Following the release of their Slash 4×4 heavy duty suspension arms in
the new cold weather plastic formula, Traxxas have introduced new
variants to suit the Slash 2wd (front or rear) or the Rustler/Stampede
(also available in front or rear lengths). The new arms are available in
six colors including white (which is what I bought for review), black,
blue, green, orange and red. Being a fan of the old school SRT, I chose
the white version for a “prototype” look against the blue of my 2wd
Fitting the front arms was a no-fuss affair. The hinge pins rotate smoothly, the screws thread in with no issues and there was no excessive slop in any direction. The rears are a different story.
The process should have been as simple as removing the stock arms and fitting the new HD versions. Unfortunately this wasn’t the case with mine. The outer hinge pins fit with no problems and that point rotates with no binding or slop. The inner hinge pins were a problem though and the two hinge pin holes are not on the same plane. The hinge pin goes through the first hole but is off by roughly 1/16″ to 1/8″ on the second hole. Here’s a shot of what I am talking about:
Fixing this issue will most likely require a little heat to massage the
two hinge pin holes back in line. I have an extra set ready to try as
well, allowing me to experiment with the first set that don’t fit. I
will be checking the second set soon to see if they fit better than the
first pair. I did install the arms on the truck as they are and here is
what they look like on my blue themed Slash (notice the extra plastic
that is forced out of the hinge pin holes):
I will update as soon as I can get back into the shop and do some work.
I got the new arms in today and unfortunately they are just as warped as
the first set. I was able to make them fit better with a little heat
and massaging. Here are some shots of the arms out of the package as
well as after the heat was applied:
After the heating process:
Once installed I noticed that the hinge pins fit very snug in these particular arms compared to the last set. The arms still move smoothly thanks to the hinge pin mounts on the transmission case and there is no real binding to speak of.
I have been in contact with Traxxas Support a few times about this issue and will update as soon as I have any new information.
I got the chance to run a few packs through the truck this afternoon with both the Traxxas Heavy Duty arms as well as the RPM arms that were originally on the truck.
I ran two packs with the RPM arms first, just blasting around the yard and hitting jumps at various angles. There are two large dips in my yard that are the result of stumps being removed and they kick the truck into the air a few feet. I was able to hit these dips at full tilt several times in a row, landing the truck on one corner or the other. The landings weren’t the most graceful but the truck would shrug off the impact and continue on its merry way. These direct shots placed the most stress on the arms and nothing went awry during my hour of tom-foolery.
While the batteries were recharging I swapped out the RPM blue arms for the Traxxas HD white units. Again the rear arms were an issue but after re-molding them with my torch they fit a bit better. I set out to drive in a similar fashion to the first run, hitting the same jumps and trying to recreate the same landings. On the first landing from a three foot jump in which the truck hit right front first the wheel tucked into the body and didn’t come back. I limped the truck back to where I was standing and saw that the caster block had slid out of place (it didn’t break, just slipped out of place). Removing the outer hinge pin revealed that the pin was not bent and everything lined back up once re-assembled. Back out I went and had no issues for a fair bit of the run, that is until I hit the same jump that caused the first issue. This landing was only slightly right-front-first and, sure enough, the wheel was tucked back into the body. Disassembly showed that the same thing had happened; arm flexed, caster block slid off the pin, wheel did its own thing. Simple fix, back to the field.
This time I tried to land the truck a little differently every time to see if the issue was with one arm or all of them. Coming off of the jump the next time I kept the throttle on a little longer and steered left slightly to bring the left rear down first. The truck hit with a solid thump and immediately spun hard left. The rear hub carrier had came free of the arm and wedged the tire into the body. Again, the hinge pin was not bent and the hub carrier was intact. The arm had flexed at the outer hinge pin just enough to allow the hub to come free, exactly the same as the front. Tire removed, hinge pin out, hub in place, hinge pin back in, tire back on. Whew, I’m getting good at this.Here’s a shot of the front arm issue to illustrate what I am talking about:
Having two of the four arms suffer the same issue leads me believe that it is not a fluke. The arms are slightly stiffer than an RPM arm but is flexing enough in the outer hinge pin to cause this issue when the truck lands on one corner. The RPM arms didn’t handle any differently than the Traxxas pieces yet don’t suffer the same issues. It appears to me that the flex engineered into the Traxxas arms allows the area where the hinge pins are located to move more than what is needed and those areas are not stiff enough to keep their shape. If the flex was moved to the area adjacent to the shock mount it would help with durability without sacrificing performance as the shock mount would still be supported.
In my opinion, the Traxxas Heavy Duty arms for the 2wd Slash aren’t worth the trouble that comes along with them. They do look great, there’s no doubt about that, but if they spend more time on the bench that in the backyard those looks don’t matter.
AS A DISCLAIMER!
When I wrote this initially, I had solved the alignment issue using a torch. I used a butane micro torch to heat the arms and straighten things out but this is not the correct way of solving this problem. Heating the arms with a flame, even only using indirect heat like I did, will cause the nylon to become degraded and ultimately fail.
To correct this problem the correct way, boil the arms for a minute or so and then insert the hinge pins. Once the pins are in and aligned, shock the arms in cold water to set them in their new position. This maintains the molecular integrity of the nylon and allows the arms to work as they should.
AGAIN, DO NOT USE A TORCH TO “ADJUST” NYLON PARTS!