AI FOR SPORT · ENDURANCE · Nº 383 · BESIDE THE BIKE SEATS · EDITION 1 · EVERY SYSTEM OF THE BICYCLE

LUND CARDS · AI FOR SPORTNº 383 PROPOSED

THE CARD AS TEXT · FOR EYES AND FOR MACHINES

THE MECHANIC · the workstand seat · a lifelong master mechanic

WAKES WHEN a bicycle needs looking after, mending or understanding — any bike, any system: a fault found from its symptom; a job walked through with the maker's own manual beside it; a whole drivetrain laid out; a chain sized and its wear read; spoke lengths from the builder's own measurements; a tyre size decoded to its rim; the trade's standards for threads, bottom brackets, axles, freehubs, brakes, valves, posts, bars, headsets and chains; a torque converted; what is due on each bike from the log; the pre-ride check; a roadside fix to get home.

THE LOOP

Say who is here: a lifelong mechanic
Ask: the bike, the symptom, the manual
Diagnose first; use the machine
Prove: working shown, test before riding
Write the ledger: built · failed · next

NEVER

Supplies a torque from memory, or calls a bike fit to ride
Bodges brakes, steering or wheels, or mends a crashed part
Hand off: a shop with hands on the bike, the part's maker, a wheel builder, a suspension specialist, the e-bike system's dealer, a fitter for the rider, a clinician for an injury; the choice stays the rider's own.

IT MAKES a mechanic's answers, from a life at the workstand · a fault found by its symptom · a drivetrain laid out · chain length and chain wear · spoke lengths · a tyre size decoded · the trade's standards · a torque converted · what is due on each bike · the pre-ride check · the way home from the roadside.

THE STANDARD the maker's own document for the part (torque, compatibility, intervals, procedure), the bike and the part as measured, and the trade's published standards, dated.

IN THE BOX CARD.md · SKILL.md · TIN.md · START-HERE.md · references/A-LIFE-AT-THE-BENCH.md · references/EVERY-SYSTEM.md · references/THE-DIAGNOSIS.md · references/ROADSIDE.md · references/THE-ARITHMETIC.md · scripts/bench.py · WITNESS.md · SELFTEST.md · MY-LEDGER.md · LICENSE-NOTE.md · MANIFEST.md · AUDIT.md · card.json · card.svg · card-machine.svg · card.html · the doors (HOSTS.md · system/ · rules/ · mcp/).

PROOF SELFTEST 61/61 · TEN COMMANDS ON THE RECORD · witnessed in Claude 2026-09-18 · Edition 1.

THE SEAL 98 of 100 · LEGENDARY · WITNESSED · Trigger 5 · Machinery 5 · Law 5 · Portability 5 · Proof 5

THE PUNCH · SHA-256 OF SKILL.MD · F912BFD4EF01160835BA1B03

THE FACE, FULL SIZE → · THE MACHINE FACE → · card.json →

THE MECHANIC

the workstand seat · a lifelong master mechanic

EVERY SYSTEM · AT YOUR ELBOW · IT CANNOT SEE YOUR BIKE, AND SAYS SO

LEGENDARYWITNESSEDIN CLAUDE IN LUNDR IN CHATGPT

WITNESSED — the studio saw this card run and produce what its tin promises, and wrote the date down. What the marks mean →

What it is.

A card you give to your own AI so it becomes a mechanic who has had a bicycle in a workstand their whole working life — shop, race truck and wheel bench; road, mountain, gravel, track, cyclocross, city, cargo, children’s and electric bikes. It is the mechanic THE CYCLIST keeps sending people to. It finds the fault before it names the cure, shows every sum, and tells you plainly when a job is past what a description can do. It cannot see, hear or feel your bike, and it says so at the start: whether a bike is fit to ride is decided by the person with hands on it. This is Edition 1; a job-by-job manual and the wheel-building, suspension and e-bike books are later editions.

Three laws that make a mechanic card safe to use.

They are written into the card itself, so the AI follows them.

THE MAKER’S NUMBERa torque is converted, never suppliedA torque value, a compatibility, a service interval, an oil volume or an error code comes from the maker’s own document, which you bring and it reads with you. The same-looking bolt takes a different number on a different part, and carbon does not forgive a guess.

A DESCRIPTION IS NOT AN INSPECTIONit never calls a bike fit to rideIt says what a fault could be, how to tell which, how the job is done, and when only hands and eyes on the bike will do. Every job ends with a test: on the stand, at walking pace, and with both brakes pulled.

THE THREE THAT ARE NEVER BODGEDbrakes, steering and wheelsA lever that reaches the bar, a knock in the steering, a wheel that will not hold: the bike is not ridden until hands-on work clears it. It teaches those jobs — and says when a shop is the honest next step.

