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'Race Studs 101'

It is essential that you select the correct size nut or stud for your application. If you are unsure of what you need please consult an expert familiar with your application and the components you have on your car. The following are some of the dimensions and parameters that you need to understand about your specific application before you purchase wheel fasteners from ACS.

Type: Stud & Nut or Wheel Bolt.
Most racing and performance applications use studs and nuts. To facilitate faster & easier wheel changes at the track or autocross, many are switching from their OE wheel bolts to stronger, more convenient studs & nuts. If you plan to install wheel spacer, stronger wheel studs are an absolute must. Additionally
some car clubs now require that you use steel nuts and steel studs if you are going to track your car.

Seat: Taper, Radius or Flat.
There are generally 3 types of seats found on OE, aftermarket and racing wheels. Tapered/Conical, Radius/Ball or Flat.
Tapered seats are common on afermarket wheels and US & Japanese cars. These seats are usually a 60* conical seat. This is the only angled type seat we currently manufacture.

Radiused or Ball seats are, as the name suggests, ground on a specific radius suitable only for wheels with that exact same radius seat. This type of seat is common on OE German wheels. Mercedes often use a 12mm radiused seat, VW/Audi use a 13mm seat and Porsche uses a 14mm radius seat.


Wheel bolt or stud diameter and thread pitch are the most important factors to selecting the proper studs and nuts. A hub with an M12 x 1.5mm theaded hole with accept ONLY a stud with a 12mm diameter shaft and a 1.5mm thread pitch.

Understanding thread dimensional nomenclature:
Often you will see studs and nuts listed with a dimension such as M12x1.5
The "M12" means that the stud or bolt shaft outer diameter (O.D.) is 12mm

The "1.5" designates the thread pitch, which is the distance between threads.
This is vehicle specific and must be checked.


For ACS "Track-Studs", length is defined as the total length of the stud shaft which includes the total length of both threaded and blank areas on the shaft.
The length is usually the dimension that give people the most difficulty. This is because there are many factors which will factor into determining the optimum stud length for your application. Some of these factors include, wheel center design, use of wheel spacers, nut depth, wheel center thickness, etc.

Hex or "Wrench Head" :

The size of the wrench you will need to use to fasten the nut or bolt. We make and sell the most common 17, 19 and 21mm styles.


Note, please be aware of any other specifics such as open or closed ended nut, surface finish, alloy, installation socket, rounded "bullet nose" etc.


The fitting of after market racing wheels can require a different style of nut or bolt in terms of seat, shaft length (due to the wheel being thicker/thinner where the bolt goes through) and sometimes a narrow head depending on the type of wheel.
eg: Porsche/Audi/VW OE wheel use a spherical seat wheel, while common aftermarket wheels such as BBS often require a conical seat bolt or nut. Please make sure you are aware of your wheel's requirements beore placing an order.

The list to the right is a guide only, always check the specification of your application to confirm.

Dealer info.

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