Prerunner Tech

How To Build A Prerunner – Part 2 Rear Suspension

In part one we showed you how to build the front of a prerunner, and all the parts you need. We’ll continue by showing you what’s needed to build the rear of your prerunner.

Now that the front of your prerunner is complete it is time to think about what you want for the rear suspension of your prerunner.

If this is going to be your daily driver then go with a bedcage, and leaf springs, like Deaver Springs. The other option for the rear is a 3-link or 4-link suspension set up, but we are going to discuss a leaf-sprung rear since that is easier and cheaper to do.

Fiberwerx F150 Fiberglass Bedsides

Before you do anything in the rear you’ll want to install a set of fiberglass bedsides, like the ones we got from Fiberwerx for 2004-2008 F150s. This will tell you how much room you have for travel in the rear.

Deaver Leaf Springs

On our F150 we used Deaver Springs because they are a multi-leaf pack that is capable of drooping out farther than factory springs and they have a progressive spring rate to help you through the whoops.

Your springs can either be mounted on top of the axle like the factory springs or you can have custom perches made to mount them under the axle. This will lower the ride height in the rear so you have to account for that in your design but it will also give you more bump travel.

On some trucks like our Ranger you will also need to flip the shackles to run Deavers so keep that in mind. The Fabrication shop doing the work for you should already know this.

Now it is time to decide the type of shocks you want to run. When building a leaf sprung truck it’s a good idea to use bypass shocks. They will help you tune the rear suspension because you can adjust the compression stroke and rebound stroke of the shocks. To save money you can use a smooth body shock but the only tuning you have available is re-valving it, which is a lot more work and cost.

Sway Away Bypass Shocks

In order to get more travel out of the rear you will need longer than stock shocks. On our F150 we went with SwayAway 3″x16″ 3-tube bypass shocks. These have an extended length of 40.57″, and this is where the bedcage comes in.

A bedcage is just another name for the upper shock mount on your prerunner’s rear suspension. Now I’m simplifying things a lot…there is a lot of design that goes into a bedcage so it functions the way it should, and just like a prerunner bumper there is no set way to design a bedcage. It can simply be a place to mount your shocks or it can be designed to hold a truck bed box for tools and gear, and it can also be designed to hold your spare tire.

F150 Prerunner Bedcage

The material you use is also up to you or your fabricator. You can use all tube to build it or like our F150 we fabricated boxed mounts out of 1/8″ plate steel and used 2″ tube to tie them together.

How the shocks are mounted referring to the angle between the top mount and lower mount has a lot to do with the way your rear suspension performs, but it is a little beyond the scope of this article. Any good fabricator will know how to mount them.

Now that the bedcage is built you will need a lower shock mount. This can be done in a number of ways but most, depending on your truck, will be done somewhere close to where the factory location is. Again this depends on your bedcage, truck model and how your shock is mounted. After this is done you are also going to need longer brake lines and limit straps just like the front suspension.

The length of your limit straps need to be determined by the length of your shocks and angle of your driveshaft at full droop. You don’t want the rear suspension drooping out so much that the shock extends all the way out and becomes your “limit strap”. It needs to be strapped at least 2″ before your shock is fully extended. Limit straps as a general rule stretch 1″ for every 12″ in length. So over time a 24″ limit strap can stretch up to 2″.

Your driveshaft will also need to be considered. Again you don’t want the rear suspension drooping out so much that you get drive shaft bind in the u-joints or worse you completely slip the driveshaft out of the transmission.

Rear Prerunner Bumper

The other items to consider when building the rear of your prerunner is a rear prerunner bumper. Factory bumpers will generally limit your departure angle and get you hung up if you ever drop over a small ledge. You can also design a prerunner bumper to do more, like hold lights, or even integrate a hitch into it. Your bumper can be fabricated to locate your spare tire and jack if your bedcage was not designed to hold those items. If you’re looking to improve your vehicle’s performance, you can get tuning diesel upgrades at Willys Workshop.

Well I think I covered all the basics of building a great prerunner. Now for the second most asked question, “How much?”

This will vary depending on the truck you build but you can expect to pay around $20k to $25k for a build like I described and this does not include the price of the truck, this is just parts and labor.

So yes this sport is expensive but what sport isn’t? Now the easiest way to build a prerunner is in stages. First attack the front like we described in part 1 of this article, then tackle the rear. This can help you save up the money you need instead of dropping $25 G’s all at once.

If you want even more details about building prerunners be sure to watch our TV show FullDroopTV. For season one we built the F150 you see here and a Silverado, so you can get a ton of great ideas for your next prerunner build.

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