May 21, 2008
DIY: Rim Truing
By VWCabrio82
Well I've heard a few people ask from time to time about rim truing, so I thought I would give a crash course in very basic truing. At this juncture I would like to say that I am fully aware that this is not even scratching the surface of the many points involved in truing a wheel, and there are much more appropriate tools, and skills. This is merely something to get the weekend warrior mobile on a Sunday afternoon. There is plenty of rim building and rim truing tutorials on the Internet, especially by the late Sheldon Brown. These are definitely worth looking up and reading if someone is wanting to further their skill in wheel building and truing.
The wheel sizes as well as spokes vary from wheel to wheel, there is also differences in spoke count, hub size, spoke thickness, nipple sizes, and many other things that a person can get into when building a wheel. For this quick tutorial we will assume that all your spokes are in good to very good condition, none are bent or broken, and that your rim is in workable condition.
First, you will need to have an appropriate spoke wrench, they come in 3 sizes. The two shown here are the most common for off road bikes. I purchased these at MEC where they were $6.00 at the time.
Now lets look at the anatomy of a wheel. Starting from the outside and working in we have the rim, sometimes referred to as a hoop. The hoop is usually the portion of the wheel that becomes damaged and causes a wobble or bend in the wheel. Next we see the spokes. The spokes are the thin metal rods that connect the rim to the center of the wheel. The spokes are connected to the rim with small round nut, called a nipple. The nipple is made of soft metal, usually brass. The end of the spoke that connects to this nipple is threaded, and to tighten or loosen the spoke this nut, or nipple, is used. Now the spoke runs toward the center of the wheel and attaches to the hub, this particular wheel is a 32 hole hub. You will also notice now that some spokes attach to one side of the hub (sprocket side, drive side) and some attach to the other side (non drive, brake side). You may have noticed as well that the spokes alternate from the rim. one to drive side, one to non drive, one to drive and one to non drive and so on. This is important for what we are doing.
Alright lets look at the wobble this wheel has. For my quick fix here we will leave my wheel on the bike, usually I remove the chain from the sprocket to allow for easy movement.
Next I attach two zip ties to the frame, pick a spot on the wheel where it looks to be as close to center of your seat stays, and cut the zip ties close to the rim. These can be moved about a little to get them so they barely touch the rim. We will be using this to show where the bend is on the rim. As the wheel is turned you will hear the zip ties rub on the rim. We need this sound to go away! Looking at your zip ties you can see where the wheel starts to stray off and rub the tie. This is the point where we will start. Make a mental note of this or even easier stick a piece of tape to this spoke, do the same at the other end where the rim no longer touches the tie.
This section of the wheel is the portion we will be working with. You can see here that this is the highest point of my bend (crown), it bubbles to the drive side of my wheel. Within this section of wheel there are some spokes that are attached to the drive side of the hub and the non drive side. As mentioned before this is important because tightening and loosening certain spokes on each side will make our wheel straight, or "true."
So what way do we turn? Well the nipples are threaded on the spokes, same as a nut is on a bolt: righty - tighty, lefty - loosy. From my vantage point with the drive side on my right, turning the wrench down or clockwise, will tighten, and turning up or counter clockwise will loosen.
Note that if you do this with your bike upside down with the seat and bars on the floor, wheels up this will be opposite.
Now because my bend is to the drive side, the spokes on the drive side must loosen to allow the rim to be able to relax back to center, and the spokes on the non drive side must be tightened to pull the bent portion of the rim back to center. So for this wheel and this bend, the right sided spokes are loosened and left side tightened.
When making your adjustments for the first time, make small 1/4 turns until you get an idea of how much difference these 1/4 or 1/2 turns are going to make. Check your work often. Make 1-2 turns then check to see how much difference it has made. Be sure to work on each spoke, don't loosen all the right side then try and tighten up the left, it will never work out. Some spokes may only need 1/4 turn while others may need 1-2 full turns.
The principals here can be used for multiple bends, like an s bend, where you may have a crown on the drive side and a crown on the non drive side, just tackle each bend like a single portion of your wheel. Remember to relax the crown side and tighten the other side. Improvements can often be made to hops in the rim with the same procedure... but instead of relaxing the crown you want to pull that portion of the rim down, and if you have a dip, or a flat spot, you have to pull the sides of the rim tighter and loosen the lower section. Flat spots are harder to do and most times are going to end up with a hoop replacement, mainly because once the integrity of the circle is broken the rim will break. Practice helps! If you have an old wheel, try it out on that first.
Remember to not get frustrated, this stuff isn't easy. Experience makes the difference.
Posted by O9man at May 21, 2008 12:04 AM