Ride Height. Yes, Noo or sometimes? The answer actually should be sometimes!
Some vehicles require you to measure the ride height as part of the wheel alignment procedure and not to do this makes the alignment and subsequent adjustment inaccurate.
What is ride height? It is the height of clearance the car has between the bottom of the car and the road. The ride height has an impact on the car’s centre of gravity, and it’s behaviour when cornering or braking.
As important as ride height is, before starting any alignment procedure it is vital to conduct a pre-alignment check; being tyre tread depths and condition, but also a tyre pressures and suspension components/bush condition check as this will alter the ride height.
From Pro-Align’s experience, because ride height is not routine with every vehicle it is easily overlooked or ignored, but in doing this it will affect the toe, camber, caster and even steering angle inclination readings.
How do you find out if the vehicle you are measuring needs ride height measurement? The manufacturer’s manuals or dealer information systems (such as Mercedes-Benz) will tell you but you need to know where to look for it.
Some alignment systems have the information within their software. In the case of the Hunter systems, as you progress through the alignment process, it will alert you at the right point in the process and give you the step by step guide to take you through the procedure with supportive notes and diagrams.
How do you measure ride height? Again where you measure to and from varies and the methods can vary too according to vehicle and manufacturer.
The simplest measurement on the majority is with the humble tape measure. Some manufacturers ask you to measure from the ramp to the sub frame/sill, as with Citroen, Renault, whereas others state wheel arch to wheel centre – as with BMW
There again, there are some models where additionally to achieve or assist with ride height, it requests the car to be weighted, simulating the vehicle with a passenger payload and/or full petrol tank. If offering a wheel alignment service you should always have a weight set as an alignment accessory (even if infrequently used).
Mercedes measure ride height in terms of angles and to do this you are required to have a Romess tool. Some 3D alignment systems such as Hunter Elite TD have ride height targets which can be attached and then at the appropriate point in the alignment process, measures the ride height automatically (but again weighting still may be required).
Now some non-purists will confirm they use a ‘nominal’ ride height specification, but these are base settings but does not take into account the vehicle’s current ride height. This is the least accurate way.
So which way? The best advice Pro-Align offers is: “Do the ride height and alignment as the motor manufacturer would for that make and model of vehicle which is always going to be the most accurate. This way you can in confidence deliver an alignment service to your customers that is well done (and proof as such is the alignment printout) and their car is set back within manufacturer’s specification.”