21/04/2006
Attaching a sidecar to your motorcycle is a significant undertaking, transforming your two-wheeled machine into a versatile three-wheeled outfit. While the initial attachment is crucial, the finer adjustments, particularly the 'sidecar lead', are paramount to achieving a safe, stable, and enjoyable riding experience. This often-overlooked setting significantly impacts how your outfit handles, especially during cornering, and can also influence tyre wear. Understanding and correctly setting the sidecar lead is a fundamental skill for any sidecar owner or mechanic.
What is Sidecar Lead?
Sidecar lead, sometimes referred to as the 'offset' or 'lead-out', is a crucial alignment dimension. It is defined as the distance between the centreline of your motorcycle's rear wheel and the centreline of the sidecar's wheel. Imagine a line drawn through the very centre of your rear tyre and another line through the centre of your sidecar tyre; the lead is the horizontal distance between these two lines when viewed from above. This measurement is typically indicated by an arrow on technical diagrams, pointing from the motorcycle's rear wheel centreline to the sidecar wheel centreline.
The Impact of Sidecar Lead on Handling
The amount of sidecar lead you set can have a profound effect on your outfit's behaviour. The typical range for this dimension can vary considerably, from 0mm to as much as 450mm, with a common setting falling between 250mm and 350mm.
Increasing the sidecar lead (moving the sidecar wheel further forward relative to the motorcycle's rear wheel) has a significant benefit: it reduces the likelihood of the sidecar tipping outwards when you turn away from the chair (i.e., turning left on a right-hand sidecar, or right on a left-hand sidecar). This is because a greater lead effectively 'pulls' the sidecar through the turn, counteracting the centrifugal forces that try to lift it. This enhanced stability can lead to a more confident and secure feeling when navigating corners.
However, this benefit comes at a cost. As the sidecar wheel is positioned further forward, it will tend to 'scrub' more during cornering. Tyre scrubbing occurs when a tyre is forced to roll at an angle to its direction of travel, causing excessive wear. Therefore, a longer lead, while improving stability, can lead to accelerated and uneven tyre wear on the sidecar wheel. It's a balancing act between stability and tyre longevity.
Factors Influencing the Ideal Sidecar Lead Setting
There isn't a single 'correct' sidecar lead for every outfit. The ideal setting is influenced by several factors:
- Type of Motorcycle: Lighter, sportier bikes may require different settings than heavier touring motorcycles.
- Sidecar Design: The weight distribution, chassis design, and attachment points of the sidecar itself play a role.
- Tyre Sizes: The diameter and width of both the motorcycle and sidecar tyres can influence the optimal alignment.
- Riding Style: A rider who frequently tackles twisty roads or rides spiritedly might favour a slightly longer lead for stability, accepting the trade-off in tyre wear.
- Load Carrying: If the sidecar is frequently loaded with passengers or heavy luggage, a longer lead might be beneficial for stability.
How to Measure and Adjust Sidecar Lead
Adjusting sidecar lead typically involves altering the mounting points of the sidecar chassis to the motorcycle. This often requires loosening clamps or bolts that secure the sidecar frame to the motorcycle's frame or subframe. Here's a general process:
- Park on a Level Surface: Ensure your motorcycle and sidecar are on a flat, level surface.
- Secure the Motorcycle: Use the motorcycle's centre stand or secure it with chocks to prevent any movement.
- Identify Centrelines: The most accurate way to find the centreline of the motorcycle's rear wheel is to measure the width of the tyre at its widest point and divide by two. Do the same for the sidecar wheel. Alternatively, you can use a string line or a laser alignment tool.
- Measure the Existing Lead: Using a tape measure or a dedicated alignment tool, measure the distance between the centreline of the rear wheel and the centreline of the sidecar wheel. Note this measurement and whether it's a positive or negative lead (positive usually means the sidecar wheel is ahead of the motorcycle's rear wheel centreline).
- Loosen Mounting Points: Carefully loosen the bolts or clamps that attach the sidecar frame to the motorcycle. Do not remove them completely.
- Adjust the Position: Gently push or pull the sidecar chassis relative to the motorcycle to achieve the desired lead measurement. You may need assistance for this step.
- Re-measure and Verify: Once you believe you have the correct position, re-measure the lead to ensure accuracy.
- Tighten Securely: Once the correct lead is set, carefully tighten all mounting bolts and clamps to the manufacturer's recommended torque settings. Ensure all fasteners are secure.
- Check Other Alignment Factors: Remember that sidecar lead is just one part of a comprehensive alignment. You also need to consider toe-in (or toe-out) and camber. It's often best to adjust these in conjunction with the lead for optimal results.
- Test Ride: Take your outfit for a short, low-speed test ride in a safe area. Pay close attention to how it handles. You may need to make further minor adjustments based on your test ride.
Table: Sidecar Lead - Pros and Cons
| Sidecar Lead | Pros | Cons |
|---|---|---|
| Longer Lead (e.g., 350mm+) |
|
|
| Shorter Lead (e.g., 0mm - 250mm) |
|
|
Frequently Asked Questions
What is the typical sidecar lead?
The typical sidecar lead ranges from 250mm to 350mm, but this can vary significantly depending on the specific motorcycle and sidecar combination.
How does sidecar lead affect tyre wear?
A longer sidecar lead, while improving stability, causes the sidecar wheel to scrub more during cornering, leading to increased and often uneven tyre wear. A shorter lead generally results in less scrubbing and better tyre life.
Can I adjust sidecar lead myself?
Yes, with the right tools and a good understanding of the process, you can adjust sidecar lead yourself. However, if you are unsure, it is highly recommended to have it done by a professional mechanic experienced with sidecars.
What happens if the sidecar lead is set incorrectly?
An incorrect sidecar lead can lead to poor handling, instability, excessive tyre wear, and even dangerous situations such as the sidecar tipping. It's crucial to get this alignment right.
Should I adjust for toe-in or toe-out as well?
Absolutely. Sidecar lead is part of a larger alignment picture that includes toe-in/toe-out and camber. All these factors work together to ensure safe and efficient handling. It's often best to have all these aspects assessed and adjusted simultaneously by an expert.
Conclusion
Mastering the adjustment of your sidecar's lead is a vital step in ensuring a safe and enjoyable experience with your three-wheeled outfit. While the exact measurement is not a rigid science and depends on various factors, understanding the principles behind it – the trade-off between stability and tyre wear – is key. By carefully measuring, adjusting, and testing, you can fine-tune your sidecar's handling characteristics to suit your riding style and preferences, ensuring many miles of comfortable and secure travel.
If you want to read more articles similar to Sidecar Alignment: Mastering the Lead, you can visit the Suspension category.