A-Arms for a heavy Slash 4x4 Monster Truck

[GotNoRice]

My main truck is a Slash 4x4 / Stampede 4x4 Hybrid. It started out as a Stampede 4x4, but I lengthened it with a Slash 4x4 chassis, used custom body-mounts to mount a custom E-Maxx body, upgraded the entire drivetrain, and put 1/8th scale electronics in there. It runs great on 3s and 4s. The only real issue is that it's a pretty heavy truck compared to most vehicles that use this platform (Stampede 4x4, Hoss, Rustler 4x4, Slash 4x4, etc) and this seems to be pushing the A-Arms to their limits.

I'm currently using RPM A-Arms. They have been great in terms of reliability, but I think I'm reaching a point where they might be a bit too flexible for what I need. My rear arms twist under heavy acceleration, giving my truck exaggerated toe-in in the rear. In the front, I'm running into issues with excessive slop in the steering, and while the front a-arms are not likely the main culprit, I'm nonetheless trying to eliminate as much extra flex in the front as I can in an effort to tighten things up.

I haven't used anything other than RPM A-Arms since I moved on from stock Stampede 4x4 A-Arms 13+ years ago. Since then Traxxas has made their stock A-Arms a lot stronger for newer vehicles, and these new arms are still compatible with my older truck. Hopefully these newer A-Arms would still be stronger than the old stock arms while still being more stiff than the RPM A-Arms. Or is there another 3rd party non-aluminum A-Arm available that might thread this needle even better?

 

[9x19]

Don't know of another plastic A-Arm, but you could try Traxxas' new 'Extreme Heavy Duty' suspension components, including the hubs and steering blocks. Would need the drive shafts as well, since the HD hubs use a larger bearing on the inside.

About $70 for all at Jennys RC (on Raptor R parts list).

 

[Tunedfrog]

I put a set of the Extreme Heavy Duty A-arms on my Xmaxx and I broke one the first time out.
My RPMs have never broke. They flex more for sure but it makes for a better shock absorber.

 

[Ramp addict]

Traxxas cold resistant a-arms like what comes on the Hoss and Rustler are the toughest you can get for a 1/10th truck. They're both stiffer and tougher than RPM. For my own "SEND IT BIG" Slash they're my a-arm of choice.

 

[GotNoRice]

Don't know of another plastic A-Arm, but you could try Traxxas' new 'Extreme Heavy Duty' suspension components, including the hubs and steering blocks. Would need the drive shafts as well, since the HD hubs use a larger bearing on the inside.

I'm already running MIP CVDs on my two main trucks (Slash 4x4 Monster Truck and a more standard Stampede 4x4) in order to handle 4S LiPo (and fully tightened down slipper clutch). The MIP CVDs have held up well, so it probably doesn't make sense for me to swap them out for the plastic axles in the Extreme Heavy Duty kit, although I am impressed at how durable they look compared to the older plastic shafts. I have other parts like the C-hubs, steering blocks, bearing carriers, and shock towers already upgraded with RPM parts.

I was looking at replacing the steering blocks and/or C-hubs with aluminum parts to help with the steering slop but I think I'll probably start by upgrading the servo bellcrank and/or the servo itself first to start working on that specific problem.

I put a set of the Extreme Heavy Duty A-arms on my Xmaxx and I broke one the first time out.
My RPMs have never broke. They flex more for sure but it makes for a better shock absorber.

Traxxas cold resistant a-arms like what comes on the Hoss and Rustler are the toughest you can get for a 1/10th truck. They're both stiffer and tougher than RPM.

I've never actually had an RPM A-Arm fail. Worst case, they get scratched up and start to warp after years of usage. The stock arms on the Hoss and new Stampede 4x4 certainly look tougher but I've already seen numerous videos where they've failed from bad landings on jumps that weren't really that big. I'm glad that at least some people are having good experiences with the new Traxxas arms though. Having the RPM arms in my bag as a backup would be good peace of mind since an A-Arm swap is pretty quick. That said, I'd be pretty disappointed if I broke a Traxxas arm on my first time out after a 13+ year flawless experience with RPM arms (at least in terms of durability).

