Bilstein Science Experiment

[Rutschpartie]

It is very strange to me also that the B14 front struts are so soft...do they maybe use softer/shorter bump stops? Or even much softer springs in the kit?

 

[Fusion Works]

Wouldn't matter, you still need a damper that can control the higher spring rate and combination of bump rubber rate and the B14 just doesn't have that kind of compression and rebound valving.

 

[kevinatfms]

Interesting and thanks for doing this testing. It looks like the B14 is oddly soft compared with the B8. Is yours from the Fiesta kit, or an off the shelf insert?

What it suggests to me is that the B14 kit, spring rates and damping were designed as an upgrade to the base model Fiesta. It looks like that might not be true of the B8 (maybe B6?)

Id say this is true but he is dynoing the B14 kit specifically for a Fiesta ST. The rear damper part number between the two B14 kits is also the same part number so the valving is the exact same between the two rear dampers.

 

[Dialcaliper]

Id say this is true but he is dynoing the B14 kit specifically for a Fiesta ST. The rear damper part number between the two B14 kits is also the same part number so the valving is the exact same between the two rear dampers.

True - Given the rear dampers and springs in the kit are identical, I’d find it difficult to believe they did anything dramatically different to the front damping curve from the non-ST kit. At best a subtle tweak to account for weight difference, but I doubt they went through the trouble.

 

[Fusion Works]

Agreed. Why bother with making something special for the base model Fiesta when the platforms are the same, just make one part. However, the damper parts are a different number on the fronts.

Base Fiesta Kit 47-167490
Base Fiesta Front damper VE3-G750/G751
Front spring E4-FD1-Y037-B00

Fiesta with ST
Damper 35-242055
Front Spring E4-FD1-Y037-B00

May have to do with the location of some tabs or something that makes the housings different.

 

[Fusion Works]

Some more boring minutia, I was staring at dampers tonight and noticed the rear B14 shock shaft is 11mm diameter as is the damper shafts for the front inserts. The B6/B8 use a 14mm shaft which is more common across the motorsports range. Means there could be some adjustable shafts installed in the rears, but the issue would be the overall length of the rear damper shafts since the Fiesta uses a very long shock. The other thought the 14mm shaft will be stronger in bending, which the damper may see in operation on the rear.

While I pull mine out for a revalve, I think I might try something with this pile of shocks. Thinking I may take the B8 front strut, put my ST front lowering spring, 174ish lbs, on the front, move my 165lb front springs to the rear and run the B8 rear damper to see how the dampers change the handling and ride. I don't care so much about the ride height as I do playing with the rates and damping for the time being. I will have to build a spacer to get the ride height back where it needs to be with the ST lowering spring as it was always too low in my opinion.

I expect the turn in to be lazier than with my current custom insert. The car should move around more, but with the higher spring rate in the rear the chassis should be a bit "free'er". Now the rear B8 damper may not be happy with that extra rate, but in reality its 20lbs more than the OE rate. Might be smarter to swap some ST rear dampers on there to see the differences in the two setups.

 

[M-Sport fan]

Agreed. Why bother with making something special for the base model Fiesta when the platforms are the same, just make one part. However, the damper parts are a different number on the fronts.

Base Fiesta Kit 47-167490
Base Fiesta Front damper VE3-G750/G751
Front spring E4-FD1-Y037-B00

Fiesta with ST
Damper 35-242055
Front Spring E4-FD1-Y037-B00

May have to do with the location of some tabs or something that makes the housings different.

Could the totally different front knuckle/upright have anything to do with this??

 

[M-Sport fan]

Some more boring minutia, I was staring at dampers tonight and noticed the rear B14 shock shaft is 11mm diameter as is the damper shafts for the front inserts. The B6/B8 use a 14mm shaft which is more common across the motorsports range. Means there could be some adjustable shafts installed in the rears, but the issue would be the overall length of the rear damper shafts since the Fiesta uses a very long shock. The other thought the 14mm shaft will be stronger in bending, which the damper may see in operation on the rear.

So, does that mean that the B8/B6 would be inherently stronger than the B14s (and maybe even some of the other lower cost, off the shelf coil over kits??) on really bad roads/hard use (i.e.; DRIVING down, NOT full bore/max attack racing down) gravel rally stage roads, at least as far as deflection, or bending loads are concerned?

 

[Dialcaliper]

So, does that mean that the B8/B6 would be inherently stronger than the B14s (and maybe even some of the other lower cost, off the shelf coil over kits??) on really bad roads/hard use (i.e.; DRIVING down, NOT full bore/max attack racing down) gravel rally stage roads, at least as far as deflection, or bending loads are concerned?

No, the B14 uses an inverted 11mm damper (the shaft is inside the lower strut housing along with the bumpstop), but has a separate large diameter bearing surface (~40mm chromed tube under the upper bellows) with a pair of bearings that holds the lateral/bending strut forces, so that the actual damper shaft is not stressed in bending.

