DIY chassis brace mk4 golf VW/Octavia MK1

In this article I want to answer the question “is a subframe brace a placebo modification or does it do something that the drive can actually feel?”

What Do They Do?

Strut bars/strut braces/chassis braces whatever you are looking at and whatever name you use are using, they are designed to reduce flex in the chassis by bracing/strengthening weak points in the chassis.

Video version of this article

How Does This Help?

How does reducing flex in the chassis help? What happens when we reduce chassis flex?

The “what” first.

We want the springs and the shocks (dampers) to deal with all of the wheel movement.

Why?

Because that is what the spring and the damper are designed to do. The spring and the shock are tuned to work together so the wheel can move up and down in a controlled manner. Having maximum control of the wheels is essential for grip. We want the wheel to follow the contours in the road completely. We do not want the wheel leaving the ground because when the tyres leaves the ground it gives no grip.

For the springs and the dampers to work correctly they need to have a solid mounting relative to the car. We do not want flex in the chassis anywhere and especially where the wishbones and dampers and springs attach to the car.

Chassis flex is inconsistent, it’s reaction to load changes according to how much the body of the car is flexed. Dampers and springs are tuned & developed in a perfect world ie against solid mounting points. For them to work as intended ie to give maximum grip, we want them to work the same way on the car ie to be mounted solidly.

Another major issue with chassis flex and movement of the wishbone and damper mounting points is geometry changes.

If a pick up point is moving, it’s going to be changing the geometry of the wheel versus the car. Considering your average wheel alignment is done down to fractions of a degree, even small movements will play a part in effecting handling.

And all of this, is why increasing chassis stiffness should in theory, make a car handle better and it should make a car ride better also.


But Does It?

Does the theory match reality? Does increasing the stiffness of the chassis make the car perform better?

To find out, I installed a front lower strut/chassis/subframe brace on the Octavia RS project. The Audi TT MK1, which uses the same chassis, has additional bracing from the factory and this includes a lower front subframe brace.

In this video I copy the TT bracing by using a subframe brace that attaches to the same points as the factory TT brace to see if it makes any difference and if so what.

Without the Subframe Brace

Without the brace the front end generally felt a bit loose, especially over sharper bumps. And sometimes this looseness could be felt through the steering column. Steering response was also a bit wolly especially on turn in.

Theoretically this sounds like the kind of situation where a chassis brace could help, but did it?

In Short

In short, yes the chassis brace improved things. The car felt more secure, more tied together over bumps. There felt like there was less movement in the shell of the car, perhaps the best way to explain the difference is that the car felt newer. I would also say small bumps were less noticeable. The car rode better. And the cabin seem to rattle less.

On the handling front things were less clear. I’m not sure I could feel a difference in grip with the brace over no brace. It’s possible that the car responded faster to steering inputs but the difference, if there were any at all could be put down to the placebo effect.

Is a Chassis Subframe Brace Worth It?

Even though the difference in cornering felt small enough to possibly be psychological, I believe the difference in ride was real. There was a noticeable improvement.

Cost

Lower front chassis braces, the 2 point type usually come in around the 100 dollar/euro/pound mark and for this money I would say they are worth doing, especially on older cars and especially on cars wearing bigger wheels and/or wider tyres.

I don’t see any down side to fitting them, although ground clearance might be compromised slightly. But the upsides are many. For a start it should reduce metal fatigue in the parts it is mounted to, in this case the front subframe brace.

On this car the brace gave a tangible increase in ride comfort/quality and for that alone, for 100 Euro, I think it’s a good investment.

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