Trim

Fixed or reclinable seat

A fixed bucket seat holds the body best and weighs less, but getting in and out is harder and the backrest angle is set by the mounting. A reclinable seat trades some support for an adjustable back and easier access, which suits a car used every day or one that carries passengers. Shell shapes differ widely between models, so sit in the seat you plan to buy if you can.

Seat rails

Seat rails have to suit both the car and the seat. Fixed buckets are usually side-mounted, bolted through brackets on the sides of the shell, while many reclinable seats bolt to the rail from underneath. Seat makers build rails by car for their own seats: Bride's FO type rails are for side-mount fixed buckets and its RO type for its reclining seats, and Recaro makes base-frame rails for its own. Low-position rails sit the driver lower, for more headroom with a helmet on. Check the rail's listing for the seats it accepts and for your car's model code and drive side.

Harnesses and competition

Seats and harnesses for competition carry FIA homologation labels: seats to FIA 8855-1999, valid for five years from manufacture, or FIA 8862-2009, valid for ten; harnesses to FIA 8853-2016. The label shows the date the product is valid until, and each organiser decides which labels it accepts and for how long, so check your series' rules before buying. A harness also needs a seat with harness slots and shoulder-strap anchorages at the right height behind the seat, which in most cars means a harness bar or a roll cage.

Steering wheels and boss kits

An aftermarket steering wheel fits through a boss kit (hub adapter) made for that car's steering column, such as those from Works Bell. Most wheels bolt on with six bolts on a 70 mm or 74 mm PCD, so check that the boss kit or quick release takes your wheel's pattern. A quick release adds length between wheel and column, which a short boss kit can take back. Replacing the original wheel removes the driver's airbag, and the rules on that differ by country: check them before fitting.

Shift knobs and trim

Shift knobs screw on with a thread that differs between makers and models, and some cars need an adapter, so choose by car. Floor mats, pedals and trim panels are made for one chassis, and often for left- or right-hand drive only.