Post by Admin on Nov 15, 2014 21:48:35 GMT
PART ONE
Why build wheels?
The wide availability of inexpensive, well-built replacement wheels has reduced the need for wheelbuilding in retail bike shops. Nevertheless, there are still times when custom-built (or rebuilt) wheels are needed, especially in the case of higher-end bikes that have expensive hubs that are too good to throw away.
Also, the combination of hub and rim that you want may not be available off the shelf: commonly, for example, if you would like to use an internal-gear hub.
Learning to build wheels is an important milestone in the education of an apprentice mechanic. A "mechanic" who has not mastered this basic skill cannot be considered to be a fully-qualified, professional, and will always feel inferior to those who can list wheelbuilding among their skills.
Although this article was originally directed to shop mechanics, a knowledge of wheelbuilding can be invaluable to any cyclist who wishes to do his or her own maintenance and repair.
Building wheels from scratch is the best way to learn the craft of wheel truing, to get the feel for how a wheel responds to spoke adjustments. It is much easier to learn this with new, undamaged parts than to start right in trying to repair damaged wheels.
Getting started
While an experienced wheelbuilder can build a wheel in well under an hour, a beginner should expect to spend several hours on the task. It is best not to try to do this all at one sitting, because you are likely to get frustrated at the slowness of the truing and tensioning process. Better to put the job aside, even overnight, than to get careless and ruin a good wheel-in-progress.
This article focuses on building a rear wheel, because that is the more complicated one. For front wheels, disregard that which does not apply. This will be a 36 spoke, cross 3 wheel.
If you're doing a 32 spoke wheel, just substitute "32" wherever I write "36", "16" where I write "18" and "8" where I write "9."
Use a similar substitution for other spoke numbers.
Tools
You will need a spoke wrench (I use a DT spoke wrench, but most people aren't ready for a $50 spoke wrench. My favorite inexpensive spoke wrench is a plastic one with a metal bit, called a "Spokey"). You will also need a small flat-bladed screwdriver; and optionally, a truing stand and a dish stick.
The truing stand and dish stick are by far the most expensive of these tools. Improvised tools or the bicycle itself can substitute. If you are on a tight budget, read the section of this article on truing, so you know the technical terms, and then check out the section near the end of this article on improvised tools.
Spoke wrench Truing stand Dish Stick
Materials
Hubs
All modern hubs of decent quality have aluminum spoking flanges. Better-quality hubs are usually made by forging, and only forged hubs should be used for radial-spoked front wheels. I would generally advise avoiding overpriced "boutique" hubs which are made by CNC machining, since their flanges are usually weaker than those of forged hubs.
Better hubs have thick flanges and spoke holes flared like the bell of a trumpet, to support the elbows of the spokes, though this is not essential -- aluminum is softer than steel, and the spokes will bed themselves into it. But if the flanges are not thick enough to pull the elbows against them, then you may need to use washers under the spoke heads.
If you are buying new hubs, the best value for the money, in most cases, is Shimano. If you want the very best, cost no object, in many applications, this is Phil Wood.
Spokes
The material of choice for spokes is stainless steel. Stainless is strong and will not rust. Cheap wheels are built with chrome-plated ("UCP") or zinc-plated ("galvanized") carbon-steel spokes which are not as strong, and are prone to rust.
The leading brands of spokes available in the U.S. market are DT and Wheelsmith.
Titanium is also used for spokes, but, in my opinion it is a waste of money. Titanium spokes should only be used with brass nipples, and the combination is not significantly lighter than stainless spokes with aluminum nipples.
Carbon fiber spokes, end of story...Carbon fiber spokes have been available, but turned out to be brittle and dangerous. If you bend one, it breaks like uncooked spaghetti! Carbon fiber, aluminum alloy and polycarbonate plastic spokes all have to be thicker than steel spokes, and the added air resistance slows you down more than the weight saving speeds you up -- unless you only ride uphill.
How Many Spokes?
