What Would Explain This?

[malekia]

Short story long:
My 2.5 years-old ERBE was setup with LT rockers/shocks, using provided LT springs. All was stock except for wheels/tires and Tekno sway bars. Never even disassembled shocks. All was right and good!

Then, one of the sway bars broke, I removed it while awaiting parts and decided to switch to P2 rockers/shocks, again all stock parts. Didn't like it.

Yesterday, I:
- Switched back to LT rockers/shocks
- Reinstalled Tekno sway bars
- Replaced shock oil with Traxxas-provided 40wt
- Replaced stock pushrods with the red aluminum ones (5318x)
- Replaced stock toe links with the black aluminum ones (5338A)

Some inconsistencies:
- Realized that I had been using the stock pushrods with the blue spacers, which are not for LT.

- The 5338A toe link instructions state that they should be 6" long, including ends. My stock ones were
at least 1/8" longer. I followed the instructions, but then had to lengthen them because they were too short.

- After refilling shocks, I noticed that if I compressed them (without springs) some would partly extend themselves others wouldn't. Not sure which is correct?

Issues:
ERBE sits low and can be pushed all the way down to the floor, but will only rise a small amount (bulkhead will be bellow where it would have been with level lower arms). This is particularly true in the rear even with the pre-load at it's compression limit.

I temporarily disconnected the sway bars, but it didn't make any difference.

I don't think this can be explained by the (now) shorter pushrods (no spacers). Right?

Even if I messed-up the shock oil replacement, it wouldn't affect sag, right?

In a stock setup, should the rear lower arms be level? Should they go back to level after the rear is pushed all the way down?

Regards,
Ali

[gordongekko]

Maybe your pillow ball are to tight???

[AnthonyV]

Pillowballs sound like the issue... i did this by accident the other day and had the same issue. I usually tighten them down completely the back off 1/4 turn for both front and rear.

[malekia]

I just checked the pillow balls, but that wasn't it. Also, I had only tightened one of them, and that was after discovering the sag issue.

[pavmentsurfer]

I think this could be explained by shorter push rods. In a REVO the pushrods work in conjunction with the rockers to alter the suspension action. Changing one, regardless of which, can make a huge difference in how the suspension works. Adding shorter pushrods (or longer) changes the geometry and could change how the truck sits in a pretty substantial way.

The shocks should ALL push out just a bit after being compressed... if some aren't doing this they are likely under filled just a bit.

The LT rockers and pushrods are actually a STRAIGHT rate setup. This means as you compress the suspension it does not get stiffer (or, in otherwords, the compression of the shock is linear with the movement of the wheel). This setup creates very very soft and smooth suspension action but it tends to allow the truck to sag ALOT and it doesnt resist bottoming off jumps very well at all. The progressive rockers and pushrods are designed to accelerate the compression of the shock as the wheel moves farther through its travel. So, when the truck is landing off a jump the suspension feels like its getting stiffer as it compresses. This is a much more desirable setup for jumping and bashing as it tends to resist bottoming more than the LT setup.

[malekia]

Thanks for all of the replies.

<<The progressive rockers.......This is a much more desirable setup for jumping and bashing as it tends to resist bottoming more than the LT setup. >>

I installed the LT setup because I thought I would have more ground clearing (for tall grass, etc...). It seems this is not a good reason to install them?

Reading the ERBE manual and instructions for other parts (Traxxas and otherwise), it's also clear that there are a lot of restrictions to using the LT setup.

In what scenario would someone choose the LT rockers?

In a stock setup with P2 rockers, should the rear lower arms be level?

Should the ERBE be level front to back?

[pavmentsurfer]

The LT rockers and rods will allow you to run more ground clearance but because the suspension will be straight rate you tend to use MORE of the travel or you'll find you end up running the suspension VERY stiff to compensate. With progressive you loose a little ground clearance but can run the suspension softer because it will automatically stiffen up as the suspension cycles.

Some of the reasons there are restrictions with the LT setup is the angle of the driveshafts. If you have the suspension drop out too far the shafts are at a very akward angle an dare much more likely to fail.

The LT rockers are excellent for articulation and SMOOTH consistent suspension action. If you want to run trails and don't jump alot they can work great. If your into jumping I think the P2 setup is better.

With any suspension setup you can set the arms to be however you want it. I prefer the arms to and driveshafts to be level or just below level... But I also use the Variable Dampening Kit so I can run the truck lower but stiffer for my track setup.

[randy0050]

just a note.. when changing the oil , make sure all the air gets out by compressing it slowly in and out as twisting the shaft , with the cap off.. should see air bubbles .. im sure you allreadt know this, but could help someone else maybe

[malekia]

Pave: back to P2s for me. I switched back to the P2 setup(again). Not fun with the sway bars, but I think I can do it in my sleep now!

