mlheck

iTrader: (1)

I have the Bilstein 5100 with adjustable preload on the truck now. The overall ride is good, but these things really pound on small bumps. I have them set at the highest setting. I know from my motorcycle riding that this one issue with high preload.
So now I'm wondering if it would be possible to set the shocks back to normal preload and just use a taller spring. Is there even such a thing made? Looking for some ideas.

joedotmac

The amount of preload and or spring rate doesn't change due to the install height. Takes the same amount of preload to support the truck at the bottom most or top most setting. The only thing that changes is where the bottom perch is oriented on the shock, will dictate how high the truck will sit.

You could go with a longer spring that has a softer rate, however the amount of preload to support the truck at X height will be consistent. With a softer spring, the compression travel will be more free to compress on small road imperfections, being ept to absorb more. During extreme hits to the suspension with large heavy wheels tires could be a negative of such change.

In your situation I would be more concerned about travel limitations of the A-Arms. Raising the truck as such to its max on the 5100's, limits the amount of down travel that was present with the OEM setup. Larger heavier wheels/tires also are a detriment on ride compliance.

mlheck

iTrader: (1)

Where to start? Spring rate and preload can be changed and do in fact effect ride height. Preload dictates how much force is needed to compress the spring. This doesnt change the rate of the spring, just how the spring carries the weight. If you take a spring with a 100lbs/1" spring rate and add zero preload, the spring will compress 1" with the first 100lbs applied. If 2" of preload is added to to spring (raising the bottom perch 2") than 300lbs needs to be applied to the spring to move the same spring 1". The spring length will be the same with no preload and 300lbs applied, or 2" of preload and 100lbs applied.

Preload is added to the stock spring when the shock is bolted together, thus the reason for a spring compressor when removing the mounting plate on the shock.

A 2" longer spring wih stock preload and stock spring rate would give you a 2" taller ride if the shock has enough travel.

mlheck

iTrader: (1)

In the most simple term lets say the front suspension on my truck is carrying 4000#. There are 2 springs, so each spring is supporting 2000# . Now lets assume the spring rate on each spring is 500#/1" and the factory preload is 2" (spring compressed 2" when top mount is installed on shock). When the truck is put down on the suspension it will travel down 2" before resting. There is now 4" of compression on the spring from its free height, not installed height.

Now lets use 4" of preload (compression) on the spring by moving the bottom perch 2" closer to the top mount. We had 2" of preload during the initial assembly and added 2" more by moving the bottom mount 2" closer. Now when truck is lowered it will touch the ground and fall no further. Now setting 2" taller with the same springs. Add 1000# of weight to the front of either truck and they will both drop 1".


The downward travel of the suspension is controlled my the shock itself and has nothing to do with the amount of preload or placement of the bottom spring perch. This is where just adding spacers to the top of the shock can be bad has it allows the suspension additional downward travel now.


The travel length of the 5100 shock is 2" longer than the stock shock, so it's assembled length is also 2" longer. If I had a 2" longer spring at the stock spring rate and preload, the truck would set 2" higher using the stock perch setting on the shock.

schmeal

I don't think longer coils exist for the F150.

Before my F150, I had a frontier with 5100's on the top setting and it rode like **** just like yours (too much preload). They say the 5100 is valved to compensate for the increased preload but after using them I believe its horse ****. They probably just take one of their yellow shocks and machine grooves in them for the snap ring.

I think your only options are to lower the preload and run a spacer on the top (which you say you're not a fan of) or go with a coil over designed to give you maximum articulation at an elevated ride height.

Z7What

I think contacting Alex @ F150Lifts with your questions is your best option. He is the only person I have spoken to that actually listens to my thoughts and understands what I'm asking. Many others just kept providing invalid info with nothing to back what they saying.

Wayne

mlheck

iTrader: (1)

Thanks, I'll give him a call.

schmeal

Invalid info? I weighed many options before I chose the setup I'm running. I didn't think I had to show my work and submit my resume before making a suggestion to the original poster.

mlheck

iTrader: (1)

I don't think he was referring to you giving invalid info. I believe he meant other vendors.

Z7What

Exactly