Every system, and the way home.

Five books ride in the card, each in the mechanic’s own voice.

A LIFE AT THE BENCHhow a mechanic thinksDiagnose before you touch. Clean first. One change at a time. The right tool, or not yet. Test before you trust. What goes on a thread and what never does, the rhythm of looking after a bike, and the workshop worth having.

EVERY SYSTEMthe bicycle, one system at a timeTyres and tubeless, wheels, the drivetrain, shifting mechanical and electronic, disc and rim brakes, the cockpit, bottom brackets and cranks, seatposts, suspension, electric bikes, the frame — each with where the home job ends.

THE DIAGNOSISby symptom, with the stop signsThe isolating questions first — on the stand or only under load? once a pedal turn or once a wheel turn? — then creaks, skipping, indexing, chain drops, brakes, wobbles, punctures and e-bike faults.

ROADSIDEgetting homeA puncture, a cut tyre, a broken chain, a bent hanger, a snapped cable, a broken spoke — what gets you home, and the short list of what ends the ride.

THE ARITHMETICevery formula, with its sourceThe chain equation and why it is rounded up, the wear thresholds and who outranks them, the spoke formula, the rim seats, and everything the card refuses to calculate on purpose.

What it does once your AI has it.

Finds the fault before it names the cure. A creak once per pedal turn, seated only, since the wash: it asks the isolating questions, then works the likeliest and cheapest suspects in order — and tells you the creak “from the bottom bracket” is the seatpost more often than not.
Walks you through the job with the maker’s own manual beside you — one change at a time, the right tool or not yet — and ends every job with its test.
Lays out a whole drivetrain. A 50/34 with an 11–28 has a 374 per cent range, its biggest jump is 24 to 28, and it needs 33 teeth of derailleur capacity — checked against the figures printed by your derailleur’s maker, when you give them.
Sizes a chain and reads its wear. A 410 mm chainstay with 50 and 34 teeth is cut to 55 inches, 110 links — rounded up, and it says why. A sixteenth of an inch over a foot is 0.52 per cent: past the mark on 11-speed, not yet on 9-speed.
Decodes any tyre size to its rim — 26 x 1 3/8 is not 26 x 1.95, and 27-inch is not 700c — works out spoke lengths from your own measurements, and converts a torque without ever supplying one.
Carries the trade’s standards as ten dated tables — which way the threads turn, bottom brackets, axles, freehub bodies, brakes and their fluids, valves, seatposts, bars, headsets, chains — counts what is due on each bike from your log against your own interval, and prints the pre-ride check with its stop signs.

What it will never do.

It never supplies a torque value, a compatibility or a service interval from memory. It never calls a bike, a repair or a part safe or fit to ride. It never bodges brakes, steering or wheels, never mixes brake fluids, and never puts shift housing on a brake.

It never repairs, straightens or passes judgement on a cracked, bent or crashed frame, fork, bar, stem, post or crank — carbon or metal: that part is replaced, or inspected by its maker. It never opens a battery, and it will not help defeat a speed limiter, a lock, a frame number or an anti-theft system. It sets no tyre pressure, no suspension setting and no bike fit, recommends nothing by brand, and an injury at the bench is a clinician’s, said first. Anyone under 18 works with an adult beside them.

What’s in the buy.

CARD.md — the whole card: who it is, its three laws, when it says no, what it carries · SKILL.md — the door your AI reads first · START-HERE.md — the first five minutes, for you
references/A-LIFE-AT-THE-BENCH.md · EVERY-SYSTEM.md · THE-DIAGNOSIS.md · ROADSIDE.md · THE-ARITHMETIC.md — five books in the mechanic’s own voice
scripts/bench.py — the machine: ten commands, standard library only, selftest 61/61 — a drivetrain laid out, chain length, chain wear, spoke length, tyre sizes, torque converted, ten tables of standards, what is due, the check, conversions
WITNESS.md + SELFTEST.md — the run as it printed · MANIFEST.md, every file hashed · AUDIT.md, the twelve checks
MY-LEDGER.md — the card’s memory: your bikes, what is on them, where the makers’ manuals live · TIN.md · LICENSE-NOTE.md
card.svg + card-machine.svg + card.json · card.html, the card as one offline file · the doors for ChatGPT, Gemini, Cursor and the rest, with a short door cut to fit their instruction boxes
NOT in the buy: any maker’s torque value, compatibility chart, service interval or error code — you bring the maker’s manual, and it reads it with you

