Although there should be one main towball size in the UK, in reality the size and shape of the towball to fit a UK caravan can vary slightly. And depending on the make and model of the caravan you may need to get a slightly different one. We cover some of the issues and size/shape variations for UK caravanners. Luckily we’re not as bad as the US where they have 3 different sizes!
Not All 50mm towballs are the same
The standard size of a modern day towball is 50mm. Clear and simple. However, if you have an AL-KO stabiliser on your caravan you may need to ensure it is stamped as ‘ISO 50’ or ‘AL-KO’. The reason for this is that an AL-KO stabiliser needs a bit of extra clearance, so a standard one may not give that extra clearance needed.
Example of an ISO 50mm Towball
Example of an AL-KO Extended Neck ISO 50mm Towball
Other Possible Sizes
Older, imperial measure towballs were completely spherical, but the metric ones should all have a flat top (on top of the ball) which is a good way to tell the difference. Obviously the older towballs shouldn’t be used.
Swan Neck Towballs
These types automatically give the clearance needed (due to their swan neck) for AL-KO stabilisers so is definitely a good choice if you have one. They’re also standard 50mm sizes so you’ll get exactly what you need.
In Conclusion – What Size Towball Do You Need?
For all cases a swan-neck 50mm (stamped ISO 50 or AL-KO) is the simplest and most straightforward choice.
Ultimately, the most important thing to check that the size of the towball is compatible with the size of the coupling head on the caravan. Also ensure that the towball size/type for your caravan is appropriate for the maximum towing capacity of your vehicle. This information can be found in your vehicle handbook. It is important not to exceed the maximum towing capacity of your vehicle as this could result in an accident.
If you are unsure of what size towball you need for your caravan, it is best to consult with a qualified mechanic or caravan dealer.