Bolinder Munktell BM-31
Built: 1949–1957 · Series: 30 er-Baureihe
More machines from model year 1949
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Bolinder-Munktell 30 series – BM-31 to BM-35/36 from Eskilstuna, 1950s: the Swedish three- and four-cylinder tractors before the Volvo era, 25 to 31 kW
Bolinder-Munktell was formed in 1932 in Eskilstuna, Sweden, from the merger of the machine works J. & C. G. Bolinder and Munktells; the 30 series with the BM-31, BM-32, BM-33/34 and BM-35/36 models belonged to the tractor programme of the 1950s, shortly before Volvo took a majority stake in Bolinder-Munktell in 1950 and gradually folded the brand into its own farm-equipment division.
Read on 3 more paragraphs
The register lists here 4 versions with 25 to 31.3 kW from three- and four-cylinder engines of 3,362 to 3,456 cm³ displacement, torque from 182 to 210 Nm at 1,500 to 1,800 rpm, unladen weights from 2,280 to 2,450 kg, lengths from 3,115 to 3,150 mm, widths from 1,690 to 1,839 mm and heights from 1,820 to 2,180 mm; the fuels recorded are paraffin, a paraffin/petrol blend and, on one model, diesel.
The 30 series was common on Swedish farms of the post-war years and marked the transition from the paraffin-fuelled pre-war tractors to the more modern diesel models that came to define Bolinder-Munktell and, later, Volvo BM and today's Valtra brand.
Used, the 30 series calls for checking engine condition and the carburettor or injection pump depending on fuel type, clutch and transmission, the cooling system, and the condition of sheet metal and tyres; parts are today offered mainly by Swedish and Nordic vintage-tractor specialists.
Sources: SpecCodex register, model data: Bolinder-Munktell 30er-Baureihe
Technical data
Engine
| Fuel | Kerosincorrect |
|---|---|
| Power | 34 hp (25 kW)correct |
| Rated speed | 1,500 rpmcorrect |
| Torque | 182 Nmcorrect |
| Speed at max. torque | 1,200 rpmcorrect |
| Cylinders | 4correct |
| Displacement | 3,456 cm³correct |
| Bore | 100 mmcorrect |
| Stroke | 110 mmcorrect |
| Compression ratio | 4.6correct |
| Cooling | water-cooledcorrect |
Dimensions and weights
| Length | 3,115 mmcorrect |
|---|---|
| Width | 1,839 mmcorrect |
| Height | 1,820 mmcorrect |
| Wheelbase | 1,960 mmcorrect |
| Ground clearance | 420 mmcorrect |
| Unladen weight | 2,295 kgcorrect |
Drivetrain and chassis
| Drive | rear-wheel drivecorrect |
|---|---|
| Gearbox | 5 V/1 Rcorrect |
| Forward gears | 5correct |
| Reverse gears | 1correct |
| Front tyres | 6.00-19 ASFcorrect |
| Rear tyres | 12-30 AScorrect |
| Top speed | 30 km/hcorrect |
Origin and approval
| Construction | frame constructioncorrect |
|---|---|
| Units built | 6,919correct |
Where this model stands
Power-to-weight ratio: 10.9 kW/t (25 kW / 2.3 t)
Power class: Compact (< 40 hp)
Stronger than 20% of the tractors in the register — out of 15,663 models with a stated power figure.
Calculated from the documented figures above — not a rating.
Frequently asked questions
How much power does the Bolinder Munktell BM-31 have?
The Bolinder Munktell BM-31 delivers 34 hp.
How much does the Bolinder Munktell BM-31 weigh?
The unladen weight is 2,295 kg.
What engine does the Bolinder Munktell BM-31 have?
4 cylinders, 3,456 cm³ displacement, Kerosin.
How fast does the Bolinder Munktell BM-31 go?
Top speed is 30 km/h.
What are the dimensions of the Bolinder Munktell BM-31?
3,115 mm × 1,839 mm × 1,820 mm.
When was the Bolinder Munktell BM-31 built?
Production years: 1949–1957.
What to check before buying
- Check the hour meter against the service records — a replaced instrument is the most common gap.
- Compare the data plate and chassis number with the papers.
- Check the weights in the papers against the figures here — attachments change them.
- Check front and rear tyre sizes: mismatched pairs strain the drivetrain.
- Shift the gearbox cold and warm — jumps only show up at temperature.
- Load the hydraulics and watch for sag.
- Ask about parts availability for this build year — the running costs hang on it.
A general list for this type of machine — no substitute for an inspection or an appraiser.
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This page carries 28 individual figures for this model. They come from 2 recorded sources; every figure can be traced there. What we cannot document is not here — we leave gaps open rather than estimate them.
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Other models in this series
Sources: Wikibooks Traktorenlexikon (CC BY-SA 4.0) (retrieved August 2026) · How we check the data
Tractor in 3D section
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