|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 1. Crank without bolt showing square hole and square spindle end
Typical Tools and Supplies Required:
*Crankbolt wrench: typically 8mm hex wrench for newer bikes, such as HR-8
*14mm or 15mm socket and driver (older cycles), or Park Tool CCW-5 for 14mm size bolt head or 8mm hex cap screw
*Crank puller- Park Tool CCP-22 or CWP-7
*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.
Self-Extracting or One-Key Release Crank Systems
Kris Holm and other crank manufacturers offer some crank models in a “self-extracting” or “one-key release” system. These systems use a retaining ring over the crank bolt. This rin may look like a “dust cap”. However the ring and crank bolt act together as a crank extractor.
The crank bolt of the self extracting system is a normal right-thread. The crank bolt tightens clockwise and loosens counter-clockwise. When the crank bolt is turned counter-clockwise, the shoulder of the bolt presses back against a crank bolt retaining ring. The ring then pulls the arm from the spindle. No additonal crank remover tool is required.
Crank Removal (Square Spindle/Cotterless)
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.
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.
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 below
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.
g. Repeat process on other crank.
Crank Installation(Square Spindle/Cotterless)
Cranks are pressed tight onto the tapered square spindle. The square spidle 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 splites and damages crank. If possible, use a torque wrench. Torque spec’s are dictated from manufacture.
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).
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.
REMOVAL OF CRANKS WITH DAMAGED THREADS (SQUARE/COTTERLESS ONLY)
If the removal threads for the crank puller in the crank are damaged, there is a possible repair. Begin by inspecting the threads. If only the outer threads are bad, you may still be able to remove it using a normal tool. Make sure the threads of the remover are clean. Start the tool straight to the threads and carefully thread it in place. Tighten the tool into the crank threads with a wrench before attempting to pull the arm. Even if there are only a few threads left, it is worth trying to remove the arm with a crank remover.
Another repair option involves a tool from the Bicycle Research Company, the TC-8. This is basically a fluted bolt that cleans the threads. It comes with a pivoting stud to align the tool centered to the threads. This tool is not a tap, it only aligns damaged and cross-threaded threads. It will not cut new threads. Typically, it will not damage threads, so there is nothing to lose in trying it. The TC-8 will work only with square drive cranks with an 8mm threaded bolt.
If the threads are completely stripped, the arm is basically ruined. A simple removal method uses the concept of how arms are kept on the bike. Pressure from the crank bolt keeps it on, so you will need to remove that pressure. Loosen the bolt or nut three or four turns. Ride the bike hard, uphill. The crank hole is a tapered fit onto a tapered spindle. The flexing under stress will cause the arm to loosen, but it will also cause the crank hole to become enlarged, ruining the arm. Use care when riding; you don’t want the arm to fall completely off when pedaling.
It is also possible to use a hacksaw to cut into the arm at the spindle joint. A cold chisel can then be used to split the arm. Again, the arm is basically ruined when the threads are completely stripped, so destructive removal should be considered as an option.
Resource from Park Tool