An electric resistance welded steel pipe for manufacturing a hollow stabilizer has a Rankford value in a pipe longitudinal direction of from 0.7 to less than 1.0. The electric resistance welded steel pipe is subjected to cold bending and then to a heat treatment including quenching and tempering to manufacture a stabilizer. The cold bending is cold rotary draw bending. When bent with a bend radius of from 1.0 times to 3.0 times an outer diameter of the pipe before cold bending, a flattening ratio is from 0% to 10%, a thickness reduction rate on a bending outside and a thickness increase rate on a bending inside are from 0% to 10%, and additionally, a circumferential length change of a bending center portion is from 0% to 10%. A Vickers hardness of the stabilizer after the heat treatment is adjusted to from 400 HV to less than 580 HV.

It is disclosed a system for leveling of load between front and rear wheels on a trailer, consisting of a rubber-torsion axle FIG. D with longitudinal members 4 which center is pivotally mounted to the torsion axles pivot arms 7. With a wheel in each end of the longitudinal members, the system is working as a complete bogie unit which has vertical spring motion effect, as shown in FIG. B. For trailers with no need of such spring motion effect, the longitudinal members can be mounted direct to the inner tube 9 in the rubber-torsion element.

Provided is a coil spring manufacturing method. In the coil spring manufacturing method, a coil spring of a vehicle suspension member is immersed in a fluidized bed in which powder coat is fluidized for coating. The fluidized bed includes a vertical stream area in which the powder coat moves upward and downward. The coil spring is immersed in the vertical stream area of the fluidized bed while an end coil of the coil spring faces upward, and is periodically subjected to a relative movement with respect to a direction containing components vertical to a central axis of the coil spring in relation to the vertical stream area.

A stabilizer includes a stabilizer bar and a rubber bush. The stabilizer bar includes a bar body made of a steel and a coating film covering the bar body. The coating film is formed on the surface of the bar body by using a resin having a water contact angle of more than 65°. By performing surface treatment for reducing the contact angle of the coating film present on an attachment part, the contact angle of the attachment part is changed to 65° or less. A pre-cured liquid adhesive agent is applied to an inner surface (adhesion surface) of the rubber bush. After a region including the attachment part of the stabilizer bar is heated, the rubber bush is overlaid on the attachment part. The adhesive agent is cured in a state where the rubber bush is pressed.

The invention provides a production method for stabilizers which produces with high productivity in a compact production line, without tempering. The production method for stabilizers of the invention includes: forming a steel bar material containing at least C: 0.15 wt % to 0.39 wt %, Mn, B and Fe into a product shape by bending; and quenching the bent steel bar material in a medium having a heat transfer coefficient higher than or close to that of water.

In a method for producing a spring leaf (2) for a leaf spring, in particular a parabolic spring or suspension spring, wherein the spring leaf (2) comprises two end regions, a central region, a top side which is subjected to tensile stress in the operative state, and a bottom side (1) which is subjected to pressure in the operative state, at least one hole (3) is introduced into the bottom side (1). The bottom side (1) is peened locally in the region around the hole (3).

A hollow spring member and hollow spring member production method can be provided, which can save the time and energy necessary for carburization, thus requiring no dedicated carburizing furnace or the like for carburization, and further can make the interior space of a steel tube a rust-prevention atmosphere. A hollow stabilizer for a vehicle includes a steel tube sealed at one end and another end thereof and a carburizing gas sealed in the interior space of the steel tube.

There are provided an electric resistance welded steel pipe for producing a high strength hollow stabilizer excellent in fatigue resistance and a high strength hollow stabilizer. In an electric resistance welded steel pipe (5) for producing a hollow stabilizer, an internal weld bead cut portion (30) has a three-peak shape and a depth (H) of a trough portion (30a) of the three-peak shape is 0.3 mm or less and an angle () formed by a central portion in the circumferential direction of the trough portion (30a) and the top of right and left peak portions (30b, 30c) located on both the right and left sides of the trough portion (30a) is 160 or more and less than 180.

This spring used for a suspension device for a vehicle is provided with: a metal wire material which constitutes a spring section and which has a cover layer provided on the surface thereof; and a seat section which is subjected to a load acting on the spring section, is formed from an elastically deformable material, and is bonded to the cover layer by an adhesive. The difference between the hardness of the seat section and the hardness of the adhesive is greater than the difference between the hardness of the adhesive and the hardness of the cover layer.

This spring used for a suspension device for a vehicle is provided with: a metal wire material which constitutes a spring section and which has a cover layer provided on the surface thereof; and a seat section which is subjected to a load acting on the spring section, is formed from an elastically deformable material, has a groove section into which the wire material fits, and is bonded to the wire material by an adhesive. The minimum thickness of the portion of the adhesive, which protrudes from the groove section, is greater than or equal to the thickness of an adhesion layer formed in the groove section.