How To: Wheel Truing & DIY Truing Bench

I have always felt curious about wheel truing in general. It also happened that I had to rebuild the front wheel of my bike, because the hub was damaged (video here). Therefore, I decided to have a look online to see if buying a truing bench could be an option, having in mind that it is a device that would be used 1 - 2 times a year.

It didn’t take me long to conclude that given the cost, perhaps it would be better to create my own device, forcing myself to learn all the way through.

Another (reasonable) option was to take the wheel to a professional and pay for the job, but what about learning something new, get some hands-on experience and contribute to my personal growth?

Anyway, let’s keep this one short! Below you will find my design requirements:

• Cost effective solution, since I would use this device for a couple times in a year
• Should fit front/rear bike wheels up to and including 28” wheel-size
• Needs to be easily assembled/disassembled for storage purposes.
• Needs to be a simple and versatile design, so anyone can use it as a starting point
• Can be assembled with one tool: a screw driver
• Generic accuracy requirement: +/- 500um deviation for lateral+axial truing. I have learned that this figure is pretty much achievable.

As supplies, you will find the following:

• Project folder that contains .STEP files for the Truing Bench CAD Assembly and corresponding Drawing, Calibration Ruler and Bill of Materials/Processes
• For those who like Autodesk 360, you can have access to the Truing Bench CAD Assembly, Truing Bench Drawings and Calibration Ruler CAD model

As you can see in the 3D-model, it looks like this design is lacking components (and slightly different) if compared to the real one showed in the video. This has been done on purpose, since the main idea was to provide a frame, a “canvas” (lets call it that way). Later you can adjust this design to your needs. Components used in this particular case (can also be found in the CoG section):

• Wooden frame (pine wood) made using the leftovers from my last Instructable.
• Adjustable feet, needed in order to level the bench in different ground types.
• Dial gauge meter. Only one to start with, as I am a beginner.

This design is built using the same methodology as in my previous Instructable and it is not poke-yoke, so some labelling might be needed. There is nothing really important about the building process, since there is only cutting and drilling involved. Just make sure that you measure everything accurately.

The only drawing I am providing is the one corresponding to the assembly, for simplicity. You will find everything that is needed in only one sheet, and I find it very useful.

I would recommend you to watch the video for a more-graphical explanation, but I would like to emphasise a few things:

Where should the rim lay with respect to the hub (axially)? How to find the (virtual) central axis (especially after replacing a hub)?

After a “few” trials, I am going to be loud and clear. If a bike uses V-brakes, then there will be a certain type of hub. If the bike uses brake rotors, then the hub will be different. These features made me think quite a lot although it is not necessary.

Now, as a rule of the thumb, place your wheel in the fork and secure it like you would normally do. Measure the space between the two sides of the fork. That distance divided by 2 is where the central axis of your wheel should be. Record it for the next step.

How do I calibrate the dial gauge meter in order to proceed with the wheel truing (setting the “zero”)?

Let’s switch to the truing bench. There are two vertical poles and between them is where the wheel will be placed. Now it is time to choose a reference plane/surface from which all measurements will be taken. In order to make is easy, I chose the inner side of one of the vertical poles. Yes, the side that would be in contact with the beginning/end of the hub, like in the bike. This reference has been labelled as LT (Lateral Truing) in the drawing.

At this point there are two options:

1. Your reference plane is coincident with the hub. No action needed.
2. There is an offset between your reference plane and the hub. You will need to measure and record it for the next step.

Now you know where the “zero” in the gauge meter should be, but how to make it possible? Some kind of interface is needed in order to set a distance and position the probe from the gauge meter.

I decided to design a rather simple tool that allows you to set a distance while serving of a “touching” interface to the gauge meter probe. You can download and 3D-print a pretty accurate model or you can order this tool made of Aluminium from my new shop.

Why choose either a 3D-printed version or a machined one?

As you can see in the video, the 3D-printed model suffered from warping because the mating interface for the gauge probe was too high. I know there are a few ways to solve this. However, that interface is the most important for the dial gauge calibration, and relies on the counterpart. The steel version will provide more accurate interfaces, ensuring less induced error during the process, apart from the added sturdiness, feel, appearance and overall quality. But, is it really needed? Not for beginners, but perhaps for more demanding users.

