Lets talk Spring Load, Not the usual Spring Rate thread

[Fusion Works]

I was doing some wondering based on the junk I had laying around the shop today. Its always pissed me off that Suspension Techniques has either lied, mis-measured, miscalculated, or whatever the spring rate of their lowering springs. First they claimed 240/250 (this is the reason they bought them) I measured one of the rears and it was 117lbs/in. That is less than the OE springs by a lot. Today I measured the front and it was 135lbs/in. So much for their reputation and accuracy.

Well I got thinking when I tried to install the ST spring on the B8 damper. It required a LOT more compression to install the top hat than the original Ford strut. So I got to wondering about how much preload these were generating at installed height. Time to drag out the scales and other measuring apparatus.

With the ST spring installed on the Ford OE strut, I have 115lbs of preload. With the spring installed on the B8 (which is 1in shorter shaft length), I have 231lbs. As I ramp up the compression, There is quite the difference in actual force generated by the spring.

The OE Ford Damper with the ST spring generates 237lbs, 373lbs, 504lbs, 580lbs of force at 1-4in worth of compression.

The B8 Strut with the ST spring generates 357lbs, 494lbs, 629lbs, 754lbs at the same 1-4in of travel.

My Custom Strut with a 162lb spring generates, 387lbs, 547lbs, 711lbs, 873lbs with 1.4in of travel. In reality my travel indicator shows over the last few months, no more than 4.5in of travel. In my case I am not getting into the bumpstop.

When I installed the ST springs on the OE dampers, I was always suprised at how low the car sat and how much it rolled in the corners. Having the same spring on the shorter damper with the high spring forces, I will be interested to see how the car behaves.

When I get a chance I will check the OE Ford springs with bumpstops. I have to get an OE spring and damper from a friend. I recycled my OE springs last week. LOL.

 

[Rutschpartie]

thx for doing this, good info. Do you know what the possible travel is (by that I mean from ride height to bump stop) where you only measured 4.5 inch in the last months, so how close you are to the bumpstop?

 

[Fusion Works]

I don't currently know for the stock ST bump stop as I only have the cut down bumpstop I used on my car for reference. I am going using a bump stop currently and it engages at 3.5in of compression travel from installed.

I am going to pick up a set of stock front springs and try my experiment again. Installed the B8 with the ST lowering springs. Even with the extra inch worth of compression, the car still sits WAY to low up front.

I want to get a set of stock spring ands and see what the spring loads look like installed on the B8 damper.

With my custom dampers I was not into the bumpstop as far as I can tell, need to measure the actual insert bumpstop rate and the point at which it engages.

 

[Fusion Works]

I just did a quick hand check. My damper gets into the bump rubber about .5in. So under a "worse case scenario" type bump. Wish I had some real time travel data, but not going down the shock pot road.

 

[Fusion Works]

More nerd shit this weekend. I got a stock Fiesta ST complete front strut assembly.

The OE spring rate is posted as 171lbs. That checks out. My numbers came up at 172lbs. The OE spring is 11.250is long. It is preloaded a minor amount. My measurement puts it a 152lbs of preload.

The travel numbers with the preload zero'd out.
1in: 323lbs
2in : 499
3in : 674
4in : 852

The OE bumpstop didn't come into play until the travel was more than 4.125in.

The OE bumpstop has the following rate. (yes I didn't do a good job of measuring at the same numbers)
0.40in : 46lbs
0.60 in : 88 lbs
1.00in 209lbs
1.25in : 323lbs
1.5in : 966lbs

 

[Fusion Works]

Since I am not happy with the ST spring on the B8 damper, ride height and spring rate, I am gonna swap the Stock spring on the B8 damper and see how that behaves. Maybe I can get that done this week.

I also left off the dust boot on the rear shock and have driven around all week and yet to hit the bump rubber. No matter the driving style and agressiveness of my driving.

 

[tri-pedaler]

More nerd shit this weekend. I got a stock Fiesta ST complete front strut assembly.