Up until the early 1980s, virtually all adult bikes had 72 spokes.
32 front/40 rear was the standard for British bikes, 36 front and rear for other countries. The exception was super-fancy special purpose racing wheels, which might have 32 spokes front and rear.
The Great Spoke Scam: In the early '80s a clever marketeer hit upon the idea of using only 32 spokes in wheels for production bikes. Because of the association of 32 spoke wheels with exotic, high-performance bikes, the manufacturers were able to cut corners and save money while presenting it as an "upgrade!" The resulting wheels were noticeably weaker than comparable 36 spoke wheels, but held up well enough for most customers.
Since then, this practice has been carried to an extreme, with 28-, 24-, even 16-spoke wheels being offered, and presented as it they were somehow an "upgrade."
Actually, such wheels normally are not an upgrade in practice. When the spokes are farther apart on the rim, it is necessary to use a heavier rim to compensate, so there isn't usually even a weight benefit from these newer wheels!
This type of wheel requires unusually high spoke tension, since the load is carried by fewer spokes. If a spoke does break, the wheel generally becomes instantly unridable. The hub may break too; see John Allen's article.
If you want highest performance, it is generally best to have more spokes in the rear wheel than the front. For instance, 28/36 is better than 32/32. People very rarely have trouble with front wheels:
Front wheels are symmetrically dished.
Front wheels carry less weight.
Front wheels don't have to deal with torsional loads (unless there's a hub brake).
If you have the same number of spokes front and rear, either the front wheel is heavier than it needs to be, or the rear wheel is weaker than it should be.
Spoke Gauges
The diameter of spokes is sometimes expressed in terms of wire gauges. There are several different national systems of gauge sizes, and this has been a great cause of confusion. A particular problem is that French gauge numbers get smaller for thinner wires, while the U.S./British gauge numbers get larger for thinner wires. The crossover point is right in the popular range of sizes used for bicycle spokes:
U.S./British 14 gauge is the same as French 13 gauge
U.S./British 13 gauge is the same as French 15 gauge
Newer I.S.O. practice is to ignore gauge numbers, and refer to spokes by their diameter in millimeters:
U.S./British 13 gauge is 2.3 mm
U.S./British 14 gauge is 2.0 mm
U.S./British 15 gauge is 1.8 mm
U.S./British 16 gauge is 1.6 mm
Spokes come in straight-gauge or swaged (butted) styles. Straight-gauge spokes have the same thickness all along their length from the threads to the heads.
Swaged spokes come in 5 varieties:
Single-butted spokes are thicker than normal at the hub end, then taper to a thinner section all the way to the threads. Single-butted spokes are not common, but are occasionally seen in heavy-duty applications where a thicker-than-normal spoke is intended to be used with a rim that has normal-sized holes.
Double-butted spokes are thicker at the ends than in the middle. The most popular diameters are 2.0/1.8/2.0 mm (also known as 14/15 gauge) and 1.8/1.6/1.8 (15/16 gauge).
Double-butted spokes do more than save weight. The thick ends make them as strong in the highly-stressed areas as straight-gauge spokes of the same thickness, but the thinner middle sections make the spokes effectively more elastic, allowing them to stretch (temporarily) more than thicker spokes.
As a result, when the wheel is subjected to sharp localized stresses, the most heavily-stressed spokes can elongate enough to shift some of the stress to adjoining spokes. This is particularly desirable when the limiting factor is how much stress the rim can withstand without cracking around the spoke holes.
Triple-butted spokes, such as the DT Alpine III, are the best choice when durability and reliability are the primary aim, as with tandems and bicycles for loaded touring. They share the advantages of single-butted and double-butted spokes. The DT Alpine III, for instance, is 2.34 mm (13 gauge) at the head, 1.8 mm (15 gauge) in the middle, and 2.0 mm (14 gauge) at the threaded end.
