Fan Belt Part Numbers and Dimensions

The fan belts listed below are quoted in old catalogues as fitting RMs. These are no longer made although it is often possible to find unused but old ones at auto jumbles or on web sites such as Ebay. Although old they are capable of giving years of good service provided they have been stored well.

Model Make and Part No. Top Width Thickness Angle (Degrees) Inside Circum. Outside Circum
RMA/RME Ferodo V118 5/8 in. (15.88mm) 7/16 in. (11.11mm) 32 43.4 in (1102.36mm)

465/32   (1172.4mm)

Raybestos R120 5/8 in. (15.88mm) 7/16 in. (11.11mm) 32 43.65 in (1108.71mm) 46.40 (1178.56)
RMB (Long) Ferodo V126 3/4 in. (19.05mm) 1/2in. (12.7mm) 32 50 in. (1270mm)

539/64 in.  (1349.77mm)

Raybestos R300 3/4 in. (19.05mm)

5325/64 in. (1356.12mm)

John Bull 53
RMB (Short) Ferodo V481 1/2in. (12.7mm) 5/16 in. (7.93mm) 40 15 in. (381mm)

1631/32 in. (431mm)

Raybestos R12
RMF/RMB2 Ferodo V150 3/4 in. (19.05mm) 1/2in. (12.7mm) 32

4419/64 in. (1125.14mm)

477/16 in.  (1204.91mm)

Raybestos  R289

Alternative Belts

Belt specifications have changed considerably since the above belts were current. Modern belts have an included angle of 40o as opposed to 32o and top widths have changed to typically 17mm (B section) or 22mm (C section). The exact top width varies slightly from supplier to supplier with the B section belt being quoted between 16.5mm and 17.0mm and as 21/32in. Similarly the C section top width is quoted as 22mm and 7/8in.

Both B section and C section belts are available from many manufacturers such as Gates, Goodyear and Dayco with lengths increasing in 1 in. steps.

From practical experience a good start point for an RMA or RME is a B44.

One supplier of fan belts is and they list the B44 V-belt as,

Top Width 17mm
Pitch Width 14mm
Bottom Width 9.4mm
Depth 11mm
Inside Length 1118mm
Pitch Length 1161mm
Outside Length 1187mm
Smooth/Cogged Smooth
Material Black Rubber

They also list a wedge belt, SPB1150 as,

Top Width 16.3mm
Pitch Width 14mm
Bottom Width 7.1mm
Depth 13mm
Inside Length 1090mm
Pitch Length 1150mm
Outside Length 1172mm

Smooth/Cogged Smooth
Material Black Rubber

From practical experience a good start point for an RMB is a C50 but if this is too tight a C51 may be needed.

The same supplier list the C50 V-belt as,

Top Width 22mm
Pitch Width 19mm
Bottom Width 12.4mm
Depth 14mm
Inside Length 1270mm (50")
Pitch Length 1322mm
Outside Length 1358mm
Smooth/Cogged Smooth
Material Black Rubber

It should be noted that the modern C section belt is 1/8 in. wider than the original belt and if it sits high in a pulley it may overlap the sides of the pulley leading to possible damage to the belt edges. In contrast a B section belt is 1/8 in. narrower than the original belt and will sit deeper in the pulley. It might therefore sit on the bottom of the pulley and slip badly. Unfortunately there is no very close equivalent to the original width of 3/4 in (19 mm).

The small fan belt used on the RMB is shown in both the Workshop Manual and the Driver’s Handbook as being a linked belt not a continuous belt as implied by the listing of original belts. Link belting is widely used on lathes and other machinery and is easily available from many sources including Ebay. It can be obtained in all normal sections including the A section which is 13mm wide. It is usually sold in one meter lengths. It may stretch a little in use as the links settle in but removal of a link is a simple process.

All pulleys wear a little in use and aluminium pulleys wear most and it is often possible to see wear ridges in them. As pulleys wear so the belt sits deeper in them and it may be necessary to use a slightly shorter belt to compensate for this.