Bilstein B8 with standard springs

[Rhys1983]

I've been reading a lot on how lowering a car can affect geometry and introduce bump steer and mess up the roll center of the car.
I currently run Bilstein B8 shocks with Eibach Pro springs which lower the car about 25-30mm.
Could I run standard springs with my Bilstein B8 struts and would this improve the handing of the car? My thinking behind this is that I've read that the ST sits slightly lower than a standard fiesta anyway, therefore is slightly 'lowered' compared to a regular fiesta.
The car I have is a late '16 model MK7.5.

 

[the duke]

I emailed Bilstein this direct question and was told to with OEM fiesta ST springs to use B6s. This was for a US 2014 ST so my car is slightly heavier but I have the older stiffer springs.

 

[Rhys1983]

I emailed Bilstein this direct question and was told to with OEM fiesta ST springs to use B6s. This was for a US 2014 ST so my car is slightly heavier but I have the older stiffer springs.

Ah right. So it looks like the standard springs won’t work with the Bilstein B8 struts.
I think I’ll stick to the Eibach pro kit then as they seem to be the ones with the least amount of lovering.
I don’t want to change my struts as they’re special ones valved by M-Sport as part of the handling pack that came with the M-Sport edition that I have.

 

[the duke]

Ah right. So it looks like the standard springs won’t work with the Bilstein B8 struts.
I think I’ll stick to the Eibach pro kit then as they seem to be the ones with the least amount of lovering.
I don’t want to change my struts as they’re special ones valved by M-Sport as part of the handling pack that came with the M-Sport edition that I have.

It'll work, and you probably would never noticed a different between a B6 and a B8. The shaft lengths are longer on the B6s, the valving is the same. There is a preference to have the main stroke within a certain limit(s) for the damper and these are different between the shocks.

I'd just run the B8s and stock springs unless your Bilsteins are dead and need replacement.

 

[Rhys1983]

It'll work, and you probably would never noticed a different between a B6 and a B8. The shaft lengths are longer on the B6s, the valving is the same. There is a preference to have the main stroke within a certain limit(s) for the damper and these are different between the shocks.

I'd just run the B8s and stock springs unless your Bilsteins are dead and need replacement.

The shocks have done less than 5k miles so are as good as new.
I’m not sure what springs to go with. Do I stick to my current ones, or change back to standard springs? And then the ‘13-‘15 springs are different to the ‘16-‘17 springs!

 

[the duke]

The shocks have done less than 5k miles so are as good as new.
I’m not sure what springs to go with. Do I stick to my current ones, or change back to standard springs? And then the ‘13-‘15 springs are different to the ‘16-‘17 springs!

Pre ST200 cars have slightly stiffer springs with more aggressive dampers. It's minute, but it is stiffer. The entire ST200 suspension was slightly softer with a larger torsion beams and I think a larger anti-roll bar as too many people complained of the original suspension was too hard. Ford softened the springs/damper and increased the torsion springs to make it more compliant over the road while still having a high rate during cornering. All cars after the ST200 was introduced have the ST200 suspension, this become the OEM suspension moving on.

Consensus for "best" coil/damper set-up is Bilsteins/Konis with Swift Engineering springs. This is a weird one though, no one has gotten a good answer from Swift as to which Bilstein to use, B6 or B8s. Swift has recommend both.

I'd grab Swifts and use the B8s.

 

[Rhys1983]

Pre ST200 cars have slightly stiffer springs with more aggressive dampers. It's minute, but it is stiffer. The entire ST200 suspension was slightly softer with a larger torsion beams and I think a larger anti-roll bar as too many people complained of the original suspension was too hard. Ford softened the springs/damper and increased the torsion springs to make it more compliant over the road while still having a high rate during cornering. All cars after the ST200 was introduced have the ST200 suspension, this become the OEM suspension moving on.

Consensus for "best" coil/damper set-up is Bilsteins/Konis with Swift Engineering springs. This is a weird one though, no one has gotten a good answer from Swift as to which Bilstein to use, B6 or B8s. Swift has recommend both.

I'd grab Swifts and use the B8s.

I’ve seen the swifts and they don’t lower the car too much either.
The only thing that puts me off is that I can see the rear springs have the same spring rates as the front which makes me worry that they could produce too much oversteer for fast road driving.

 

[Dialcaliper]

There can be endless debate over this topic, but you will likely be fine with either the B8’s on stock springs The shock bodies are ~1” shorter and the B6/B8 were originally designed for the base Fiesta, not the ST. You’ll lose a bit of droop travel, especially in the rear, but it won’t come into play in normal cornering unless the road is rough.

