Getting More Aggressive - K5 Blazer Rear Suspension & TiresPosted in How To on March 1, 2012 0) (
I have no doubt that many of you can understand how off-road projects can take longer than you’d ever think possible. We all start out with an idea of what we want and good intentions of a timely build, with a reasonable dollar amount attached to the project.
If it were only that easy.
Good intentions pay for squat. The reality of most truck builds are that they take twice as long (if not five times as long) as you think they will, and cost at least twice what you thought you’d spend. And I think there might be some direct correlation between the amount of time a build takes and how much money you spend as well.
And such is the story of my K5 Blazer. While it was initially completed enough to run 4 Wheel Off-Road’s Ultimate Adventure in just two short months, there have been long downtimes in between trips, as parts broke and things were never really finished on the truck. Around 2008, the TH400 tranny started to have issues and shortly after the aftermarket fuel-injection system started acting up—and it’s been getting progressively worse ever since.
Last year, I finally got my K5 back out of the garage (“Get That Truck Out of Mothballs,” August 2010 issue) and started working on it again. Since then, it’s gotten a new Gearstar TH400 transmission, had the drivetrain improved and serviced, and SMP-Fabworks in Sun Valley, California, has been helping me finally finish the suspension and rollcage that was never quite completed. I’ve definitely still got some fuel-injection homework to do, and progress is going slower than originally suspected (surprise, surprise). But the plan is to have this totally ready to go (with shakedown runs already accomplished) in time for our Fullsize Invasion in Moab, Utah, in the beginning of April 2012. It’s time to get a little more aggressive with this build, first finishing the rear suspension and adding a set of Toyo Open County M/Ts on some new TrailReady 20-inch beadlocks.
01. The rear suspension on this Blazer was four-linked with Radflo 18-inch-stroke coilover shocks years ago, but that was the only thing done. There were no bumpstops, no sway bar, no limiting strap, and only two tabs holding the upper coilover bolt. Steven Parks started by boxing in our upper coilover mount so it would stop bending.
03. The 14.25-inch-long (effective length) Speedway sway bar arms were connected with 6.75-inch links to the axle. When originally building the rear four-link, 1/4-inch plate had already been added for a sway bar link.
02. With the coilovers now properly mounted and the four-link working perfectly, we had to lessen the sway of the rear end. With no sway bar, the double-triangulated four-link and coilovers would practically allow this Blazer to flip on its side while still keeping the rear tires on the ground.
I had a 35-inch-long, solid 1-inch-diameter Speedway Engineering sway bar from an old project sitting at my house, and it just happened to be the perfect one (seriously, perfect length and sway bar rate) to deal with the 2,500-pound rear end while fitting directly under the stock fuel tank (still the stock tank, just with dimple-died holes in the tank skid).
04. With the sway bar controlling the rear’s movement, it was time to keep the rear end from bottoming out. This Blazer has so much travel that bottoming out hasn’t really been an issue, but I didn’t want to find out what would happen if I ever did whack everything too hard. Parks welded in some bumpstop cans and added a crossmember to keep these bumpstops from twisted the channels of the frame when they’re bottomed out.
05. A Bilstein 2.0 bumpstop with four inches of travel fit in perfectly. There was five inches of suspension travel before engagement, and the 2.0 body would be enough to slow down the 2,500-pound rear end. And with standard 2.0 bump cans, I can swap parts for testing purposes (which is something we occasionally do around here).
06. The finished rear end that SMP came up with is exactly what I wanted. Notice that the coilovers link directly to the axle and not to trailing arms. I could have used trailing arms and gotten more travel, but there were three good reasons why we didn’t do that: First, trailing arms hang a lot lower and would be a lot heavier than the lower links I used—they would get caught up in rocks and wouldn’t be great for multi-purpose off-road use. Secondly, I don’t think the rear 1350 U-joint driveshaft would handle much more travel. Lastly, I don’t really need more suspension than the 20 usable inches of travel the rear of this Blazer has right now.
07. To make sure the rear does not overextend, possibly flipping the sway bar link the wrong way and pulling apart the coilover shocks, SMP used 28-inch-long Crow Enterprizes limiting straps. The Crow ones work the same as any other limiting strap, but I like the fact that there are no big labels on the plain black Crow straps.
08. I’m a huge fan of the Toyo Open Country M/T. It’s an excellent tire that works well on the road and in the dirt, but I personally only use it on fullsize trucks because I feel the sidewall is too thick for a lighter vehicle that won’t get proper tire flex out of it.
But to use a 40-inch Toyo, I have to go with a minimum of a 20-inch wheel size. This did present me with the perfect opportunity to try out TrailReady’s new 20-inch HD Series wheels. Alex Kreidl and I wrestled with these for a while, trying to get the wheels into the tires. Soap and water help a lot to install the wheels.
09. The HD Series is a purpose-built cast aluminum wheel that starts life as a beadlock. That means there is no lip cut off the wheel, nor any new lip welded to it. We went with the standard slim ring in polished aluminum on a black powdercoated wheel.
10. The 28-bolt beadlock rings were carefully set as straight as possible on the tires before trying to pull them in with bolts. This is important so that all the bolts go in smoothly and don’t crossthread. Once all the bolts were loosely in, we started snugging them down, one bolt on one side, then the next bolt 180 degrees opposite.
11. With the fuel injection still not working correctly and a few other things to do, the Blazer is still not ready but it was okay to tow out on a Carson trailer for a little shakedown run to make sure everything in the rear suspension worked.
12. The difference in the rear end is huge. The lack of sway keeps the truck upright and much more drivable, thanks to the Speedway sway bar. And I can barely feel the rear bumpstops actuating and slowing down the suspension, even though there is evidence of them touching.
Now it’s time to finish the rest of the truck….