Kraton Rear a-arm breakage every drive.

[RC Steve]

My Kraton is the M2C catalog with a 1/6 motor so I know it's heavy. The problem is even off of small jumps I break my rear a-arms. They break at the inner hinge pin forward. I've gone through dozens of RPM rear arms. It may be how I'm landing my truck? If any of you have been through this I would like your thoughts on it. Having a ramp truck that can't handle the kitty side of the dirtpark isn't much fun.

 

[Cheez]

Maybe adjust droop screws.

 

[MMoelmann]

Do you have the new version on the RPM arms? I have come to the conclusion that they are not as strong as the factory arms. I started a thread about it maybe a month ago. I had the RPM arms and they broke 2 times in a row and switched back to stock and haven't broken since.

 

[RC Steve]

I have 2mm of shock extension left. There's alot of flex in the system so that might not be enough.

 

[Hammer Down]

Is it cold wherever you are? If it’s below 50°F that’s probably part of the issue.

 

[RC Steve]

Do you have the new version on the RPM arms? I have come to the conclusion that they are not as strong as the factory arms. I started a thread about it maybe a month ago. I had the RPM arms and they broke 2 times in a row and switched back to stock and haven't broken since.

Yes. I've come to the same conclusion. I've been breaking a lot of EXB too. Not nearly as many as RPM.

Is it cold wherever you are? If it’s below 50°F that’s probably part of the issue.

Northwest WA, 45 to 55F.

 

[Hammer Down]

Northwest WA, 45 to 55F.

Probably brittle plastic due to cold.. hopefully you have better luck when it warms up a bit.

 

[MMoelmann]

Just wondering. How much does a full M2C equipped Kraton weigh? I always was curious.

 

[RcDad23]

My Kraton is the M2C catalog with a 1/6 motor so I know it's heavy. The problem is even off of small jumps I break my rear a-arms. They break at the inner hinge pin forward. I've gone through dozens of RPM rear arms. It may be how I'm landing my truck? If any of you have been through this I would like your thoughts on it. Having a ramp truck that can't handle the kitty side of the dirtpark isn't much fun.

I have a Regular K6 and Xl k6 and the Rpm on the rear is a No,No I have on my Regular K6 and for more than a year never had to change a rear one.keep using the stock ones and maybe is me but always I clean my rc cars and use WD40 hey it work for me hope works for u

 

[Diem Turner]

Soaking plastic parts in a bag of WD40 for 36 hours can make a huge difference when it comes to pliability and resilience to breakage. This is a demonstration with bumper pieces but I think it's safe to say that it should translate to other components. If you're not familiar with his channel, it's well worth a sub. Lots of great Kraton content and all round solid on tips and tricks for maximizing durability.

 

[RC Steve]

I weighed myself then the truck and me, 17lb RTR. I don't know how accurate that is.
I think the cold is a major factor, the WD40 is a good idea, and I think I'm landing too rear bias and it's jamming my a-arms forward. I have some rear EXBs soaking in WD now. When you live in the cold you don't think about it, thank you for pointing that out. Tomorrow we'll find out just how spungy you can make a set of a-arms with WD.

 

[Garcbomber]

Fireteam/Kraton XL is less than 14lbs, typical 6S 6000mah pack is just under 2 pounds for reference. She’s a big girl, are upper end links upgraded? Those typically break first on big side rear landings on all my EXB v5 equipped wide arm rigs. I run year round sub 0

Upgrading failure modes will always transfer somewhere, pick your poison but you downgraded arms.

 

[RcDad23]

In a 60 degree weather one in Massachusetts one of my red rpm was gone in a little jump and I use to jump not like thunder rc or others but really high and that why inlaid do jot use rpm on the rear
That happens months ago and my arms still running

 

[RC Steve]

I don't have M2C wheel hexes or the esc plate, the rest of the catalog is bolted to my truck plus a 1/6 Hobbywing motor.
Enough people have told me the RPMs are substandard plus my own experience, I think I'm going back to the EXBs. When my EXB roller was stock I beat it to death and didn't have this problem so I think you're right about the RPM.

 

[fozzy71]

17lb RTR......

ffs, time for 12s.

 

[RC Steve]

17lbs didn't seem right so I tried it again. This time I got 14lbs with batteries and a bit of mud. Monday I'll put it on the UPS scale at work and we'll see what it really weighs.

 

[MMoelmann]

I weighed myself then the truck and me, 17lb RTR. I don't know how accurate that is.
I think the cold is a major factor, the WD40 is a good idea, and I think I'm landing too rear bias and it's jamming my a-arms forward. I have some rear EXBs soaking in WD now. When you live in the cold you don't think about it, thank you for pointing that out. Tomorrow we'll find out just how spungy you can make a set of a-arms with WD.

I've heard that regular WD doesn't work as well as WD Penetrant oil. I'm sure regular WD still helps.
WD-40 Specialist Penetrant with SMART STRAW SPRAYS 2 WAYS, 11 OZ https://a.co/d/bNXPNkW

I've also used PB Blaster. That stuff penetrates so well it soaked through 2 zip lock bags.

 

[Surchaufeur]

My exb and notorious have run 50+ packs without any arm failure.. the only big failure i had was on my notorious on -20c weather landed directly on the rear right wheel and snaped the arm off. I boil my A arms before use that might be why i break little to none. The ones i have replaced either were the top fron arms who cracked in the middle or the others who developped slop on the hinge pin.
boil the arms or leave them in hot water(cooling boiling water) im going to say my notorious this winter only broke an A arm and finished a 3D RC wing mount off.

 

[fozzy71]

17lbs didn't seem right so I tried it again. This time I got 14lbs with batteries and a bit of mud. Monday I'll put it on the UPS scale at work and we'll see what it really weighs.

u can get an accurate postal or better scale for $20 on amazon...

I don't have a scale that can handle over 500g or 1Kg yet but my goal is to get my FT < 10#.......

SRC Road Crushers = 1 pound extra weight over 53/107... 42/100 shaves another 10? ounces IIRC.......

 

[RC Steve]

I installed the oil soaked EXB a-arms today and beat the truck to death and nothing broke. I would like to thank all of you for your sound advice and help resolving this issue. I haven't had this much fun beating my truck in a long time.