When fitting a towbar to Class A, Class C or Coachbulits motorhomes, the frame extension is an essential part of the overall construction. This chassis extender is used to bridge the long overhang of the living unit and must be selected in the appropriate length depending on the motorhome model.
Many manufacturers therefore offer different lengths of frame extensions to meet individual requirements. However, this often leads to uncertainty, as can be read in numerous forums and discussion groups. Typical questions are:
- What length of frame extension do I need for my motorhome?
- How do I determine the correct length of chassis extension?
- Is there a calculator for determining the frame extension length?
Approach of the suppliers
Many suppliers of motorhome accessories such as towtal.co.uk, www.rhinoinstalls.co.uk, www.motorhometowbarcentre.co.uk, www.just-tow.co.uk or www.motrhome.com require photos or specific measurements directly on the vehicle in order to determine the right extension.
However, the online provider X-CAMPING offers an innovative approach: when purchasing a towbar for RV, it provides a calculator to determine the length of the frame extension.
How does the X-CAMPING’s calculator work?
The calculator is based on an extensive database of RV models and analyses various values and dimensions of the vehicles. To determine the appropriate frame extension, all you need to do is enter the total length of the vehicle. Where you can find it?
In some countries you can find this information on the registration certificate, unfortunately the UK V5C does not offer this data, so it would be best to check it in the vehicle specification or manual.
We publish a frame extension lenght calculator that works on the same principle on TOWBARS-Online.
The algorithm is designed to calculate the minimum required length of the frame extension for motorhome. This enables a precise selection, avoiding unnecessary adjustments such as shortening longer extensions. Workshops, which otherwise often use longer extensions and cut them to the overhang length, benefit from the ability to install customised variants directly.
Frame extension length – calculator
Limitations of the chassis extension calculator
However, the calculator currently has some limitations:
- Compatible vehicle models:
- Fiat Ducato type 250, 290, 295 (model years 2006 to present).
- Identical models:
- Citroën Jumper,
- Peugeot Boxer,
- Opel Movano (from year of construction 2021),
- Toyota Proace Max (from year of construction 2024).
- Frame types: The calculator only works for vehicles with original Fiat frames. Other chassis types such as AL-KO or SLC from Hymer (Super-Light Chassis by Hymer) are not supported.
- Limited product selection: The calculator is only compatible with XIMPLIO and LEMET brand products. Products from other manufacturers such as SAWIKO, LINNEPE, SMV-Metal or Umbra Rimorchi cannot be taken into account.
Future developments: Transit, Sprinter, Master and more!
According to X-CAMPING, the calculator will soon be available for other popular RV models such as the Ford Transit, Mercedes Sprinter and Renault Master, which will significantly expand the possible uses.
Alternative methods for determining the frame extension length
The length of the frame extension can also be determined without a calculator. To do this, you either measure
- the overhang of the motorhome from the rear axle to the rear bumper or
- the distance from the end of the original chassis to the rear bumper.
These methods are described in detail in many blogs and forums. Thorough research can also help to determine the correct length.
Conclusion: how to choose the correct frame extension for motorhome?
The frame extension’s lenght calculator from X-CAMPING offers a convenient way to quickly and accurately determine the right frame extender for motorhomes. If you prefer an alternative, you can measure the length manually or contact experienced suppliers and workshops. The continuous expansion of compatibility for other vehicle models makes the calculator particularly future-orientated and practical for motorhome owners.
You can find more interesting topics relating to motorhomes here on TOWBARS Online!
