YEAR 1925

       One year later, 1925, the R37 motorcycle outputs twice the power of it's predecessor: 16bhp from a 500ccm engine. This motorcycle provides the basis for the BMW racing machines and makes the brand well known throughout the whole motorcycle world. The result: from 1924 to 1929, all German Championships in the 500 ccm category are won by BMW.

BMW - R37 - 1925-1926

 BMW - R37 Specifications


Date 1925-1926
 
Number sold 152
 
Price 2.900,- RM

Engine
internal designation	M 2 B 33
engine type	four-stroke two-cylinder flat-twin
bore x stroke	68 x 68 mm
displacement	494 cm3
output	16 PS at 4000 U /min
compression ratio	6,2 : 1
valves	ohv
carburetion system	1 carburettor, Typ BMW Spezial three-valve 26 mm
engine lubricating	forced-feed lubrication
oil pump	gear pump
Power transmission
Clutch	single discs, dry
no. of gears	3
shifting	manual
Gear ratios	2,27 / 1,50 / 1,08
rear wheel ratio	1 : 4,41 (with sidecar 1 : 5,36)
bevel/crown wheel	17 / 75 teeth (with sidecar 14 / 75 teeth)
Electrical system
Alternator	magneto generator on request
Ignition	Bosch magneto ignition
Spark plugs	Bosch W 175
Suspension
designation	R 37
frame	twin-loop tubular frame
front wheel suspension	twin cantilever spring
rear wheel suspension	rigid
wheel rims	26 x 2,5
tyres, front	26 x 3
tyres, rear	26 x 3
brakes, front	drum brake Ø 150 mm
Brakes rear	block brake
Dimensions and weights
Length x width x height	2100 x 800 x 950 mm
Wheel base	1380 mm
Tank capacity	14 l
Unladen weight, full tank	134 kg (with Original-sidecar 184 kg)
load rating	k.A.
Fuel consumption	ca. 4 l / 100 km
oil consumption	ca. 3 l / 1000 km
Top speed	115 km/h BMW - R39 - 1925-19267   BMW R39 - Specifications Date 1925 - 1927 Number sold 855 Price 1.870,- RM Engine internal designation M 40 engine type four-stroke two-cylinder flat-twin Bore/stroke 68 x 68 mm Cubic capacity 247 cm3 Max power 6,5 PS at 4500 U /min Compression ratio 6,0 : 1 Valves per cylinder ohv Carburation system carburettor BMW Spezial 20 mm Engine lubrication forced-feed lubrication oil pump gear pump Power transmission Clutch single discs, dry Number of gears 3 shifting manual Gear ratios 6 / 9,28 / 13,7 Rear wheel ratio 1 : 2,64 Bevel/crown wheel 14 / 37 teeth Electrical system Alternator Bosch magneto ignition Ignition Bosch magneto generator Type G 1, 6 V /15 W Spark plugs Bosch W 175 Suspension designation R 39 Type of frame twin-loop tubular frame Front suspension plate spring, 4 laminae Rear suspension rigid wheel rims 27 x 3, 50 Typ CC 1 Tyres front 27 x 3, 50 balloon or with 26 x 3 high-pressure tyres Tyres rear 27 x 3, 50 balloon or with 26 x 3 high-pressure tyres Brakes front internal shoe brake (drum brake) Ø 150 mm Brakes rear external shoe brake at the gearing (on cardan shaft) Dimensions and weights Length x width x height 2050 x 800 x 950 mm Tank capacity 10 l Unladen weight, full tank 110 kg Fuel consumption ca. 2,5 l / 100 km oil consumption ca. 1 - 2 l / 1000 km Top speed 100 km/h   In 1925 the R32 gets front brake, a drum brake Ø 150 mm.