While it is possible to make do and mend by adjusting the tension of the undamaged spokes, whether you have any spare spokes with you will dictate whether you have a truly effective remedy to get your wheel back into working order. Regardless of this, the first thing you need to do is make the wheel safe for you or anyone else who might come into contact with it.
A flailing segment of spoke can end up puncturing you or another rider. Fragments left in the hub should be slid through the spoke hole in the hub flange. Depending on where the breakage is, this might be a frustrating process if there is a disc rotor or cassette in the way. If it proves impossible you should wrap or tie the free end round a neighbouring spoke. If long enough, any fragment left in the rim can also be lashed to another spoke.
For complete removal it will need the tyre, inner tube and rim tape to be taken off (picture L below) to expose the rim drillings and allow you to extract the nipple through the rim. Once the steps above are out of the way the following are some options
(a) No replacement spoke
Far from an ideal situation but one which appears to be the norm with the majority of riders. The only option open here is to adjust the tension in the surrounding spokes and bring the wheel as close to true as possible. See basics of wheel alignment here.
(b) Replacing a spoke
It is assumed that both ends of the broken spoke have been removed and the correct size of spoke is being carried.
1. Before beginning, compare a neighbouring cluster of spokes to determine the correct path for the replacement.
2. Remove the nipple from the selected replacement and screw it onto another spare spoke from the top. You may be lucky enough to be able to use the end of the busted spoke for this. Whatever happens you'll want to end up with something like what you see in the the middle picture. The nipple will now be easier to apply, through the spoke holes, on to the new spoke and, equally importantly, harder to lose.
3. Insert threaded end of the replacement trough the vacant hole in hub flange and weave it through its partners toward the empty spoke drilling in the rim.
4. Poke the prepared nipple through the rim drillings (pic. on R) and engage as many turns onto the threads of the replacement spoke s you can. A tiny drop of oil placed on the tip of the new spoke will make everything that bit easier and reduce problems by allowing the system to tighten with less risk of binding.
5. As soon as there is enough of the thread engaged on the new spoke, pull on it so that it is held firm against the rim. This will anchor it enough to allow the carrier spoke to be unscrewed.
6. Tighten new spoke to the required tension and adjust its neighbours accordingly.
7. Check the wheel, to make sre it is running true, before replacing the rim tape/strip.
8. Make sure the threaded end has not protruded from the nipple to risk puncturing the rim tape. To do this, place your thumb ove the hole and press. If it can be felt through the tape it represents a threat. If you have no way of filing or cutting the spoke down all is not lost. Place something between the inner tube and the rim strip to give extra protection
2. Spoke sizes and patterns:
Wheels are built with a variety of spoke configurations. It's a fairly in-depth subject and one that's a bit beyond most of us. The imoprtant thing to remember when doing a DIY repair is to look carefully at neighbouring spokes. The majority of wheels use patterns where spokes cross one another. The crossing of the spokes adds strength and resilience. Basically, the more spokes used and the more they cross one another the greater the potential toughness of the wheel.
Spoke lengths will vary according to combinations of the following factors
- Hub size
- Rim circumference
- Spoke pattern applied
- Rear wheel (drive side VS non-drive side)
- Front wheel (disc or non-disc)
Even if you don't intend to carry replacement spokes on the trail it makes sense to have some available before a breakage occurs. That way any delay in getting the bike up and running again will not be affected by availability of spares. Decent bike shops will have a chart that will tell them what spoke length is required for most hub/rim combinations. Emergency spokes can be used on the trail and are covered below.
3. How the bits fit together in a traditional wheel (simplified)
Bare hubs are used ie no gear casette is in place on the rear wheel and no rotors are in place on any disc wheels. The absence of these components makes the insertion of the spokes easier.
The spokes are passed, thread end first, through the holes in the hub flange. The heads are slightly larger than the holes in the flange and the spoke becomes anchored to the hub at the bend.
The spokes are offered to the rim in line with the drillings in it alternating between elbow in and elbow out. Spoke nipples are passed through the rim from the outer edge and wound on to the spokes' threads. The lengths of the spokes will have been determined beforehand to fit in with the chosen pattern and to make sure the threaded ends do not protrude beyond the top of the nipples and risk damage to the inner tube when the wheel is in use. These steps are repeated until all spokes are in place.
4. Common causes of spoke breakage & wheel failure
When new, well built wheels are extermely strong. Then we then go and use and abuse them. The wear and tear will eventually weaken and damage them. How hard the wheel is ridden will decide how long this process takes but it every wheel will succumb eventually. Below are some common reasons for spoke failure.
