Replaced bilstein with fox after 25,000 miles, f150

meep

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The local fab guy who actually has a lot of experience in the industry absolutely hates Fox due to poor customer service.

Curious if they respond to you and if they're helpful
@D60 , you are so far correct. They came in with no guidelines for setting ride height, or even for just the basic spring adjustments. They came with 2 double-sided pages on how to change the shock decals.

i wrote tirerack, who sold them, for ride height settings, since their website advertises the 0-2” lift. TR has always been great for me so i’ll see what they say. The rear units are a step up from what was on before, and levels beyond oem, so I would like to see this work out.
 

meep

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Update. Lots of internet digging while looking for oem ride height settings, in part because ford truck weights vary. spring settings were varying a lot, with many folks doing it twice (which is, as I’ve learned, a full removal and adjustment using a press-type spring compressor) to get it where they want it. they can’t be adjusted like we expect threaded coil overs to allow.

so I found markings on the springs sent in my kit: 650 lb. huh. did some more digging. Found this helpful chart (Attached).

ford let’s you know the spring rate based on the front GAWR, which on mine is 3450 lbs. The 20” oem wheel size and 36 gallon fuel tank are contributors. The 2.7L may also take a few pounds off. Either way, that’s a spring rate of 473, and the rears are similar at 450.

there’s a big difference between 650 and 473. The truck can be had with as little as 314 lbs/inch. Still enjoying the damping from the new rears, I examined the springs and perches to see if the oem springs could simply be carried to the new assy.. I’d still pay someone to pull them over with the oem springs if it’d work. Sadly, no. The oem springs need a stepped landing while the upgraded eibach-sourced units are happy with a flat perch.

I’ll probably send these back to tirerack and reconsider my options.
 

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Never been a huge Bilstein fan. They always end up leaking and clunking for me, on the rear of my Liberty I couldn't get more than 20k out of a set before they'd be trashed so finally put Old Man Emu stuff in and those have been fine for 75k. Can get about 60-70k out of the front shocks before they start leaking, so still running Bilstein on the front of it.
 
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Interesting - i note the payload package trucks come with nearly the same spring rate as your new fox, id be tempted to try it.

Be interesting to call FRPP and see if they will tell you what the spring rate on M-18000-F15AA is.

Then Roush and see if they will tell you the same for their fox kit.
 
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Man IDK. i wonder if the FX4 has a stiffer spring rate that isn’t right for these, and they loosened up just enough to “cross the line” for me? They were never “firm,” more of a floaty comfy feel. Idk if that’s right for 5100s or not?

the fox 2.0s have settled in nicely in the rear, like, perfectly for my taste. It is controlled, probably a touch on the firm side, but they open up before it becomes harsh. They remind me very much of KYB GR-2s. Sold. I’ve ordered the fronts. I’ve written fox to ask for the adjustments to keep the oem ride height. I hope the changeover isnt too difficult.


I would not in any way describe my 2011 XLT with 5100s as floaty. I’d almost call it sporty, or crisp? Certainly more so than our 2018 with OE. Both trucks have worn p-metric and LT tires so that’s not it either.
 

meep

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i ended up calling a Custom Trucks Unlimited and they were super helpful. The suspension guy there agreed that unbalanced spring rates front to rear would not be pleasant and might require more tweaking, and this kind of tweaking gets expensive fast.

eibach seems to have the lowest spring rates for their coils at 500. 600 is where King seems to start. 650 is common, and it makes sense… folks looking at these are dealing with body armor, bumpers and probably taller, sloppier rubber. If I had 300 more pounds hanging off the front, I’d probably jump all over heavier springs.

turns out fox does have a front shock which accepts the oem springs. National back order, and they’ve got 8 month old back orders right now. I may put the order in through the local guy - that keeps the oem springs, and I’m in no hurry.

I would not in any way describe my 2011 XLT with 5100s as floaty. I’d almost call it sporty, or crisp? Certainly more so than our 2018 with OE. Both trucks have worn p-metric and LT tires so that’s not it either.
my last set of 5100s was fine - I liked them a lot and put a lot of miles on them. This most recent pair for the rears seemed to lose all rebound dampening, the tail was exaggerating every dip in the road by springing up into the air, with 300lbs in the bed.

Interesting - i note the payload package trucks come with nearly the same spring rate as your new fox, id be tempted to try it.
you are right - i certainly thought about it - and that could be a solid play if I was willing to update the rear springs if needed to balance it out.
 
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