Big Rock Considering a Big Rock? Things you need to know

[stalled mule]

*****UPDATE*****
If you don't have cash to spend on broken parts, do not buy this truck.. It is a blast to drive on 6s but it will break something every time you drive it. Replace all your driveshaft pins with traxxas #TRA5145 straight it of the box. Change out your pinion immediately as well. Stock up on these pins, bumpers and roll hoops. I have a love hate relationship with this truck. Tons of fun to drive, tons of parts Broken consistently.



First off, this truck is hands down the best truck I've owned. I've had it for about 3 weeks and have been beating the crap out of it. It is a BEAST. Wheelies at any point in the throttle range and is insanely fast for being such a huge truck. The Tactic controller is wonderful, good range, highly responsive and has a lot of adjustment for a rtr controller. No need for an upgrade IMO.. The Diff Brain is one of the coolest things I have ever had on an RC. Quick tip, Shift your diff brain at a slow roll, not stopped as you can put a bit of undue strain on the setup. Pins into holes, if they are not lined up they will bind a bit and cause issues. Don't switch at speed ever.

But...

There are a few things I've found to be a bit frustrating.

First, if you buy this truck, buy a TON of driveshaft Grub screws right when you order the rig. I upgraded to the Traxxas Revo grub screw Part #TRA5145. Don't waste your time with the AARMA pins they are weak and only come 2 to a pack. The traxxas ones come 6 to a pack. I have sheered 3 of these pins and bent 1 with roughly 10 sessions run trough the truck. Its a FAST field fix if it does break as long as you have them. Worth noting, I have only damaged these on 6s. On 4s is not issue at all. Also I love that this is the first major weak point in the drivetrain. I think ARRMA thought about this. It is a smart weak point and so easily diagnosed and serviced in the field. Also Its a much cheaper option than letting things further down the line take the abuse. Worth noting, the Traxxas screw head is a bit taller and will NOT seat completely flush into the plastic collar around The driveshafts, tighten it until the pin seats with the diff gear shaft and barely to the point the plastic collar starts to lift, no further. I could see someone overtightening them and stripping out that collar because the ARRMA pins go much deeper into the collar. Don't worry, they will clear The housing. The Traxxas pins are all holding up much better under 6s power but this is still a wear out item. I check them after every run. Also they do sometimes have a tendency to back out, if you hear a weird grinding that isn't really affecting the driveabilty of the truck, check these first.

Second, the Steering servo.. Its Garbage. It doesn't have enough power to really do it's job. Again with the size of the truck it need a much more. I changed mine out after the second run to a SAVOX Gold Model 1230SG. This is a steel gear servo with around 500 oz-in of torque at 6v and around 416 on 4.8v. It required a quick waterproofing with some strategic tape and some plasti dip. Lots of vids on YouTube on the process. Also, this new servo was a bit taller so I had to remove the electical clips in the chassis plate below the factory servo. No wires really run here anyway so no big deal. Also I upgraded to an aluminum step down style 25t servo horn. The regular straight style horns will hit the belly pan when turning. Absolutely worth doing to every nero.

I have found that the factory Servo Saver was lacking under hard hits and aggresive driving so I upgraded to the Hot Racing Aluminum servo saver. It looks bad ass and Allows for much better control of the front end when driving it hard. Not necessary but good mod for sure.

Stock up on the Roll hoop. I have broken 2. With the Weight of this truck a bad landing will break the Roll hoop/carry handle every time. Not a huge deal but kinda sick to have to replace it every time you drive it. Cheap and easy fix.

The rear bumper takes a LOT of abuse. And I have ripped one of them off after a gnarly cartwheel. More my fault than the trucks. Maybe upgrade to the T-Bone stuff? I'll get here at some point.

I purchased some team associated rod ends as well after seeing a lot of complaints about this part stripping out or ovaling out the connecrions. It has not happened to me yet but, with the angles of this cantilever setup I could see that being a problem.

The body is awesome, incredibly thick lexan takes a beating. The body clip hold downs are the best thing since sliced bread. But AARMA kind of failed when they painted the outside of the body. It creates a cool flat paint but when you screw up, and you will screw up due to the sheer power of the truck under 6s, you scratch off a lot of paint. I painted the inside of the body black and that solved my issue with being able to see through the lexan. Again, no big deal.