Single- and triple-butted spokes solve one of the great problems of wheel design: Since spokes use rolled, not cut threads, the outside diameter of the threads is larger than the base diameter of the spoke wire. Since the holes in the hub flanges must be large enough for the threads to fit through, the holes, in turn, are larger than the wire requires. This is undesirable, because a tight match between the spoke diameter at the elbow and the diameter of the flange hole is crucial to resisting fatigue-related breakage.
Since single- and triple-butted spokes are thicker at the head end than at the thread end, they may be used with hubs that have holes just large enough to pass the thick wire at the head end.
Æro (elliptical) spokes are a variety of double-butted spoke in which the thin part is swaged into an elliptical cross section, making these spokes a bit more ærodynamic than round-section spokes. The most widely available spokes of this type are the Wheelsmith Æro. These are 2.2 x 1.8 mm at the ends, and the middles are equivalent to 16 gauge, but in the form of a 1.8 x 1.2 mm ellipse. The Wheelsmith Æro is my favorite spoke for high-performance applications, not just because of whatever ærodynamic advantage it may offer, but because the flat center section provides an excellent visual indicator to help the wheelbuilder eliminate any residual twist in the spoke. This helps build a wheel that will stay true.
Æro (bladed) spokes have a more pronounced æro shape, flat, rather than elliptical. Although they are the most ærodynamic of spokes, they won't normally fit through the holes in a standard hub because they are too wide. To use "blades", the hub must be slotted with a file. Slotting the holes can weaken the flange, and will usually void the warranty of the hub. It is also a lot of trouble.
There was a fad in the early '90s for Hoshi "blades" which had a double bend instead of a conventional head. The double bend allowed the spokes to be inserted "head first" into the hub flange, so that they could be used with normal hubs. Unfortunately, they turned out to be prone to breakage, and I can't recommend them.
[Following comment is by John Allen]
I recommend thicker spokes for the right side of a dished rear wheel (a wheel used with a cassette) than the left side, because the left-side spokes are under lower tension. The thinner spokes on the left side will be working more nearly at the tension for which they are designed, and so they will be stretched more and less likely to go slack. For more details, see my article on spoke tension.
[Now, returning control to Sheldon...]
My Bicycle Glossary has a Table of Spoke Weights, for those who care about such things.
Nipples
Nipples are commonly made of nickel-plated brass. This is a good material choice, because brass takes very smooth threads, and brass nipples don't get corroded into position too easily.
For light-weight, high-performance wheels, aluminum nipples are available. Aluminum nipples do save a small amount of weight, and they can be quite reliable if used properly. They should only be used with rims that have eyelets of some material other than aluminum, because aluminum/aluminum contact between rim and nipple can result in chemical welding, immobilizing the nipples.
Rims
Older rims were made of steel, but steel rims are now obsolete, and only found on the cheapest, crummiest bicycles. Aluminum rims have superseded steel, because they are lighter, stronger, rust-proof and provide better braking.
Modern rims are made of extruded aluminum, that is, the semi-molten aluminum is squeezed out of specially-shaped openings which determine the cross section of the rim. The extrusions are formed into hoops, then joined either by welding or by the insertion of a filler piece into the hollows of each end of the rim.
[Following paragraphs added by John Allen]
An impact with a pothole edge, rock, etc. can damage a rim. Rim brakes wear down the sidewalls of aluminum rims, especially in wet-sandy conditions. Eventually, the air pressure in the tire can bulge a sidewall out, causing a blowout. You can usually just transfer the old spokes to a new rim, avoiding the need to relace the wheel -- see Jobst Brandt's article.
A single-wall rim has a simple U shape with a a single layer of metal across the bottom where the spokes attach. a double-wall (or box-section) rim has two layers, with a cavity in between. The spokes then attach at the lower layer, closer to the hub, and the upper layer has holes large enough to allow insertion of the nipple heads or a screwdriver. Many good quality rims have "eyelets" or "ferrules" to reinforce the spoke holes.The best double-wall rims have ferrules which spread the load to both layers, allowing these rims to be lighter and/or stronger.
