guides:specifications
Table of Contents
Specifications
Technical data for the production Sinclair C5 (1985). Where period sources disagree, the conflict is noted rather than resolved.
Summary
| Item | Value | Source |
|---|---|---|
| Vehicle class (UK) | Electrically Assisted Pedal Cycle (EAPC), 3-wheel | EAPC Regulations 1983; Unofficial Service Manual |
| Manufacturer | Sinclair Vehicles Ltd, Coventry | Owner's documents |
| Assembler | Hoover plc, Merthyr Tydfil, Wales | Museum Wales; Unofficial Service Manual fig. 10 |
| Launched | 10 January 1985, Alexandra Palace, London | Wikipedia; Twist & Go |
| Launch price | £399 + £29 delivery | Twist & Go magazine |
| Length | 1744 mm (5 ft 9 in) | Twist & Go spec panel; Wikipedia |
| Width | 744 mm (2 ft 5 in) | as above |
| Height | 795 mm (2 ft 7 in) | as above |
| Wheelbase | 1304 mm (4 ft 3 in) | as above |
| Ground clearance | 56 mm (2¼ in) | Twist & Go |
| Turning circle | 5800 mm (19 ft) – “about 2/3 that of a Mini” | 1985 sales brochure |
| Weight | 30 kg without battery; ~45 kg with one 15 kg battery | Service Manual; brochure |
| Max. gross weight (incl. driver) | 150 kg recommended | 2nd-gear.blogspot (from Milner/Newman data) |
| Boot | 1 cu ft (≈28 litres), integral, lockable | Brochure |
| Body | Injection-moulded polypropylene, two shells | Brochure; Wikipedia |
| Chassis | “Y-configuration” corrosion-protected steel spine, developed with Lotus; no separate suspension | Brochure |
| Wheels | Reinforced nylon (plastic) | Brochure |
| Steering | Under-seat handlebar (“steering bars”) beneath the knees, rod linkage to front fork | Brochure |
| Brakes | Front: caliper (bicycle-type) on front wheel. Rear: twin-shoe drum on one rear wheel only | Brochure; Twist & Go; Service Manual |
| Parking brake | Latch on rear brake lever | Brochure |
| Pedals | Bicycle-type cranks, chain drive to rear axle | Brochure |
Official specification (Owner's Handbook, p. 32)
| Item | Value |
|---|---|
| Overall length / width / height | 1744 mm (5′8½″) / 744 mm (2′5¼″) / 795 mm (2′7¼″) |
| Ground clearance | 56 mm (2¼″) |
| Rear track | 630 mm (2′0¾″) |
| Wheelbase | 1304 mm (4′3¼″) |
| Vehicle weight (without battery) | approx. 30 kg (66 lb) |
| Max. recommended gross weight | 150 kg (330 lb) |
| Boot capacity / max. load | 28 litres (1 cu ft) / 10 kg (22 lb) |
| Max. speed (electric drive) | 24 km/h (15 mph) |
| Motor | 250 W continuous, 4,100 rpm max. |
| Gearbox | Two-stage single-speed reduction unit, overall ratio 13:1 |
| Front brake | Cable-operated caliper brake with high-performance blocks |
| Rear brake | Cable-operated twin-shoe hub brake on the off-side (right-hand) wheel, with parking brake |
| Front wheel/tyre | 12½″ nylon composite wheel; 12½ × 2¼″ low-rolling-resistance tyre |
| Rear wheels/tyres | 16″ nylon composite wheels; 16 × 2″ low-rolling-resistance tyres |
| Tyre pressures | Front 2.1 bar (30 psi); rear 2.4 bar (35 psi) |
| Castor trail | 11 mm (7/16″) |
| Turning circle | 5.8 m (19 ft) |
| Pedal drive | Steel drive sprocket 42 T; rear sprocket with freewheel 20 T; chain ½″ pitch × ⅛″, 181 links |
| Bulbs | 12 V 5 W wedge base, type W10/5 (front and rear) |
| Fuses | Main 5 A, auxiliary 1 A; glass cartridge, 20 mm long |
| Battery | 12 V nominal, 36 Ah at the 5-hour rate, approx. 15 kg, 236 × 136 × 206 mm (9 5/16 × 5⅜ × 8⅛″), 6-cell |
