RPM and Popping Dog Bones

[Jluther@becoinc]

Ok I’m at work now but I’ll send one as soon as I get home. It’s about 3/8” diameter rounded on the end and has rough burrs on it. I think I got it at Lowes

 

[olds97_lss]

Did you still put the shims on or did you remove those as well?

 

[Jluther@becoinc]

I took the shims out so the pillow balls will screw in deeper

 

[TOURING18]

Just wanted to thank everyone for this info! I've been battling this issue since day 1 with my 6s Noto. I just tried removing the shims but had the left side pop out today after just 5mins of bashing. This will be the 4/5th time so I'm getting annoyed. Wish it was as easy as running longer CVD's and calling it a day. LOL I'm def going to try shaving next! -Jim

 

[Jimbobjr]

Just wanted to thank everyone for this info! I've been battling this issue since day 1 with my 6s Noto. I've tried the shims already but had them pop out again after just 5mins of bashing today. This will be the 4/5th time so I'm getting annoyed. Wish it was as easy as running longer dog bones and calling it a day. LOL I'm def going to try shaving next! -JimView attachment 161827View attachment 161828

you at Posh/Catty woods in Lehigh Valley. Pic looks like that place.

 

[TOURING18]

you at Posh/Catty woods in Lehigh Valley. Pic looks like that place.

"The Garden - Chicago Dirt Jumps" BMX track. First time checking this place out. Thankfully it was only 25mins away because it was short lived. I will be back though once I try all the tips/tricks above.

 

[Jimbobjr]

Place looks amazing. Posh/Catty woods is pretty awesome too but since they became legit, organized trails (big legal battle, went on for several years) its pretty much off limits to RC's but some of the best BMX/dirt jump trails anywhere.

 

[Primarrma]

Just wanted to thank everyone for this info! I've been battling this issue since day 1 with my 6s Noto. I just tried removing the shims but had the left side pop out today after just 5mins of bashing. This will be the 4/5th time so I'm getting annoyed. Wish it was as easy as running longer CVD's and calling it a day. LOL I'm def going to try shaving next! -JimView attachment 161827View attachment 161828

How much droop are you running?

Do you know when they are popping out, is it extension or compression of the arms?

 

[TOURING18]

How much droop are you running?

Do you know when they are popping out, is it extension or compression of the arms?

To be honest I never touched the droop. I did today though and also checked the diff. It need a shim for sure because it's sliding in place left to right just enough to notice. The ball joints also needed to be tightened. Literally every adjustment seems to contribute at this point.... That's why I wish I could just buy longer CVDs and call it a day. Lol

 

[pstill9302]

I've installed RPM arms all around on my Kraton some months ago (during the winter). At first I did not have any problems, but now I suddenly started having some problems too with dogbones popping out the diff cups on the front of my Kraton. I started reading online about this problem and I've found out that many people dealt with this problem. I think the weather (outside temperature) has a lot to do with this problem also. Especially if you're running RPM arms. Now it is getting hotter outside. The RPM arms are very flexible, but in the winter they are more stiff. Now that it's hotter outside the nylon material from the RPM arms is even more flexible and that's when the problems started. I've read up on this problem on different forums, and I've found the most easy solution is to remove the shims as discussed here before. I've also limited the shock travel by installing a rubber grommet on the shock shaft. Both these changes I've made helped me to illuminate the problem. At least during the last test run on 4S the dogbones/CVD's stayed put! I will do some more testing and jumping on 6S. But I'm pretty confident it's solved.

When the problem will come back I might trim down the A-arms a bit, like suggested here before. Maybe cutting/shaving down 1-2mm should be enough to completely illuminate the problem. But I hope that will not be necessary.

Thanks for all the good tips and idea's here

Thanks all for your tips. I have experienced the same situation as Tomberland described. Installed RPM arms during the colder months and had no issues, now in the heat/months after installing its starting to happen regularly. Twice today and getting annoying, was about to post and ask about, low and behold saw this thread already existed. I will remove the shims, etc. and see what happens. Question to all, has anyone done a comparison RPM vs. the arrma exb arms up front? I've read the exb arms are much better than stock (which I snapped on my first outing,) but haven't seen comapison to the RPM. If the exb arms are roughly as durable as the RPM and don't exhibit as much flex and stretch to allow the dogbones to pop, this is perhaps another option?