Why build wheels?
The wide availability of inexpensive, well-built replacement wheels has reduced the need for wheelbuilding in retail bike shops. Nevertheless, there are still times when custom-built (or rebuilt) wheels are needed, especially in the case of higher-end bikes that have expensive hubs that are too good to throw away.
Also, the combination of hub and rim that you want may not be available off the shelf: commonly, for example, if you would like to use an internal-gear hub.
Learning to build wheels is an important milestone in the education of an apprentice mechanic. A "mechanic" who has not mastered this basic skill cannot be considered to be a fully-qualified, professional, and will always feel inferior to those who can list wheelbuilding among their skills.
Although this article was originally directed to shop mechanics, a knowledge of wheelbuilding can be invaluable to any cyclist who wishes to do his or her own maintenance and repair.
Building wheels from scratch is the best way to learn the craft of wheel truing, to get the feel for how a wheel responds to spoke adjustments. It is much easier to learn this with new, undamaged parts than to start right in trying to repair damaged wheels.
Getting started
While an experienced wheelbuilder can build a wheel in well under an hour, a beginner should expect to spend several hours on the task. It is best not to try to do this all at one sitting, because you are likely to get frustrated at the slowness of the truing and tensioning process. Better to put the job aside, even overnight, than to get careless and ruin a good wheel-in-progress.
This article focuses on building a rear wheel, because that is the more complicated one. For front wheels, disregard that which does not apply. This will be a 36 spoke, cross 3 wheel.
If you're doing a 32 spoke wheel, just substitute "32" wherever I write "36", "16" where I write "18" and "8" where I write "9."
Use a similar substitution for other spoke numbers.
Tools
You will need a spoke wrench (I use a DT spoke wrench, but most people aren't ready for a $50 spoke wrench. My favorite inexpensive spoke wrench is a plastic one with a metal bit, called a "Spokey"). You will also need a small flat-bladed screwdriver; and optionally, a truing stand and a dish stick.
The truing stand and dish stick are by far the most expensive of these tools. Improvised tools or the bicycle itself can substitute. If you are on a tight budget, read the section of this article on truing, so you know the technical terms, and then check out the section near the end of this article on improvised tools.
Spoke wrench Truing stand Dish Stick
Materials
Hubs
All modern hubs of decent quality have aluminum spoking flanges. Better-quality hubs are usually made by forging, and only forged hubs should be used for radial-spoked front wheels. I would generally advise avoiding overpriced "boutique" hubs which are made by CNC machining, since their flanges are usually weaker than those of forged hubs.
Better hubs have thick flanges and spoke holes flared like the bell of a trumpet, to support the elbows of the spokes, though this is not essential -- aluminum is softer than steel, and the spokes will bed themselves into it. But if the flanges are not thick enough to pull the elbows against them, then you may need to use washers under the spoke heads.
If you are buying new hubs, the best value for the money, in most cases, is Shimano. If you want the very best, cost no object, in many applications, this is Phil Wood.
Spokes
The material of choice for spokes is stainless steel. Stainless is strong and will not rust. Cheap wheels are built with chrome-plated ("UCP") or zinc-plated ("galvanized") carbon-steel spokes which are not as strong, and are prone to rust.
The leading brands of spokes available in the U.S. market are DT and Wheelsmith.
Titanium is also used for spokes, but, in my opinion it is a waste of money. Titanium spokes should only be used with brass nipples, and the combination is not significantly lighter than stainless spokes with aluminum nipples.
Carbon fiber spokes, end of story...Carbon fiber spokes have been available, but turned out to be brittle and dangerous. If you bend one, it breaks like uncooked spaghetti! Carbon fiber, aluminum alloy and polycarbonate plastic spokes all have to be thicker than steel spokes, and the added air resistance slows you down more than the weight saving speeds you up -- unless you only ride uphill.
How Many Spokes?
Up until the early 1980s, virtually all adult bikes had 72 spokes.
