Ball Race Part Numbers

Ball races are usually sold with designations as follows

Open with no shields covering the balls      
2Z with sealing shields on both sides    
2RS with lip seals on both sides giving axial sealing action

Ball races used on RMs are open sided thus allowing new grease or oil to be added to them during use.  

While lip shields prevent dirt from entering the bearing they also prevent new grease or oil being added but fortunately they can be prised out easily.

Ball races may also have a C number designation,  This specifies the internal clearance and the higher the C number the greater the clearance.  Most bearings will be either unmarked or marked CN and these are suitable for RM Rileys.  Where tighter clearances are required for a special application a bearing may be marked C2 and where looser clearances are need (perhaps high speed applications) a bearing may be marked C3 or higher.  

Ransome and Marles bearings were mostly used originally but there are many alternatives such as SKF and a search on Google or Ebay using the Part Number will find them easily usually at very competative prices.   Riley's contract with R&M excluded the use of taper roller bearings.  Unless specified otherwise RMB includes all 2½ variants except RMB2/RMF/RMH.

In the table below the Riley Part Numbers and points of embodiments are taken from the Riley Illustrated Parts Lists.  Dimensions have been taken from the bearing manufacturer's web sites.  More detailed information on a bearing can be found by searching using its generic number on the SKF Product Search web site at

When replacing a bearing always check that the number on the new bearing matches that on the old one.  New bearings should not be packed with grease but some grease may be put into the bearing housing next to the bearing.

Position Model Generic Part No. R&M Part No. Riley Part No. OD/ID/Width  (mm)
Front Hub Inner 1½ litre 6306 MJ30 A2538 72/30/19
2½ litre 6308 MJ35 A2615 80/35/21
Front Hub Outer
1½ litre 6304 MJ20 A2539 52/20/25
2½ litre 6305 MJ25 A1695 62/25/17
Water Pump Front 1½ and RMB 6203 LRJ17 R1195 40/17/12
RMB2 6302 MJ15 42/15/13
Water Pump Rear 1½ and RMB 6303 MJ17 S138 47/17/14
RMB2 6302 MJ15 42/15/13
Fan Front RMB 6203 LJ17  R1195 40/17/12
Fan Rear RMB 6303 MJ17  S118 47/17/14
Torque Tube Front RMA 10001-16155 6205 LJ25 A1772 52/25/15 
RMA 16156-20504 4205 LDJ25 52/25/18
RMB 4205 LDJ25 A1809 52/25/18
Bevel Pinion Front RMA 3206 LDJT28 A1771/R 62/30/23.8
RME 02474-02420 68.262/28.575/22.225/17.462
RMB RMS8 MJ1 A1105/R 63050/25.40/19.05
Bevel Pinion Rear RMA N306 MRJ30 A1770/R 72/30/19
RME 3478-3420 79.38/34.93/29.37
RMB CFM9 MRJA1J A1408/R 71.44/28.58/20.64
Bevel Pinion Thrust Front RMB LT1 1/8
LT1 1/8 A1102 48.42/28.58/15.88
Bevel Pinion Thrust Rear RMB MT1 1/8
MT1 1/8 A1103 71.44/28.58/20.64
Differential RMA 7208 LJT40 80/40/18
RME  to 1954 7208 LJT40 80/40/18
RME 1955 7209 LJT45 85/45/19
RMB 7208 LJT40 80/40/18
RMF 27LJT40 27LJT40 80/40/18
Differntial Thrust RMB MT1 1/8 MT1 1/8 71.44/28.58/20.64
Intermediate Propshaft RME and RMF 6206FF 62/30/24/16
Gearbox Drive Gear Bearing 1½ litre 6307NR 80/35/21
2½ litre 6308NR 80/35/21
Gearbox Main Shaft Bearing 1½ litre 6305NR 62/25/17
2½ litre 6307NR 80/35/21
Rear Hub RMA to 15000 6208 LJ40 A1769 80/40/28
RMA after 15000 6307 MJ35 A2615 80/35/21
RMB  6308 MJ40 A2283 90/40/23
Steering Gear Stem All 11BC-13C A3588 49.23/33.02/11.51

Note 1: The front water pump bearing LRJ17 is a roller bearing and can still be found under that number.  The bearing 6203 listed as the Generic number is a ball race with the same dimensions.  It is much cheaper to buy than the roller bearing.

Below are the bearing part numbers take from the Ransome and Marles (R&M) catalgue no. 77-A .  Unfortunately this copy appears to have been made by applying optical character regonition to the original and some of the characters have not been recognised properly so use with caution.