DIY: Basic wheel alignment checks for single-axle caravans

John Hughes and the team at the RV Repair Centre walk us through some basic DIY wheel alignment checks for single-axle caravans.

When we hear the words ‘wheel alignment’ we tend to think of our tow vehicle, but alignment is important for caravans too. In simple terms, we want our caravan wheels to point where they should while the van is towed along by the car. Misaligned wheels cause uneven/premature tyre wear and can compromise the handling of the rig.

Wheels can become misaligned due to general wear and tear and often through being subjected to significant knocks such as hitting large potholes at speed. The RV Repair Centre shows us how to perform a few basic (approximate) DIY checks on a single, solid beam axle caravan. We do not attempt to perform a wheel alignment.

Each check involves taking measurements and part of the expertise is interpreting these numbers. For each check following we provide a rough guide on typical acceptable measurements. Ideally, you want to obtain the acceptable specs from the caravan manufacturer. If you find your numbers are ‘out’ or your tyres show signs of irregular wear we recommend you take your van to a van alignment specialist who can perform a more accurate check and alignment if necessary.

First, a little explanation on wheel alignment concepts. There are three key elements to alignment.

1. Axle triangulation

The axle should be square on the caravan. In other words, the wheels on each side of the van should be the same distance from the coupling to allow the van to easily track in a straight line. This squareness is checked by ‘axle triangulation’. The wheels are removed and an accurate measurement of the distance between the wheel hub and the coupling is made on each side to see how equal they are.

2. Camber

Camber is a measure of how vertical or off vertical the wheels are. A perfectly vertical wheel has zero camber. A wheel that tilts in at the top has negative camber. A wheel that tilts out at the top has a positive camber. Excessive negative camber will cause more wear on the inside edge of the tyre. Excessive positive camber will cause more wear on the outside edge of the tyre.

3. Toe

Toe is a measure of how straight the wheels are pointing when viewed from above. Wheels that point straight ahead have zero toe. When a wheel points in it is referred to as toe in and if the wheel points out it is referred to toe out. Excessive toe out causes more wear on the inside edge of the tyre. Excessive toe in causes more wear on the outside edge of the tyre.

Preparing for wheel alignment checks

The van must be placed on a horizontal, stable surface such as concrete. (The workshop had the advantage of a hoist but interestingly the hoist platforms tilt in slightly under load, necessitating some ply and packers to be used to create a horizontal reference point.) Check all caravan tyres have suitable, equal pressures.

Triangulation

Measurement differences between the two sides greater than 3–4mm would indicate further investigation is required.

STEP 1: Attach a string with a weight to the midpoint of the coupling to use as a vertical reference point	STEP 2: Get some help to measure from the axle/wheel hub to the string	STEP 3: In this instance, the outside edge of the wheel hub was used
STEP 4: Record the measurement. It is important to keep the tape measure tight and straight for an accurate measurement	STEP 5: Repeat the process on the opposite side of the caravan	STEP 6: Ensure the measurement is taken from the same point on the axle or wheel hub
STEP 7: Record and compare the measurement of the two sides

Camber

Measurement differences between the two sides greater than 2–3mm would indicate further investigation is required.

STEP 1: A horizontal surface is required as a reference point in conjunction with a square	STEP 2: Place the square up against the tyre wall	STEP 3: At the lowest point of the rim, measure the distance from the outside edge of the rim to the edge of the square
STEP 4: Record the measurement	STEP 5: At the highest point of the rim, measure the distance from the outside edge of the rim to the edge of the square	STEP 6: Record the measurement
STEP 7: Repeat the process on the opposite side of the caravan starting with using a horizontal surface as a reference point	STEP 8: At the lowest point of the rim, measure the distance from the outside edge of the rim to the edge of the square and take a record	STEP 9: At the highest point of the rim, measure the distance from the outside edge of the rim to the edge of the square and take a record

Toe

Measurement differences between the two sides greater than 2–3mm would indicate further investigation is required.

STEP 1: Jack the van up safely so the wheels can be removed	STEP 2: Remove the wheel nuts	STEP 3: Remove the wheel
STEP 4: Repeat the wheel removal process on the opposite side of the van	STEP 5: Place a straight edge across the flat surface of the hub	STEP 6: Measure the distance from the chassis face to the straight edge
STEP 7: Take a record of the measurement	STEP 8: Reposition the straight edge so a measurement can be taken on the other side of the hub	STEP 9: Take a record of the measurement
STEP 10: Repeat the process on the opposite wheel using a straight edge and measuring tape	STEP 11: Take a record of the measurement	STEP 12: Reposition the straight edge so a measurement can be taken on the other side of the hub
STEP 13: Take a record of the measurement

If in doubt, consult a professional

Improper maintenance can lead to injury, death or property damage. Maintenance work of this nature should only be undertaken by people with suitable competence. The information provided is general in nature, not comprehensive and should only be taken as a guide. Individual discretion must be exercised and persons undertaking described tasks do so completely at their own risk. Publishers and creators of this content accept no responsibility for loss or damage.

Thanks to Andrew Phillips and the team from the RV Repair Centre, 120 Canterbury Road, Bayswater North Vic 3151, P: 03 9761 4189

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