As a kid, I used to love it when grandpa would throw me a block of wood, some nails and a hammer and let me help knock up the next home-made improvement for the family camper. Granted, the idea was probably more to keep me out of his hair rather than actually help with the job, but memories like this really do stick with you for a lifetime, I reckon. That old hardfloor camper’s been right around Australia, more than once if memory serves me correctly, and it’s still got the stickers plastered down the side to prove it, too.
I can only imagine the sights this old beauty has seen over the years, but ever since grandpa passed, the old hardfloor camper trailer has been tucked nicely away in my shed with a great deal of sentimental value and memories to go with it.
To be honest, it’s starting to look a bit second-hand lately, so I figured it was time to get the old gem out, give it a freshen up and start making a few memories of my own in it, you know, for grandpa. So let’s check out the progress I’ve made so far.
OUTDATED RUNNING GEAR
The first thing I wanted to do is replace the wheel bearings and hubs, but do you think I could find the right parts? Nope. It turns out this particular camper was actually imported from New Zealand, and had aftermarket stub axles welded to the original 50mm square (hollow) axle to suit the super old style Mini hubs, which are now obsolete and completely different to the later mini stuff available these days.
Obviously, if you get stuck in the middle of nowhere, you want to be able to find spare parts easily, so it was time to update everything. By everything I mean, I fitted a brand new axle, along with all the later mini-style stuff (fresh hubs and bearings to suit). What I didn’t realise is the old wheels would no longer suit the later style hubs because the new wheel studs are actually too big, so yep, you guessed it; it was time to splurge on a brand spanking new set of 10in alloy rims, along with some new rubber for good measure. That also meant all the old spare parts like tyres and bearings would no longer suit, so it’s safe to say my wallet’s copped a hard time, lately!
Now you might be wondering why I stuck to the original size wheels and tyres instead of jumping up a few sizes, and there are actually two reasons for that. The first is that there’s just not enough clearance around the wheels due to the closed-in guards, and the second is because raising the height of the camper will throw out the balance of things when you’re trying to open it up, and cause the hardfloor to over-extend without even more modifications.
UNDERSTANDING TYRE SIZES
I couldn’t find the same size tyre as a replacement but I needed one of the same height, as the tyre sits close to the floor. So to calculate, I referred to the code indicating its technical specifications on the tyre wall.
To explain how it’s done, let’s examine the following size: 205/65 R15. The 205 indicates the tyre width in millimetres, the 65 reveals its aspect ratio as a percentage, or the tyre’s section height in relation to its section width. So in this example, the tyre section’s height is 65 per cent of the tyre’s width, to equal 133.25mm. The R15 stands for the diameter of the wheel (15in).
To calculate the overall height, we double the tyre section height (133.25mm x 2 = 266.5mm) to account for the top and bottom of the tyre, convert the answer to inches (10.5in) and add in the diameter of the wheel (15in) for a tyre that is 25.5in tall.
MEASURING AN AXLE
If you are straight out replacing your camper’s axle, it’s a pretty straightforward job measuring the axle up to get the right one. To work out the length, you’ll need to measure the axle track, which is basically the measurement between the two hub faces. You can do this by running a tape measure from the outside of one hub face (where the wheel mounts up) to the outside of the hub face on the other side and recording the measurement. This will basically ensure the axle is the right length for the wheels to be positioned exactly where they were beforehand.
If you are replacing your wheels too, you’ll need to make sure the new rims have the same offset as this will affect how far the outside of your wheel sticks out from the hub face. If the offset is different, but you still need the wheels to be in exactly the same position as before to clear wheel arches or inner guards, you’ll need to account for this when you determine your new axle length.
So if the new rim offset causes the tyre to stick out an extra inch (each wheel), you’ll need to shorten the axle by two inches.
WHAT’S A PCD?
When it comes to matching a new wheel to a particular hub, you’ll need to know the stud pattern, which is determined by the Pitch Circle Diameter (PCD). This is basically the diameter of the circle that passes through the centre of the wheel studs. The PCD will indicate the number of studs in total, along with the diameter (usually in millimetres). So, if it’s a PCD of 4x100mm, it’s saying that there are four studs/holes with a total diameter of 100mm.
To measure the PCD, start by identifying the size of the rim first, which will narrow the possibilities down. For either a four- or six-stud pattern, simply measure between two diametrically opposite holes. For five-stud patterns, measure between two adjacent holes (next to each other) and multiply it by 1.701. Remember to measure it from the centre of each hole/stud. Once you have the PCD you can generally look up which wheels or hubs will suit your need.
There are other methods of calculations, but these will generally get you out of strife.
Check out the full feature in issue #96 January 2016 of Camper Trailer Australia magazine. Subscribe today for all the latest camper trailer news, reviews and travel inspiration.