While this is not a great picture, it does show how the arms have begun to retain a perminant bend, resulting in more toe-in than intended.

 

[Greywolf74]

Those arms don't look very warped to me. I'm not sure how much your rig weighs, but I have a 100+MPH Rustler that weighs 13.5lbs and has RPM Stampede arms on it and those are supporting that weight.

 

[Weezel]

Those arms don't look very warped to me. I'm not sure how much your rig weighs, but I have a 100+MPH Rustler that weighs 13.5lbs and has RPM Stampede arms on it and those are supporting that weight.

That's one heavy Rustler! My Erevo 2.0 weighs less than that.

 

[GotNoRice]

Those arms don't look very warped to me.

Like I mentioned, it's not the best picture, but one thing that allows you to see the bend easily is it's relation to the shock guards. The front of the A-Arms are supposed to run essentially parallel to the bottom of the shock guards. But you can see these arms now bending upward starting just past where the bottom of the shocks attach, to the extent that the outer part of each shock guard is now hanging noticeably below each A-Arm instead of parallel with the bottom of each A-Arm. More-so on the front of the A-Arm than the rear, making it more of an A-Arm "twisting" issue, and why the rear of the A-Arm still looks mostly straight.

I'm not sure how much your rig weighs, but I have a 100+MPH Rustler that weighs 13.5lbs and has RPM Stampede arms on it and those are supporting that weight.

My truck is about 10lbs. I don't think it's simply an issue of the weight of the truck itself. It's a combination of a lot of things:
-The weight/mass of the truck, which may not be the heaviest but still heavier than most vehicles that use this platform.
-The powerplant. Running a Mamba Monster X and Castle 2200kv 1515 on 4S LiPo.
-The gearing. Running 18/54, which was pretty close to the lowest gearing I could get away with while still getting the gears to mesh using this motor in this chassis (geared for low-end torque, not max speed).
-Slipper-clutch is a revo-spec (larger) slipper, fully tightened down to where it doesn't slip.
-This is a basher, often involving big jumps and not always perfect landings.
-These A-Arms are probably about ~6 years old at this point. They are my 3rd pair. Each time I buy a new pair I put the newest pair on my Slash 4x4 Monster truck and then pass down the other arms to my secondary trucks. But the bending/twisting issue does seem to get worse over time.

In the picture below you can see how bad the toe-in is getting in the rear. I know that a bit of toe-in is good, but it seems to be getting borderline excessive. There is bending in the front A-Arms also, but the toe-in in the front is adjustable... where-as you are basically at the mercy of the rear A-Arm for the rear toe-in.

 

[Greywolf74]

IDK what to tell you Rice. The only other arms I know of are the heavy-duty ones from Traxxas and aluminum, but I wouldn't recommend aluminum.

That's one heavy Rustler! My Erevo 2.0 weighs less than that.

Yeah shes a pig. I had to weigh her down so shes stay on the ground lol

 

[Ramp addict]

All the best 4s SCT trucks started life out as 1/8th scale buggies. They can handle both the power and weight right out of the box.

 

[MaX-D]

I've been using the stock a-arms on my MaX-D Slash 4x4. It's got some weight to it. I have yet to break an a-arm. I break axle spindles the most with those big ole tires. I will go with the cold weather a-arms if I ever break one.

 

[cocoune]

Maybe you already did it but if you change the servo and go for a metal bellcrank it will cancel alot of the play in the steering. can't talk about the a arms tho. I have longer rpm a arms and it works great but I'm only on 2s.

 

[Finesavageboy2]

I have front and rear extreme heavy duty A arms on mine and no matter what I do they just don't break. I wouldn't really go with aluminium since they are prone to bending..