Why we don't base height adjust

Base height adjustment is flawed

One of the biggest differences between MCA Suspension products and most other brands or products around our price point is the fundamental design and adjustment method.

For whatever reason, most cheaper products from overseas use a “base height adjustment” method of height adjustment. We have no idea how this method of design and adjustment came into existence, however we can only assume that it was due to a decision to make cheap/affordable adjustable suspension (when previously nothing like this existed) but without the knowledge, passion and understanding required.

Rather than going into detail explaining how shockabsorber lengths work in relation to wheel travel, it’s easier to discuss the supposed selling points of base height adjustment.

One of the main “selling points” when adjusting ride height via the bottom mount position is that you get to keep the same suspension travel no matter the ride height. This is definitely true, however it’s actually not something that you want as the amount of room your tyre can move up into your wheel arch is limited by the body/chassis/trim above the tyre and changes with every ride height change. The tyre can’t move upwards forever and it should be controlled and stopped before it makes contact with fenders and such above it.

It can also help to clarify what part of the suspension system is actually controlling how far the wheel/tyre is allowed to move upwards into the wheel arch before it’s stopped. This should be controlled by the bumpstops, and in most cases these are located on a shockabsorber.

What adjusting via the "base height" method does

Let’s say at a hypothetical ride height you have 60mm of distance between the top of the tyre and the wheel arch trim above the tyre. In this scenario ideally you should also have 60mm of wheel travel allowed by the suspension, this way the suspension will fully compress and “bottom out” stopping the wheel contacting the wheel arch trim by stopping it travelling too far upwards. This is what we could call a correct scenario.

If you wanted to lower the car 20mm by using the bottom mount position, there would now be 40mm of distance between the top of the tyre and the wheel arch trim, but still 60mm of wheel travel allowed by the suspension. This means that your suspension would allow your tyre to travel upwards to the point of making contact with parts of your car, and 20mm past that. As you can imagine, that’s not ideal for a number of reasons.

60mm shaft travel and 60mm wheel to arch room

60mm shaft travel and 40mm wheel to arch room

Result of the shock absorber at full compression, the tyre will hit and possibly cause damage.

In that same hypothetical scenario, if you were to raise the car via the bottom mount, you’d now have 80mm of distance between the top of the tyre and the wheel arch trim, but still only 60mm of allowed wheel travel by the suspension. So in this case you’re now running a higher ride height, but still have the same travel you had at a lower ride height, meaning you’re missing out on additional travel, which helps both ride quality and performance.

60mm shaft travel and 60mm wheel to arch room

60mm shaft travel and 80mm wheel to arch room

Result of the shock absorber at full compression, there is still 20mm of room between the wheel arch and tyre resulting in wasted.

How height adjustment should be done

In this same scenario, if the car had MCA Suspension and you lowered it 20mm by moving the bottom spring seat position instead of the bottom mount position, you’d have 40mm of wheel travel allowed by the suspension to match the 40mm of distance from the top of the tyre to the wheel arch trim. So this is still an ideal scenario, and this relationship of allowed wheel travel and distance from the top of the tyre to the wheel arch trim will stay the same no matter the height adjustments you make.

60mm shaft travel and 60mm wheel to arch room

40mm shaft travel and 40mm wheel to arch room

The tyre uses all the available space and stops before hitting the wheel arch.

Why you can't set ride height correctly using a product designed for "base height"

The reason you can’t adjust a set of suspension that’s designed for “base height adjustment” the correct way (via the bottom spring seat position) is because for the bottom spring seat method to work, the operating lengths (combination of travel range and bottom mount position) must be set correctly first to suit this method.  This is something that’s correctly preset on MCA Suspension products.

Correct height adjustment raising or lowering spring seat.

In summary

In our opinion if you have a suspension product that uses base height adjustment, then you are just gambling with your wheel travel and don’t really know how much travel you have and where that travel is positioned in relation to the body of your car. This can lead to minor vehicle damage or even an accident and more than likely a less than ideal suspension setup.

It’s also important to note that the tyre contacting the wheel arch trim is just one of the possibilities of not controlling the wheel travel range properly. Other possible scenarios include suspension components (such as suspension arms) hitting the chassis, brake lines going tight and snapping, suspension pivot points reaching their limits, etc.

Where as with MCA Suspension products, we’ve done the extra homework and have sent out the suspension with the bottom mount set at the position we determined during the design process after measuring up the car here in our workshop and finding it’s ideal wheel travel range. This way you should have nothing to worry about.

If you do have very unique requirements and need to be able to customise your wheel travel range to suit your particular situation, that’s also no problem. If you CLICK HERE you’ll be taken to another page of our website that goes through how to check/set the wheel travel yourself to suit your exact car.