On the Battery trays. Its a great concept and has decent execution. My problem is the body has to come off anyway to change batteries so the "quick release" purpose is defeated in my eyes. I do love that they create a really solid cage to protect the LIPO. I have not had them pop open on me one time. But if It starts to have an issue down the road there is an incredibly easy solution. Drill a hole in the front of the tray where the outer wall of the tray and the door of the tray meet.. Use a body clip to lock the two together. Keep the button area clean, I check it after every 2 runs or so, it would be Easy to pack the lock mechanism with dirt which will lead to the latch not actually latching. Easy. Also I do use the foam blocks religiously. Pinch the Battery in such a way that it can't move. Not rocket science and ARRMA includes the foam. I don't understand everyone's issue here but we will see how that goes over the coming months.

The tires do balloon heavily so I'm still exploring options in that arena. Thinking bead locks with a slightly different foam and tire design but they do their job well on most surfaces as long as you're not trying to run the included high speed pinion. That will destroy these tires fast.

Suspension out of the box needs a bit of tuning but overall isn't bad. I upgraded my Rocker Arms with the Hot Racing Aluminum Rockers. Again, they look cool but also serve to allow for a bit more adjustability over the factory setup to dial it for my style of driving.

That's is about it. Again I have to say this is an incredibly rugged truck. I have rolled, flipped, crashed into hard things, and landed from very high and it drives away from things that no truck I have ever owned can drive away from. And still no hard or expensive things broken. This is just a list of the things I wish someone had told me from the start. I have had 0 major failures. ARRMA has surpassed any expectations I ever had of them. I love this truck and will be spending some $ to make it completely badass. Since the day I pulled it out of the box it has impressed me and everyone that has seen it. I can't wait to get my new body from Empire Graphics, between that and the new wheels and tires I've got coming. Lets just say I am going to have a MEAN Truck. Highly suggested. Hope this helps a few of you figure out whether spending the $ is worth it. I couldn't be happier.

 

[BUILTLIGHTWOUNDTIGHT]

First off, this truck is hands down the best truck I've owned. I've had it for about 3 weeks and have been beating the crap out of it. It is a BEAST. Wheelies at any point in the throttle range and is insanely fast for being such a huge truck. The Tactic controller is wonderful, good range, highly responsive and has a lot of adjustment for a rtr controller. No need for an upgrade IMO.. The Diff Brain is one of the coolest things I have ever had on an RC. Quick tip, Shift your diff brain at a slow roll, not stopped as you can put a bit of undue strain on the setup. Pins into holes, if they are not lined up they will bind a bit and cause issues. Don't switch at speed ever.

But...

There are a few things I've found to be a bit frustrating.

First, if you buy this truck, buy a TON of driveshaft Grub screws right when you order the rig. I upgraded to the Traxxas Revo grub screw Part #TRA5145. Don't waste your time with the AARMA pins they are weak and only come 2 to a pack. The traxxas ones come 6 to a pack. I have sheered 3 of these pins and bent 1 with roughly 10 sessions run trough the truck. Its a FAST field fix if it does break as long as you have them. Worth noting, I have only damaged these on 6s. On 4s is not issue at all. Also I love that this is the first major weak point in the drivetrain. I think ARRMA thought about this. It is a smart weak point and so easily diagnosed and serviced in the field. Also Its a much cheaper option than letting things further down the line take the abuse. Worth noting, the Traxxas screw head is a bit taller and will NOT seat completely flush into the plastic collar around The driveshafts, tighten it until the pin seats with the diff gear shaft and barely to the point the plastic collar starts to lift, no further. I could see someone overtightening them and stripping out that collar because the ARRMA pins go much deeper into the collar. Don't worry, they will clear The housing. The Traxxas pins are all holding up much better under 6s power but this is still a wear out item. I check them after every run. Also they do sometimes have a tendency to back out, if you hear a weird grinding that isn't really affecting the driveabilty of the truck, check these first.