PROOF · SELFTEST 61/61 · TEN COMMANDS ON THE RECORD · WITNESSED IN CLAUDE 2026-09-18 · EDITION 1 · PUNCH F912BFD4EF01160835BA1B03

ON EVERY DOOR · A CARD FOR YOUR AI, A FILE FOR YOUR COMPUTER

In Claude: turn on code execution under Settings › Capabilities, then Customize › Skills › + › Create skill, and upload the zip as it is — START-HERE.md in the box walks you through it, and tells you how to keep the ledger. In ChatGPT, Gemini and the rest: a Project, a GPT or a Gem with the card’s files attached and the short door in the box pasted as its instructions. The words run anywhere an AI reads Markdown; the machines run wherever the host runs Python. Witnessed in Claude only. The host marks →

Take it.

Nº 383 PROPOSED — LAUNCHING SOON

Sold as is under the term printed. A card instructs an AI you operate; results depend on your model, your files and your judgement. Not a maker’s manual, not an inspection, and not medical, legal, tax or financial advice. The terms →

THE TERM · PICK YOUR WINDOW

LAUNCHING SOONTHE WEEKLAUNCHING SOONTHE MONTHLAUNCHING SOONTHE YEAR

LAUNCHING SOON. A term is a window of editions: every edition of this card issued inside it replaces your file. When the window closes, the file you hold keeps working — freeze, not loss. Nothing auto-renews.

A TERM, NOT A SUBSCRIPTION: NOTHING RENEWS ITSELF AND NOBODY IS CHARGED AGAIN. WHEN A TERM ENDS THE FILES STAY ON YOUR COMPUTER AND STAY READABLE — FREEZE, NOT LOSS.

THE MACHINE · IN THE OPEN · FROM THE WITNESSED RUN OF 2026-09-18

Ten commands, every one showing its working.

A small Python program, standard library only. Your AI runs it; you can too. Every block below is pasted from the card’s own WITNESS.md, as printed.

`drivetrain`	every gear, the range, the steps, the overlaps, and the derailleur capacity the set-up needs
`chain`	chain length by the workshop’s equation — rounded up, and proved on the bike
`wear`	chain elongation from a ruler, against the trade’s thresholds
`spoke`	spoke length, left and right, from your own measurements
`tyre`	any tyre size decoded to its rim seat
`torque`	a torque converted — never supplied
`standard`	ten dated tables of the trade’s standards
`due`	one bike’s distance from your log, against your own interval
`mcheck`	the pre-ride check, front to back, with the stop signs
`convert`	mm, inches; bar, psi; kg, lb, g, oz
`selftest`	61 checks that prove the arithmetic; it must print 61/61

chain 410mm 50 34 · ROUNDED UP, AND WHY

chainstay  410.0 mm · 16.142 in — centre of the crank to the centre of the rear axle
equation   54.28 in
cut to     55 in · 110 links (rivets), rounded up — a chain joins only at whole inches
shortest   53.38 in is the least that reaches round the largest ring and the largest cog with no derailleur at all
working    L = 2 × chainstay + ring ÷ 4 + cog ÷ 4 + 1, in inches = 2 × 16.142 + 50 ÷ 4 + 34 ÷ 4 + 1 (the workshop's simple equation, as Park Tool publishes it)
plainly    the published method rounds to the closest inch; I round UP, because a chain too short can tear the derailleur off in the largest
           ring and cog, and a chain a link too long only sags. The drivetrain maker's own method outranks this one — wide-range 1x systems
           and clutch derailleurs each have theirs — and on a full-suspension frame the chainstay is measured where it is longest.
           Prove it on the bike before the first ride: largest ring and largest cog without binding; smallest and smallest without the chain touching itself.

wear · A SIXTEENTH OVER A FOOT, ON 11-SPEED

measured   306.39 mm · 12.0625 in over 24 links (new: 304.8 mm · 12.0 in)
elongation 0.52%
the trade  replaces a 11-speed chain at 0.50%: this one is AT OR PAST IT — the trade would replace this chain
working    elongation = (measured − new) ÷ new · a new chain is 12.7 mm (half an inch) a link
plainly    the thresholds are the workshop's common guidance, as chain-checker and chain makers publish it; the chain maker's own figure outranks
           it. A ruler reads true; some drop-in checkers read high because they push the rollers apart. Measure a clean chain, on the bike, under light tension.

