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Fasteners Information
Metric Fasteners
Most of the fasteners used for this vehicle are JIS-defined and ISO-defined metric fasteners. When replacing any fasteners, it is most important that replacement fasteners be the correct diameter, thread pitch and strength.
CAUTION:
Even when the nominal diameter (1) of thread is the same, the thread pitch (2) or the width across flats (3) may vary between ISO and JIS. Refer to “JIS-TO-ISO main fasteners comparison table” for the difference.
Installing a mismatched bolt or nut will cause damage to the thread.
Before installing, check the thread pitch for correct matching and then tighten it by hand temporarily. If it is tight, recheck the thread pitch.
JIS-TO-ISO main fasteners comparison table
Standard Nominal diameter
M6 M8 M10 M12 M14
JIS Thread pitch 1.0 1.25 1.25 1.25 1.5
Width across flats 10 12 14 17 19
ISO Thread pitch 1.0 1.25 1.5 1.5 1.5
Width across flats 10 13 16 18 21
Fastener Strength Identification
Most commonly used metric fastener strength property classes are 4T, 6.8, 7T, 8.8 and radial line with the class identification embossed on the head of each bolt. Some metric nuts will be marked with punch, 6 or 8 mark strength identification on the nut face. Figure shows the different strength markings.
When replacing metric fasteners, be careful to use bolts and nuts of the same strength or greater than the original fasteners (the same number marking or higher). It is likewise important to select replacement fasteners of the correct diameter and thread pitch. Correct replacement bolts and nuts are available through the parts division.
Metric bolts: Identification class numbers or marks correspond to bolt strength (increasing numbers represent increasing strength).
1. Nut strength identification
Standard Tightening Torque
Each fastener should be tightened to the torque specified in each section. If no description or specification is provided, refer to the following tightening torque chart for the applicable torque for each fastener. When a fastener of greater strength than the original one is used, however, use the torque specified for the original fastener.
NOTE:
• For the flanged bolt, flanged nut and self-lock nut of 4T and 7T strength, add 10% to the tightening torque given in the following chart.
• The following chart is applicable only where the fastened parts are made of steel light alloy.
Tightening torque chart
  Strength Unit Thread diameter (Nominal diameter) (mm)
4 5 6 8 10 12 14 16 18
  An equivalent of 4T strength fastener N·m 1.5 3.0 5.5 13 29 45 65 105 160
kg-m 0.15 0.30 0.55 1.3 2.9 4.5 6.5 10.5 16.0
lbf-ft 1.0 2.5 4.0 9.5 21.0 32.5 47.0 76.0 116.0
 
  An equivalent of 6.8 strength fastener without flange N·m 2.4 4.7 8.4 20 42 80 125 193 280
kg-m 0.24 0.47 0.84 2.0 4.2 8.0 12.5 19.3 28.0
lbf-ft 2.0 3.5 6.0 14.5 30.5 58.0 90.5 139.5 202.5
 
  An equivalent of 6.8 strength fastener with flange
*: Self-lock nut 		N·m 2.4 4.9 8.8 21 44 84 133 203 298
kg-m 0.24 0.49 0.88 2.1 4.4 8.4 13.3 20.3 29.8
lbf-ft 2.0 3.5 6.5 15.5 32.0 61.0 96.5 147.0 215.5
 
  An equivalent of 7T strength fastener N·m 2.3 4.5 10 23 50 85 135 210 240
kg-m 0.23 0.45 1.0 2.3 5.0 8.5 13.5 21.0 24.0
lbf-ft 2.0 3.5 7.5 17.0 36.5 61.5 98.0 152.0 174.0
 
  An equivalent of 8.8 strength fastener without flange N·m 3.1 6.3 11 27 56 105 168 258 373
kg-m 0.31 0.63 1.1 2.7 5.6 10.5 16.8 25.8 37.3
lbf-ft 2.5 4.5 8.0 19.5 40.5 76.0 121.5 187.0 270.0
 
  An equivalent of 8.8 strength fastener with flange N·m 3.2 6.5 12 29 59 113 175 270 395
kg-m 0.32 0.65 1.2 2.9 5.9 11.3 17.5 27.0 39.5
lbf-ft 2.5 5.0 9.0 21.0 43.0 82.0 126.5 195.5 286.0
 
*:Self-lock nut