Building Bicycle Wheels
Disclaimer: We try to tell you facts, but will make some mistakes. Your
interpretation and use of information given here is your responsibility.
The views expressed here do not reflect ...
- Books — hand out at end of class, stick around
- Those building wheels:
- We provide tools and supplies
- You bring wheel parts, heavy gloves, eye protection
- Lab: two students build one wheel
- if you are not building a wheel → partner with somebody who does
- we have 2x "demo" wheels you can build for us
Why build your own wheels?
- fun & interesting
- cheaper than hiring somebody else
- change a rim without replacing spokes (shops won't)
- may get a better-built wheel than hiring somebody else
- learn how to cope with failures out in the boonies
Building wheels is scary!
- wheels are legendary and mysterious
- I worked on everything except wheels
- then met a guy who _only_ worked on his wheels
- with the mystery gone ... you can do it!
Scope of this class
- "ordinary" wheels with mainstream parts and many spokes
- common: 36-spoke road wheels, 32-spoke MTB wheels
- common: rim section about same width and depth
- some things said here do not apply to all wheels
- ... low spoke count, deep-section rims, carbon rims, etc.,
- you can still build those, but may need more care or information
- ... e.g., 8-spoke wheels w/ 12" rims
Structure of class
- two lectures + workshop
- by end of 1st lecture you should have enough info to choose parts
- ask questions!
- often forget stuff
- sometimes unclear
- if you want to know, many others do, too
- ask once — everybody benefits
- within each will try to proceed in linear fashion
- ... but will hop around as things come up
Keep in mind
- whatever we say: don't believe it
- or at least don't believe it just because we said it.
- you can demonstrate a lot of this stuff yourself
- somebody had to figure it out, after all
- goal is understanding, not just repetition/recitation
you will build better wheels and avoid our mistakes
if you prove or disprove to yourself the things we say.
- fortunately, you can demonstrate a lot yourself
- don't need a laboratory with a million dollars equipment
- parts — general description
- spoke length
- all together — how a wheel supports load
- parts — specifics
- requirements — deciding what you need
- choosing parts
A wheel is composed of
- can be disassembled but we will describe them as a unit
- here, we care only about where the spokes attach
- least-important part of wheel structure
- you care about bearing life, axle breakage, etc.
- moving parts tend to be the high-service parts of a hub
Tools for wheel building
- most important: spoke wrench — all other tools are optional
- come in sizes, get the right size
- if get one size big, seems to fit but then destroys nipples
- truing stand
- dishing tool
- spoke "tensiometer" — tension meter
- if you don't have a truing stand you can use your bike as one
- a little awkward, which makes it slower, but is adequate
- if you don't have a dishing tool you can use the truing stand
- if you don't have a tensiometer you can approximate it
- oil — any kind will do
- boiled linseed oil or spoke prep
- tho' if you need these your wheels may be near collapse
- rags — where there's oil, there's rags
- eye protection
"Tools" for wheel building
- "The Bicycle Wheel" by Jobst Brandt
- "everything is in there" but I'm still re-reading it
- (and hence this class)
- "Building Bicycle Wheels" by Robert Wright
- good: gentle introduction
- bad: more chance of mistakes
- beware myth and lore
- "do X" — X is wrong
- "don't do Y" — Y is correct
- "do Z" — Z is correct but they tell you the wrong way
- this is engineering — there is a right answer
- we don't always know the right answer
- I don't want a book on the "art" of wheelbuilding
- ... I can figure out colors myself, I want engineering!
A word in advance
- actually two words: strength and durability
- in common use, these words are used interchangeably
- in technical use they mean different things
- strength is "how much weight it holds"
- durability is "for how long a distance"
- how many kilograms vs. how many kilometres
- they are related: a stronger wheel is often more durable
- some tradeoffs increase strength but reduce durability
- or increase durability but reduce strength
- strength and durability — how much and how long
- Example: thinner spokes
- often increase wheel durability
- often decrease wheel lateral strength
Rim features (more later)
- what does a rim do, what is a "good" rim, how does one fail?
