Choosing the right thru-axle for your bike is crucial for safe and reliable riding. A seemingly small difference like 5mm between a 130mm and a 135mm thru-axle can have significant consequences if you get it wrong. This guide clarifies the difference and shows you how to accurately measure your bike's thru-axle needs.
Understanding Thru-Axle Dimensions
Thru-axles are a vital component of modern bicycles, providing a more rigid and secure wheel connection compared to quick-release skewers. The most important measurement of a thru-axle is its length. This length directly affects the spacing between your bike's dropouts (the metal pieces at the end of the frame where the wheel sits). Using the wrong length will prevent your wheel from fitting correctly.
130mm Thru-Axle: A Common Standard
A 130mm thru-axle is a fairly standard length found on many mountain bikes and some road bikes, particularly those with boost spacing. Boost spacing is a wider hub standard that increases wheel stiffness and allows for larger tire clearance.
135mm Thru-Axle: The Older Standard
The 135mm thru-axle was more common on older mountain bikes and some road bikes. While still used, it's becoming less prevalent as Boost spacing gains popularity.
How to Measure Your Thru-Axle: A Step-by-Step Guide
Accurately measuring your thru-axle or the required length for your bike frame is paramount. Here's how:
- Remove your wheel: Carefully remove the wheel from your bike.
- Inspect the axle: Locate your thru-axle. It's the solid axle that passes through the hub and frame.
- Measure the exposed length: Use a ruler or caliper to measure the exposed length of the axle between the end of the axle and where it enters the hub. Do not measure the entire axle length, only the portion that sits outside the hub and the frame.
- Note the measurement: Record this measurement precisely; it's this number that indicates the correct size you need.
Important Note: The measurement you take from step 3 is not the exact size you need to buy. This is only to confirm what you are currently using. You should always reference the manufacturer specifications for your frame or wheelset. A slight discrepancy is okay, but an incorrect length will prevent you from installing the wheel correctly.
What Happens if You Use the Wrong Thru-Axle?
Using an incorrectly sized thru-axle is dangerous and can lead to various problems:
- Wheel instability: The wheel might not be securely seated, leading to unpredictable handling and potential accidents.
- Frame damage: Forcing a wrong-sized axle could damage your frame.
- Hub damage: Improper installation can cause damage to your wheel hub.
Beyond Length: Other Thru-Axle Considerations
While length is critical, several other factors influence thru-axle compatibility:
- Diameter: Thru-axles come in various diameters (e.g., 12mm, 15mm). Check your bike frame and hub specifications.
- Thread pitch: The threading on the axle must match your frame and hub.
- Type: There are different types of thru-axles (e.g., with a lever for easy removal, requiring a tool, etc.). Ensure your replacement matches the type installed.
Conclusion: Accuracy is Key
Determining the correct thru-axle size—be it 130mm or 135mm—requires careful measurement and attention to detail. Always refer to your bike's documentation and use the correct tools to avoid damage or safety risks. Remember that this is crucial for the safety and performance of your bike. If you are unsure, consult a professional bike mechanic for assistance.
