	4 x 4.25"
4 x 114.3 mm	4 x 4.5"
4 x 139.7 mm	4 x 5.5"
4 x 160 mm	4 x 6.3"
5-lug bolt patterns
5 x 98 mm	5 x 3.86"
5 x 100 mm	5 x 3.94"
5 x 108 mm	5 x 4.25"
5 x 110 mm	5 x 4.33"
5 x 112 mm	5 x 4.41"
5 x 114.3mm	5 x 4.5"
5 x 115 mm	5 x 4.53"
5 x 118 mm	5 x 4.65"
5 x 120 mm	5 x 4.72"
5 x 120.6mm	5 x 4.75"
5 x 120.65mm	5 x 4.75"
5 x 120.7mm	5 x 4.75"
5 x 127 mm	5 x 5"
5 x 128 mm	5 x 5.04"
5 x 130 mm	5 x 5.12"
5 x 135 mm	5 x 5.31"
5 x 139.7 mm	5 x 5.5"
5 x 150 mm	5 x 5.91"
5 x 155 mm	5 x 6.1"
5 x 170 mm	5 x 6.69"
5 x 205 mm	5 x 8.07"
6-lug bolt patterns
6 x 114.3 mm	6 x 4.5"
6 x 115 mm	6 x 4.53"
6 x 120 mm	6 x 4.72"
6 x 127 mm	6 x 5"
6 x 139.7 mm	6 x 5.5"
8-lug bolt patterns
8 x 139.7 mm	8 x 5.5"
8 x 165.1 mm	8 x 6.5"
8 x 170 mm	8 x 6.69"
8 x 200 mm	8 x 7.87"

School's out for today, you might say. That's all about bolt pattern in metric and inches, hope you've learned something.