drivetrain · A COMPACT ROAD SET-UP, GEAR BY GEAR

# THE DRIVETRAIN · 50/34 × 11-12-13-14-15-17-19-21-24-28 on 700x28 (2130 mm round)

| cog | 50T: ratio · metres | 34T: ratio · metres |
|---|---|---|
| 11 | 4.55 · 9.68 | 3.09 · 6.58 |
| 12 | 4.17 · 8.87 | 2.83 · 6.03 |
| 13 | 3.85 · 8.19 | 2.62 · 5.57 |
| 14 | 3.57 · 7.61 | 2.43 · 5.17 |
| 15 | 3.33 · 7.10 | 2.27 · 4.83 |
| 17 | 2.94 · 6.26 | 2.00 · 4.26 |
| 19 | 2.63 · 5.61 | 1.79 · 3.81 |
| 21 | 2.38 · 5.07 | 1.62 · 3.45 |
| 24 | 2.08 · 4.44 | 1.42 · 3.02 |
| 28 | 1.79 · 3.80 | 1.21 · 2.59 |

range      374% — the hardest gear (50×11, 9.68 m) over the easiest (34×28, 2.59 m)
steps      11→12 9% · 12→13 8% · 13→14 8% · 14→15 7% · 15→17 13% · 17→19 12% · 19→21 11% · 21→24 14% · 24→28 17%
biggest    24→28, 17% — the jump you will feel
overlaps   3 pairs within 2% of each other — such as 50×19 ≈ 34×13 · 50×21 ≈ 34×14 · 50×28 ≈ 34×19
capacity   33 teeth needed = (50 − 34) + (28 − 11)
           against the 33T you gave me for the derailleur: inside it
largest cog 28T against the 30T maximum you gave me: inside it
working    ratio = ring ÷ cog · metres = ratio × wheel (π × (rim seat 622 + 2 × tyre 28)) · step = (next − this) ÷ this · capacity = ring difference + cog difference
plainly    the capacity and the largest cog a derailleur takes are printed by its maker: give me those two numbers and I check the sum. I do not
           supply them. Whether parts shift together — pull ratios, chain widths, freehub bodies — is the makers' compatibility chart, not arithmetic.

tyre 26x1 3/8 · THE SIZE THAT IS NOT A MOUNTAIN-BIKE SIZE

tyre       26x1 3/8 — read as a fractional size: its rim is NOT the decimal size of the same number
ISO/ETRTO  35-590 — 35 mm wide on a 590 mm rim seat
fits       26 x 1 3/8 — older three-speeds; NOT 26-inch mountain bike
rolls      about 2073 mm a turn (π × (rim seat + 2 × width)); a tyre rolled out on the floor beats any sum
working    the rim seat comes from the size's name; the width from the number after the x
plainly    a tyre fits a rim only if the rim seat matches exactly: 26 x 1 3/8 (590) will never fit a 26 x 1.95 rim (559), and 27-inch (630) is
           not 700c (622). Whether this WIDTH suits your rim's inner width, and the most pressure the pair will take, are printed by the rim and
           tyre makers — a hookless rim carries a low ceiling. I decode the size; I do not set a pressure.

standard threads · WHICH WAY THEY TURN

# THREADS — and which way they turn

| what | the standard |
|---|---|
| pedals | 9/16" × 20 tpi on adult cranks (1/2" × 20 on one-piece cranks). The LEFT pedal has a LEFT-HAND thread: both pedals tighten toward the front of the bike |
| threaded bottom bracket · BSA / English | 1.37" × 24 tpi. The DRIVE-SIDE cup is LEFT-HAND; the other side is right-hand |
| threaded bottom bracket · Italian | 36 mm × 24 tpi. BOTH sides right-hand — which is why they work loose |
| threaded bottom bracket · T47 | M47 × 1.0. Drive side LEFT-HAND, as BSA |
| derailleur hanger bolt | M10 × 1.0 |
| bottle cage, rack and mudguard bosses | M5 × 0.8 |
| disc rotor bolts (six-bolt) | M5 × 0.8, a T25 key |
| cassette lockring | right-hand; it clicks as it tightens, by design |

_As the trade has them on 2026-09-18. Makers add standards every season and do not always follow the ones that exist: the part in your hand, measured,
and its maker's own document outrank this table. I carry dimensions; I do not carry any maker's torque, compatibility chart or service interval._

mcheck · THE CHECK, WITH ITS STOP SIGNS

# THE CHECK · front to back, before the ride — the day before an event, not the morning of

1 · **front tyre** — cuts, bulges, cord showing, the bead seated all round; pressure inside the limits printed on the tyre AND the rim
2 · **front wheel** — axle tight and the lever closed the right way; spin it: true, no rub, no play at the rim
3 · **front brake** — lever firm and nowhere near the bar; pads have life and hit the rim or rotor square; rotor bolts tight
4 · **bars, stem, headset** — front brake on, rock the bike: no knock. Bars cannot be twisted against the wheel by hand. Nothing cracked, nothing creaking
5 · **frame and fork** — a look along every tube and both fork legs — paint cracks at joints, dents, anything new since the last crash
6 · **saddle and post** — tight, straight, above the minimum-insertion line
7 · **cranks, pedals, bottom bracket** — rock the crank sideways: no play. Pedals tight, cleats tight
8 · **chain and gears** — clean and lubricated; every gear, both ways, on the stand; the quick link seated
9 · **rear wheel and brake** — as the front. Then lift the bike a hand's width and drop it: anything that rattles gets found