Second, the Steering servo.. Its Garbage. It doesn't have enough power to really do it's job. Again with the size of the truck it need a much more. I changed mine out after the second run to a SAVOX Gold Model 1230SG. This is a steel gear servo with around 500 oz-in of torque at 6v and around 416 on 4.8v. It required a quick waterproofing with some strategic tape and some plasti dip. Lots of vids on YouTube on the process. Also, this new servo was a bit taller so I had to remove the electical clips in the chassis plate below the factory servo. No wires really run here anyway so no big deal. Also I upgraded to an aluminum step down style 25t servo horn. The regular straight style horns will hit the belly pan when turning. Absolutely worth doing to every nero.

I have found that the factory Servo Saver was lacking under hard hits and aggresive driving so I upgraded to the Hot Racing Aluminum servo saver. It looks bad ass and Allows for much better control of the front end when driving it hard. Not necessary but good mod for sure.

Stock up on the Roll hoop. I have broken 2. With the Weight of this truck a bad landing will break the Roll hoop/carry handle every time. Not a huge deal but kinda sick to have to replace it every time you drive it. Cheap and easy fix.

The rear bumper takes a LOT of abuse. And I have ripped one of them off after a gnarly cartwheel. More my fault than the trucks. Maybe upgrade to the T-Bone stuff? I'll get here at some point.

I purchased some team associated rod ends as well after seeing a lot of complaints about this part stripping out or ovaling out the connecrions. It has not happened to me yet but, with the angles of this cantilever setup I could see that being a problem.

The body is awesome, incredibly thick lexan takes a beating. The body clip hold downs are the best thing since sliced bread. But AARMA kind of failed when they painted the outside of the body. It creates a cool flat paint but when you screw up, and you will screw up due to the sheer power of the truck under 6s, you scratch off a lot of paint. I painted the inside of the body black and that solved my issue with being able to see through the lexan. Again, no big deal.

On the Battery trays. Its a great concept and has decent execution. My problem is the body has to come off anyway to change batteries so the "quick release" purpose is defeated in my eyes. I do love that they create a really solid cage to protect the LIPO. I have not had them pop open on me one time. But if It starts to have an issue down the road there is an incredibly easy solution. Drill a hole in the front of the tray where the outer wall of the tray and the door of the tray meet.. Use a body clip to lock the two together. Keep the button area clean, I check it after every 2 runs or so, it would be Easy to pack the lock mechanism with dirt which will lead to the latch not actually latching. Easy. Also I do use the foam blocks religiously. Pinch the Battery in such a way that it can't move. Not rocket science and ARRMA includes the foam. I don't understand everyone's issue here but we will see how that goes over the coming months.

The tires do balloon heavily so I'm still exploring options in that arena. Thinking bead locks with a slightly different foam and tire design but they do their job well on most surfaces as long as you're not trying to run the included high speed pinion. That will destroy these tires fast.

Suspension out of the box needs a bit of tuning but overall isn't bad. I upgraded my Rocker Arms with the Hot Racing Aluminum Rockers. Again, they look cool but also serve to allow for a bit more adjustability over the factory setup to dial it for my style of driving.

That's is about it. Again I have to say this is an incredibly rugged truck. I have rolled, flipped, crashed into hard things, and landed from very high and it drives away from things that no truck I have ever owned can drive away from. And still no hard or expensive things broken. This is just a list of the things I wish someone had told me from the start. I have had 0 major failures. ARRMA has surpassed any expectations I ever had of them. I love this truck and will be spending some $ to make it completely badass. Since the day I pulled it out of the box it has impressed me and everyone that has seen it. I can't wait to get my new body from Empire Graphics, between that and the new wheels and tires I've got coming. Lets just say I am going to have a MEAN Truck. Highly suggested. Hope this helps a few of you figure out whether spending the $ is worth it. I couldn't be happier.

AWESOMENESS!!! & Thank you for the heads up

 

[lonee]

First of all,... I am very lucky with my Big Rock.
But in all cases you will find some points to optimize mechanical parts!
@stalled mule
Hi, I have my Big Rock now since around 6 weeks.
I did not broke a pin till yet but also running 6s (with small gear) but not all the time.
Most just 4s offload. To prevent you're rear bumper, you have the options original (which is not very stable and will break easy)
than T-Bone bar or homemade. Take a look into the gallery, there you will find my solution which is working fine.
If you like to have a g-code file for a cnc-milling, I can send you.
The only damages I had was a broken body stand and a lot of scratches outside of the body.

