Can You Fit a New Steering Wheel and Quick Release Without a Boss Kit?

Steering wheel fitting guide

It is one of the questions we are asked most: can I fit an aftermarket steering wheel and a quick release straight onto my car, without a boss kit? The answer is no. Every car needs a boss kit, sometimes called a hub adaptor, made for its steering column.

This guide explains why, how the three parts fit together, when you can leave the quick release out, and what to check on bolt patterns and airbags before you order anything.

An aftermarket wheel will not bolt to a standard steering column on its own
The boss kit is made for your car and matches its column splines
The order is column, boss kit, quick release (optional), then wheel
Most MOMO, Sparco and OMP wheels use a 6 x 70 mm bolt pattern
Removing a wheel with a driver airbag means losing that airbag

A black and silver B-G Racing quick release hub beside its silver splined boss on a glass shelf in the GSM Performance showroom, with Sparco boxes behind — A B-G Racing quick release, both halves, on the glass shelf in our showroom.

What is on this page

Why a boss kit
How it fits
Without a quick release
Bolt patterns
Airbags

Why you need a boss kit

The end of your steering column is made for the factory wheel. The number and size of the splines, the thread on the retaining nut, and the space around it for the indicator stalks and the clock spring all differ from car to car. An aftermarket wheel has none of that; it only has a ring of bolt holes in the middle.

The boss kit bridges the two. One side is splined to fit your column. The other side is drilled with the bolt pattern the wheel or quick release uses. It also sets how far the wheel sits from the dash, which affects your reach to the stalks and the clearance for your knees.

How the parts fit together

From the car outwards, the stack is:

The boss kit, bolted or pressed onto the column, made for your car.
The quick release, if you want one, bolted to the front of the boss kit.
The steering wheel, bolted to the quick release or straight to the boss kit.

A quick release is a universal part. It does not replace the boss kit, it sits in front of it, so you need both.

A Sparco steering wheel, a Sabelt steering wheel and steering wheel boss kits on glass display shelves in the GSM Performance showroom — Wheels and boss kits on the steering display in our showroom.

Can you leave out the quick release?

Yes. The wheel bolts straight to the boss kit, which keeps the wheel closer to the dash and saves a little cost. A quick release earns its place when getting in and out is awkward, such as a car with a roll cage and a fixed back bucket seat, or when you want to take the wheel with you when the car is parked.

Bear in mind that a quick release adds depth, pushing the wheel towards you. In a car where you already sit close to the wheel, that can matter, so it is worth checking your driving position before you decide.

Bolt patterns: check before you buy

The ring of bolts that holds the wheel on is called the PCD. Most wheels from MOMO, Sparco and OMP, and many others, use six bolts on a 70 mm circle, written 6 x 70 mm. Some wheels, including many from Nardi, use 6 x 74 mm, and older classic bosses from makers such as Mountney and Moto-Lita use larger patterns. Adaptors exist to join different patterns, but it is simpler to buy parts that match.

Check the horn too. Many competition wheels come without a horn push, and the boss kit or quick release needs to carry the horn contact through if you want one working.

Cars with a driver airbag

If your car has a driver airbag, it lives in the factory wheel, and it is lost when that wheel comes off. Disconnect the battery and leave the system to discharge before you start, and have the airbag handled properly, not left hanging off the column. Garreth’s advice is to think about what losing the airbag means for how you use the car before you buy the parts. Our brand guides, such as the B-G and MOMO Volkswagen hub guide, list the boss kits for each car.