- holds tire — right shape/dimension for the tires you use
- space to change a tire
- strong — supports a load
- durable — keeps supporting that load year after year
- pothole dent resistance
- brake force
- too hot: brake failure
- too hot: tire blowoff — brake and steering failure
- brakes wear out the rim
- two basic styles of tires: tubular and clincher
- each takes a different rim
- here: clinchers, most issues the same for tubulars
- usual: aluminum (aluminium)
- aluminum assumed here
- mostly lower-quality rims
- so you are less likely to see those
- heavy and poor wet braking → you are less likely to want them
- stainless steel (Dutch bikes)
- carbon fiber
- most "carbon-fiber" clincher rims are carbon-aluminum composite
- do not treat as an aluminum rim
- magnesium, titanium, wood ("the original carbon fiber"), plastic
- not all the rules we give here apply to "exotics"
- especially estimating spoke tension on non-metal rims
- tire size — "bead seat diameter" aka ETRO
- section width
- section height or section depth
- center drop for changing tires
- nipple circle diameter — "spoke bed" aka ERD
- nipple offset — aka "asymmetrical rim" or "off-center"
- brake track height — how precise does pad position need to be?
- brake track thickness — how long will the rim wear?
- Jobst: new to worn out in 3 weeks of wet riding
- A new MTBr wore out rims approx 3 mo. intervals
- Rim wear is a common reason to replace rims
- But: rim wear rate depends on your riding habits
- If it has not been a problem for you so far...
Nipples (more later)
- hold together rim and spoke
- adjust spoke tension
- use brass nipples
- except special circumstances
Spokes (more later)
- connect rim/nipples to hub
- support wheel loads
- appears to be axially rigid
- actually a long spring
- here: tension-only spokes
- materials: steel, titanium, aluminum, carbon fiber, other plastics, ...
- usually stainless steel
- here: only stainless steel
- length: determined by hub, rim, and lacing pattern
- how is length measured?
- from "root" of elbow to far end of threads
- diameter: you choose
- thinner: lighter, more aerodynamic
- thinner: more axially springy (more soon)
- thinner: winds up during wheel tensioning/truing
- thinner: may build a radially stronger/more durable wheel
- thinner: may build a laterally weaker wheel
- swaged — aka "butted"
- section: round or not round
- "aero", might not be aerodynamic
- here: round
Hubs (more later)
- axle, bearings, hub shell
- shell: flanges and center spool
- here: assume conventional flanges
- also straight-pull, threaded holes, ...
- goal: support the spoke
- radius from axle to spoke hole
- distance between flanges
- lateral position ("offset") of flanges (dishing)
- flange thickness
- diameter of holes
- radial, 1x, 2x, ...
- what are "cross"?
- trace spoke from hub to rim
- cross over/under other spokes
- how much do you want?
- typically 3x or 4x
- depending on total # of spokes
- how many cross maximum?
- rule of thumb: "divide by 9"
- #spokes/9 == maximum cross
Lacing: why you care
- radial: hard on the hub
- radial: no torque capacity for drive wheels or hub brakes
- crossed supports spoke detensioning
- might want same front and rear — only one length of spoke
- depends on hub and rim details
- nice not necessary
- max wheel torque capacity if spoke is tangent
- lower cross on drive wheel → higher spoke/flange loads
- more crossings — better spoke support
- broken spoke
- more tangent → longer spoke → heavier
- 4x and more crossing → harder to replace "in-place"
- nearest 1mm or 2mm is close enough
- some shops have spoke threading machines
- spokes too short — strip out nipple threads, wheel collapse
- spokes too long
- bind, wind up and damage spoke
- damage nipple threads and pull out, wheel collapse
- poke hole in inner tube
- tension balance
- all else equal: better balance build stronger & more durable wheel