Bicycle Crank Arm Shorteners

Description Bicycle Crank Arm Shorteners are innovative bolt-on adapters designed to adjust crank length, offering a tailored solution for cyclists dealing with knee or hip limitations, or those experiencing discomfort from longer cranks. There are four different pedal settings available, which can reduce crank length by 24mm, 41 mm, 59 mm or 76 mm.  Reduced crank length or shorter cranks can improve cycling comfort and efficiency beyond those who require it as part of rehabilitation. Our article, “What Crank Arm Length is Best,” goes into depth on the impact of crank length if you are interested in reading more. What Are the Features and Benefits of Crank Arm Shorteners? Precision Engineering: Crafted in the USA from high-grade aluminum alloy, these shorteners boast a sleek design and secure attachment to your existing crank. Durable Construction: Handcrafted stainless steel bolts ensure strength and longevity without marring or damaging your cranks. Adaptability: Originally designed for recovery and orthopedic needs, these shorteners provide a versatile solution for adjusting crank length without replacing the entire crankset. The crank arm length can also be adjusted as your range of motion increases during the injury recovery process. Comfort Enhancement: Ideal for cyclists with shorter inseams (under 80cm) or those recovering from injury, these shorteners reduce knee and hip stress, potentially alleviating pain and discomfort caused by cranks that are too long. Quick Installation: Easy to install within 10 minutes, these shorteners enable fast adjustments to fit your evolving needs. How do I Choose the Right Crank Arm Shortener? We source crank arm shorteners from different manufacturers, and there are some slight variations in design, application, and installation. Here is a quick overview of finding the right one for your setup: Please carefully read the options and select the most appropriate one for your needs. Width Narrow: This model fits cranks from 5/8″ wide to 1-1/8″ wide (18 mm to 30 mm wide). This typically applies to steel cranks and “older style” aluminum cranks, common on some brands of stationary indoor exercise bike. Wide: This model fits cranks 1″ wide to 1-1/2″ wide. (25 mm – 40 mm wide). This typically applies to “new style” aluminum cranks, used on most modern bikes, and Peloton brand bikes. To determine the best width, measure the width of your existing crank arm 2″  (50mm) up from the pedal. Side Attachment Method Crank shorteners are secured to the existing crank arm through the original pedal hole. Depending on the model, this attachment may be accomplished using either a single threaded bolt or a combination of a bolt and flange. This detail, while functional, does not significantly impact performance. The shorteners are centered on the existing crank arm using one of two side attachment methods: Set Screws: These are small screws with a nylon-tipped point. They are designed for relatively straight crank arms and are known for their secure hold. However, there is a risk that they may mark the crank arms, so they are best used where minimal impact on the crank arm surface is acceptable. Cams: These are wide nylon cylinders mounted on an offset bolt. They can be rotated to adjust the gap between them, making them ideal for strongly curved crank arms. Cams offer a larger surface area for better grip and stability, especially on crank arms that show an increasing gap between the original arm and the shortener as the distance from the end of the arm increases. This design helps bridge the gap effectively and prevents the crank shortener from slipping. Crank Arm Shortener Color Choices Color is predetermined by the variations selected. 3 of the 4 variations are silver. The Wide/Cam version is black.  Intended Use These shorteners are primarily intended for indoor and stationary bicycles where shorter cranksets are unavailable. They can also be used for children’s bikes, recumbent bikes, or e-bikes when shorter cranksets are not an option. When suitable crankset arm lengths are available, using those is preferred. If you only need an adjustment on one side due to restricted range of motion from surgery or a condition like osteoarthritis, consider the Swing Crank, which allows for a modified pedal stroke on the compromised leg while maintaining normal extension on the other side. Compatibility Standard 9/16″ pedal axle holes (1/2″ adapters available separately) Suitable for use on regular bicycles, e-bikes, and indoor exercise bikes such as the Peloton bike NOT compatible with newer Shimano 105, Ultegra or Dura-Ace cranksets due to the design of the drive side arm and spider. Consider an aftermarket crankset for these models (these may be more expensive). Compatible with Shimano GRX, but select the wide – cam version which offers a touch more width than the wide set screw version. NOTE 1: If you have an older style stationary exercise bike or kids bike, it may have pedals with 1/2″ axles which are smaller than standard.  To connect the crank shortener to your existing crank you will need the optional 1/2 bolt  (1 per side), available here. NO LONGER AVAILABLE FOR NARROW SET SCREW VERSION. NOTE 2: The use of this product will increase the stance width of the cyclist, equivalent to the width of the crank arm on each side. NOTE3: RIDER WEIGHT LIMIT – The CAM STYLE shorteners are not recommended for riders over 200lb. Precautions Crank arm shorteners are not crank arms.  Although they have benefits, they also add a “weak link” to the drivetrain. You can weaken and break the link if: you weight over 200lbs, AND are using these for Peloton / Spin classes that encourage a lot of riding out of the saddle. The resultant leverage forces will stress the lateral stabilizes (cams or flanges and set screws) that locate and hold the shortener along the crank arm. If one of these fatigues and breaks you will get an unexpected and different pedal push that could result in accident and injury. Be sensible with how you ride an indoor exercise bike or outdoor bike equipped with crank arm shorteners.  They are not for power training! What’s in the Box? Left and right-side adapters i.e one pair.  We don’t offer single side only. Hex wrenches for installation and adjustment. How Do I Install Crank Arm Shorteners? Click here for Installation instructions If your pedals are an older style with flats requiring a pedal wrench for removal and installation, you will need a pedal wrench to move your pedals from your existing crank arms onto the crank arm shorteners. This wrench is NOT included. Specifications Narrow Model Weight: Approx. 265 grams per set. Wide Model Weight: Approx. 295 grams per set. Crank Length Reduction: 24mm, 41mm, 59mm, or 76mm. Pedal Axle Holes: Standard 9/16″; optional 1/2″ adapters available. Do Crank Arm Shorteners Help with Rehabilitation Bicycle Crank Arm Shorteners address a significant challenge faced by individuals with limited knee or hip range of motion, such as those with arthritis or those recovering from knee surgery. These shorteners effectively mitigate the problem of riding discomfort caused by insufficient crank length by reducing the amount of knee bending required during pedaling. By moving the pedals closer to the crank, the shorteners create a smaller pedaling circle, which requires less knee motion. This adjustment can help individuals with knee pain or limited mobility to engage in cycling with reduced discomfort and within their manageable range of motion, allowing them to maintain a cardio workout effectively. Crank arm shorteners are particularly beneficial for individuals with range limitations as low as 60 degrees of knee flexion and 20 degrees of knee extension. This makes them a valuable tool for those in the rehabilitation phase, including individuals preparing for Total Knee Replacement Surgery who may order them in advance to facilitate post-surgery recovery and ease the transition back to cycling. Beyond rehabilitation, these shorteners offer versatility for various applications. They are useful for cyclists with physical disabilities, adolescent racers who need adjustments for optimal performance, and participants in adaptive sports. They are also practical for situations where kids are riding on tandems behind adults or where shorter cranksets are not otherwise available, such as on stationary exercise bikes or certain types of bicycles. The crank arm shorteners ensure that cyclists of all kinds can benefit from a more customized and comfortable riding experience.