Loose spoke : Due to vibration and repeated stressing/destressing a nipple can begin to turn and release tension from the spoke. The offending spoke no longer does its share of the work and passes its duties to the others who become overloaded and ultimately give up.
Tight spoke : Making any spoke too tight can add too much strain . It might fail as it will be doing more work than its neighbours.
Corrosion : Spokes should be stainless steel to avoid this. If they are not salt & other agents can eat the metal away at places where dirt gathers. Such corosion can also be an issue with wheels built using aluminium alloy nipples. The main reason for using such nipples (traditional ones are brass) is to save weight. They also have a greater tendency for their faces to strip making adjustment problematic. Even though the majority are anodised they can aneal and bod with either the rime eyelet, the spoke thread. Useful for racers and probably less of an issue for lightweight riders aliminium nipples have to be considered carefully for wilderness riding.
Chips & scratches : Flying stones, careless placing/dropping the bike on the ground, crashes and contact with the chain or derailleur can result in wee (or big) scratches and gouges in the spokes. These can cause stresses to become channelled into the sharp angles created in the surface. Instead of being eveny distributed the forces work in one spot and eventually and the metal fails.
Old age : Use means components in any system will eventually reach the end of their designed fatigue life. Like us they can only take so much.
Impacts : Occasionally you might strike something so hard that the tyre becomes fully compressed and the rim contacts a hard surface. If the dunt is strong enough it may damage the rim. If a sharp object is struck, an obvious sign of the point of impact may be left. If the object is flat, the rim may compress from its circular form (imagine the image of an under inflated car tyre?) In a really heavy impact the rim will not recover from this and a flat spot will develop on it. The spokes in the imact area will loosen and continue to do so unless attended to. Bigger impacts will sometimes trash rims in one, spectacular, go. Whahey!
5. How to recognise problems
Obviously, a severe defect will be self-evident. A well skelped wheel (something from the final category above) may end up so mishapen that it looks like it could have come out of a Pringles tube. A newly snapped spoke will clang off its neighbours and announce its presence. Other things can remain undetected until they result in a disaster.
Thankfully, before the majority of things get to the stage of falure, there are little tell-tale signs that can be picked up on . Early action can prevent them developing into a major defect.
Look out for the following signs. The methods employed to detect them can be dialled into pre-ride checks.
When you acquire the habit the checks, and the quick fix remedies, beome pretty instinctive and can be performed any old time. The 5 'S' principle might help you remember most of the main considerations.
Sight : Viewed end on, or from above, an uneven wheel will be seen to wobble. In the case of a flat spot on the rim which takes it out of being perfectly circular the wheel has to be viewed side on.
Sensation : When held by the axles and spun, the movement in a perfectly built wheel will be almost undetectable. Wheels that are out of true to one side or the other will induce a wobble that will be felt through the fingers. A wheel with a flat spot in its circumferences will produce a 'limping' sensation.
Sound : Spoke tensions (on any given side) should be even. Pinging each spoke on the same side of a wheel should produce the same sound. Higher notes mean higher tensions. A dull "plunck" found between sweet "piiinnngggs" indicates a spoke that will brobably need tightening. NB The sound made by drive-side spokes will always be considerably higher pitched than that made by a non-drive-side ones. You can pluck the spokes individually or spin the wheel and allow a plastic tyre lever to strike them. If it sounds like a Les Dawson piano recital you've got problems.
Squeeze : Pinching pairs of spokes will reveal any that are flabby and need a wee tweak.
Scrapes : Another sound category but it will only be heard by those using rim brakes. If the wheel is out of true there will be an intermittent rubbing of the rim against the brake pads. NB If the rubbing is constant either the brake needs adjusting or the wheel may not be fully seated in the droput!
Once you've identified that there is a problem, and before doing anything about it, you'll need to find its precise site and nature before going any further. Spokes are not the only source of problems. Wobbles can also be caused by poorly adjusted bearings. A defect in a tyre, or how it is mounted, may give the impression of a problem with the rim. If the tyre has a bulge it will only be the tyre that will deviate. If the source is a loose bearing the oscilations will tend to be random. If it is an issue arising from rim alignment the deflection will be in the same spot every time. The best way to differentiate is to have a fixed point against which the system can be compared.
