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  1. #1
    RC Racer RC Dad's Avatar
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    Plastic vs. aluminum suspension arms. Minimizing $$$ damages

    I accidentally posted this in the TRX-4 forum this morning....

    I recently switched out the stiff plastic VXL front arms on our Rustler, as the winter months are here and they seem to get brittle. My little guy just snapped one, which is why I started tearing things apart...

    I also decided to remove the aluminum rear arms (and the front/rear aluminum towers), in favor of plastic, having noticed damage to hinge pins and shock shafts as a result of crashes.

    The RPM arms seem very flexible, and Iím wondering if this could cause the drive shafts to oscillate more at the bearings, and cause tranny issues. Has anybody had experience with this? My gut says to use the softer RPM stuff up front, and VXL plastic in the rear. But thatís pure speculation.

    Does anybody have a magic combo thatís worked well? Iíve bent STRC hardened steel and Lunsford titanium hinge pins that were installed on the aluminum arms in the back.



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  2. #2
    RC Champion FnFancy's Avatar
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    Funny, I use the combination of rpm fronts and stock rears on my rusty. I think I've broken one rear arm in the several years of running this set up. I know most of the people here (including myself) would caution using aluminum arms, they tend to break other parts. As always, what works for one might not work for another, but, it's a cheap experiment to try. On a side note, I used the slash 4x4 rpm arms on the front, they're not a direct drop in replacement but with some shims and a drill can be fitted. I've had people be amazed at the handling it has. Long story short, try it out. See if it works for you. What ever you do just remember, keep having fun!

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  3. #3
    RC Racer RC Dad's Avatar
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    Quote Originally Posted by FnFancy View Post
    Funny, I use the combination of rpm fronts and stock rears on my rusty. I think I've broken one rear arm in the several years of running this set up. I know most of the people here (including myself) would caution using aluminum arms, they tend to break other parts. As always, what works for one might not work for another, but, it's a cheap experiment to try. On a side note, I used the slash 4x4 rpm arms on the front, they're not a direct drop in replacement but with some shims and a drill can be fitted. I've had people be amazed at the handling it has. Long story short, try it out. See if it works for you. What ever you do just remember, keep having fun!

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    Interesting... when using the slash front arms, were you able to use the rustler c-blocks and carriers, or did you swap it all to slash components?


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  4. #4
    RC Champion zedorda's Avatar
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    Are any of the newer "cold weather" Traxxas arms compatible? Because those are better than the RPM imo.

  5. #5
    RC Champion FnFancy's Avatar
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    Quote Originally Posted by RC Dad View Post
    Interesting... when using the slash front arms, were you able to use the rustler c-blocks and carriers, or did you swap it all to slash components?


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    Here is a couple pictures, slash 4x4 rpm arms on front and traxxas 2wd aluminum c-blocks and carriers. I had to drill out the aluminum bits to accept the larger pin required for the arms, also used the plastic shim to take out the slop due to the arms being wider at the point where it connects to the chassis. Actually worked out really well.

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  6. #6
    RC Racer RC Dad's Avatar
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    That does look nice! Based on that, Iíd say you could probably pull off those new cold weather front arms. They list them for the rustler 4x4 and slash ultimate.

    So that uses a larger diameter hinge pin? Iíll have to check that out. My other driver is my four year old son. Bit of a cowboy on the trigger

    Also, what did you use for that shim? That looks pretty thick (5mm?).


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  7. #7
    RC Qualifier GotNoRice's Avatar
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    Quote Originally Posted by RC Dad View Post
    The RPM arms seem very flexible, and I’m wondering if this could cause the drive shafts to oscillate more at the bearings, and cause tranny issues. Has anybody had experience with this?
    I use RPM Arms on my 2wd Rustler VXL as well as my Stampede 4x4 and my Slash 4x4 MT. Some of those trucks have had their RPM Arms for over 8 years at this point. The Rustler runs 3s, the Stampede 4x4 and Slash 4x4 MT run 4s. I've never had any drive-shaft, bearing, or transmission issues with any of them that had anything to do with the arms.

    The RPM Arms are flexible, but everything is relative. They aren't rubber, they are still plastic. They are still "stiff" enough to not allow wobbling, etc. That is true even with my Slash 4x4 MT, which in addition to running on 4s is simply heavier than most vehicles since it uses a heavier 1/8th scale ESC and motor, heavy MIP CVDs, bigger battery, a larger heavier body, etc.

    I would say that the only real negative issue related to the RPM Arms and bending is over the long-term. If you simply set your vehicle on the floor or the shelf when you are done with it, resting on the tires, then your RPM arms will bend slowly over time simply due to the arms constantly supporting the weight of the vehicle. Even then, all you have to do is to remove them from the vehicle, bend them back, and put them back on. You can stop it from happening at all by placing your vehicle on a stand. It doesn't have to be anything fancy, I use a pack of blank DVDs under the middle of each chassis, which keeps all 4 wheels off the ground when they aren't being used.
    Last edited by GotNoRice; 11-21-2019 at 02:31 PM.

  8. #8
    RC Champion FnFancy's Avatar
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    Quote Originally Posted by RC Dad View Post
    That does look nice! Based on that, Iíd say you could probably pull off those new cold weather front arms. They list them for the rustler 4x4 and slash ultimate.