The servo point: Yes, its not strong and if you like to crawl with a Nero it´s to week.
On the other hand, for normal driving it is strong enough but you have to move forward.
I do also approve that Arrma have to do an Upgrade concerning that point.
I will change it if the old one will be broken, cause if we want to buy a factory-waterproof-servo we have
not so much selection options comparing the original diameter.
Thats has confused me that Arrma did not made enough space around the servo to put a much bigger and faster servo in.
The servo safer is not nice and not so precise but it is working if you make the setup correctly.

Rocker arms and Pins:
I agree that there is the same problem the Nero prefer already have had. Arms or shock absorber ends and the plastics at the rods.
The plastic arms will bend and the space in area of the shocker ends are not enough.
Opposite to you, I prefer the GKA-Rocker arms, course the will put in the force symmetric on the pin with less bending.
Also these pins are a litte tiny. I also prefer bigger pins with M5 tap. Similar to the Traxxas.
The rod ends also a litte small, i putted rowings around the plastics and have no damaging till yet.

Tires...yeah,. thats a big point.
The originals are working fine up to 4s, but with less traction offroad.
On the other hand, if you have more traction, you also have more force on the driveshaft screws.
Normally i expect these pins as an designed breaking point to prevent the drivetrain if a wheel is blocked.
Otherwise the pins had to be so stable that they stay in normal conditions which this car is designed for!

I have one point more.. It ist the constriction of the servo mechanics of the diff locks.
I miss a kind of servo saver between the claw and the servo, that it is not possible to block the servo.
The pins insite seams to be also a little weak. some guys had broken / bend them.
Mine are still OK, but I take a lot of care that I switch them over with very low speed.

Battery tray... Hm, i think there is one more point to make things better.
The tray locker is not a quite good design comparing what fore this car is designed.
Inroad it is OK, but dirt and mud makes it very quick out of function. I do not like to clean them up while i am outside.
It ist very often that the red locker keeps inside an did not reach the other mechanics. Result will be that the tray pops up and you're LiPo is flying away. I had it tree times now. Not funny, cause if a soft case LiPo crashes against a tree, in the badest case you had to buy new ones.

Mainly it´s a great car and it´s make a lot of fun! I did not regret that i chose this car instead of E-Revo / Summit!
Hopefully Arrma see´s this points and can offer us an solution to fix the "weak" points.
If there do so, the Nero will getting more and more popular and will be special in it´s art.

Regards,
lonee

 

[mrfurious40k]

Great reviews and suggestions for upgrades. Thanks!

 

[Ekfchan]

The rod ends also a litte small, i putted rowings around the plastics and have no damaging till yet.

Hi ionee,

Could you elaborate on this modification? A YouTube review by many's rc garage mentioned something like this but I couldn't figure it out.

I had the rod end on my steering link break and would like to make them stronger.

I think the same rod end is used on shocks but not sure.

 

[lonee]

If you are looking for carbon rowings you´ll find what I mean. But you have to use 2 component long time drying glue.
It ist just wrap the plastics with the rowings by putting glue on it. But do not make it too thick, cause thats have no positive effect.
Two Layers are enough!
I used a german glue Pattex Endfest, which will be dry after 24h but it is a little more flexible than 15Min Epoxy.
You can also put a tube of aluminium and press it on the plastic part. that is also working on my AX10.
Later on i will change them to aluminium rods which where used on big RC planes. They have M4 by 4.
I am looking for M4 for the pushrod and a 3mm hole for the other end. I saw them already on an chineese website.

But I´ll change them when my moddet ends are will break.

