Sliding friction material

A sliding friction material including sliding surfaces,

• wherein the sliding friction material is configured such that the sliding surfaces are only partially in contact with a sliding surface of a sliding partner material at a beginning of use and an area in contact with the sliding partner material gradually increases over time to full-area contact during an initial running-in period,
• wherein a relative angle of the sliding surfaces of the sliding friction material to the sliding surface of the sliding partner material before the initial running-in period is 1 to 20 minutes,
• wherein the surface of the sliding friction material has a circumferential groove,
• wherein the sliding surface of the sliding friction material includes a land which is configured and arranged to come into contact with the sliding partner material first, and an axial width of the land is 0.1 to 0.7 mm,
• wherein the sliding friction material comprises 5 to 40 wt % of phenolic resin relative to the whole sliding friction material, and further comprises 30 to 80 wt % of carbon material, 5 to 40 wt % of inorganic fibers or inorganic particles, and the total amount of the above-mentioned components being 100 wt % or less relative to the whole sliding friction material.

A combination comprising a synchronizer ring and a partner gear,

• wherein the synchronizer ring includes a base material and a sliding friction material including sliding surfaces, the sliding friction material being disposed on the base material,
• wherein the partner gear includes a conical surface which slides against the sliding friction material of the synchronizer ring,
• wherein the sliding friction material is configured such that the sliding surfaces are only partially in contact with a sliding surface of the conical surface of the partner gear at a beginning of use and an area in contact with the sliding partner material gradually increases over time to full-area contact during an initial running-in period,
• wherein the sliding surface of the sliding friction material includes a land which is configured and arranged to come into contact with the sliding partner material first, and an axial width of the land is 0.1 to 1.0 mm.