32 front/40 rear was the standard for British bikes, 36 front and rear for other countries. The exception was super-fancy special purpose racing wheels, which might have 32 spokes front and rear.
The Great Spoke Scam: In the early '80s a clever marketeer hit upon the idea of using only 32 spokes in wheels for production bikes. Because of the association of 32 spoke wheels with exotic, high-performance bikes, the manufacturers were able to cut corners and save money while presenting it as an "upgrade!" The resulting wheels were noticeably weaker than comparable 36 spoke wheels, but held up well enough for most customers.
Since then, this practice has been carried to an extreme, with 28-, 24-, even 16-spoke wheels being offered, and presented as it they were somehow an "upgrade."
Actually, such wheels normally are not an upgrade in practice. When the spokes are farther apart on the rim, it is necessary to use a heavier rim to compensate, so there isn't usually even a weight benefit from these newer wheels!
This type of wheel requires unusually high spoke tension, since the load is carried by fewer spokes. If a spoke does break, the wheel generally becomes instantly unridable. The hub may break too; see John Allen's article.
If you want highest performance, it is generally best to have more spokes in the rear wheel than the front. For instance, 28/36 is better than 32/32. People very rarely have trouble with front wheels:
Front wheels are symmetrically dished.
Front wheels carry less weight.
Front wheels don't have to deal with torsional loads (unless there's a hub brake).
If you have the same number of spokes front and rear, either the front wheel is heavier than it needs to be, or the rear wheel is weaker than it should be.
Spoke Gauges
The diameter of spokes is sometimes expressed in terms of wire gauges. There are several different national systems of gauge sizes, and this has been a great cause of confusion. A particular problem is that French gauge numbers get smaller for thinner wires, while the U.S./British gauge numbers get larger for thinner wires. The crossover point is right in the popular range of sizes used for bicycle spokes:
U.S./British 14 gauge is the same as French 13 gauge
U.S./British 13 gauge is the same as French 15 gauge
Newer I.S.O. practice is to ignore gauge numbers, and refer to spokes by their diameter in millimeters:
U.S./British 13 gauge is 2.3 mm
U.S./British 14 gauge is 2.0 mm
U.S./British 15 gauge is 1.8 mm
U.S./British 16 gauge is 1.6 mm
Spokes come in straight-gauge or swaged (butted) styles. Straight-gauge spokes have the same thickness all along their length from the threads to the heads.
Swaged spokes come in 5 varieties:
Single-butted spokes are thicker than normal at the hub end, then taper to a thinner section all the way to the threads. Single-butted spokes are not common, but are occasionally seen in heavy-duty applications where a thicker-than-normal spoke is intended to be used with a rim that has normal-sized holes.
Double-butted spokes are thicker at the ends than in the middle. The most popular diameters are 2.0/1.8/2.0 mm (also known as 14/15 gauge) and 1.8/1.6/1.8 (15/16 gauge).
Double-butted spokes do more than save weight. The thick ends make them as strong in the highly-stressed areas as straight-gauge spokes of the same thickness, but the thinner middle sections make the spokes effectively more elastic, allowing them to stretch (temporarily) more than thicker spokes.
As a result, when the wheel is subjected to sharp localized stresses, the most heavily-stressed spokes can elongate enough to shift some of the stress to adjoining spokes. This is particularly desirable when the limiting factor is how much stress the rim can withstand without cracking around the spoke holes.
Triple-butted spokes, such as the DT Alpine III, are the best choice when durability and reliability are the primary aim, as with tandems and bicycles for loaded touring. They share the advantages of single-butted and double-butted spokes. The DT Alpine III, for instance, is 2.34 mm (13 gauge) at the head, 1.8 mm (15 gauge) in the middle, and 2.0 mm (14 gauge) at the threaded end.
