Granite A arms keep braking

[bicketybam]

Have you experimented with soaking parts in WD40 or other things to make them more flexible. I've also noticed that every a-arm that brakes is right where the shock screw is.

I haven't soaked them. I would check your shocks for shock oil like someone already suggested. Do they feel springy like a pogo stick are can you feel the dampening and rebound provided by the oil?

 

[Sledgehog]

Never soak parts with wd40. It will make them more brittle over time specially in the cold. I know kev talbot does this and says wd40 works but he actually uses muck off (MO 94) which has a different chemical makeup than wd40 which is petroleum based. Its fine to clean plastic parts with and wipe off but not to soak.

Also like bick asked, are your shocks really stiff and not doing their job? Remember you want a bit of chassis slap on landings to help soak and distribute the force. Some people think if their chassis hits the ground its a bad thing and stiffen their shocks too much. If only the shocks are taking the landings all the force is going right into the arms.

 

[Notorious J]

Take it or leave it. I knew I had seen a video about this once. This guy did a home test on the affects of different types of treatment on a arms. It's a little long winded, but the results are kind of interesting.

 

[Jbails]

Have you experimented with soaking parts in WD40 or other things to make them more flexible. I've also noticed that every a-arm that brakes is right where the shock screw is.

Exactly where mine broke. First run, wheelied, tried to save it from rolling, hit my fence. I’ll be the first to say it was driver error/ inexperience (my first RC). Just wish I could have enjoyed it for more than 45 seconds lol

 

[crimsonfancy]

I have never broken an arm on any truck in my life except slash once and I hit a street sign pole. I partially sheared a Talion arm on a culvert but it still runs it's ass off as is. Im trying to imagine how hard it takes to bash and land on a suspension arm to get it to snap. Cold weather I can see but maybe I'm not blasting my trucks hard enough.
I'm gonna try to kill it this weekend enough to break something new besides my wheelie bars and wing mounts.

 

[crimsonfancy]

Take it or leave it. I knew I had seen a video about this once. This guy did a home test on the affects of different types of treatment on a arms. It's a little long winded, but the results are kind of interesting.

The torque twist is interesting. I imagine it would be especially useful for Crawler arms comparison.
I'd like to see his results if they were able to translate to impact resistance. The slow and steady bend vs head-on collision or crash / immediate stress.

 

[olds97_lss]

I have never broken an arm on any truck in my life except slash once and I hit a street sign pole. I partially sheared a Talion arm on a culvert but it still runs it's ass off as is. Im trying to imagine how hard it takes to bash and land on a suspension arm to get it to snap. Cold weather I can see but maybe I'm not blasting my trucks hard enough.
I'm gonna try to kill it this weekend enough to break something new besides my wheelie bars and wing mounts.

Maybe your just lucky. I've busted arms on every truck I've owned at least once. Even some RPM arms. I snapped a rear RPM arm on my outcast shortly after installing them.

 

[Notorious J]

The torque twist is interesting. I imagine it would be especially useful for Crawler arms comparison.
I'd like to see his results if they were able to translate to impact resistance. The slow and steady bend vs head-on collision or crash / immediate stress.

Not that I take this guys video as scientific proof, but it just raises the question about being able to alter the plastic using different chemicals or procedures. Boiling, WD40, and others I've heard, that can change the composition of plastic. This video was one of the only ones I found where someone tested more than one of the options and for me, it's still inconclusive. Run em til you break em, then change em. No need to try to alter em. Chemistry is a whole other hobby, one which I would fail at worse than rc.

 

[Megasty]

Out of every car I've ever owned, I have not broken an arm on 7 (not counting duplicate or mods): Typhon 6s, Senton 6s, Muckraker, Epidemic, Sabertooth, SCT410, & Bushmaster 8e. The only things they have in common are either the arms are really short & stout or super flexible. Super rigid plastic like the kind in the 4x4 models don't handle chemicals very well or benefit from them in the slightest.

 

[blackgoat04]

I went through 2 arms. ran across these and haven't had any issues since. You will have to drill out the hinge pins holes a little bigger to fit our hinge pins in them. and drill a hole for the pin keeper screw for the cup

 

[Jeremy in WI]

I went through 2 arms. ran across these and haven't had any issues since. You will have to drill out the hinge pins holes a little bigger to fit our hinge pins in them. and drill a hole for the pin keeper screw for the cup

Are those the same length? It would be nice to catch something a little longer...

 

[blackgoat04]

Are those the same length? It would be nice to catch something a little longer...

it also has multiple holes to choose from for shock mount

 

[Jeremy in WI]

Huh, almost negligible. Bummer. I think the typhons are 8 or 10 mm longer which is probably worth the wait.

 

[blackgoat04]

Huh, almost negligible. Bummer. I think the typhons are 8 or 10 mm longer which is probably worth the wait.

true...but these arms can be found at most hobby shops. rpm makes these and traaxas of course makes them too. I use them because they seem to be stronger than Arrma composite plastic, little bit longer, and multiple shock mount holes. and I can grab them right off the shelf instead of waiting 4 days for delivery

 

[olds97_lss]

true...but these arms can be found at most hobby shops. rpm makes these and traaxas of course makes them too. I use them because they seem to be stronger than Arrma composite plastic, little bit longer, and multiple shock mount holes. and I can grab them right off the shelf instead of waiting 4 days for delivery

As with anything, they aren't impervious to damage. I just busted/cracked one on the rear of my stampede 4x4 this weekend. It was about 40F and I was bashing in snow. I noticed it was stressed before that though as the blue rpm plastic looked white in the spot where the split is now.

