39mm Round Stub Axle, Castellated Nut, washer and split pin 39mm round stub axle is used on small trailers and as spare wheel carriers on boat trailers. We understand how to make a lousy axle and know what makes an axle great. Poorly turned axles cause bearing failure. The axle rating is 375kg each or 750kg per pair. Hollow Axles Hollow axles are rated the same as solid solids up to 750kg. American imported trailers have hollow axles. How to install a stub into a hollow tube Cut the tube to length, including the stub measurement. Drill a hole no smaller than 12mm on all four sides. Mark the 45mm tube 25mm back from the end of the stub when inserted. Insert the stub weld into place. Weld the stub holes to secure the end of the stub into the tube. Finally, the hollow axle stub must protrude past the springs and u-bolts once affixed into position. Standard Bearing Sizes are Inner LM Bearing Sizes ID 31.75mm OD 59.10mm Outer LM Bearing Sizes ID 19.05mm OD 45.20mm LM Seal ID 37.5mm OD 59.10mm Dust Cap 45.20mm We recommend you use only Japanese Bearings. 50mm Round tube with a wall thickness of 5mm retains the 750kg rating for a pair of 39mm Round Stubs. Reduce axle flex with a shorter length axle or more oversized diameter axle. If your camper, caravan or trailer is around 2400mm in length, select a 45mm Square Axle for a rating around the 1500kg mark.