Tube OD
Centerline Radius
2.00"
2.25"
2.38"
2.50"
2.75"
3.00"
3.50"
4.00"
4.500"
5.00"
6.00"
7.00"
8.00"
9.00"
10.00"
1.250"
412525
1.380"
413825
1.500"
415020
415025
415030
415040
1.625"
416320
416325
416330
416340
1.750"
417520
417525
417530
417540
417550
417560
1.875"
418820
418825
418830
418840
418850
418860
2.000"
420020
420025
420030
420035
420040
420050
420060
2.125"
421325
421330
421335
421340
421350
421360
2.250"
422522
422530
422535
422540
422560
2.375"
423838
423830
423835
423840
423860
2.500"
425025
425030
425040
425050
425060
2.625"
426340
2.750"
427527
427540
3.000"
430030
430040
430060
3.500"
435035
435070
4.000"
440040
440080
4.500"
445045
445090
5.000"
450050
450010

Nesting mandrel bends is as simple as adding or subtracting the tube O.D. from the CLR (centerline radius). A 2.00" O.D. U bend with a 3.0" CLR. will nest inside a 2.0" O.D. 45 degree bend with a 5.0" CLR. The illustration shows the measurement from the inner radius to the outer radius.

That measurement must be equal to or greater than the tube size you are working with.

O.D. (outside diameter) is the standard means of measuring tubing.

I.D. (inside diameter) is typically used to describe pipe sizes.

To find the I.D. of tubing double the wall and subtract it from the O.D.

2.00" - (.065" + .065") = 1.870"

As you can see from the equation above 1-7/8" tubing (1.875) will not slide into
2" 16 gauge (.065) tubing.

The centerline is the absolute center of the tube.

Just as a race track is measured some distance off of the wall to accurately reflect the usable track surface, the primary tube lengths of a header are calculated using the centerline of the tube.

1008 (Mild) Carbon steel

CREW - Cold Rolled Electronically Welded

AKDQ - Aluminum Killed Drawing Quality

304 stainless steel is the most common stainless alloy tube used in aftermarket exhaust.
To insure quality and consistency we use only A-269 spec. 304 fully annealed, seam welded tubing from Rath-Gibson mills.

304 / 304L is a non-magnetic stainless from the Austenitic family of alloyed steel containing 18% Chromium & 8% Nickel.
It does almost everything you ever wanted your stainless to do and for a relatively low price. It has high strength, ductility, excellent weldability, resistants to corrosion, and polishes to a mirror finish.

304 stainless does have some limitations, it is not well suited for extreme temperatures such as those produced by turbo charged engines. Although 321 stainless is more expensive, the resistance to fatigue at high temperatures makes it a better choice in some applications, saving you money in the long run.

321 Stainless Bends are stocked in U's and 1D 90's only.

Due to the high cost of material J's, 45's and wide radius 90's are only available by special order.

321 stainless steel has a small percentage of titanium added as a stabilizer, giving it better corrosion resistance, vibrational stability and a higher resistance to heat fatigue than 304 stainless.

Lighter gauge 321 tubing such as 18ga. (.049) and 20ga. (.035) is commonly used for aircraft exhaust

16 gauge (.065) 321 tubing is recommended for turbo-charged applications.

We stock tubing in three wall thickness or gauges.

16 gauge (.065")

18 gauge (.049")

20 gauge (.035")

Mild steel tubing is available in:
16 gauge (.065") and 18 gauge (.049").

Stainless steel tubing is available in:
16 gauge (.065") and 18 gauge (.049").

Some 304 & 321 stainless bends are also available in 20 gauge (.035")

Centerline Radius (CLR) bending is an industry standard.

Leg lengths vary  based on the bend radius and tube size. 

45 - bends with a CLR up to 4" have
6" legs (
+/-.250"tolerance)  

45 - bends with a CLR greater than 4” have 8” legs (+/-.250"tolerance)

Call for leg lengths on 4.0" to 5.0" mild and 3.5" to 5.0" stainless.

Tangent is the point at which the straight section (leg) of the tubing meets the bent section.

Overall Width is a easy way to visualize the bend you need to order.

The prefix 4 denotes a 45 degree bend in our part numbering system.

Use the buttons above the P/N example to see how we build a part number.

Use the buttons on the left to learn more about the specs and terminology.