Claud Butler's 1939 catalogue lists the Mass-Start, a welded 531 frame on 27 × 1⅜in high-pressure tyres with a Simplex 3-speed, and a four-speed version. As the Massed Start it was Models 42 and 42a in 1951, with brazed lugs, and Model 51 from 1952 to 1954, with 72° parallel angles in 1952.
Known components
Listed exactly as our confirmed sources give them, with the year and source for each. A part listed for one year or version may not apply to every bike, so check against yours.
Frame and fork
- Welded 531 frame1939 — Ebykr catalogue archive, p.17
- Brazed lugs1951 · 42, 42a — Ebykr catalogue archive, p.8; 1952 · 51 — Ebykr catalogue archive, p.8; 1954 · 51 — Ebykr catalogue archive, p.10
- Reynolds 5311951 · 42, 42a — Ebykr catalogue archive, p.8
- Brazed lug frame1953 · 51 — Ebykr catalogue archive, p.11
- KROMO or Reynolds 5311953 · 51 — Ebykr catalogue archive, p.11
Gears and drivetrain
- Simplex 3-speed1939 — Ebykr catalogue archive, p.17
- also a four-speed version1939 — Ebykr catalogue archive, p.17
- Gnutti chainset1951 · 42, 42a — Ebykr catalogue archive, p.8
Wheels and tyres
- 27 × 1⅜in high-pressure tyres1939 — Ebykr catalogue archive, p.17
- Airlite hubs1951 · 42, 42a — Ebykr catalogue archive, p.8
Catalogue appearances
| Year | Name as printed · model no. | Details | Source |
|---|---|---|---|
| 1939 | C.B. Mass-Start Model | Welded 531 frame; 27 × 1⅜in high-pressure tyres; Simplex 3-speed; also a four-speed version. | Ebykr catalogue archive, p.17 |
| 1951 | Massed Start · 42, 42a | Brazed lugs; Reynolds 531; Gnutti chainset; Airlite hubs. | Ebykr catalogue archive, p.8 |
| 1952 | Massed Start · 51 | Brazed lugs; 72° parallel. | Ebykr catalogue archive, p.8 |
| 1953 | Massed Start · 51 | Brazed lug frame; KROMO or Reynolds 531. | Ebykr catalogue archive, p.11 |
| 1954 | Massed Start · 51 | Brazed lugs; complete machine to order. | Ebykr catalogue archive, p.10 |
Specs are as printed in the catalogue. Years are when the model appears in a source, not exact production dates.
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Sources
Last updated 19 October 2026. Every fact on this page comes from one of these.
- Ebykr catalogue archive: Claud Butler 1939 catalogue (transcription) (p.17)
- Ebykr catalogue archive: Claud Butler 1951 catalogue (transcription) (p.8)
- Ebykr catalogue archive: Claud Butler 1952 catalogue (transcription) (p.8)
- Ebykr catalogue archive: Claud Butler 1953 catalogue (transcription) (p.11)
- Ebykr catalogue archive: Claud Butler 1954 catalogue (transcription) (p.10)