The importance of parallel (accurate) interfaces.

Let me be brief as I this could turn into a very-technical topic but can be easily explained. Parallelism between interfaces is really important. Otherwise, you will create components (horizontal and vertical) and your measurements will be wrong. Please watch the video for a more graphical insight.

With the theory in mind and assuming the bench is fully assembled:

1. Make sure that the bench is in a levelled surface. Otherwise, you can add adjustable feet to the bench like I did (or freak out later in the process)
2. If this is the first time, you need to verify that the height of the holes in which the rod will go through is the same.
3. Now, place the wheel/rim and choose your measurement reference plane. Remember, if your reference is coincident with the beginning/end of the hub, then you will have replicated the same situation as with the fork in the bike.
4. Ensure that the vertical poles are separated the same distance. Take measurements at the bottom (your reference) and at the top. You can use washers and nuts in order to adjust the distance.
5. If succeeded in the last two steps, you will have accounted for (most of) parallelism too.
6. Place the ruler as in the video and set the distance. What distance? Well, you measured in the last step. Remember to account for any offset if needed. Secure the ruler. Do you still have doubts? Watch the video.
7. Place the dial gauge meter, ensure that its probe is touching the ruler’s designated contact interface and set the dial to “zero”. Bear in mind that the probe cannot be extended/compressed all the way. Otherwise, there is no stroke left and you will notice it during the truing process because the rim will not be able to spin or the probe will not be touching the rim anymore.

This process may take you a few trials, so take your time and be patient!

I would recommend you to get some knowledge on how the truing process works. My references were:

• About truing a wheel
• About building a wheel

How did I manage to address vertical, horizontal and dish with my bench?

This is a good question as you may see that at leats 2 tools are normally used. I was not looking for a specific deviation (e.g. vertical/horizontal bump). I wanted to rebuild a wheel from scratch:

• “Vertical truing” is addressed by giving the same tension to the spokes (see the video) and this means tightening the nipples the same amount of turns (or by using a spoke tensioner). Yes, this can get messy as you need to remember the number of turns and you are also assuming that all spokes are perfectly equal in length for each side. I did this from the beginning, achieving pretty good results.
• “Lateral truing” is addressed at the same time thanks to the dial gauge
• “Dish” is already included as you already measured where the rim’s central axis should be located and the “zero” in the dial gauge was set based on that measurement.

What if I want to correct some deviation without having to loosen all nipples? I haven’t tried this yet. Here are my thoughts applied to this truing bench:

• “Lateral truing” and “dish” would be addressed the same way as I described before.
• “Vertical truing” (check diagram) would probably require a spoke tensioner. You should be able to use the SAME tool I proposed before, but one of the poles should be slightly taller! No worries, I already took care of it in the CAD model. Also, remember to remove the tyre and tube for best results. Now, your reference can be placed at the bottom of the bench and is denoted by VT (Vertical Truing) in the drawing and diagram. The dial gauge is not really functional in this case as it will rely on a very small surface (top flange on the rim). Hence, we will rely on the back of the ruler, that is perfectly aligned with the mark at 2cm, and will hopefully touch at two different points. Now that “0” makes sense, right? The aluminium version of the ruler comes with a plastic protective film that will avoid the scratching of your rim due to friction. The 3D-printed one should be just fine.

The diagram also shows why the calibration distance is achieved in such a way. As the detailed view shows, it may happen that the rod you are using is considerably smaller in diameter if compared to the real thru-axle. This could induce errors of up to 2mm, which means that everything is wrong since the very beginning. I think the rest is quite clear.

• How was the experience for a beginner? Very intense, but very instructive. I learned quite a lot from such simple “thingy”
• Any tips and tricks? Yes, patience and time. Frustration is waiting for you to come, though!
• What about smaller wheels? You can drill more holes vertically, so you can position the rod at different heights! Now you get the idea of a “canvas”, right?
• Why would I recommend this setup? It is cost effective, allows one to make mistakes, makes you save bananas, making you more self-sufficient and in the end the process becomes even easy!
• Any future work? I would like to address vertical truing with the same ruler I have designed. I know this will happen, in a while crocodile…