Suspension

...now browsing by category

Posts that focus on the suspension components of the TB.

 

Tires

Wednesday, August 3rd, 2011

Choosing tires can be a daunting endeavor.  Often they are considered the most important part of a vehicle, as they are the only point of contact with the ground.

There are a few things to decide on.

  • Tread Pattern (Mud-terrain vs. All-terrain)
  • Depending on your terrain and normal travel paths, you may opt for an aggressive mud-terrain pattern or a more mannered all-terrain. Of course, there are many options that full the spectrum between the two main categories, but in general terms, there are 2 main options. The M/T option gives better traction in mud and most off-road situations than the A/T, but the M/T notoriously are noisier and less fuel efficient.

  • Tire Diameter
  • This decision is not only affected by the lift and clearance you have, but also the gearing. This is a bit of a balancing act. You want a large tire to gain more clearance and roll over obstacles easier. However you don’t want to decrease the thrust to unbearable levels. As a tire gets larger, the torque at X RPM stays the same, thus the available thrust will decrease. Through the years I’ve come to the conclusion that 32″ tires are perfect for my needs off road, and don’t make thrust levels unbearable to the point of constant downshifting on the interstate.

  • Tread Width
  • There are long standing debates on the proper tire width for off-road/overland vehicles. Many of the crawling crowd will go for 305mm width or beyond for traction purposes. Many of the overlanding mindset will choose a thinner tire (235-265mm) for fuel efficiency. Since our mindset is more aligned with overlanding – here’s a link to a good discussion on tire width that concludes that skinnier tires are generally the way to go: http://www.expeditionswest.com/research/white_papers/tire_selection_rev1.html. I ended up going with a 255mm width tire for the Trailblazer.

  • Weight Rating
  • For a light truck tire, the load rating is given by a letter (B, C, D, E, or F) depending on sidewall plies and directly relate to max air pressure ratings. I find the load range C to complement the Trailblazer well. Others have had luck with D and E. D and E are known for being somewhat more resistant to sidewall damage, especially when aired way down.

I ended up deciding on BFG Mud Terrains. The size, 255/75/17, are commonly found on Jeep Rubicons as OEM equipment, so ultra-low-mileage tires are fairly easy to find for around $125 each. I’m on my second set of these tires, with the first set wearing amazingly well – maintaining good tread depth through 55k miles. I expect the tires could go to 70k easily. They are a slightly special tread pattern, denoted by “DT”, pictured at right.

Wheel Spacers

Thursday, April 14th, 2011

Hubcentric Wheelspacers

The TrailBlazer is further unfriendly to people wishing to do a lift or increase the tire size. The first obstacle is the positioning of the upper ball joint that is located on the steering knuckle, above the tire (see the picture below). This severely inhibits a larger tire size unless you install wheel hub spacers (pictured to the right) or purchase wheels with a backspacing of less than 4. I purchased wheel spacers from WheelAdapter.com after the recommendation from fellow TrailVoy members.

If you wish, a wheel spacer can also act as an adapter to change the lug pattern to match a new wheel. I requested four 1.5″ hub and wheel-centric billet aluminum spacers. Fred (the owner of Wheel Adapter) knew all of the necessary dimensions and shipped them out the next day.

If you are planning to use the stock bolt pattern, remember, it is NOT 6×5.5″, as most Chevy trucks are. Our stock lug pattern is 6×5″, or 6x127mm.

Shocks

Thursday, April 14th, 2011

Bilstein Shocks

I chose Bilstein HDs (pictured to the right) from ShockWarehouse.com. I have read great reviews of these shocks, which are developed to provide better stability and bump rebound control. With the improved performance combined with the club discount from TrailVoy.com, they are a no-brainer addition. Since the front strut is already all apart when doing a spacer lift, it’s highly advised to replace the front shocks at the same time.

Rear Shocks:

For rear shocks, it seems the simple choice are BDS shocks. They have two options for the 360 platform, gas-charged shocks, and hydraulic shocks. I went with the 55-series hydraulic shocks, however will switch to gas-charged once the 55s die.

Rear Springs

Thursday, April 7th, 2011

The last part of the lift equation is the rear springs and shocks. Stiffer rear springs are desirable here because of the heavy loads I tend to carry with me. The stiffer springs also produce additional lift and can be coupled with lift spacers.

Z71 Springs

Here again, the TrailBlazer aftermarket is poor. Amazingly, a member of TrailVoy Off Road found that Z71 Tahoe springs and shocks (pictured to the right) were direct bolt-ons for our vehicle. While they have the same resting length as our stock springs, they have a non-linear spring rate, and sit about 1.5″ higher than stock when on our vehicles. This means they will compress less when loaded down or towing.  To find these jems, search eBay (and include the description in your search) for the GM part number, 15234633.

The Z71 shocks are also somewhat beneficial in that they are slightly longer than our stock shocks (to allow slightly greater articulation) and they have a more aggressive dampening effect.  However there are much better options available.

Trailblazer Suspension Lift

Thursday, April 7th, 2011

it was time to begin the big modifications. A proper suspension lift takes a lot of planning on these vehicles. By proper, I mean upgrading the necessary secondary parts along with the lift. I also did not want to go through a portion of time with a lift and undersized stock tires, so bigger tires were to accompany the lift ‘package.’ For me, the package included the lift, rear springs, front shocks, and wheel spacers.

The TrailBlazer is unfriendly to being lifted due to the front differential’s unusual mount to the engine’s oil pan. The half-shaft actually runs through the pan. I believe this was done by the Chevy engineers in an attempt to make the engine as low as possible. While this does make a lift greater than about 3″ impossible without extreme changes, the resulting low hood does provide the driver with a good view of the trail and the low CG gives us decent lateral stability.

The TrailBlazer aftermarket is rather small when it comes to lifts. We have a few options that I know of, and they are all covered in relative detail on offroadtb.com.  Link here: The Complete Lifts and Suspension Accessories Thread

The BDS kit, which I have and personally prefer, (to the right) advertises 2″ of lift, front and rear spacers included. While the BDS kit is the most expensive of the options, I feel it offers the greatest strength and durability, and that matters off the road. It replaces the front upper strut mounting plate and is made completely of steel. The rear BDS spacer mounts to the top of the spring and is retained by a couple bolts. The kit includes new upper strut mounting bushings and new hardware.

There have been some questions regarding how strut spacers work, so I made the below diagram to help explain how they add lift, yet retain the stock (and safe) maximum suspension extension.

How a strut spacer works. Just a simple spacer above the spring.