Torque settings
| Fastener | Torque |
|---|---|
| Motor clamping bolt | 8 Nm (6 lb ft) |
| Head bearing and steering head lock nuts | 42 Nm (31 lb ft) |
| Crank axle bearing lock ring | 37 Nm (27 lb ft) |
| Steering stem nut | 11 Nm (8 lb ft) |
| Steering bar clamp nut | 8 Nm (6 lb ft) |
| LH rear wheel bolt | 25 Nm (18 lb ft) |
| RH rear wheel locknut | 25 Nm (18 lb ft) |
| Front wheel securing nuts | 22 Nm (16 lb ft) |
| Front brake blocks to caliper | 4 Nm (3.5 lb ft) |
Lubricants
| Point | Lubricant | Quantity |
|---|---|---|
| Wheel bearings, crank axle bearings, front fork and steering head bearing | General-purpose grease, −40 °C to +100 °C | 3.5 ml |
| Gearbox | Lithium/polyethylene-based semi-fluid grease, viscosity 14.5 s at 100 °C. The Unofficial Service Manual suggests Castrol LMB. | 5.0 ml |
| Chain, cables, steering and brake pivots | Light machine oil or lubricant spray, every 6 months | – |
Motor and transmission
| Item | Value |
|---|---|
| Motor type | 12 V DC permanent-magnet, brushed |
| Rating | 250 W continuous (legal maximum for the class) |
| Max. motor speed | 4100 rpm (no-load) |
| Wheel speed at max. revs | ~315 rpm at the rear wheels |
| Reduction | Two stages, ≈13:1 overall – epicyclic gearbox on the motor, then a toothed belt to the rear axle |
| Driven wheel | Left-hand rear wheel |
| Stall current | Up to ~140 A |
| Maker | Polymotor (Italy), part of the Philips group. The design came from a truck cooling-fan motor. It is not a washing-machine motor, despite the popular myth. |
| Top speed | 15 mph (24 km/h) on the level; Service Manual Table I gives 22 km/h |
Battery and charging
| Item | Value |
|---|---|
| Battery | 12 V flat-plate semi-traction lead-acid, made for Sinclair by Oldham Batteries |
| Weight | 15 kg |
| Capacity | 36 Ah at the 5-hour rate (Service Manual also quotes 35 Ah) |
| Usable in service | 15–28 Ah depending on load |
| Depth of discharge | 80 % of 5-hour capacity |
| Cycle life | 300 cycles to 20 % capacity loss (as specified) |
| Compatible replacements | Oldham types 015 and 038 fit the original battery top/key switch (c5owners.com) |
| Charger | Potted hybrid unit. Two-stage constant-current then constant-voltage profile. Two SCRs phase-controlled; two LEDs (charging / finished) |
| Charge time | Typically 8 hours from fully discharged |
| Second battery | A second battery could be fitted (spare battery kit); range figures below |
Performance (Unofficial Service Manual, Table I)
Average-weight driver, motor only, no pedalling.
| Test | Result |
|---|---|
| Standing-start acceleration | 1.7 m/s² |
| 0–8 km/h | 1.8 s |
| 0–16 km/h | 6.9 s |
| Maximum speed | 22 km/h |
| Braking, dry, 16 km/h–0 | 3 m |
| Braking, dry, max speed–0 | 5.5 m |
| Braking, wet, 16 km/h–0 | 5 m |
The 1985 brochure shows a stopping distance of about 4.6 m (15 ft) from 24 km/h (15 mph) on a dry, level road.
Range
| Configuration | Approx. range (motor only, cruising in the right-most green load segment) |
|---|---|
| 1 battery | ~13 miles (21 km) |
| 2 batteries used one after the other | ~25 miles (40 km) |
| 2 batteries wired in parallel | ~33 miles (52 km) |
- Sinclair's advertised range was “up to 20 miles” per charge. The Museum Wales record quotes up to 30 miles.