On the topic of lowering - lowering the rear is fine as the torsion beam geometry doesn’t change much, but the front struts are where it can hurt you. Starting from the base Fiesta, Ford lowered the rear of the car a full inch, but only dropped a tiny 3/16” of an inch in the front because of this.

Because of packaging, the FiST front control arms already sit at a fairly shallow 6 degree angle from horizontal at stock ride height. At about 1.25” lowering from stock, the control arms drop below horizontal. As you lower the car, the front roll center drops faster than the center of gravity, slightly increasing body roll and also worsening the camber curve resulting in more positive camber as the car rolls.

The loss of camber is the main thing you will notice, causing terminal understeer at the limit as the tire rolls over. You can mitigate this slightly on a track car by running stiff springs and front sway bars, but stiffening the front also tends towards understeer. You can also try to run even more negative static camber, but more than 2-3 deg will result in accelerated tire wear.

 

[Rhys1983]

There can be endless debate over this topic, but you will likely be fine with either the B8’s on stock springs The shock bodies are ~1” shorter and the B6/B8 were originally designed for the base Fiesta, not the ST. You’ll lose a bit of droop travel, especially in the rear, but it won’t come into play in normal cornering unless the road is rough.

On the topic of lowering - lowering the rear is fine as the torsion beam geometry doesn’t change much, but the front struts are where it can hurt you. Starting from the base Fiesta, Ford lowered the rear of the car a full inch, but only dropped a tiny 3/16” of an inch in the front because of this.

Because of packaging, the FiST front control arms already sit at a fairly shallow 6 degree angle from horizontal at stock ride height. At about 1.25” lowering from stock, the control arms drop below horizontal. As you lower the car, the front roll center drops faster than the center of gravity, slightly increasing body roll and also worsening the camber curve resulting in more positive camber as the car rolls.

The loss of camber is the main thing you will notice, causing terminal understeer at the limit as the tire rolls over. You can mitigate this slightly on a track car by running stiff springs and front sway bars, but stiffening the front also tends towards understeer. You can also try to run even more negative static camber, but more than 2-3 deg will result in accelerated tire wear.

What springs would you recommend? The Eibach pro springs lower the car about 25mm from standard, but with the Bilstein B8’s this is probably just over an inch.
I’ve had a look at the car from underneath and the control arms look to be about parallel at the moment.
Would you recommend going back to original front springs, or is it better to stick with the slight lowering of the Eibachs. The front Eibach springs are linear and are very close to the spring rate on the older ‘13- early ‘16 cars.
The car is used on British B roads mainly which can be undulating and rough.
Any help would be much appreciated!

 

[Rutschpartie]

What springs would you recommend? The Eibach pro springs lower the car about 25mm from standard, but with the Bilstein B8’s this is probably just over an inch.
I’ve had a look at the car from underneath and the control arms look to be about parallel at the moment.
Would you recommend going back to original front springs, or is it better to stick with the slight lowering of the Eibachs. The front Eibach springs are linear and are very close to the spring rate on the older ‘13- early ‘16 cars.
The car is used on British B roads mainly which can be undulating and rough.
Any help would be much appreciated!

I would stick with eibach pro -25mm and b8 on asphalt, body roll feels less (it seems eibach springs are stiffer) and handles better than stock springs + B6, even if control arms are parallel, i already drove this combo on the racetrack. Ofc this is my personal feeling/opinion, I drove both setups myself (stock with B6 vs eibach with B6). Maybe you can find out the exact spring rates of both to confirm what I felt: if the eibachs are indeed stiffer. Dialcalper is ofc right, you can mitigate the problems from lowering with stiffer springs/bars to some extent, so if they have the same/similar spring rate I could be wrong.

 

[Rhys1983]

I would stick with eibach pro -25mm and b8 on asphalt, body roll feels less (it seems eibach springs are stiffer) and handles better than stock springs + B6, even if control arms are parallel, i already drove this combo on the racetrack. Ofc this is my personal feeling/opinion, I drove both setups myself (stock with B6 vs eibach with B6). Maybe you can find out the exact spring rates of both to confirm what I felt: if the eibachs are indeed stiffer. Dialcalper is ofc right, you can mitigate the problems from lowering with stiffer springs/bars to some extent, so if they have the same/similar spring rate I could be wrong.

