Quilting and stitching in a car interior: diamond, flutes or plain

What quilting is

It is a seam that runs through the leather and a layer of foam beneath it. So the thread doesn’t tear the foam, the foam has a fabric bonded to its back. Sailrite, which sells it, explains that this backing is there to hold the stitches when sewing pleats or channels, and Albrights, another upholstery supplier, that its knitted backing stops the thread pulling through the foam.

Where the stitching runs, the leather is drawn in; between the seams, the foam pushes it out. That relief is the quilting.

Diamond, flutes or plain

The diamond is the pattern makers keep for their most elaborate interiors. Bentley puts “Diamond-in-Diamond” quilting on the seats of its Mulliner versions, and Porsche’s leather package for the 911 Targa quilts the centres of the front and rear seats and the door panels.

Parallel flutes, or channels, are the other great pattern: more restrained, and the one Sailrite shows how to sew with the same foam. And then there is plain, which lets the leather speak.

Thread colour

The thread can match the leather or contrast with it. Porsche does both: on the 911 S/T the quilting is stitched in a contrasting silver, while the decorative stitching of the Heritage package is tone on tone.

In contrast, the pattern reads from across the street; tone on tone, you notice it only through the relief.

Settled before sewing

Sailrite points out that the needle leaves a permanent hole in leather. A seam you don’t like can’t be unpicked without trace, so the pattern, its size and where it starts and stops are fixed on the panel before any sewing.

Perforation and quilting

Quilting lives alongside perforation. Bentley introduced a new diamond perforation pattern on its 2024 Mulliner models, and a US patent describes perforating leather while leaving unperforated bands along which the diamond stitching is later sewn.

If the seat is ventilated, the perforation isn’t just decoration: it is where the air comes out. It is worth planning together with the quilting.

What to decide before sewing

With these answered, the quilting is sewn once, and right:

Pattern

Diamond, flutes or plain? How large?

Placement

Seat centres only, or backrests, door cards and bolsters too?

Thread

Matching or contrasting? Which exact colour?

Perforation

Is there any? Is the seat ventilated?

Sample

Can you see a sewn sample in the chosen leather and thread?