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Bicycle Fastener Torque Specification

The general formula for calculating torque is:
Torque = 0.2 x nominal diameter of screw x load where load is 80% of yield strength. Torque for bolts with nuts may be slightly higher. The load depends upon the friction cooeficient of the screw (and the material into which the fastener is attached) and the depth of the thread. Lubrication and/or platings can effect torque values by as much as 25%. Some platings increase torque and some actually decrease it.

The use of lubricants is especially valuable where steel bolts go into aluminium components. The lubricant helps to prevent galling of the threads on assembly, helps to prevent galvanic corrosion in service and helps with removal. Various thread locking compounds (eg. Loctite) are also lubricants and can help to prevent corrosion and galling of threads. Bear in mind that torques are specified for clean dry threads, by lubricating the threads you increase the axial force for a given torque. Given a wide range of friction cooeficients for different materials in combination with different lubricants the actual tightening torque for a specific fastener can not apriori be defined. Fortunately, in bicycle applications, the torque is not critical (bicycle mechanics have only in the past few years, if at all, started to use torque wrenches).

The torque value to be set depends upon:

  1. Material of the screw
    1. Mechanical properties
    2. Whether the screw is plated and the coating.
  2. Parent material (Al, Steel)
  3. Dry or lubricated threads.
  4. The depth of the thread.
Mechanical Properties of Metric Compared to SAE Fasteners
Class
ISO Grade 4.6 4.8 5.6 5.8 6.6 6.8 6.9 8.8 10.9 12.9 14.9
SAE Grade 1 2 2 2 3 3 3 5 8 n/a n/a
Brinell(HRB)  110-170 140-215 170-245 225-300  280-365 330-425 390 min.
Rockwell(HRC) n/a n/a n/a 18-31 27-38  34-44 40-49
Yield(psi)  45,000 56,000  76,000 76,000 91,000 128,000 153,000  180,000
Tensile(kpsi) 56-78 70-100 85-113 85-99 113-128 142-170 170-200  200-230

The table includes common torques for steel screws.

Tightening Torques (Untreated Screw)
Size Grade
8.8 10.9 12.9
M3 1.37 Nm 1.92 Nm 2.30 Nm
M4 3.1 Nm 4.4 Nm 5.25 Nm
M5 6.2 Nm 6.65 Nm 10.4 Nm
M6 10.5 Nm 15 Nm 18 Nm
M7 17.5 Nm 25 Nm 29 Nm
M8 26 Nm 36 Nm 43 Nm

Specific Bicycle Parts
Vendor Component Torque Comments
Campagnolo Cartridge Bottom Bracket 70 Nm (51.66 lb.ft) Record/Chorus/Athena
Exa-drive sproket retaining ring 50 Nm (36.9 lb.ft) Assumed lubricated (to prevent siezing). Torque here tighten during use, is relatively uncritical beyond "tight".
Crank Bolt 32 - 39 Nm (23.6-28 lb.ft) Crank bolt is lubricated. Campagnolo explicitly states: "ATTENTION: Remove any possible traces of grease from bottom bracket-spindel tapers before installing cranks."
Should the tapers be lubricated (as is generally the case for press fit applications) less torque should be applied.
Chainring Bolts (steel) 10 Nm (7.0-10 lb.ft) Assumed lubricated with an assembly paste
Chaintring Bolts (Al)5 Nm
Setpost binder Bolt4-6 Nm (3-5 lb.ft)
Pedal into crank35-40 Nm (29.5 lb.ft)
Dual Pivot Brake (to frame) 10 Nm (7.38 lb.ft)
Ergopower Controller (to bar) 10 Nm (7.4 lb.ft)
Front Derailleur Mounting Bolt 7 Nm (5.15 ft.lb)
Rear Derailleur Mounting Bolt 14 Nm (11 ft.lb)
Cable bolts 5 Nm (3.69 lb.ft)
Cinelli Spinachi Assembly <1.5 kg.m ( 14.5 Nm or 10.5 lb.ft) Assumed lubricated. The specified value is a Max. Both the coupling to handlebar and to extension should be greased with an assemby paste. The screws should be tightened (to under max. torque) untill movement is blocked.

The following table is based upon fasteners being free of excessive rust, dirt and lubricants, and that the threads have been properly formed within standard tolerances.

Common Torques of Bicycle Parts (Lubricated)
Torque Torque
Stem binder bolt 11-13.5 Nm (100-120 lb.in) Brake levers to handlebars 8.5-10.5 Nm (75-95 lb.in)
Handlebar binder 16-22.5 Nm (145-200 lb.in) Brake cable binders 6-8.5 Nm (55-75 lb.in)
Controls to frame 4-5 Nm (35-45 lb.in) Straddle nut (yoke) 5.5-8 Nm (50-70 lb.in)
Front shifter to frame 2.5-5 Nm (25-45 lb.in) Brake pads to brake 5-8.5 Nm (45-75 lb.in)
Front shifter to cable binder 2.5-5 Nm (25-45 lb.in) Brake dome nut 5.5-9 Nm (50-80 lb.in)
Rear shifter to frame 13.5-16 Nm (120-145 lb.in) Crank bolt 28-34 Nm (250-300 lb.in)
Rear shifter cable binder 2.5-5 Nm (25-45 lb.in) Chainring bolts 11-13.5 Nm (100-120 lb.in)
Jockey wheel bolt 2.5-5 Nm (25-45 lb.in) Nutted front hub 20 Nm (180 lb.in)
Seat binder bolt 4-6 Nm (35-55 lb.in) Nutted rear hub 34 Nm (300 lb.in)
Caliper brakes to frame 11-13.5 Nm (100-120 lb.in) Waterbottle cage 2.5-4 Nm (25-35 lb.in)
Cantilever brake to frame 5-6.5 Nm (45-60 lb.in) Fender to frame bolts 5.5-6 Nm (50-60 lb.in)
Cantilever brake link wire 4-5 Nm (35-45 lb.in) Toeclips to pedals 2.5-5 Nm (25-45 lb.in)
Kickstand 6.5 Nm (60 lb.in)
Conversions
Kg.cm 0.0981 Nm
Kg.m 9.81 Nm
lb.in 0.083 lb.ft 0.113 Nm
lb.ft 12.0 lb.in 1.356 Nm
Nm 8.851 lb.in 0.738 lb.ft
kpm 7.23 lb.ft 86.8 lb.in 9.807 Nm


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