Before we begin to repair a wheel, it's important to first understand what it is supposed to look like. And the picture to the left shows us a set of wheels as they should be.
Note that on the rear wheel, the left side has a cassette on it, of course. This left side of the wheel is referred to as the "drive-side" of the rear wheel. You'll hear spokes being referred to as drive-side and non drive-side spokes on rear wheels. Also note that the drive-side spokes are shorter in length than the non drive-side spokes. This allows for the wheel to be centered.between the two ends of the rear hub while still allowing room for the cassette to exist on the hub.
Before we begin to repair a wheel, it's important to first understand what it is supposed to look like. And the above picture shows us a set of wheels as they should be.
Note that on the rear wheel, the left side has a cassette on it, of course. This left side of the wheel is referred to as the "drive-side" of the rear wheel. You'll hear spokes being referred to as drive-side and non drive-side spokes on rear wheels. Also note that the drive-side spokes are shorter in length than the non drive-side spokes. This allows for the wheel to be centered.between the two ends of the rear hub while still allowing room for the cassette to exist on the hub. Of course, the front wheel has equal length spokes on both sides of the rim.
Spoked wheels have been around since we figured out that spokes can help make a wheel almost as good as a solid wheel with a fraction of the weight. There is one important difference between a wagon wheel and a bicycle wheel, however - that is how the spoke attaches to the rim. In a wagon wheel, spokes are radially attached, but in a bicycle wheel they are generally attached tangentially. This difference drastically alters how the spoke bears the load of the wheel.
Which way do I turn this spoke to tighten it?
OK, first thing, you won't be turning the spoke, you'll actually be turning the spoke nipple (see picture at right). The best way to figure out which way you want to turn the nipple is to visualize the spoke as a bolt and the nipple as a nut which
The wagon wheel bears all its load through the compression of the bottom spoke. The bicycle wheel's bottom spoke is the unloaded spoke, with the load being distributed evenly across all the other spokes. The figure illustrates which spokes feel load and which feel stress while the wheel is loaded.
Radial lacing is the type of spoke lacing shown in the wagon wheel. The spokes emanate directly from the hub to the rim. Spokes which cross over or under other spokes before attaching to the rim are referred to as 2 cross lacing or 3 cross lacing, the number representing the number of spokes crossed. The more times a spoke crosses another spoke, the more load and strain that spoke can tolerate, i.e. crossing spokes makes the spoke stronger and makes for a very strong and stiff wheel.
It is not unusual to see some high end wheels use radial lacing. This is as a result of better materials in the rims and sometimes, spokes, which allow increased loads to be tolerated by radial laced spokes. This also makes for a weight savings in the wheel as the spokes are shorter and typically fewer spokes are used in a radially laced wheel. But a cross laced wheel is always going to be a stronger wheel.
Referencing the wheel above, the red and dark blue spokes are on 1 side of the hub. The other side of the hub has the light blue and orange spokes. This wheel is a 36 spoked, 3 cross laced wheel. You can follow the red spoke and see how it crosses 3 of the dark blue spokes. If you're going to be building a wheel from scratch, the above figure is very helpful to show how a 3 cross laced wheel should be built. All spokes of the same color on one side of the hub should be installed before going to the other side of the hub and installing a 2nd color and then repeating the process.
just happens to be attached to the rim. After all, the spoke does have a head on one end to prevent it from being pulled through the hole and it is threaded on the other. The spoke nipple is internally threaded to receive the threaded spoke end. Now the next important part is to be aware of your frame of reference. That's how things get turned around backwards. You could be dealing with a spoke with the wheel turned such that the nipple is at the top of the wheel, or reversed, with the nipple at the bottom of the wheel as shown below. I'm going to discuss the
latter configuration with you standing and working on the wheel at chest level, so that you would look down to see the nipple.
We'll be using a spoke wrench to tighten or loosen the nipple. There is more than one size of spoke wrenches and they are usually identified to a standard color. Chances are good that you'll use a black or red colored spoke wrench.
Using this visualization, you can now use your hard learned "righty tighty lefty loosey rule". This means that if you're looking down at the nipple in the confiruation at right, you would turn the nipple in the direction shown to TIGHTEN the spoke. The reverse direction would loosen the spoke.
A quick discussion about rims, you can see that the above rim has two walls through which the nipple must pass. This is called a double wall rim. Most quality rims are double walled rims because they are inherently stronger and offer more protection to the inner tube. The cheaper rim has just a single wall.
If you stop and think about the "righty tighty lefty loosey rule", the direction the nut is facing and your own frame of rererence (the fact that you're looking down at the nipple (nut)) then it will make sense why the direction shown will tighten the spoke.
