VW Splines Explained, How to dial in your height
Spring Plates Explained
Here is a quick overview and the all-important rear suspension / spring plate adjustment chart so you can workout how much to lower your vehicle by.
Important notice: Remember to mark the current position so you can revert back if need be but also so you can count the amount of splines you’re adjusting by.
Quick overview of Beetle Suspension Design
Running at the rear of all Beetles is a torsion tube. Inside this are two torsion bars, which are solid round metal bars with splines at both ends. These locate solidly in the centre of the car and have the spring plates pushed onto their outer ends. As either rear wheel goes up or down, it causes a twisting motion in the torsion bar which performs the rear suspension action. The spring plates also handily serve to locate the rear axles and stop them flopping about uncontrollably.
Method and tips to lowering the rear spring plates
To lower the rear of a Beetle, you simply unbolt the spring plate from the axle, pull it off its outer splines, rotate it either up to lower the car or down to raise it and pop it back on again. Here's a few handy tips to help this process be as streamline as possible:
The first is that the spring plate covers that contain the rubber bushes rot and the bolts shear off when you try and remove them. This won’t stop you getting them off, but it will stop you getting them back on again. If this happens, your best bet is to heat the broken bit of bolt up with a blowlamp until it is cherry red and then try and twist it out with a pair of mole grips.
The second thing that often happens is that you either forget to mark the spring plate or, in trying to lever the spring plate off the outer splines, you pull it out of the inner splines instead. This isn’t a massive problem though as you’ll be able to feel (as you can’t see) where it goes back on and start again. Just don’t mix the bars up side for side, whatever you do.
To avoid losing your original position, mark the relative positions of the spring plate and torsion bar with paint when you’ve removed the cover plate and, once you’ve levered the spring plate off its stop, scribe its position relative to the chassis before you remove it. At least then you’ll have some reference points to go back to.
It’s also a good idea to support the axle end of the spring plate when you start pulling it away from the chassis. Once it comes off it’s ‘stop’ it can swing very fast toward the ground. Some people chain it up to the chassis and release it once it clears the stop while others use a jack. The jack option is what we’d use as you can gentle lower the plate down once it’s clear of the stop and continue to free it from the torsion bar splines.
How much should I lower by?
By far the most common confusion is how many splines to rotate the spring plate by, but the using handy table below, it will tell you all you need to know. Different people will give you different answers as to what the perfect amount to lower the back of a Beetle is, and it’ll often be a combination of inner and outer splines, but keeping it as simple as we can, one outer notch or spline equates to roughly two inches out of the suspension height. This doesn’t sound like much but you’ll notice it and it won’t cause you any extra grief.
Two outer splines (almost five inches) is excessive for a regularly used car, but then that might be the look you’re after.
While you’ve got your spring plates off you might as well change the inner and outer rubber bushes as well. You can see our full range available here
Spline adjustment chart
|Inner Spline||Outer Spline||Approximate drop|