Single- and triple-butted spokes solve one of the great problems of wheel design: Since spokes use rolled, not cut threads, the outside diameter of the threads is larger than the base diameter of the spoke wire. Since the holes in the hub flanges must be large enough for the threads to fit through, the holes, in turn, are larger than the wire requires. This is undesirable, because a tight match between the spoke diameter at the elbow and the diameter of the flange hole is crucial to resisting fatigue-related breakage.
Since single- and triple-butted spokes are thicker at the head end than at the thread end, they may be used with hubs that have holes just large enough to pass the thick wire at the head end.
Æro (elliptical) spokes are a variety of double-butted spoke in which the thin part is swaged into an elliptical cross section, making these spokes a bit more ærodynamic than round-section spokes. The most widely available spokes of this type are the Wheelsmith Æro. These are 2.2 x 1.8 mm at the ends, and the middles are equivalent to 16 gauge, but in the form of a 1.8 x 1.2 mm ellipse. The Wheelsmith Æro is my favorite spoke for high-performance applications, not just because of whatever ærodynamic advantage it may offer, but because the flat center section provides an excellent visual indicator to help the wheelbuilder eliminate any residual twist in the spoke. This helps build a wheel that will stay true.
Æro (bladed) spokes have a more pronounced æro shape, flat, rather than elliptical. Although they are the most ærodynamic of spokes, they won't normally fit through the holes in a standard hub because they are too wide. To use "blades", the hub must be slotted with a file. Slotting the holes can weaken the flange, and will usually void the warranty of the hub. It is also a lot of trouble.
There was a fad in the early '90s for Hoshi "blades" which had a double bend instead of a conventional head. The double bend allowed the spokes to be inserted "head first" into the hub flange, so that they could be used with normal hubs. Unfortunately, they turned out to be prone to breakage, and I can't recommend them.
[Following comment is by John Allen]
I recommend thicker spokes for the right side of a dished rear wheel (a wheel used with a cassette) than the left side, because the left-side spokes are under lower tension. The thinner spokes on the left side will be working more nearly at the tension for which they are designed, and so they will be stretched more and less likely to go slack. For more details, see my article on spoke tension.
[Now, returning control to Sheldon...]
My Bicycle Glossary has a Table of Spoke Weights, for those who care about such things.
Nipples
Nipples are commonly made of nickel-plated brass. This is a good material choice, because brass takes very smooth threads, and brass nipples don't get corroded into position too easily.
For light-weight, high-performance wheels, aluminum nipples are available. Aluminum nipples do save a small amount of weight, and they can be quite reliable if used properly. They should only be used with rims that have eyelets of some material other than aluminum, because aluminum/aluminum contact between rim and nipple can result in chemical welding, immobilizing the nipples.
Rims
Older rims were made of steel, but steel rims are now obsolete, and only found on the cheapest, crummiest bicycles. Aluminum rims have superseded steel, because they are lighter, stronger, rust-proof and provide better braking.
Modern rims are made of extruded aluminum, that is, the semi-molten aluminum is squeezed out of specially-shaped openings which determine the cross section of the rim. The extrusions are formed into hoops, then joined either by welding or by the insertion of a filler piece into the hollows of each end of the rim.
[Following paragraphs added by John Allen]
An impact with a pothole edge, rock, etc. can damage a rim. Rim brakes wear down the sidewalls of aluminum rims, especially in wet-sandy conditions. Eventually, the air pressure in the tire can bulge a sidewall out, causing a blowout. You can usually just transfer the old spokes to a new rim, avoiding the need to relace the wheel -- see Jobst Brandt's article.
A single-wall rim has a simple U shape with a a single layer of metal across the bottom where the spokes attach. a double-wall (or box-section) rim has two layers, with a cavity in between. The spokes then attach at the lower layer, closer to the hub, and the upper layer has holes large enough to allow insertion of the nipple heads or a screwdriver. Many good quality rims have "eyelets" or "ferrules" to reinforce the spoke holes.The best double-wall rims have ferrules which spread the load to both layers, allowing these rims to be lighter and/or stronger.