This is in contrast to the “upright” OEM and B6/B8 strut, which uses a long ~22mm shaft that both actuates the damper piston and also has to support the lateral/bending forces

The shaft bushings are also more constrained in height inside the damper, because they eat up shaft space allowing less damper travel for the same strut length.

The inverted strut is significantly stronger, stiffer and because of the more complicated design, it’s also more expensive to make. increased strength is reason rally cars and other motorsports gravitate towards the inverted design.

 

[Fusion Works]

Could the totally different front knuckle/upright have anything to do with this??

Is there a different knuckle height on the regular Fiesta, I thought the major change was the steering arm length was shorter on the ST. Never had the base and ST knuckle side by side.

 

[Fusion Works]

So, does that mean that the B8/B6 would be inherently stronger than the B14s (and maybe even some of the other lower cost, off the shelf coil over kits??) on really bad roads/hard use (i.e.; DRIVING down, NOT full bore/max attack racing down) gravel rally stage roads, at least as far as deflection, or bending loads are concerned?

On the rear yes. The larger shaft size would provide some extra insurance against bending loads. That is why you see 22mm and larger shafts on the off road dampers.

The fronts as mentioned, are better as the B14 (or custom inverted damper) vs the B8/B6 twin tube dampers because of the larger overall diameter of the load bearing surface.

Now as I referenced earlier I think, based on the dimensions data, I can create a longer version of my insert for use on the Fiesta that would work fine with a stock spring length or even a longer coil over setup if I built a custom hat to handle a larger spring. My car uses a 10in spring, I bet you could get a 12in spring and take advantage of the longer travel.

The custom package that I built is basically what the 36mm universal motorsport strut was back when Bilstein sold that. I ask and they still have some 46mm damper bodies, but no housings and other associated parts. That would be an even stiffer package from an off road standpoint.

 

[M-Sport fan]

^^^Yes, the M-Sport/Bilstein Fiesta R1 setup was that 46mm, inverted front, 'motorsport' damper with a treaded coil over collar added.

Totally not adjustable for rebound or compression though (but they could be re-valved), and even that setup was north of $3K USD when it was still available.

I am just curious IF the B8/B6es are actually stronger as far as bending loads go, than our factory dampers, even on the fronts.

 

[M-Sport fan]

Is there a different knuckle height on the regular Fiesta, I thought the major change was the steering arm length was shorter on the ST. Never had the base and ST knuckle side by side.

Absolutely, check it out.

When swapping the R2 Reiger setup onto this car one must change back to the base Fiesta knuckles, since that is what the R2 cars are built on, and that suspension was designed around that specific geometry, and knuckle mounting height.

 

[Fusion Works]

^^^Yes, the M-Sport/Bilstein Fiesta R1 setup was that 46mm, inverted front, 'motorsport' damper with a treaded coil over collar added.

Totally not adjustable for rebound or compression though (but they could be re-valved), and even that setup was north of $3K USD when it was still available.

I am just curious IF the B8/B6es are actually stronger as far as bending loads go, than our factory dampers, even on the fronts.

I would say No, because the sahaft sizes are the same on the Stock Ford front strut and the Bilstein. The 22mm shaft won't be as strong in bending as the 36mm Bilstein inverted damper and definintely not as strong as the 46mm purpose built rally stuff.

I would speculate my custom setup would run $3K when its all said and done. If I could find a less labor intensive rear damper, that would make it a bit cheaper to make.

I would like to see the two knuckles side by side. I can't see a reason to use a "taller" base model Fiesta knuckle. You would lose shock travel.

 

[M-Sport fan]

As screwy as it may sound, the rationale I was given for this, when I asked about it was "axle/half shaft clearance", when using either the Bilstein R1, or Reiger R2 front coil over setups, on a Fiesta ST.

 

[Fusion Works]

I could possibly see that. The Shaft lock nut on my front upright is pretty close to the axle boot.

 

[M-Sport fan]

^^^Our axles/half shafts are also a bit larger in diameter than the base car's as well.

Some FWD base Fiesta rally cars (as well as the R2T/rally 4 Fiestas worldwide) running the domestic ARA series do an upgrade swap to our axles, just for the added strength that brings.

 

[foodtruck]

vs the B8/B6 twin tube dampers

This particular bit is confusing, because Bilstein says B6s are monotube on their website

 

[Fusion Works]

I haven't cut them apart yet, but the B6/B8 is not an inverted damper like the B14. The inverted damper is traditionally a monotube arrangement. I have take those apart a lot. The B6/B8 behaves like a normal twin tube damper when you compress it. It also has a crimped seal head which suggest there is no taking it apart without actually machining it.

Don't worry, I am gonna cut them apart when I get a chance.

 

[Dialcaliper]

This particular bit is confusing, because Bilstein says B6s are monotube on their website
View attachment 55728

Not entirely clear what ours is, but Bilstein seems to have a small body 30mm monotube that’s used in at least some of the B6/B8 kits (and usually also crimped just like the twin tubes) in addition to the larger 46mm monotube and also a twin tube design that’s used other places.