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  1. #1
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    Alum shock caps a waste?

    I bought 4 alum shock caps to prevent blow off's, and have had more problems with them leaking than I expected. It seems like if you tighten them down the whole way they tear the rubber bladder, and if you don't oil seeps out. Anybody have any tips?
    Slash 4X4, Blitz ESE, Motocross, Mtn. Biking

  2. #2
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    Try using teflon tape around the top of the shocks before you put the shock cap on.

  3. #3
    Traxxas Marshal cooleocool's Avatar
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    I don't have any problems with the Big Bore aluminum shock caps. I agree with pettyeagles... teflon tape would probably help.
    "Happiness depends upon ourselves." -Aristotle

  4. #4
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    I have been down this road and I will tell you that teflon tape is probably the only way to keep them from leaking....but make sure with alum caps, that you leave at least a 1mm gap at bottom. Never tighten them all the way down.

  5. #5
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    i tightened them all the way down with no teflon tape and have had no leaks. maybe production variances? its good to know that they could leak.
    What?

  6. #6
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    One other thing I think I am going to try this time is putting some clear rtv along the outside edge of the cap, after I tighten it.

    BTW, when you tighten the cap all the way down it smashes the diaphragms edges and makes it useless. Just grab the old shock cap and look at the difference. You can see that the threads do not go all the way down and that when tighten on the shock body, they sit 1mm off the edge. You can verify this by measuring the threads on the shock body and compare those to the threads on the alum cap...then, measure the thickness of the diaphragm and you will see that you need to leave at least a 1mm gap just below the alum cap.

  7. #7
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    oops mine are the whole way down..will loosen them up and try again. Thanks for the help.
    Slash 4X4, Blitz ESE, Motocross, Mtn. Biking

  8. #8
    RC Turnbuckle Jr. El Sob's Avatar
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    I have all of mine tightened all the way down. I noticed the other day when I looked that the diafram was torn. I will leave space next time.

  9. #9
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    i have my aluminum ultrashock caps, not the BB's but the new red+blue ones. they have sealed all the oil up perfectly and have never blown off
    Lead, follow, or get out of my way!

  10. #10
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    You probably need new bladders now after tightning them down all the way. So new bladders and teflon tap. No problems here. But I have had broke a shoke right under the threads. Took me a long while to find why that shock would not hold fluid. No matter what I did it leeked aroung the cap. But then finaly seen fluid squirt out.
    Broken parts=New better parts

  11. #11
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    shock bladders traxxas 1765
    Moving into the future since the last century.

  12. #12
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    i have heard from a couple different veterans if u get oil on the threads ur screwed, i just tried my best to keep the oil off the threads and have had no problems
    Yes, I drive an electric converted Nitro Hawk.

  13. #13
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    Which ones do you have? Do you have the gunmetal looking ones (which are for the big bore) or do you have the red or blue ones? I do know that for some reason, if you use the Gunmetal ones that are really for the big bore, they will leak on regular shock bodies. Don't ask me why - dunno if its a thread issue, but I've run into that with at least 4 people...
    Imperial Racing
    Slash 2wd/ 2wd Mod / 4x4

  14. #14
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    Quote Originally Posted by cooleocool
    I don't have any problems with the Big Bore aluminum shock caps. I agree with pettyeagles... teflon tape would probably help.
    The Bigbore caps or the alum ultrashock caps will always leak. Traxxas should have made an O-ring around the base of thread on the shock body to further seal the the oil, much like STRC's alum shock bodies. I've never had such a leaky alum shocks before. I have a much better solution than teflon tapes. I've been using clear aquarium silicone sealant on my Big Bore. It seals the oil pretty good and VERY easy to remove each time you need to refill the shock oil and will not attack the fragile diaphragm. Just apply it on the shock body's thread prior to attaching the shock cap. I now have ZERO leak, and the caps stay 100% dry free of dirt and oil volume stays consistent even after 3 months of track abuse.

    @IndianChief1000
    I have both the BB caps(gun metal) and the TRX alum ultra shock caps. I'd tried both on the plastic shock bodies, the BB caps are much tighter in tolerance and pretty hard to screw it in and will possibly contort the thread and lead to leaking.
    Last edited by Out of Sight; 09-15-2010 at 08:35 PM.
    Myth busted: Blitz is not faster on the track.

  15. #15
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    Yeah I agree with you on the BB caps. However, I've yet to have a problem with any of the Red Alum's leaking and I have them on three vehicles
    Imperial Racing
    Slash 2wd/ 2wd Mod / 4x4

  16. #16
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    I use the big bore caps (the grayish ones) and have not had them leak ever, even after huge jumps.

  17. #17
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    i have aluminum ones on both my trucks. and all are on tight and only 1 leaks. and thats because the bladder has a weird spot on it. so i just need to replace it.
    Slash 4x4 MMP-HV 5.5
    Slash Sidewinder SC 3800kv

  18. #18
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    I had alot of problems with my aluminum caps too. I blew my first shock cap the second day I had the truck (My first high performance RC, so you should have seen my face when I saw the whole front right of the truck slopping all over the place and leaking fluid lol) Bought all 4 aluminum caps, and installed them.
    They were SUPER hard to screw on, at first I didnt even think they were the same size. Then I grew a pair and decided to try anyway.
    they seemed to fit, but were awkwardly tight.

    They seemed to be working fine, until I noticed 2 or 3 runs later, that dirt was caked all over the shocks and bodies. They were leaking so much that they only had about a half of the fluid still in them..

    It took me about 5 minutes of elbow grease, some of those rubber pad things to help you open bottles, and a screwdriver through the mounting hole to get the caps off. I probably put them on a bit too tight, but I didnt really know what I was doing.

    The rubber bladders did not seem to fit into the aluminum caps. They would kinda fold over in one corner. ALL OF THE TIME
    I tried about 3 times to get it right... filling shock, putting bladder in cap, CAREFULLY screwing on the cap as to not disturb the bladder...

    every time, it would do the same thing. I would even just take the caps right back off, and magically the bladder was all folded over.

    I ran my shocks with no fluid and twice as many preload spacers as stock until my Big Bores came in the mail lol...

    I havnt had any problems with them since.

    I re-purposed my old bodies and hadware (using the stock caps) with some (I didnt have fuel tubing) plastic bushings to make some lowered street suspention.

    I feel like I just rambled.

    EDIT: and to whoever said big bores leak: mine dont. not one teensy bit.
    I am lucky I don't have any money.

  19. #19
    RC Turnbuckle Jr. El Sob's Avatar
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    Well I just got a new set of bladders. Tomorrow I am going to try it again. Does anyone have a pic of how they should look?

  20. #20
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    If you have any problems getting your shock caps on and off get the RPM shock tools. They are GREAT and you avoid deforming the shock by squeezing it too hard.
    -- > Republic Racing < --

  21. #21
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    They should be all the way inside the cap (use i.e. a small hex driver to press the edge down all around, and fully round. Once you got them properly seated, the edge will be smoothly down against the cap all around, nothing lifted, folded or whatever. You can slightly lube the inside edge (the one facing the shock, not the cap) with a bit of silicone oil, that way there's less risk of it snagging when tightening down, and getting torn.

  22. #22
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    I have alum caps and had 80 w oil in my rustler; I blew the bottom of the shock completly off. Taught me a lesson real quick. Now I just dab a bit of CA on my stock caps
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