Shock rebuilding

[rag6]

I have been rebuilding my traxxas shocks for years now. I always rebuild them to stock specs, except in the case of my aluminum strc shock bodies, these seem to have much less resistance. Are they too big for the pistons? Example, I have to use 60 wt oil to get the same dampening that I was getting from 40 wt before. The pistons I used are the 2 hole and were taken from a brand new set I bought off ebay. Any hints/tips for these aluminum bodies?

 

[Boogie]

The holes may be a bit bigger, allowing more oil to flow through (if they are different pistons). It's also possible that the inside diameter of the aluminum shock bodies are slightly larger, allowing oil to come around the sides of the piston. I will say that I've had aluminum strc bodies on my crawler and they worked great and I never noticed any issues like you are speaking of, maybe these were a different model sent by mistake or something...who knows.

 

[the_juice101]

what kind of shock oil do you buy? where do you usually get it from? does anyone have a guide on how to rebuild and refill shocks for the slash?

 

[the_juice101]

how much were the shocks? do you have a written process for rebuilding the shocks or do you just do it off the top of your head?

 

[jonpfive]

I have been rebuilding my traxxas shocks for years now. I always rebuild them to stock specs, except in the case of my aluminum strc shock bodies, these seem to have much less resistance. Are they too big for the pistons? Example, I have to use 60 wt oil to get the same dampening that I was getting from 40 wt before. The pistons I used are the 2 hole and were taken from a brand new set I bought off ebay. Any hints/tips for these aluminum bodies?

If you are sure that the pistons are the same size as the stock ones you were using than the STRC shocks are likely to have a larger inside diameter.

If you measure the I.D. of the bodies (use a caliper for accuracy) and they are indeed different, using the heavier oil to compensate will work. If you are picky about it, you can venture to the LHS and start measuring pistons from other manufacturers and find some that are a tighter fit. For this application, I would think that .005-.010 smaller O.D. on the piston than the I.D. of the shock bore is what you are looking for. I think I remember reading that the RPM pistons are slightly larger than stock Traxxas pistons, maybe start by looking at those.

As always, make sure the "nubs" are trimmed and filed off of the pistons where they come off of the "tree".

what kind of shock oil do you buy? where do you usually get it from? does anyone have a guide on how to rebuild and refill shocks for the slash?

There are many ways to do this. Here's how I do it and haven't had any issues:

1. Clean the shocks before disassembly.
2. Disassemble and inspect, pay close attention to the bladder on top.
3. Drain shock oil, remove as much as possible.
4. Fill shock about 2/3 full with new oil, slowly stroke the shaft to work any air out of the oil. I usually let mine sit for 5-10 min once I have gotten the air out from under the piston. This is typically enough time to let the air bubbles work their way out(up).
5. Fill shock to just below the top. The outer edges of the meniscus should be at the top of the shock body, and the curve of the meniscus will sit just below.
6. Install bladder. Start on one side of the shock body (hold with finger), plunge shock shaft about halfway (oil should seep out). With shaft partially compressed, easily work the bladder the rest of the way down. As you do this, more oil should "burp" out of the bladder.
7. Install cap.
8. Once complete, stroke the shock a few times. It should be smooth and free of air. On full compression, the shaft should come back out 1/4 to 1/2 of an inch. On full extension, the shaft should suck back in 1/4 to 1/2 of an inch.

I am still running my original o-rings in my stock shocks, over 6 months of racing use and no leaks at all. I also run stock plastic caps as the aluminum caps are a little tight on the bladders.

Hope this helps!

 

[the_juice101]

You make it sound so easy. I'll try it out this weekend and see how it goes. hopefully I can rebuild the front and the back and get better response. thanks