Wheels are a vital part of your bike. Without them it doesn't really do much? Whether they are traditionally constructed hoops or hi-tec modern sets an enormous amount of force passes through them. They transfer all the energy from you to the ground and vice versa. Spokes, the heart of the system, can loosen and, if neglected, a knock on effect may begin in which a series of spokes break. Ultimately this can result in total failiure of the wheel. Should a wheel fail it can have a number of consequences. Injury, expense, and the inconvenience of having to walk back are pretty obvious.
1. Spoke Anatomy
Not exciting but useful to know. In traditional wheels spokes are anchored at the rim with a specially designed nut known as a nipple. This is applied to a threaded portion on the spoke and used to bring the system into the tightness that gives the wheel strength. Spoke nipples are made in sizes and require a specific tool to tighten them.
At the other end there is a bend in the spoke sometimes referred to as the elbow. The elbow is finished off with a flange which is larger than the drillings in the rim and anchors the spoke at that point when the wheel is assembled.
The system is then tightened to the required levels. Then it's stressed to seat the bends, heads, nipples and points where the spokes cross. This is quite a physical process and one of the things that makes the big difference between a machine built wheel and one crafted by a real wheelbuilder. In handbuilt wheels the spokes are tweaked and tuned once more to make a final product that is designed to take the punishment you will inflict on it.
Rim tapes or strips are then applied to cover the spoke holes (not in tubeless rims) and the wheel is now ready to have a tyre, tube, cassette and/or rotors mounted.
On the trail, cassettes and disc rotors have to be worked around. Later, you'll see options that can help cut some the hassles involved.
SCOTTISH MOUNTAIN BIKING
ADVENTURES
Trail Tips
WHEELS
Printer friendly pages to work with at your bike
One of the easiest ways to learn about all aspects of how a wheel functions is to get hold of one and work on it. Bikes are always ending up on skips and practising on a discarded wheel will let you make mistakes that wont cost anything. The fact that these old wheels will have dents, dings, siezed/bent/broken spokes will only help in the long run as it's fixing that sort of stuff that will get you home one day! It's not until some folk actually begin to handle a wheel for maintenance purposes that they realise that (in the vertical plane) spokes support the rim when they are pulled on. Your weight goes through the frame/forks into the hubs and the spokes above the hubs pull on the upper part of the rim. So, if you thought that spokes supported weight on top of them you're not alone.
Finding the trouble spot
The exact site of the problem needs to be located before it can be remedied. On the trail something needs to be found that will do the approximate job of a wheelbuilding jig. Thankfully, for a running repair, all you need is a fixed point from which movement in the rim (both side to side and vertical) can be viewed as the wheel is rotated. All of the options shown below work well, it's just a question of finding one which suits you.
Rim brakes : If your bike has rim brakes attached their proximity to the wheel surface will let you know where the problem lies. By using cable and/or spring tension on V brakes you can bring the pads right up to the rim to act as a pretty accurate tool to see movement in the rim.
Brake bosses but no brakes : A length of reasonably stiff wire can be wound round a blanking bolt and bent toward the rim. The picture on the L shows a doubled loop p 30A fuse wire but plastic coated garden wire can just as easily be used.
No brake bosses : A rubber band can be used to lash a tyre lever into a suitable position as shown below R. Alternatively a longer length of wire can be wrapped round a stay or fork leg to end up with something similar to the L hand picture.
Once you've set up your makeshift guage you spin the wheel to watch and listen for the clues. Largely a matter of common sense and experience it's something that becomes reasonably easy after a while.
Reading the signs
All the wee wobbles and limps on a rim tell a story.
It may take a while to learn to read them instinctively. That's when the use of an old dud wheel to practice on (as suggested above) will prove its worth. By messing around with an already goosed bit of kit your mistakes will not cost money. You can make as many as you like without risk and that's a great way to learn and boost confidence.
Below are some of the common signs, the likely causes they tend to reveal, and suggestions as to what to do after identifying them.
Sign
Slight wobble to one side. The affected area will rub against the guage you have put in place. The point of maximum deviation indicates the centre of the area needing attention.
Likely cause
One or two loose spokes.
What to do
1. Look for a loss of spoke tension on the side opposite the deviation. So, if the rim is deviating to the R, a loose spoke found on the L will confirm the cause and vice versa
3. Test the suspect spokes using one or more of the checks described in section 5 of of P1.
4. If you find any, mark the culprits with a bit of thread, wool or blade of grass tied round them. This way when the weel is spun you'll be able to see which ones you're working on.
5. Begin to tighten the offending spoke or spokes 1/4 turn at a time until rim runs true. Don't be brutal and make sure to ease the pressure on. A wee dribble of oil always helps the process.
