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Crank Installation and Removal- Square Spindle Type

This article will discuss the removal and installation of cranks from square spindle bottom brackets. Crank pullers are used for two basic crank types: the square spindle type arms, and the splined type spindle arms. Figure 1 below is a crank with the bolt removed. The square spindle can be seen inside the square fitting in the arm. Figure 2 shows a bottom bracket bearing unit with square spindle.

Square type crank
Figure 1. Crank without bolt showing square hole and square spindle end

Square type bottom bracket spindle
Figure 2. Common square spindle in a bottom bracket bearing assembly

For the splined Shimano® Octalink and ISIS Drive® type cranks see Spline Cranks.

Typical Tools and Supplies Required:

  • Crank bolt wrench: typically 8mm hex wrench for newer bikes, such as HR-8
  • 14mm or 15mm socket and driver (older bikes), or Park Tool CCW-5 for 14mm size bolt head or 8mm hex cap screw
  • Crank puller- Park Tool CCP-22 or CWP-7
  • Adjustable wrench
  • Rags
  • Grease such as PPL-1
  • Torque wrench, if available, such as TW-2 or TW-6, and correct socket bits, such as the SBS-1 for crank bolt/nut

Cranks connect the pedals to the bottom bracket spindle. The arms are pressed tightly to the bottom bracket spindle. Cranks must be removed from the spindle to service the bottom bracket bearings. On some models of cranks, the cranks must be removed to replace the chainrings.

One-Key Release ("self extracting")

Some cranks are sold with a "one-key release" or "self extracting" system (Figure 3). No crank remover is required. Leave the retaining ring ("dust cap") in place and turn the crank bolt counter-clockwise.

For more detail, see Self-Extracting Crank Systems.

 

One-Key-Release System
Figure 3. One-key system with pin holes in retaining cap

 

Crank Removal (Square Spindle Type)

The video below provides a visual overview of the removal process:

 

Procedure:

a. Shift chain to largest chainring to protect hands against chainring teeth.

b. Look for bolt or nut at end of crank in line with bottom bracket spindle. If no bolt is visible, remove dust caps (Figure 4). Some caps pry out and some thread out. NOTE: If the bike has a one-key release system, leave this cap in place. A retaining ring surrounds the bolt. Simply turn the center bolt counter-clockwise to remove arm of one-key release system.

Dust cap
Figure 4. Dust cap hiding bolt beneath

c. Inspect for bolt or nut (Figure 5, 6 and 7). Turn counter-clockwise to remove. Inspect inside arms for washers. Remove washers if present.

Hex head crankbolt
Figure 5. Hex head bolt

Socket head crank bolt
Figure 6. Socket head bolt

Nut type
Figure 7. Crank nut on threaded spindle stud

d. Before installing crank puller into crank, turn puller nut away from internal driver as much as possible. If puller nut happens to unthread from internal driver, thread it back on only 3-4 turns.

e. Thread large external thread of puller (nut) into arm, taking care not to cross thread. Tighten puller nut into crank using wrench (Figure 8). If puller nut will not thread into arm, or if threads in arm are stripped, see Removal of Cranks with Damaged Threads.

Secure nut into arm
Figure 8. Secure puller nut into crank

f. Thread internal driver into puller nut. Using handle or adjustable wrench, tighten driver until crank is loose on spindle (Figure 9). Pull arm from spindle and unthread both parts of tool from arm. Use care not to skin knuckles when removing tool.

 

Turn center thread to remove
Figure 9. Turn handle to pull arm from spindle

g. Repeat process on other crank.

 

Crank Installation(Square Spindle Type)

 

The video below provides a visual overview of the installation process:

Cranks are pressed tight onto the tapered square spindle. The square spindle is made with a slight upward sloping taper. The crank square fitting also has a slight taper (Figure 10). The crank bolt or nut acts as the pressing tool and forces the arm up the slope of the spindle. The bolt or nut must be tight enough to keep from loosening, but not so tight that the spindle splits and damages crank. If possible, use a torque wrench. See Torque Recommendations.

Spindle to crank fit
Figure 10. The square hole and square spindle end

Aluminum cranks typically do not require lubrication of this press fit. Aluminum by its nature is self-lubricating as it is covered with a thin layer of oxidation. Adequate torque is typically enough to keep arms from creaking.

 

a. Wipe both sides of spindle and inside crank mounting holes with a rag.

b. Grease under head and threads of both bolts or nuts.

c. Install right crank onto right side of spindle.

d. Thread crank bolt/nut to spindle.

e. Tighten crank bolt/nut to manufacturer's recommended torques (Figure 11).

Tighten crankbolts
Figure 11. Fully tighten crank bolt or nut

f. Grease threads of dust cap (if any) and install snug.

g. Install left crank onto left side of spindle with arm pointing opposite direction of right side arm.

h. Install crank bolt/nut and tighten.

i. Grease threads of dust cap (if any) and install snug.