I like the Timbren brand as a company. I own but have not installed their simple short-travel trailing arm trailer suspension on my little camp trailer project. But when it comes to the rear suspension of our F150s, they are a soft-but-abrupt limiter on rear suspension travel.

The RAS on the other hand is far different. I cannot tell you how to proceed, of course; all I can say is I have the RAS on my truck installed with their minimum recommended preload of 1mm coil gap in addition to the Bistein 6112 up front (with the slightly higher-than-stock-for-my-truck 500 in/lb coil spring)/5160 shocks on the rear axle and my truck's handling is fantastic. Again, I keep +/-400lbs in the bed at all times and have almost 50/50 front/rear weight distribution as measured on a CAT truck stop scale.

used even less than the 1mm coil gap preload for awhile but when I raised the front ride height I needed a little more rear ride height. I'm going to try to get to it this week to add even more preload (to RAS' suggested second preload setting of 2mm coil gap, for when I hang my little trailer's 150 lbs tongue weight on the hitch that there may remain some slight forward rake to my truck. Slight.).

Tweakers gonna tweak.

 

I agree with your assessment on the soft but abrupt limiter on suspension travel. When I put them on, the goal was to improve handling when pulling the boat. I did realize improved handling while towing, but I sill have a little more sag than I would like. I'm going to play around this spring and see what happens when I take delivery of the new boat. If I'm not happy, then I'll put the factory bump stop back on and add RAS.

 

Have been wanting since I bought my truck.
Have had them since October and finally got around to getting them installed. Set at 1 3/4”
They are everything we’ve heard about. The ride is very refined. It handles even better.
Had my winter wheels put in as well. A little wimpy, but they stay tucked nicely inside the OEM flares.

 

Has anyone tried the Rancho Kit?
Rancho Ford F-150 Strut Leveling Kit Loaded quickLIFT RS9000XL With Rear Shocks 4WD 2014-2020 (cjponyparts.com)

 

First, the kit is Out Of Stock at this seller (CJ Offroad/CJ Pony Parts)

Second, and I'm a Bilstein guy, I LIKE THIS KIT. Too, it is for 4WD F150s only (front shock length, etc)

Third, their specs reveal a fairly robust set of dampers. I like the sound of it. I like that the damping is adjustable. What we don't know is the front coil spring rate, and the amount of lift although that can be deduced from the claim of this being a "level" kit for 2014-2020 4WD F150s.

The price is right (if a little inexpensive for very high quality). It covers all four corners of the truck with matched front/rear damping. And I've seen a lot of SuperDuty F-Series fitted with Rancho rear shocks in the past. Really can't go wrong for the price, and! you get what looks like FoMoCo F150 top mounts (and insulators) with the deal. These parts total $200 if purchased separately over-the-counter.

A call to Rancho will clarify: front coil spring rate and the front shock assembly parts' question (top mounts and insulator's source).

Thank you for bringing this kit to the attention of those 4WD F150 owners who want an easier, effective level kit for their trucks that offers SO MUCH MORE than a spacer over the lousy stock shock. This kit offers the biggest prize, and that is better suspension damping (shocks' action).

 

I will have to check on the spring rate. I am in need of shocks all around (91,000 miles) and figured that I might as well do it all at once, level & shocks.
What is the factory spring rate?

 

I did consider them. I picked the Billsteins for the front because I had previously added them to the rear, and it made such a positive difference, and I read so many positive reports on the fronts. Read most of that right here.
I bought the rears, the fronts, installed the rears myself, in fifteen minutes, paid my local shop to install the fronts at 1 3/4 inch, and had the front end aligned at another local shop, for $660 for all. Not cheap, but it is a lot nicer truck than before.

 

Yes, I have the units for the front, didn't need the rears, have Fox 2.0s back there.
I had these on a '17 3.5, and now on a '20 5.0. They advertise as a 2.75 lift, both my trucks wound up with 2.5" lift. Don't be misled, the adjustment is for damping, NOT lift. They are plenty decent for onroad, and light offroad. They go on very easy, like most coilovers. I was going to go with Fox on the front as well, but got mine at a very good price. I'd had coilovers before, and thought I'd try another brand for a change, and even the regular price on them is decent. I'm happy enough with them. Ya, they took out a lot of body roll when cornering, truck just rides slightly stiffer, just like any aftermarket quality shock would. What I don't like, is they are painted steel, and even with me spraying them with rust stop, they still show a bit of rust. Likely go with the Fox like I planned earlier when I feel these are no longer doing the work.

 

The Ranchos are extremely well-known... I was debating between them and the Bilstein 5100's. I like my Bilsteins, but I also liked the idea of the "complete unit" Ranchos that require no assembly/disassembly labor for the strut itself. This means you can also remove and keep your entire factory strut, fully assembled, should you need it down the road or decide to go back to stock.

 

That's a loaded question! For my 2WD F150 alone! there are at least SEVEN different coil spring part #s... it all depends on your drivetrain and how your truck was optioned from the factory.

Bilstein splits it right down the middle and supplies a 500 in/lb coil for both their 4WD 6112 and the 2WD calibration and shock length 6112 kits.

To answer your question, you'll just take that leap of faith that Rancho ballparked the spring rate appropriately as did Bilstein.