Thanks for your detailed reply.
From my understanding, the Eibach springs are about 5% stiffer than the old st springs which were stiffer again than the new st springs!
I’ve been looking on the internet and I’ve seen a company who offer a form of spacer which would raise my front suspension 12mm. This should be perfect as it would still be about 1/2 an inch lower than standard which would help with body roll and under braking, but not be too low as to cause problems with the roll centre.
The rear of the car still sits about 2cm higher than the front at the moment.

 

[Rutschpartie]

Thanks for your detailed reply.
From my understanding, the Eibach springs are about 5% stiffer than the old st springs which were stiffer again than the new st springs!
I’ve been looking on the internet and I’ve seen a company who offer a form of spacer which would raise my front suspension 12mm. This should be perfect as it would still be about 1/2 an inch lower than standard which would help with body roll and under braking, but not be too low as to cause problems with the roll centre.
The rear of the car still sits about 2cm higher than the front at the moment.

5% is not a lot! So if old stock springs are higher and you rly want to raise, I think I would prefer them to spring spacers, u can get almost new ones very cheap.

 

[Rhys1983]

5% is not a lot! So if old stock springs are higher and you rly want to raise, I think I would prefer them to spring spacers, u can get almost new ones very cheap.

Thanks.
Yes, the other option would be is to get a set of the old front springs. This would raise the front a little.

 

[M-Sport fan]

Ah right. So it looks like the standard springs won’t work with the Bilstein B8 struts.
I think I’ll stick to the Eibach pro kit then as they seem to be the ones with the least amount of lovering.
I don’t want to change my struts as they’re special ones valved by M-Sport as part of the handling pack that came with the M-Sport edition that I have.

HA, just get the M-Sport R2 Reiger tarmac $u$pen$ion!

(Yeah, I know, same problem I have, that co$t$ almost as much as the car is worth currently. )

 

[Rhys1983]

HA, just get the M-Sport R2 Reiger tarmac $u$pen$ion!

(Yeah, I know, same problem I have, that co$t$ almost as much as the car is worth currently. )

I’ve just spent over £5500 ($7,000) on EXE-TC fast road suspension for my Subaru P1!!! 🤣
The reiger tarmac suspension would properly solve our dilemma though on the St!

The way I see it is I’m either going to fit a 12mm spacer onto my Eibach springs which would keep the same characteristics of my current set up but with a better roll centre, or fit some older original springs to my Bilstein B8’s.

 

[the duke]

I think you’re vastly over complicating this. Especially if you’ve got no determined goals for competitive racing. Much like tire, you don’t need the grippiest. Fretting over the best or correct way is not worth it. 80/20 rule my friend. B8s with your Eibachs are fine. Otherwise a set of swifts are better if you want correct geometry and height. Grab some camber bolts and the car will be good.

Or just ball out and buy a set of custom MOTONs but then you’ll be on OEM geometry.

 

[Dialcaliper]

What springs would you recommend? The Eibach pro springs lower the car about 25mm from standard, but with the Bilstein B8’s this is probably just over an inch.
I’ve had a look at the car from underneath and the control arms look to be about parallel at the moment.
Would you recommend going back to original front springs, or is it better to stick with the slight lowering of the Eibachs. The front Eibach springs are linear and are very close to the spring rate on the older ‘13- early ‘16 cars.
The car is used on British B roads mainly which can be undulating and rough.
Any help would be much appreciated!

If you need the ride height, you will probably be fine with stock springs on B8’s. Just don’t try to fit the taller springs from a base Fiesta

 

[Rhys1983]

I think you’re vastly over complicating this. Especially if you’ve got no determined goals for competitive racing. Much like tire, you don’t need the grippiest. Fretting over the best or correct way is not worth it. 80/20 rule my friend. B8s with your Eibachs are fine. Otherwise a set of swifts are better if you want correct geometry and height. Grab some camber bolts and the car will be good.

Or just ball out and buy a set of custom MOTONs but then you’ll be on OEM geometry.

You’re right. I’m alway guilty of overthinking and looking for the best performance which is not really needed for fast road use!

 

[Rutschpartie]

before you try this consider: standard bilstein b8+stock ST springs could raise the car compared to stock fiesta ST height (10mm+), knuckles and maybe steering/control arms are different from the base model, so it will likely not be "factory" RC and CG if you want that

 

[Rhys1983]

before you try this consider: standard bilstein b8+stock ST springs could raise the car compared to stock fiesta ST height (10mm+), knuckles and maybe steering/control arms are different from the base model, so it will likely not be "factory" RC and CG if you want that

I would have thought that the Bilstein B8’s with the original ST springs would sit slightly lower than original struts + springs due to the B8 struts being slightly shorter?