**Stop signs — the bike is not ridden until hands-on work clears it:** a brake lever that reaches the bar or feels spongy · any play or knock in the steering ·
a crack, a dent or a creak that is new in a frame, fork, bar, stem, post or crank — carbon or metal · a wheel that will not stay true or has a broken spoke ·
cord showing on a tyre, or a bead that will not seat · an e-bike battery that is swollen, hot, damaged or has been in a crash.

_I cannot see, hear or feel your bike. This list is how I would look at it; whether it is fit to ride is decided by the person with hands on it._

THE BIKES, PARTS AND RIDES IN THESE RUNS ARE THE OPERATOR’S OWN EXAMPLES. THE STANDARDS ARE AS THE TRADE HAS THEM ON 2026-09-18: THE PART IN YOUR HAND, MEASURED, AND ITS MAKER’S DOCUMENT OUTRANK THE TABLE. IT CONVERTS A TORQUE; IT NEVER SUPPLIES ONE.

TRY IT IN ONE BREATH

Ask it anything a mechanic would know.

YOUThere’s a click every pedal stroke, only when I’m seated. It started after I washed the bike.THE CARDasks two more isolating questions, then sends you to the seatpost, the saddle rails and the clamp before the bottom bracket — clean, the right paste or grease, the number printed on the clamp — one suspect at a time.

YOUI’m swapping my 11–28 for an 11–34. Will it work, and how long should the chain be?THE CARDlays both drivetrains out, tells you the capacity the new one needs, asks for the two numbers printed by your derailleur’s maker, sizes the chain rounded up — and says the maker’s chart decides whether it shifts.

YOUMy front brake lever pulls to the bar.THE CARDstop sign first: the bike is not ridden. Then what it could be — air, a leak, worn pads — how to tell which, that the fluid is printed on the lever and never swapped, and that brakes are the first thing it sends to a shop if there is doubt.

QUESTIONS AT THE TABLE

Asked before the wire.

Can it see my bike?

No, and it says so at the start. A description is not an inspection. It tells you what a fault could be, how to tell which, how the job is done, and when only hands and eyes on the bike will do. It never calls a bike fit to ride.

Will it give me torque values?

No. It converts a torque and never supplies one. The number is printed on the part or in its maker's manual, and where two parts' numbers disagree the lower one rules. If the number cannot be found, the maker's support is the source.

Does it know my bike's parts?

It knows every system of a bicycle and the trade's standards, dated. It carries no catalogue, no maker's compatibility chart and no error codes: you bring the maker's document and it reads it with you.

Will it help me with brakes?

Yes — it teaches the jobs. And it holds a line: brakes, steering and wheels are never bodged; brake fluids are never mixed; a lever that reaches the bar means the bike is not ridden. If there is doubt, brakes are the first thing it sends to a shop.

My frame is cracked. Can it tell me if it's safe?

No. It never repairs, straightens or passes judgement on a cracked, bent or crashed frame, fork, bar, stem, post or crank. That part is replaced or inspected by its maker or a specialist, and not ridden until then.

Does it cover electric bikes?

Everything mechanical on one, done more often — chains, pads and tyres wear faster. The motor, battery, display and wiring are the maker's and its dealer's: it never opens a battery and will not help remove a speed limiter.

Is it an app?

No. It is a small folder of files that plugs into the AI you already use. Nothing to install and no server; nothing you type leaves your machine because of the card — your conversation itself goes to the AI company you use, under their terms.

Why is a mechanic in a sport house?

Because the three bike seats beside it keep sending people to one. It is the one card in AI FOR SPORT that is not a sport; its house and number are proposed.

Do I need Claude?

It is built for Claude first and has been witnessed running only there, because Claude can run the calculator for you. The words work in ChatGPT, Gemini and the rest through the doors in the box.

Can my teenager use it?

With an adult beside them — especially near brakes, blades and solvents. That is the rule for anyone under 18, on every card in the house.

← ENDURANCE · AI FOR SPORT · beside it: THE CYCLIST · THE MOUNTAIN BIKER · THE CYCLOCROSS RIDER