 

[Julian]

I Have always immediately swapped out the stock servo. I have 1270tg 367 oz/inin all my Arrmas - its water resistant. Ive only been in this hobby a year its me and my ten year old......My problem back when I got the Nero in July - was not knowing enough about 4s vs 6s and the MT tire set limitations. So my Nero ripped through two TrencherXs day one, got pissed and ordered a set of Big Joe2 s and they lasted till day 3.5 - did a wheelie and BLAM - both popped... lol Got some super swampers .... got them unassembled - so i glued em and then on some other MT set I tried braided fishing line on the outside - which kind of worked ....until I went off-road...went on and on till I freakin woke up and asked around. I recently have come across two sets I really enjoy and have never given me issues. Proline Badlands 3.8 for my Senton BLX. They are big but no rubbing. Had to get some tall posts - I used my aluminum ones from my TRMT8e and set the shocks /preload as high as I could & shaved the shell. These tires handle 6S no problem and its got a Castle 1515 2200Kv motor and they are never coming off that SCT.

Second set - of which Ive bought two sets they are so good. Backflips. I got my son a Outcast for XMAS but I got a set of Backflips for my Kraton and it ended up crushing my fazon on SRC Crushers which are useless in anything but dry pavement in a wet costco parking lot xmas break. They run in the snow they run in wet slush, they grass, but more importantly they handle 6S no prob as well. Don't want to jinx myself. I glue all sets whether or not assembled after alll the rips....

 

[stalled mule]

Another update.. Managed to sheer off half of the pinion gear today. First problem is it is a cheap pot metal pinion.. If the spur gear was plastic it might not be as big of a problem but with a steel spur it just shredded the pinion. This part is a whore to change out. 2.5 hours almost. Rediculous.

Broken pinion gear. Never seen this before. Why would they put in a cast metal part here?!?!

 

[BUILTLIGHTWOUNDTIGHT]

Another update.. Managed to sheer off half of the pinion gear today. First problem is it is a cheap pot metal pinion.. If the spur gear was plastic it might not be as big of a problem but with a steel spur it just shredded the pinion. This part is a whore to change out. 2.5 hours almost. Rediculous.

Broken pinion gear. Never seen this before. Why would they put in a cast metal part here?!?! View attachment 5390

UHM WOW!!!

 

[lonee]

There are some scratches on the top surface of the gear... was it get loosen while driving?
One more guy had an similar issue, but in his case the spur gear has lost his teeth..
But be honest, a plastic or nylon gear also will be damaged if it´s blocked.
On big nitros the gears are also most metal or timing belts with their gears.
But never seen a small timing belt which could transfer these high power of the 1:8th Neros...

 

[BUILTLIGHTWOUNDTIGHT]

As much Torque as this 2'000KV Motor is putting out, I could see a tiny rock or something else along those lines. Getting in between the Pinion and Spur Gear. Not saying this is the cause, but could be a definite possibly...

There are some scratches on the top surface of the gear... was it get loosen while driving?
On more guy had an similar issue, but in his case the spur gear has lost his teeth..
But be honest, a plastic or nylon gear also will be damaged if it´s blocked.
On big intros the gears are also most metal or timing belts with their gears.
But never seen a small timing belt which could transfer these high power of the 1:8th Neros...

I could see the potential for it coming loose. Heavy truck lot's of weight and power. Definitely a possibility !!!

 

[stalled mule]

Did not come loose. Actually had to put heat to the gear to get it to seperate from the motor. And no indications of rocks getting into the gears. I honestly think that when the truck was put together at ARRMA that they didn't set the slop in that mesh correctly. Above and beyond that the cast pinion is very weak. I was driving it a few days back and herd a new noise. Found a bent grub screw that was rubbing one of the diffs. I fixed that and didn't think anything more of it. Took it out yesterday and the noise got MUCH worse. Got home and took the belly pan off to see what might be causing it and found that. I Replaced the carp pinion with a Robinson racing 16t pinion and adjusted everything. Going to go beat on it tomorrow to see how everything is.

 

[Julian]

All my Arrma stock pinions are taken off asap. I use hardened steel Robinson Racing pinions. Once on with locktite - they just don't break. My outcast since Xmas went through 2 pinions on 6s. The third I put on myself and the grub screwed in tight but it still rotated and then tight rotated then tight - it was stripped. I was so frustrated- I set it tight and put it back. Huge mistake. Next day - it ran well on 4s. Then I went to 6s and ended up breaking the entire motor shaft and broke the fiddlesticking spur gear too. Thankfully -I am putting in a Max8 combo in my Kraton and can use that motor. Just need a new spur. My hobby shop only uses Robinson racing pinions and says Arrma is great but the composite pinions are a joke. From now on. - my smaller trucks will run 4s. Senton, outcast and for now - typhon. I also took my stock servos and put them in the HPI sprint 2 flux & my boys Ken Block.

