Spark Exhaust Bent Tube 30° Ø 54 × 1.0 mm Stainless Steel Universal G9107

Fifty-four millimetres through thirty degrees. A collector-section diameter, in the angle that reconciles two fixed points at either end of a long run.

Key Features

• Mandrel-formed 30° bend, AISI 304 stainless steel.
• Ø 54 mm outside, 1.0 mm wall thickness.
• Straight tangents at both ends for cutting and welding.
• Matches Spark's 54 mm straight tube, article G9003.
• Spark part number G9107, made in Mantova, Italy.

Two Fixed Points and a Bend Between Them

On a four-cylinder build almost nothing about the exhaust is free. The collector leaves the engine where the header geometry puts it; the silencer has to arrive at a mount the frame decides. Everything between is the fabricator's problem, and a shallow bend is the tool for it.

Thirty degrees changes direction little enough that the run still reads as a straight line and enough to move the far end by a useful amount over half a metre.

Angle Against Length

The further the silencer is from the bend, the more a small angle moves it. A thirty degree deviation displaces the end of a 400 mm run by around two hundred millimetres — which is why a shallow bend early in a system has more effect than a sharp one late in it.

Put the correction where it does the most work and the system needs fewer pieces.

Growth in a Long Run

Stainless expands about seventeen microns per metre per degree. A metre of pipe going from cold to five hundred degrees grows more than eight millimetres, and a bend is where that growth turns into a bending load rather than a sliding one.

One sliding joint per run absorbs it. A system welded solid at both ends cracks at a tangent weld, usually within a season.

Where the Mount Goes

Not on the curve. A bracket welded to the outside of a bend puts a hard point on the part of the tube that is already thinnest and most stressed. Weld the tab to a straight section and let the bend float.

Clamping It

Only on the tangents, and only with soft jaws. Fifty-four millimetres of one millimetre wall takes a permanent set from bare vice jaws in seconds, and an oval end is what stops the next joint going together.

Ordering

One bend per article. Available in 30°, 45° and 90° at this diameter.