    So that uses a larger diameter hinge pin? Iíll have to check that out. My other driver is my four year old son. Bit of a cowboy on the trigger

    Also, what did you use for that shim? That looks pretty thick (5mm?).


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    Thank you sir, traxxas parts are pretty universal. I would imagine the new cold weather arms, with the correct modification can work just fine. As far as the shims, I can't be certain but I think they are from the og erbe. I believe they came with the truck, to adjust the roll center or camber or something like that. I used the slash 4x4 hinge pins, they are thicker so I had to drill out the c-blocks and such.

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  9. #9
    RC Racer RC Dad's Avatar
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    Quote Originally Posted by GotNoRice View Post
    I use RPM Arms on my 2wd Rustler VXL as well as my Stampede 4x4 and my Slash 4x4 MT. Some of those trucks have had their RPM Arms for over 8 years at this point. The Rustler runs 3s, the Stampede 4x4 and Slash 4x4 MT run 4s. I've never had any drive-shaft, bearing, or transmission issues with any of them that had anything to do with the arms.

    The RPM Arms are flexible, but everything is relative. They aren't rubber, they are still plastic. They are still "stiff" enough to not allow wobbling, etc. That is true even with my Slash 4x4 MT, which in addition to running on 4s is simply heavier than most vehicles since it uses a heavier 1/8th scale ESC and motor, heavy MIP CVDs, bigger battery, a larger heavier body, etc.

    I would say that the only real negative issue related to the RPM Arms and bending is over the long-term. If you simply set your vehicle on the floor or the shelf when you are done with it, resting on the tires, then your RPM arms will bend slowly over time simply due to the arms constantly supporting the weight of the vehicle. Even then, all you have to do is to remove them from the vehicle, bend them back, and put them back on. You can stop it from happening at all by placing your vehicle on a stand. It doesn't have to be anything fancy, I use a pack of blank DVDs under the middle of each chassis, which keeps all 4 wheels off the ground when they aren't being used.
    Thanks for the info! Iím going to stick with the RPM arms for a while, especially with winter arriving. That VXL plastic gets very brittle.


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  10. #10
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    Quote Originally Posted by FnFancy View Post
    Thank you sir, traxxas parts are pretty universal. I would imagine the new cold weather arms, with the correct modification can work just fine. As far as the shims, I can't be certain but I think they are from the og erbe. I believe they came with the truck, to adjust the roll center or camber or something like that. I used the slash 4x4 hinge pins, they are thicker so I had to drill out the c-blocks and such.

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    Gotcha. Iíll definitely keep this on the back burner, maybe try it out next spring. Thanks again for the info!


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  11. #11
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    FnFancy thatís a well made conversion!

    There are some measurements here on spacer size and turnbuckles needed etc...

    http://www.ultimatetraxxas.com/misc/...pede-wide-mod/

    RPM also make a wide arm that fits, but you still obviously need to change out the turnbuckles.

    https://www.amainhobbies.com/rpm-wid...m70662/p441618

  12. #12
    RC Champion FnFancy's Avatar
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    Quote Originally Posted by boosta View Post
    FnFancy thatís a well made conversion!

    There are some measurements here on spacer size and turnbuckles needed etc...

    http://www.ultimatetraxxas.com/misc/...pede-wide-mod/

    RPM also make a wide arm that fits, but you still obviously need to change out the turnbuckles.

    https://www.amainhobbies.com/rpm-wid...m70662/p441618
    Thank you, Jang was the original wide mod. I read that article a while ago and decided I could do it with the spare parts in my shed. Didn't cost me a penny (well, any more than I had already spent I guess)

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  13. #13
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    Seeing your post just then really inspired me to give it a go hey! Thatís a nice truck mate!

    The Jang was great hey. I wonder what heís doing these days. Really glad heís kept his site up all these years, itís a great resource.

  14. #14
    RC Racer hammie4c's Avatar
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    Jang now makes lego videos. Here is a link to his channel which is great even if you are not a fan of lego. He did a great video recently explaining the new COPPA rules on youtube. https://www.youtube.com/channel/UCH0...qsVsOh0XmapzLQ

  15. #15
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    Awesome! Thanks for that. I will take a look for sure. Interested in the new rules too but havenít found a concise explanation yet. Iím sure Jang will do a good job of it.

  16. #16
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    Quote Originally Posted by zedorda View Post
    Are any of the newer "cold weather" Traxxas arms compatible? Because those are better than the RPM imo.
    I just looked these up. Do they have them for 2wd fronts? All I see are 4x4 ones.

  17. #17
    RC Champion zedorda's Avatar
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    Quote Originally Posted by Dakratfink View Post
    I just looked these up. Do they have them for 2wd fronts? All I see are 4x4 ones.
    I don't know for sure. I heard a rumor Traxxas was going to release "cold weather" versions of many more a-arms for other models but nothing worth hold my breath for. Also heard of people using 4x4 arms on 2wd models but never delved into that myself so I have no details. Sry

  18. #18
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    The more common 4x4 slash/rustler/stampede arms are the same as rear rustler and stampede arms, 3655x. Front may need some fiddling with camber and turnbuckle length, I have to dry that to see if 4wd arms can work on the front. But with the wider front the understeer may get worse with the light front end....I liked the stance of the cars with rpm front wide arms but they push like crazy to the degree that I went back to stock 2wd front arms.
    Last edited by TwoBelugas; 11-22-2019 at 02:05 PM.

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