Which spoke do I tighten to true my wheel?
Now that you've learned which way to turn the nipple to tighten or loosen a spoke, we'll put it to use for the purpose of truing the wheel. You'll need some frame of reference to determine to which side your rim is out of true. A shop would use a truing wheel; the Park Tool truing wheel is shown below. It's a great truing wheel and a professional's standard. There are other lesser expensive versions which are reasonably fine. In a pinch, you can use your rear triangle of your bikeframe as a reference. Most people commonly use the brake pads as a reference, but be careful as they can move back and forth, thereby changing your frame of reference. Taping something inflexible like a popsicle stick in place to your rear triangle of the frame so that it just reaches out to barely touch your rim is a great way to make a non-moving frame of reference.
You'll need to understand the effect of tightening and loosening spokes. When a single spoke is tightened, it pulls the rim section to where it is attached in the direction of the hub side to which
the other end of the spoke is attached. If you tighten two spokes on the same side of the hub which are near each other, the effect is more pronounced on the affected section of rim. The upper right illustration shows that if you grab two adjacent spokes, on the same side of the hub and squeeze them together, the rim section to which the spokes are attached moves in the direction shown. Squeezing these two spokes together serves the same function as tightening the spokes with their nipples.
OK, so you've got your frame of reference set (I'll assume you're using a reference to only one side of a rim) and as you spin your wheel, you see that there is a section of the rim that touches your reference point while the remainer of the rim is not touching it. Your move would be to move the section of rim that is touching the reference point away from the reference point so that it's the same distance away as the remainder of the rim.
A good rule to prevent overcorrection: Make your adjustments to a nipple in 1/4 turn incrementsand then recheck its proximity to your reference point.
Putting a drop of oil at the spoke and nipple interface will help to prevent stripping a nipple.
Look at the spokes at the rim in the affected section. Is there a spoke that is showing substantially more thread above its nipple than the surrounding spokes? If so AND this spoke leads to the opposite side of the hub from the side the reference point is on, then most likely you just have a single loose spoke. Tightening this spoke will correct the majority of the problem.
If there is not a spoke that stands out, it is best to adjust more than one spoke so that too much tension is not applied to one spoke, thereby increasing its risk of breaking under fatigue stress. On the rim, each spoke goes to the opposite side of the hub as the spoke adjacent to it. So, on the rim, every other spoke goes to the same side of the rim. Let's say that the affected rim section covers an area of 4 adjacent spokes. Identify the 2 spokes of the 4 adjacent spokes which are attached to the opposite side of the hub from the side that the reference point is on. Tighten these spoke nipples 1/4 turn or less in order to shorten these spokes and pull the affected rim section away from the reference point. Recheck the distance of the affected rim section to the reference point and make further adjustments as necessary.
If you pull the affected rim section too far away from the reference point than you had intended, just loosening the same nipples will move it towards the reference point.
If you find that the chosen spokes are just too tight to tighten because either the spoke is just obviously too tight already or the nipple has been tightened quite far up the spoke then you can achieve the same effect of moving the affected rim section away from the reference point by loosening the nipples of the other 2 spokes of the 4 adjacent spokes in the affected rim section. These 2 spokes would be attached to the hub side which is on the same side as the reference point. Loosening these 2 spokes releases some of the tension pulling the rim section towards the reference point and causes the rim section to move away from the reference point.
If you're having to adjust a large number of spokes, it is important to try and maintain roughly the same amount of tension in all spokes of the rim. To do this, you'll be tightening some nipples and loosening the adjacent nipples so that the forces are more equally distributed.
If you find that after tightening a number of spokes to the point of them being obviously too tight or the other spokes being too loose and the distance to the reference point is still not acceptable at all points on the rim, then you have a rim that is NOT tunable. Sorry, but it's trashed. Your rim has been bent farther than what spoke tightening and loosening can cure. Typically, only deviations of just less than 1 inch of the rim can be adjusted via spoke tension changes.
Obvious deviations in the rim like this are called taco'ed wheels cuz...well...they kinda make a taco shape when they're really bad. Like this one...which is NOT fixable, at all...don't even try. But you can take it to your local bike shop for a good laugh and it'll be the source of a good story for some time to come.
What if I taco'ed my wheel but I'm still on the trail?
Well, hopefully it's not as bad as the one to the left. If it's not too bad, you can try and beat it back into shape so that you can at least ride out.
To beat the rim back, take the wheel off the bike and hit it upon the ground as illustrated. You might find that you'll have to hit it upon the ground harder than you thought. This may serve to at least get the rim back closer into alignment to allow you to ride out, though wobbly.
You may also have to release the brakes on the bent wheel so that they don't rub on the rim.
