Traxxas recently released a slew of new suspension arms for the Slash/Stampede/Rustler 4×4. The arms come in several different colors to match most color schemes or add a bit of contrast to an otherwise monochromatic chassis layout. What makes the arms so special, other than their unique colors, is that they are molded in a new compound specifically designed for cold weather running. I use RPM arms on my Stampede 4×4 and have had zero issues with them in cold weather and thought this would be a good benchmark to compare the new TRX pieces to. I picked up two sets of white arms (#3655a) as they remind me of the original SRT white arms from all those years ago and I thought they would match the Ivan Stewart body that I run on my Slash 4×4.
The arms are direct replacements for the stock pieces and include all of the same shock mounting holes and sway bar mounting locations. The white is very clean and bright; time will tell if they yellow like the old TRX parts did. It only took me around 15 minutes to swap out all four arms and the holes held the screws very tightly. I think the arms that I had on the truck were just about at the end of their life-span; the screw were noticeably easier to thread in and out. The hinge pin holes were similarly tight. There was no binding but the amount of slop present was reduced significantly.
When I had two of the arms off the truck I compared their “stiffness” to the new arms. The stock pieces don’t have any flex across their length and only a slight amount of flex (less than 1/8″) when twisting from corner to corner. I never realized how stiff the stock arms are until I tested them side by side with the new arms and the RPM units. The white TRX arms also have no flex when trying to bend them from the inner and outer hinge pin areas but have a fair amount of give when twisting them. I set the arms on my desk with a hex driver inserted through each hinge pin location and gave them a twist. I was able to hold one end flat and twist the arm enough to raise the opposite corner by 3/4″. This surprised me as the arms feel stiff when you hold them in hand but once some significant force is applied they will bend to absorb the impact. The RPM arms flex a little more (around 1″ of twist is possible using a similar force) but like the TRX arms this required a fair bit of effort.
I have never had any issues with my RPM arms sagging despite that being a common complaint about the Slash/Stampede 4×4 arms. I store my trucks with all four wheels off the ground (my storage rack keeps all of my cars suspended this way) which alleviates stress on the suspension and also prevents flat spots in the tires. I don’t expect the TRX arms to suffer from any sagging issues as they are so firm across their length. Time will tell how they hold over time.
I’ll be doing some testing with these arms next week once the ground dries up a little. I’ll be running the Slash alongside my Stampede 4×4 with its RPM arms to see how the new parts compare. Sorry for the office pics but my shop is full of interior doors for my house that are being painted this week and I can’t get in to do much other that that. On to the pics!
Update:
The new arms feel very similar to stock when driving. The truck handles just like it did with the stock arms and didn’t do anything that surprised me. I wondered if there would be any deflection in the arms under hard braking or over large deviations in the terrain but they held their shape well. With the amount of twist that is capable in the arms I was concerned that they would bend using the lower shock mounting screw as a pivot but there have been no issues so far.
There is a large maple tree in my front yard with some of its roots exposed that make a nice jump if hit head-on but can wreak havoc if approached off kilter. I spent the better part of a pack just launching the truck off of these roots at different angles and seeing if I could recover before the truck got out of control. Some of the hits were directly to the arms themselves: these roots are that high. Each time the truck would come back for more, whether it landed on its wheels or not. Overall the cold weather arms work well and I have no complaints.
Driving the two trucks back to back really showed how much of a difference there is between the cold weather arms and the RPM units. The RPM’s don’t have any issues with deflection under hard braking in corners or over rough terrain (just like stock or the cold weather TRX units) but do show some advantages when the truck takes a hit. There were a few crashes that sent the truck rolling violently corner-to-corner and each bounce sent he truck several feet into the air. On the Slash the body helps absorb the impact but the arms were still having to deal with the stress each time a tire came into contact with the ground. The Stampede offered no protection and the RPM arms had to deal with all of the force, which they did with no issues. You can see the wheel deflecting slightly to absorb the impact as the arm flexes. After what I feared would be a run ending tumble I checked to see if the hinge pin mounts were torn out or if the hinge pins had bent but to my surprise the RPM arms had taken all of the force without issue. I can’t say with scientific certainty but I feel that the stiffer TRX arms would have transferred too much force into other parts of the chassis possibly causing breakage somewhere else due to their lower amount of flex.
Don’t get me wrong, I love the look of the white TRX arms and the fact that they are slightly more durable than stock is a huge improvement in my book but for my money (and less money to boot as the RPM arms are a few dollars cheaper than the TRX arms) I would still go RPM. Not only are they more durable but even if they do break RPM offers a limited lifetime guarantee to replace them; something the Traxxas parts can’t match.