Randy: I thought I had gotten the air out, but I took them apart yesterday and a few of them had big air bubbles at the top. I filled them as much as possible and screwed the top backs on, with oil oozing out of the small hole.

I did have some problems. I could no longer compress two of the shocks (no springs) all the way in. In one case I reopened and saw that the blue diaphragm was slightly collapsed.

Is it possible to overfill the shocks?

Could this be from over-tightening the tops? How tight do they have to be?

I assume that when the tops are correctly tightened, the small hole will be blocked, right?

[randy0050]

i might be hard to compress the shock.. thats where you get the lift when pushing the model down. also make sure you didn't alter some linkages when you started having the problem.. make your shocks are assembled as the were ..its not possible to overfill. make sure the oil is correct, if seen people put crazy stuff inthere blocking the workings of the shock. do what i told you and after all the bubbles go away pust the the shaft all the way up , fill if there is any extra space , then put top on shock body as you are still holdin the shat up.. this should work..

p.s. i wish i could get my shocks not to compress all trhe way !!

[Foxprogt]

Best way to use LT and not bottom out is to use LT with summit springs! I get a nice tall stance, soft enough springs to move freely but stiff enough to not bottom out.

This isnt a great track setup tho X(

[pavmentsurfer]

It actually IS possible to overfill. If your shock can't be compressed fully it is overfilled. Once the cap is fully screwed down the bleed hole is blocked and the rubber diaphragm seals between the cap and the shock body. If the shock is overfilled the shock can't compress fully. In this situation what I do is remove the shock cap and use a paper towel to simply dab out a tiny bit of oil. Its likely that you only need to remove a few drops...

[randy0050]

you cant overfill a shock. viscosity and being put togther correctly means alot. the bladder controls the expansion needed ,along with the sping tension.. if the bladder is put in incorrectly, then of course it can be over filled. I stand corrected pavementsurfer.

[pavmentsurfer]

The reason there is a bladder in an RC shock is because as the shock compresses the actual shock shaft itself takes up space inside the shock body using up some of the space the oil used to occupy. The bladder at the top is designed to give some added room for the oil to use up when the shock is fully compressed. If there is too much oil in the shock when you put it together and the bladder is even the slightest bit compressed when you screw the cap down there wont be enough room in the cap for the bladder and extra oil to fill.

I didnt think it was really possible either until it was explained to me this way about a month ago in the stampede forum. Sure enough, the shocks i had that wouldn't compress just needed a tiny bit of oil removed and they worked great.

[randy0050]

nicely explained !

[TheKennyKiller1]

I find the best way to re-fill shocks is to extend the piston out all the way then fill it with oil making sure to leave a little room for the bladder, work the piston up and down to help release the air bubbles. When all the bubbles are gone I tighten the shock cap up until it's nearly tight then slowly move the piston up to the top of the shock body and tighten all the way. As you're tightening the cap and moving the piston up some excess oil should come out of the little hole in the cap, if done right when the piston is fully compressed without the spring installed it should slowly rebound about 3mm. I used this method just the other day when filling some shocks with 70wt oil and they work fine, I'm also using LT rockers and springs. It's not a bad idea to use around 50wt oil with the LT springs and rockers.

[malekia]

We can now move away from the theoretical argument and confirm the statement "overfilling IS possible".

Took the ERBE out for a spin on Monday and within a few minutes I noticed that something was wrong. Closer inspection revealed that the cap on one of the shocks had busted open, spilling oil all over the car.

Can I just refill this or does something need to be replaced?

On a related matter: I have only been able to unscrew one rod end from each of the red aluminum push rods (5318x). Is this normal?

[randy0050]

i haven't seen those t-rods on a shock assembly before. are you sure they fit there ? doesn't look like they would let the shock work .. take that crap off (tie-rod) and put the shock back together

[TheKennyKiller1]

We can now move away from the theoretical argument and confirm the statement "overfilling IS possible".

Took the ERBE out for a spin on Monday and within a few minutes I noticed that something was wrong. Closer inspection revealed that the cap on one of the shocks had busted open, spilling oil all over the car.

Can I just refill this or does something need to be replaced?

On a related matter: I have only been able to unscrew one rod end from each of the red aluminum push rods (5318x). Is this normal?

Check that the thread in the cap isn't damaged and if it's not just re-assemble your shocks.

Unscrewing both rod ends can be a little tricky, you need to get a good grip on the pushrod to get the second one off.

[malekia]

What tie rods? Those are Tekno sway bars.

[randy0050]

ok .. keep them on there .. good luck

[randy0050]

what was the question again ? I'm out.. i thought this was the new ERBE.. to many modifications for me to help with...