Mk7 Zetec S v ST Suspension

[Daniel.M]

Hiya guys,

I had a little search around but can't find my answer.. 

I'm trying to find a comparison between the Mk7 Zetec S and ST suspension.. I know the ZS has quite firm suspension and is a little lower than other models, but is the ST firmer and lower still, or do they have the same setup?

Thanks.

[Jim H]

Hello and Welcome to the Forum

You are correct in saying, the Zetec S has a sportier lower and firmer suspension than normal models. As far as I know the ST has an even firmer still set-up. I'm not sure about ride height between the two though. Some people find the ride too firm on the ST especially at slow speeds and the ZS (or ST-L) a good compromise. 

I have no idea if the ST springs & dampers will fit on a ZS, or vice verse, if that is what you are wanting to do.

[Neb_engineer]

1 hour ago, Jim H said:

Hello and Welcome to the Forum

You are correct in saying, the Zetec S has a sportier lower and firmer suspension than normal models. As far as I know the ST has an even firmer still set-up. I'm not sure about ride height between the two though. Some people find the ride too firm on the ST especially at slow speeds and the ZS (or ST-L) a good compromise. 

I have no idea if the ST springs & dampers will fit on a ZS, or vice verse, if that is what you are wanting to do.

They will but you will have to also get an alignment as the change of ride hight will throw your toe and Camber adjustment off, also be aware it's far easier to bottom out the travel of the a zs or st suspension compared to a normal zetec's as although they are stiffer,t hey have less travel to begin with

[alexp999]

The ST suspension is typically tuned for a heavier engine. If you fit it to a lighter variant you can actually end up increasing ride height.  

[Daniel.M]

Hi guys, thanks for the replies.

What about if I went down the route of having ST shock absorbers and lowering springs?

I have a mk7 Zetec S 1.0 ecoboost.. I'm looking for a little more precision in my driving and just want it hunkered down a little more with a bit more stiffness. 

[Neb_engineer]

5 hours ago, Daniel.M said:

Hi guys, thanks for the replies.

What about if I went down the route of having ST shock absorbers and lowering springs?

I have a mk7 Zetec S 1.0 ecoboost.. I'm looking for a little more precision in my driving and just want it hunkered down a little more with a bit more stiffness. 

Your better off upgrading components on the sway bar such as bushes and drop links

[Eatonm112]

I can tell you that the ST suspension will just bolt onto your Zetec S but I cant say how it will drive. I have been down this road but I am running air suspension and ended up changing my hubs to the ST ones as my camber was off and couldnt be adjusted to near stock so was running too much camber and thus wearing out my tyres.

The ST hubs are the way to go if you want to lower the car 30mm or so as you can keep the stock alignment.

https://photos.app.goo.gl/tZRd1axPXZEEPHLp9

My picture shows a standard 1.0 hub on the right and ST hub on the left.

[Daniel.M]

2 hours ago, Eatonm112 said:

I can tell you that the ST suspension will just bolt onto your Zetec S but I cant say how it will drive. I have been down this road but I am running air suspension and ended up changing my hubs to the ST ones as my camber was off and couldnt be adjusted to near stock so was running too much camber and thus wearing out my tyres.

The ST hubs are the way to go if you want to lower the car 30mm or so as you can keep the stock alignment.

https://photos.app.goo.gl/tZRd1axPXZEEPHLp9

My picture shows a standard 1.0 hub on the right and ST hub on the left.

So if I was to get the hubs, shocks and springs, it would drop it down on that alone? Wouldn't there be a weight difference due to the engines though making it sit differently?

[Eatonm112]

2 hours ago, Daniel.M said:

So if I was to get the hubs, shocks and springs, it would drop it down on that alone? Wouldn't there be a weight difference due to the engines though making it sit differently?

There is a good 50 to 60 Kg difference due to engine and gearbox oin the ST so not too sure how it would sit. Have you thought about going for aftermarket suspension? As you will have more adjustment although a much firmer ride.

[Daniel.M]

On 1/21/2022 at 11:08 PM, Eatonm112 said:

There is a good 50 to 60 Kg difference due to engine and gearbox oin the ST so not too sure how it would sit. Have you thought about going for aftermarket suspension? As you will have more adjustment although a much firmer ride.

Yeah, I did think about it, but I was hoping to save some money by getting some second hand ST shocks and springs.. but if I need to buy the whole lot including hubs and all, then I'll just wait until I have the money for the aftermarket.

[Marky146]

A brief theory exercise at this point for new comers.

 

The ST as standard has very little negative camber if any at all at rest, despite the low r ride height.

 

To understand what's going on, Imagine your car head on. Draw a line through the lower arm inner bushings and the bottom ball joint. That Line travels in in an angled upwards line. Now draw a line inward from your top mount at 90' to it. The two lines will cross somewhere 50m to one side of the car. Now from that point draw back to the centre of your tyre on the ground. if you do that for both sides the two lines cross the centreline of the car somewhere near the sump. That is your roll centre. As you corner, the Centre of gravity which is higher than this point causes a rolling torque, it's resisted by the anti roll car and springs. 

It's changes you must think of. Lowering the car, will make the lower arm more horizontal. Remember that. What it does on a McPherson Strut is lower the roll centre about 4 times the lowering of the car. This means the CoG may drop 25mm but your roll centre drops 100mm. The roll torque makes the car wallow unless you fit really stiffer springs.

Now, camber. As you roll, the wheel that compresses will want to generate negative camber. it does this by allowing the lower arm to move the ball joint outwards, because of the arm's angle. If the car is lowered and the arm horizontal, you can't get more negative camber- you've got all you are going to get already.

Hence the ST hubs position the lower ball joint further down.

On a Subaru the ball joint is a bolt in and kits are available to fit a lengthened ball joint to do the same thing. 

The back end is easier, it's a simple beam and roll centre is ALWAYS at the ground level. Any lowering reduces roll. It's as simple as that.

If you repeat the roll centre exercise above, you now get two points, Now skewer your car through those two points fore and aft and imagine your car pivoting on this axis around corners. If you can visualise it well, you'll now know why rear beam sports hatches, Golf GTI, Pug GTi, St ,etc. always lift their inner rear wheel when cornering hard.

 

 

  

[Marky146]

Daniel, I'd say if I were you I'd consider the ST hubs or see if a kit is there to replace the lower ball joint with a longer one.