1937 BSA Double Diamond Tandem with Watsonian Sidecar


During the 1930s, a car was not essential transport like it is today. The country was coming out of the Great Depression, and people were budget-conscious. They did not generally sit around working on a computer or watching TV, so they were fit. A bicycle was a very sociable means of transportation, and the tandem had been known as a ‘courting machine’ during its early years. It was perfect for weekend pleasure trips. After a couple married and had children, a tandem could be fitted with a child’s cycle sidecar to provide what, in terms of a motorcar, would be known as a ‘family runaround.’


You could buy cheaper outfits, but if you wanted a top-of-the-range quality outfit, you’d buy a BSA tandem fitted with a Watsonian sidecar. This was one of the most expensive pedal-operated vehicles available, and not much cheaper than a motorcycle.

Compare the tandem outfit with other economy forms of transport on sale in 1937:

1. A normal lightweight bicycle cost around £5.

2. A BSA tandem cost 16 guineas (£16 16/-); the Watsonian single-seat sidecar was £3 1/- 4d. So the total was £19 17/- 4d.

3. You could buy a quality solo motorcycle for around £50; a slightly outdated Douglas 600cc S/V Combination was on offer at £39 (see advert below).

4. The new budget range of Red Panther 250cc OHV motorcycles from Pride & Clark were offered at a very cheap price of £29 17/- 6d. This was one of the best deals for a four-stroke OHV motorcycle.

5. Grose & Sons offered a Cyc-Auto Autocycle (see advert below) with single-speed 98cc Villiers engine at £18 (£18 18/-).

6. An Austin Seven van at £115 was one of the cheapest motorcar options. In the days before ‘health and safety,’ parents put their kids in the back. My dad did the same; he used his Morris Eight van for work during the week and when he took me out I’d stand in the back and hold on to the back of his seat.



pride and clark douglas combination 1937

bsa tandem


21″ Frame

26″ Wheels

Double BSA Rat-Trap Pedals with Toe-clips

fitted with Watsonian ‘Model 7’ Sidecar

(Now sold)



This fabulous BSA Tandem Sidecar Outfit needs only minor ‘fettling’ to put it on the road – it requires new tyres, handlebar grips, and the chain refitting; the rear plastic mudguard is cracked, but could be fixed; the rear leather saddle is damaged but usable.

The sidecar needs the clear plastic side screens replacing; the hood either needs tidying and trimming or replacing; the front part of the leatherette body covering needs gluing in place (this is a common place for wear and a piece of aluminium trim over it is a good preventative measure); the seat needs some foam underneath and the chains attached to new hooks at the front to raise it up. Watsonian sidecar transfers (decals) are available (illustration below), and can be fitted to the sidecar’s metal mudguard (the rest of the sidecar body is covered with leatherette).

Apparently the sidecar was fitted to the tandem from new. The tandem has some lovely original accessories, such as the mudflap on the front mudguard, two pairs of matching BSA rat trap pedals with toe clips, BSA wing nuts, hub brakes, and a cyclometer on the front wheel.

watsonian sidecar decal







1937 BSA Tandem sidecar 101












1937 BSA Tandem sidecar 102



































By 1945, BSA tandems evoked memories of a prewar, peaceful England. An England where young couples took holidays together, cycling down quiet country roads and staying at b&b’s, hostels or inns.

BSA bicycles are notoriously difficult to date accurately. Frame numbers did not run sequentially, and few factory records or shop records exist. Catalogue descriptions are usually the only way to identify their age.

There’s little to distinguish Piled Arms tandems throughout their 1930s model years. The change of model number from year to year would appear to reflect only the new year’s catalogue model, eg T64 is 1936, T74 is 1937, T94 is 1939. I’ve only spotted a few changes from the catalogue descriptions.

If you compare the catalogues below, the 1934 tandem would appear to be fitted with a different gear trigger to the 1936 model.

In 1937 the Brooks ‘B15’ saddle was fitted as standard, replacing the Terry Leather Top saddle. This tandem has Brooks saddles, so I’ve dated it as 1937 accordingly. (Of course, saddles can be easily updated, so this tandem might actually be earlier).

The 1939 catalogue appears to offer only Cyclo gears.

A tandem is not mentioned in the 1940 catalogue, so I assume 1939 to be the Piled Arms Tandem’s final year.

This might become a reference point for these marvelous beasts. So I’ll continue my research and update this section bit-by-bit as I find out more.

1934 BSA Tandem Models T1 & T2

1936 BSA Tandem Models T61, T62, T63, T64

1937 BSA Tandem Models T71, T72, T73, T74

1938 BSA Tandem Models T81, T82

1939 BSA Tandem Models T92, T94

There were no tandems built during the war, a fact that BSA used in some of their wartime adverts. When you have leisure for pleasure again…


1937 BSA Tandem sidecar 87

My daughter Delphy refused to sit inside the sidecar; however, she was happy enough to sit in the driving seat.

1937 BSA Tandem sidecar 99

To see more bicycle sidecars