 

[Toolzero]

My buddy bought a Big Rock and in less than 10 minutes the pinion gear shredded. We don't know how it happened.

Note: the Nero platform requires the pinion gears with 2 set screws.

He ordered a replacement pinion and it only had one set screw. Even with Loctite the single set screw pinion came loose in seconds.

 

[stalled mule]

The robbinson racing pinion works fine you just have to make sure you get the set screw in the groove on the motor. And make it tight. I ran it for over an hour today with no issues on the pinion.
Also while changing the pinion I Replaced every grub screw on all driveshafts with the traxxas pins. Not one broke and I ran hard with 6s the whole time. Definite improvement there. This is a mandatory change for anyone with this truck. Don't waste your time on the ARRMA brand stuff for that part.

HOWEVER. More breakage.
Roll hoop AGAIN, front skid plate, front bumper and BOTH sets of body posts (at the point that attaches to the vertical plates on the chassis. This thing is getting expensive to drive. But when it's working, it's a lot of fun

Also.. The body is still completely usable. Even breaking the body posts did not break it. The rear of the truck where the bumper recesses has ripped but that's from bad landings/takeoff dragging the rear of the truck on the ground.

 

[jonUF02]

I second the Backflip tires from the Outcast. I loved the Badlands on Revo, but they're small on Nero, so Backflip is nearly the same, but larger. I was loving them for one run, until I broke the standard u-joint on my Nero, and the shock cap popped off, all on 1 hard landing. Replaced shock cap with new one, installed HD rear axles. We'll see how it holds up next time. I find the stock MAX8 ESC way too punchy and not much tuning options. Will be replaced with Mamba Monster X if I keep the truck much longer.

 

[BUILTLIGHTWOUNDTIGHT]

The robbinson racing pinion works fine you just have to make sure you get the set screw in the groove on the motor. And make it tight. I ran it for over an hour today with no issues on the pinion.
Also while changing the pinion I Replaced every grub screw on all driveshafts with the traxxas pins. Not one broke and I ran hard with 6s the whole time. Definite improvement there. This is a mandatory change for anyone with this truck. Don't waste your time on the ARRMA brand stuff for that part.

HOWEVER. More breakage.
Roll hoop AGAIN, front skid plate, front bumper and BOTH sets of body posts (at the point that attaches to the vertical plates on the chassis. This thing is getting expensive to drive. But when it's working, it's a lot of fun

Also.. The body is still completely usable. Even breaking the body posts did not break it. The rear of the truck where the bumper recesses has ripped but that's from bad landings/takeoff dragging the rear of the truck on the ground.

Drive it like you stole'd it!!! AWESOMENESS!!!

 

[stalled mule]

I ordered some Huntsman bead locks and 3.8 pitbull rock beast xl tires that will be going on later this week. But for the record the factory tires are still going strong. It's all the "little" stuff that is really adding up in breakage.

 

[Stanleybb50]

I ordered some Huntsman bead locks and 3.8 pitbull rock beast xl tires that will be going on later this week. But for the record the factory tires are still going strong. It's all the "little" stuff that is really adding up in breakage.

Those wheels and tires look sweet.

Edit... Wow - not cheap though! You heard good things on these?

 

[Va-jeeper]

I ordered some Huntsman bead locks and 3.8 pitbull rock beast xl tires that will be going on later this week. But for the record the factory tires are still going strong. It's all the "little" stuff that is really adding up in breakage.

Be careful with those rock beast II. They will not hold up on 6s. I run a set of those on my Kraton on 4s with a blx200 system and 17 tooth pinion and they become pizza cutters at speed. The car almost become uncontrolable. Pretty sure they will blow up on 6s. Just my $.02.

I have been playing around with the diff fluid to try and reduce the ballooning but not really an option on the BR unless you drive with the center diff locked all the time.