The OE spring rate is posted as 171lbs. That checks out. My numbers came up at 172lbs. The OE spring is 11.250is long. It is preloaded a minor amount. My measurement puts it a 275lbs of preload.

The travel numbers with the preload zero'd out.
1in: 298lbs
2in : 470
3in : 642
4in : 819

The OE bumpstop didn't come into play until the travel was more than 4.125in.

The OE bumpstop has the following rate. (yes I didn't do a good job of measuring at the same numbers)
0.40in : 46lbs
0.60 in : 88 lbs
1.00in 209lbs
1.25in : 323lbs
1.5in : 966lbs

Good to know. What year was the spring from?

 

[Fusion Works]

16. If someone has some other springs I can test them for length and rate, but I expect the Ford Data to be pretty accurate.

 

[M-Sport fan]

I wish that I knew the EXACT, PRECISE production line 'break point' date in the '16 MY run when they switched to the lower rate front (and rear as well??) springs.

 

[Fusion Works]

The Springs I measured were from a early 16 or late 15. This car didn't have the lip on the trailing edge of the front wing window. My car is a 5/16. I am 90% certain I tossed my own springs.

 

[M-Sport fan]

The Springs I measured were from a early 16 or late 15. This car didn't have the lip on the trailing edge of the front wing window. My car is a 5/16. I am 90% certain I tossed my own springs.

Mine was built ~the first or second week of 8/16, so I most likely have the lower rate boingers.

My car does have that 'turbulator' on that window frame (which somehow I thought that ALL model year STs got, and only the other and base Fiestas did not get??).

 

[kevinatfms]

The Springs I measured were from a early 16 or late 15. This car didn't have the lip on the trailing edge of the front wing window. My car is a 5/16. I am 90% certain I tossed my own springs.

100% an 2015 car. The later cars softened the front spring rate from the 172lbs/in listed in the Ford supplement.

 

[tri-pedaler]

I wish that I knew the EXACT, PRECISE production line 'break point' date in the '16 MY run when they switched to the lower rate front (and rear as well??) springs.

I thought it was 2/16/16 for the switch - at least that’s the lore: https://www.fiestastforum.com/threa...-changes-between-early-late-production.16260/

 

[Fusion Works]

Too bad I don't have my springs that came on my car. They got recycled as well. Just didn't have a need for them. (I thought). The set I recycled last week came from a 19 model, they would have been a good one to test, judging from the 19 Supplement they should have been 152lb fronts. Basically similar to what the ST lowering springs are in terms of rate.

This is useful information for the autocross guys since the Fiesta is listed on one line, they can mix and match OE parts to get better tuning out of the platform.

 

[Rutschpartie]

do you guys know the standard fiesta spring rate (non ST) for comparision? I thought ~150lbs was something the base model could have before reading your comments

 

[Fusion Works]

Squishy. Why? You want to start with the stock Fiesta Springs?

 

[Rutschpartie]

Squishy. Why? You want to start with the stock Fiesta Springs?

out of curiosity

 

[Fusion Works]

I would expect in the 130-150lb fronts and 100ish rear.

 

[Dialcaliper]

I wish that I knew the EXACT, PRECISE production line 'break point' date in the '16 MY run when they switched to the lower rate front (and rear as well??) springs.

According to Tasca, the changeover for all the other suspension parts (sway bar, rear torsion axle, etc) was 2/16. The springs don’t list a date because it seems like they just decided to obsolete the older/stiffer springs at some point. Maybe they just decided that anyone replacing them at this point wouldn’t notice the difference between an old spring that’s lost some rate and a new lower rate spring…and honestly how many times do springs actually get replaced?

 

[Fusion Works]

I have the thicker rear beam and larger front sway bar on my car if I remember right. I think I meant to measure that at one point. I can measure it again to double check.
The 16 Supplement shows the rear beam at 7.5mm and the front bar at 19mm. The 19 Supplement shows 8.5mm and 21mm. That is kinda interesting. Guess they overall softened the springs and stiffened the rear beam to stabilize it in roll. Kinda of a big bar soft springs setup.