Before I got them, I broke 3 stock arms in about a month running 2S and less sticky tires. I'm now running a big 3S (7200mah 3S2P), 2.8 trenchers and 15mm axle extensions, so there's a lot more strain than there was when I broke stock arms. I ran the same tires and everything, except 2S for about a year after installing these. I've only been running 3S the past month or two and the extensions were just installed before I cracked the arm. The stress marks were there before the extensions for quite a while.

You can see the stress points, the right side has a crack in it:

 

[blackgoat04]

As with anything, they aren't impervious to damage. I just busted/cracked one on the rear of my stampede 4x4 this weekend. It was about 40F and I was bashing in snow. I noticed it was stressed before that though as the blue rpm plastic looked white in the spot where the split is now.

Before I got them, I broke 3 stock arms in about a month running 2S and less sticky tires. I'm now running a big 3S (7200mah 3S2P), 2.8 trenchers and 15mm axle extensions, so there's a lot more strain than there was when I broke stock arms.

You can see the stress points, the right side has a crack in it:

those stress marks seem to indicate your shocks are stronger than the arm they are mounted on....IMO. but I can't see the other side of the mounting point either. all of my breaks have been on the oustide leading edge of the arms I believe. I tend to run into non moveable objects every once in a while. Are you doing lots of jumps with your car?

 

[olds97_lss]

those stress marks seem to indicate your shocks are stronger than the arm they are mounted on....IMO. but I can't see the other side of the mounting point either. all of my breaks have been on the oustide leading edge of the arms I believe. I tend to run into non moveable objects every once in a while. Are you doing lots of jumps with your car?

That could be. I've been toying with the shocks a lot and yes, I air this thing out a ton. However, the shocks are mounted further out than the stress point. If it was bending due to that, I'd think it would bend where the shocks are mounted vs where it did.

Then again... this is the 3rd set of shocks I've had on it and the 5th or 6th oil/spring/piston combo. I may have mounted some on the holes to the inside at some point to raise it up a bit... then after seeing the stress, moved them back out to where they are now. That said, I don't believe I ever mounted the shocks on that furthest inside hole as that is where the shock/arm protectors mounted. I just quite running them as they were more of a nuisance than they were worth and they didn't fit the RPM arms very well.

When I install the new arms, I'll replace both and mount the shocks where I have them now and see how it does as the hole I'm using now goes into a cross bar that I drill out and use a longer screw to get more threads in the meat of the arm:

I don't get @Rich Duperbash air, but I'll get it up over 10 feet or so.

 

[blackgoat04]

very nice!!

 

[olds97_lss]

I only mentioned it at all because people lately seem to think when someone says something is tough that it means they never break then post a flaming thread about how much of a piece of garbage something is when they get it and break it.

As far as RPM goes, I've only had one breakage that I thought was worthy of using the warranty, but I have broke 6 or 7 RPM arms over the past 20 years. Was almost always when doing something ridiculous or hitting something immobile at a high rate of speed. I usually replace them at some point due to wear at the hinge pins every couple of years anyway. The only one breakage I thought was odd was on my outcast after just installing them. One of my rear arms shattered during a not so big crash. I have to think it was just due to a defect/air bubble in the part or something because I replaced it with RPM and have crashed so much harder so many times without issue since. Regardless, I still didn't send it in because I didn't feel like buying packaging, paying for shipping and going to the post office for a $7 part ($14 for 2).

In the end, everything has a limit.

 

[blackgoat04]

That could be. I've been toying with the shocks a lot and yes, I air this thing out a ton. However, the shocks are mounted further out than the stress point. If it was bending due to that, I'd think it would bend where the shocks are mounted vs where it did.

Then again... this is the 3rd set of shocks I've had on it and the 5th or 6th oil/spring/piston combo. I may have mounted some on the holes to the inside at some point to raise it up a bit... then after seeing the stress, moved them back out to where they are now. That said, I don't believe I ever mounted the shocks on that furthest inside hole as that is where the shock/arm protectors mounted. I just quite running them as they were more of a nuisance than they were worth and they didn't fit the RPM arms very well.

When I install the new arms, I'll replace both and mount the shocks where I have them now and see how it does as the hole I'm using now goes into a cross bar that I drill out and use a longer screw to get more threads in the meat of the arm:

I don't get @Rich Duperbash air, but I'll get it up over 10 feet or so.

was sitting here trying to picture your a arm in my head and how it got those stress marks. try to picture this in your head. your wheel would essentially be the handle end of a long lever. Your shock mount would be the fulcrum. the other end of this lever is essentially attached and non-moving. yes there is a hinge pin but it does not allow it to actually move in an up-and-down motion on that side of the lever. what you're seeing is not a stress mark from the arm bending, it is a stress mark from the arm tearing. essentially the arm is ripping instead of being bent. does that make sense. of course they make the holes for the shock mount with more meat around them in order to create less stress at that point.