What Is a Motorcycle Undermount Mirror (Clamp-On Mirror)? A Guide to Choosing and Replacing One!

What are the pros and cons of under-bar mirrors (clamp-on mirrors)?

Source: http://www.redirondenim2017.com/entry/2017/04/12/000000

Typically, motorcycle mirrors are mounted above the handlebars, but under-bar mirrors are a type of mirror mounted below the handlebars.
They are installed by passing a clamp through the handlebars and securing it by tightening bolts, but what are the advantages and disadvantages of installing under-bar mirrors?

Advantages of under-bar mirrors (clamp-on mirrors)

First, under-bar mirrors have several advantages.
・Visual impact
・Stylish appearance
・Gives a customized feel
The above are the advantages of choosing under-bar mirrors. The visual aspect is a major advantage. Since they are positioned significantly differently from standard mirrors, they create a strong impression.
Downward-facing mirrors are so famous that they are considered a staple of American custom motorcycles, so the impact of changing them is significant. Since the mirrors, which are normally mounted facing upwards, are positioned below the handlebars, they can offer a surprising design element to onlookers.
With clamp-on mounts, you can choose the mounting position on the handlebars relatively freely, allowing you to install them in a position that suits your body shape and preferences.
Another advantage is that, unlike genuine mirrors that extend above the handlebars, under-bar mirrors can create a sense of openness by clearing the forward view.

Disadvantages of under-bar mirrors (clamp-on mirrors)

Conversely, let's look at the disadvantages of installing under-bar mirrors.
・May not be installable due to interference with the tank or steering angle.
・Rear and side visibility are compromised.
・It is necessary to choose a sturdy mirror for vehicle inspection compliance.
The above are the disadvantages of choosing under-bar mirrors. Since these mirrors prioritize appearance, visibility is compromised. If safety is a concern, you may need to choose not to install under-bar mirrors.
Also, since mirrors are installed in a location where they are not typically present, it is necessary to thoroughly check for interference with the tank or body of the motorcycle before installation.
Initially, you may feel uncomfortable until you get used to the mirror's position, but this can be resolved by paying close attention to where the mirrors used to be and getting accustomed to the new position over time.
Furthermore, if you set an extreme mounting angle or force an incompatible mirror to be installed as an under-bar mirror, it may interfere with the fuel tank or pinch your hand when turning the handlebars. Issues that would not occur with mirrors in their original position can arise with under-bar mirrors, so be aware of this beforehand to avoid potential drawbacks.

How to choose under-bar mirrors (clamp-on mirrors)?

Source: https://bikeman.jp/

While it's good to choose under-bar mirrors primarily for their design, it's important to note that if they don't comply with safety standards, they won't pass vehicle inspection. So, the first thing to check is whether the mirror conforms to safety standards. Even for motorcycles that don't require inspection, if the mirror surface area is extremely small, you could still be stopped by the police for violating safety standards.
Also, check if there is enough space to install them. Whether it's a clamp-on type or a bar-end type, there's no point in buying an under-bar mirror if there's no space to install it. Make sure to check if there is space around the handlebars, and if the bar ends are replaceable, before making a purchase.

Ensuring visibility is also a key selection point. Depending on the handlebar angle and type, if you opt for under-bar mirrors, you may lose rear and side visibility, so be mindful of checking as much as possible.

How to replace/install under-bar mirrors (clamp-on mirrors)?

Source: https://bikeman.jp/

Under-bar mirrors are fixed in a different position than the original, but the procedure is not that difficult.
By following the steps, you should be able to replace them without much trouble.
Here are the steps for installing under-bar mirrors.

Step 1: Remove the existing mirrors

First, remove the installed mirrors.
Genuine mirrors usually have a rubber cover to protect them from rain and dust, so peel up the rubber cover and loosen the nut visible inside.
In most cases, there are two nuts; first, loosen the nut on the mirror side (upper side), then loosen the nut below it, and the mirror will detach by turning it.
If the nuts or mirrors are stuck due to rust or other reasons, do not try to force them off; it is better to leave it to a professional mechanic at a motorcycle dealership.
Forcing them off can cause the nuts or mirror screws to break inside, making it unmanageable.
Once the mirror is removed, it is a good idea to check the diameter of the mirror's threaded part.
In most cases, it will be 8mm or 10mm, so match the diameter of the replacement mirror to that dimension.

Step 2: Attach the clamps

Attach the clamp fittings to the handlebars.
The U-shaped clamps are secured by bolts in a way that they sandwich the handlebars, but for now, tighten them lightly as you will adjust the mirror position at the end.
For clamp installations using the original mirror holes, the clamp is fixed with bolts using those mirror holes.

Step 3: Install the mirrors

Once the clamps are attached, install the mirrors onto the clamps.
After installing the mirrors, sit on the seat and check if the mirror position is correct and if the handlebars interfere with the tank or other parts when turned.
Once the mirror position is determined, securely fasten the clamps and mirrors.