6. Work patiently and consider that you may need to release tension on the RH spokes as well.
If caught early on and sorted with a bit of skill this might be regarded as a permanent repair.
Sign
Flat spot on the rim with loose spokes, on both sides, immediately underneath.
Likely cause
An impact has flattened the rim disrupting the balance of spokes.
What to do
Getting a wheel back to a perfect circle, following a dunt, can be done but it's pretty difficult. Normally, on the trail, the best that can be managed is to tighten up the offending spokes. The remainder of the spokes in the system should also be assessed to check that they are not under too much strain.
A rebuild is usually inevitable when this sort of damage has been sustained.
Wheel Specific Trail Tools
To perform any of the adjustments above you will need a spoke key. This is nothing more than a small spanner for adjusting spoke nipples which, in turn, are just small nuts. Normally made of brass, but sometimes of aluminium alloy, the nipples come in different sizes and need a properly sized tool to adjust them. The soft metal from which they are constructed means that it is pretty easy to round off the faces and angles so take care. .
In the images below (approx life size) the nipples shown are made of electroplated brass. It can be seen that they are of different lengths. Given identical materials and quality, the one on the R will be stronger and more resistant to loosening as the threaded portion inside it is longer. Weight conscious riders, obsessing about rotatitng weight, may opt for the smaller and/or aluminium versions. For most of us, reliability is the main criterion to be considered. A case has to be made for taking the more resilient option whenever there is a choice.
Make sure you carry a spoke key that will fit the nipples on your wheels. Many riders carry workshop quality keys with them on the trail. Generally made as one separate key for each spoke size they weigh next to nothing and are definitely easier to use. If you go down that road just make sure you know what size nipples were used for any rebuilds or specifiy your requirements to the builder at the start of the process.
In the absence of a spoke key, a quality adjustable spanner can be used at a pinch.
Iif you get plenty of practice in with an old knackered wheel, as suggested the ability to spot the flaws and the remedies required comes reasonably quickly. Bringing a rim deliberately in and out of true you'll become pretty efficient and be confident enough to attend to most stuff on the trail.
The tool on the L (below) is kept handy in a jersey pocket. The the two nipple sizes of the keys (14 & 15) seem to be fitted to the bulk of wheels.
The contraption on the R forms part of the Crank Bros multi tool that lives in my backpack. It's main purpose is a chain tool but the body can be removed to allow use as a spoke key. It has a further two spoke nipple keys on the opposite side giving a total of four sizes.
On a front wheel or the non-drive side on ordinary rear wheels the steps above can be followed without too much difficulty. Add the fun and games involved with disc rotors and rear cassettes and it all becomes a bit more problematic.
While it is relatively simple to take a rotor off it is very time consuming. It's also easy to contaminate the braking surface in the process or lose some of the bolts in the grass.
Working on a cassette in the field can be a real barrel of laughs! Bits are easily mislaid and a frustrating time can be had trying to return individual sprockets back to front. Removing the casette alone presents a difficulty. There are devices that can be used to remove the lockring but they are are not something many would want to splash out on. Some of these actually use the structure of your frame to get the necessary leverage. If you're precious about your paintwork, or it's a delicate cut out assembly, that may be too horrific to contemplate.
Far better to have a solution that is quick, easy and avoids as many of these inconveniences as possible. CArrying an emergency spoke that can be applied without removing disc or cassette is a good idea
(c) Emergency spokes
If you have somewhere safe to keep them, it is perfectly feasible to carry adapted spokes that will allow use in the rear drive side or behind the most awkward rotor configuration. To customise a spoke for this purpose, file off 3 sides from the head of an ordinary spare spoke. This will allow it to be fished through awkward spots (without too much profanity) by anyone with the patience.
Traditionally, spare spokes have been carried, by generations of roadies and touring cyclists, strapped to frames, inside seatopsts or within the hollow of a pump piston rod. The 1st two don't work too well on a bike that gets the battering of a mountain bike and few riders now carry pumps long enough to stow a spoke. The most readily available solution in the UK is the Simson emergency spoke.
With a threaded end for the nipple and a hooked end for hub insertion, swaged to a length of steel cable, it really does the trick. Dead easy to fit and dead easy to carry they take out most of the hassle. They come in packs of two from St John's Street Cycles.
The Fiberfix is another prouct and is even more effective in that you don't necessarily need to take the old broken spoke out to apply it. The Fiberfix is made of kevlar cord and comes in a wee container that's so easy to carry. You can see how it works here.
