Trademarks other than those owned by BSn used throughout this manual belong to the owners and are used here in a purely editorial fashion.
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:
The table includes common torques for steel screws.
|Tightening Torques (Untreated Screw)|
|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|
|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
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 Bolt||4-6 Nm (3-5 lb.ft)|
|Pedal into crank||35-40 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)|
|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)|
|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|
Copyright © 1998 Basis Systeme netzwerk/Munich Cycling Resources