- Pedalling away from rest and using “burn and coast” can roughly double the range. Cold weather can cut it by up to 50 %, and top speed can fall to about 12.5 mph.
- A second battery in parallel is worth about 1.5 batteries, because each one discharges at half the rate. A second battery used separately is worth only about 0.9, because of the extra 15 kg you carry.
- Contemporary tests found much less. The AA (May 1985) and Which? (June 1985) both reported real-world ranges well under the claimed 20 miles.
Hills
- Motor only: about 1 in 12 (8 %). With pedalling: about 1 in 7 (14 %). (The Times, Feb 1985.)
- On any grade steeper than about 2.5 %, a long enough climb will eventually trigger a thermal cut-out. Example from the Service Manual: from a cold motor, a 10 % grade is climbed at about 13 km/h drawing about 60 A, and thermal shutdown comes after about 7 minutes and 1500 m.
Wheels and tyres
Wheel sizes are a well-known source of confusion. Sinclair, the brochure and the actual rims all quote different figures.
| Front | Rear (×2) | |
|---|---|---|
| Owner's Handbook | 12½ in | 16 in |
| Brochure (as printed) | 317 mm × 57 mm | 406 mm × 51 mm |
| Original tyre sidewall | SINCLAIR 12½ x 2½, 62-203, Made in Thailand | SINCLAIR 16 x 2, 54-305, Made in Thailand |
| ISO/ETRTO bead seat (buy by this) | 203 mm (same as a 12½“ child's bike) | 305 mm (16” “Chopper”-type size) |
- The quoted inch figures are overall diameters including the tyre, which is the old bicycle convention.
- Rear-tyre replacements owners have used include Raleigh Chopper-style 16“ tyres and Schwalbe Big Apple / City Jet. A Kenda 12½” fits the front.
- Pressures: the Owner's Handbook specifies 30 psi front / 35 psi rear, inflated with a foot or cycle pump. It says not to use garage air lines. Production tyre sidewalls are marked 40 psi, which is the tyre's maximum. The Lotus GRP prototype's tyres were stamped 35 psi.
Electrics and lighting
| Item | Value |
|---|---|
| System voltage | 12 V |
| Headlamp | 12 V, 5 W bulb in a body-moulded housing |
| Rear lamp | Tail lamp plus two reflectors in one cluster |
| Instrument pod | Two 5-segment LED bar graphs, plus a buzzer: left = motor load, right = battery state |
| Power control | Push button under the rubber of the left steering-bar grip (on/off relay control, no proportional throttle) |
| Light switch | Under the seat |
| Master switch | Key-operated “master security switch” that clips onto the battery top, with a manual emergency cut-out button |
| Pre-wired for | Indicators and horn (accessory kits plug into existing harness) |
See Electrical System for how the pod, ULA and control box work.
Production figures
| Figure | Value | Note |
|---|---|---|
| Production line capacity | 50–56 vehicles per hour per line; up to ~8,000 a week planned | Museum Wales; Wikipedia |
| Built by early Jan 1985 | >2,500 | Wikipedia |
| Total built | ~12,000–14,000 | Sources disagree: RCAHMW and Twist & Go say ~12,000; Wikipedia says 14,000. Some later retellings say 17,000, which is poorly supported. |
| Production ended | August 1985 |
Sources
- The Unofficial Sinclair C5 Service Manual (P.J. Milner, P. Newman, R. Woodward). See Documents and Sources.
- Sinclair C5 sales brochure A New Power in Personal Transport (1985).
- Twist & Go magazine C5 feature, pp. 48–51 (c. 2005).
- 2nd-gear.blogspot.com, “Specifications for the Sinclair C5 Electric Vehicle” (2012) and its comments.
- Wikipedia, “Sinclair C5” (accessed Oct 2026).
- Amgueddfa Cymru – Museum Wales object records 86.189I and 1996.111/1.
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