Tow Ring

A friend recently snapped a driveshaft on his Mini and had to get his car towed and I realised that at some point during the build I will probably need to winch the Mini onto a trailer or tow it, so I'll need a tow hook/tow ring to connect a cable or rope. I took the tow ring out of my other (2007) car for a general guide for design and dimensions.

For the ring part, I initially used a M12 lifting eye which has a similar hole size as the modern tow ring. I machined down a 22mm diameter solid steel bar on the lathe, drilled/tapped one end with a M12 thread for the lift eye, and drilled/tapped with a 1/2" thread on the other end.

Some time after I had finished the work, I realised that the letters "C15E" stamped on the lift eye indicated a Working Load Limit (WLL) rating of 340kg. For a static load (i.e. winching onto a trailer) this would be fine but I was concerned the rating was too low if the Mini was towed behind another vehicle. I sourced a bigger M16 lift eye which had a WLL of 700kg, and machined/re-threaded the steel shaft for the bigger M16 thread. 

All bolts used to mount the front subframe to the body are 5/16" UNF, with the only exception being a pair of the bolts which I chose to be a larger 1/2" for the tow ring. I drilled out the hole in the subframe from 5/16" to 1/2" for this larger bolt size. To install the tow ring, it is simply inserted through either of the factory holes (left or right hand side) in the front apron and screwed onto the 1/2" subframe mount bolt (this bolt has longer thread specifically to accept the tow ring).