Step 4: Check and adjust mirror position

Once the mirrors are secured, fine-tune the rearward visibility of the mirrors for driving, and you're done.
In addition to mirror visibility, double-check one more time for any interference with the tank or other parts.
Also, after driving a short distance, check if they have loosened due to vibrations, and if they have, retighten the bolts.

Addressing common concerns about customization!

Source: https://minkara.carview.co.jp/userid/397381/car/2410847/5013841/1/note.aspx#title

Here, we've compiled common concerns about installing under-bar mirrors.
Reading through this before installation will help you anticipate potential problems and allow you to install with greater care.

Under-bar mirrors (clamp-on mirrors) are hard to see! (How to improve usability?)

Under-bar mirrors can instantly give your bike a stylish custom look, but many designs prioritize aesthetics over functionality, leading to concerns like "they're hard to see."
Choosing larger mirrors, or square-shaped mirrors over round ones, can help. If you've already customized your bike, adjusting the clamp position or mirror angle can often resolve the issue. However, if visibility remains poor regardless of adjustments due to body shape or other factors, you can use an adapter that allows for height adjustment.
Mirrors with short stems, in particular, may look more stylish but are also more prone to poor visibility, so caution is advised.

Are clamp-on bar-end mirrors spinning?

If your clamp-on bar-end mirrors are spinning, first check if the mounting bolts are properly tightened. If they are correctly tightened but still move during riding, you can improve this by applying more torque when tightening them.
If they still move, it's often because the clamping force is weak and the contact with the handlebars is insufficient. In such cases, you can improve adhesion by wrapping thin tape, such as plumber's tape used for water pipes, around the handlebars before attaching the clip.

Do under-bar mirrors (clamp-on mirrors) pass vehicle inspection?

We often see questions about whether under-bar mirrors pass vehicle inspection. If the mounting position and mirror size meet safety standards, under-bar mirrors will pass inspection as long as they provide a clear view of the rear. Motorcycle mirrors must meet the following safety standards, and failure to meet any of them will result in a failed inspection:
・Must have an area of 69 cm².
・Must not obscure a circle with a diameter of 78mm.
・If round, must be between 94mm and 150mm in diameter.
The mounting position must be at least 280mm outward from the steering part, and both sides must be robustly (firmly) attached to comply with safety standards.

I want to reduce rattling vibrations.

Mirror vibrations are particularly common on American and single-cylinder motorcycles, so first, ensure that the mirrors are securely fixed.
If vibrations occur despite being fixed, remove the mirror and insert a thin washer or rubber bush between the mirror and the mounting part to absorb the vibrations.

Cheap and affordable! 3 cost-effective under-bar mirrors recommended.

Next, we will introduce four recommended under-bar mirrors with a focus on cost-effectiveness, so please use them as a reference when choosing your mirrors.

https://bikeman.jp/

By using a stay holder, many more mirrors can be attached as under-bar mirrors.
It's a convenient item that expands your choices, such as allowing you to select based on design.
Black options are also available to match your bike or mirror color, so choose according to your preference.

KIJIMA Euro Mirror Round 4 inch, Universal Left/Right

https://bikeman.jp/

The KIJIMA Euro Mirror Round 4 inch is a simple round mirror that would suit naked bikes, American cruisers, or vintage-style motorcycles.
By using a stay holder, it can also be installed as an under-bar mirror.
It is designed for universal left/right use, but if installing on both sides, two units are required.

KIJIMA Mini Slender Mirror Chrome 8mm (Left/Right separate)

(Right side)
https://bikeman.jp/

The KIJIMA Mini Slender Mirror Chrome 8mm can be purchased for a little over 2,000 yen including a stay holder.
Its stylish oval shape makes it a recommended mirror for those who prioritize dressing up their bike.
Please note that it is sold separately for the right and left sides.

(Left side)

KIJIMA Mini Mirror Black M10 Right-Hand Thread

https://bikeman.jp/

The KIJIMA Mini Mirror Black M10 Right-Hand Thread features a compact mirror surface.
The mirror itself is highly cost-effective, priced under 1,000 yen, and even with a stay holder, it's about 2,000 yen (as of March 2020).
While cost-effectiveness is important, for those looking for a higher quality mirror that will last, there are even better recommended mirrors.

Left/Right Set Valen T.T. Mirrors M10 10mm Right-Hand Thread Chrome Plated Left/Right Set

https://bikeman.jp/

This product is a mirror manufactured by Tanax. As it's made by Tanax, a company that produces many mirrors, the quality is guaranteed, and it's also compliant with vehicle inspections, so you can install it with peace of mind. Also, unlike bar-end mirrors, these are Valen mirrors, meaning they can be adjusted to be either downward or upward-facing, which is convenient if visibility becomes an issue, as you can easily change their orientation.

Furthermore, Tanax has extensive mirror technology, including the development of Napoleon mirrors, ensuring excellent visibility, so you can install them with confidence. While this product is a chrome-plated type, black versions are also available in their lineup.

You can choose black if you want a subtle placement, or chrome-plated if you want to add a distinctive custom touch, allowing you to select mirrors that match your bike, which is another recommended feature.