 

[Primarrma]

The other thing you can do is add a shock rod limiter, it helps by not allowing the suspension to fully compress. You can add a few orings or a piece of Nitro fuel tube on the shock shaft between the spring perch and the shock cylinder. Only needs to be a small amount to have a big effect.

You can also add orings or tube to the inside of the shock to limit the travel on extension.

If you use droop and the limiters you shouldn't loose your dog bones and you should still be able to use your camber adjustment washers.

 

[pstill9302]

The other thing you can do is add a shock rod limiter, it helps by not allowing the suspension to fully compress. You can add a few orings or a piece of Nitro fuel tube on the shock shaft between the spring perch and the shock cylinder. Only needs to be a small amount to have a big effect.

You can also add orings or tube to the inside of the shock to limit the travel on extension.

If you use droop and the limiters you shouldn't loose your dog bones and you should still be able to use your camber adjustment washers.

Removed upper and lower thick washers/spcaers from arm ends. Kept a thinner shim up top in place for camber. Good so far. Also replaced stock springs up front with 70mm lg mohave springs for a little more force. Liking that so far as well.

 

[olds97_lss]

The other thing you can do is add a shock rod limiter, it helps by not allowing the suspension to fully compress. You can add a few orings or a piece of Nitro fuel tube on the shock shaft between the spring perch and the shock cylinder. Only needs to be a small amount to have a big effect.

You can also add orings or tube to the inside of the shock to limit the travel on extension.

If you use droop and the limiters you shouldn't loose your dog bones and you should still be able to use your camber adjustment washers.

Adding a shock limiter like that though also cuts down on the shocks doing their job. The outcast already sits so low that the shocks take out only the initial sting of a jump. Which I guess is their job, but would be nice if the geometry was a bit taller so it didn't drag in short grass so much. Extension limiters will make that worse.

 

[SrC]

RPM arms will flex and stretch to the point the bones can pop. I prefer RPM arms at the rear. I tend to break the stockers at the rear much more often.

 

[Primarrma]

Adding a shock limiter like that though also cuts down on the shocks doing their job. The outcast already sits so low that the shocks take out only the initial sting of a jump. Which I guess is their job, but would be nice if the geometry was a bit taller so it didn't drag in short grass so much. Extension limiters will make that worse.

The ride height shouldn't be effected, that is unless you're fitting a lot of orings inside the shocks. On compression the limiter only stops the shock rod going into the shock body fully.

The shock limiter on the inside of a shock cylinder will prevent the shock extending all the way back out, this is only at full extension which wouldn't be a normal position to be running your ride height at anyway?

 

[SrC]

^^^

Conversely, running less droop will prevent some extreme dog bone deflection at full extension.

 

[olds97_lss]

The ride height shouldn't be effected, that is unless you're fitting a lot of orings inside the shocks. On compression the limiter only stops the shock rod going into the shock body fully.

The shock limiter on the inside of a shock cylinder will prevent the shock extending all the way back out, this is only at full extension which wouldn't be a normal position to be running your ride height at anyway?

Any time you accelerate, the shocks extend in the front at least, so limiting that won't help with plowing through 2-3 inch tall grass.

I've fought with it more on my revo than my outcast because if I raise it using the various mounting positions for the pushrods on the arms, the pillow balls rip out when crashing or the rocker posts snap off when landing jumps, so I have to live with it being lower to the ground, which does cause my motor/esc temps to go up some due to the extra drag. On my outcast, I use the inside holes on RPM arms, so it's raised a bit more than stock.

 

[SrC]

To be honest I never touched the droop. I did today though and also checked the diff. It need a shim for sure because it's sliding in place left to right just enough to notice. The ball joints also needed to be tightened. Literally every adjustment seems to contribute at this point.... That's why I wish I could just buy longer CVDs and call it a day. Lol

Longer CVD's??? No such animal. The CVD's are spec'd properly. It's the components surrounding the issue that matter. Longer would just be a band-aid and mask the real problem and incorrect IMHO. A tear down is necessary. Get squared away with your diff shims for starters., Get Droop correct etc. Leave the Pivot ball shims and washers removed. Make sure your arms are in good condition. Droop must be correct. Out the box I had these issues until I learned about the rig much better and drive better.. I never pop bones any longer. User error with driving is also part of the equation to some extent. Cartwheeling, "On throttle" landing from jumps etc. Lots of factors to consider here.