Anyone else have leaky shocks?

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
After every run I noticed oil residue on the top of my 2 rear shocks. Thinking they were not tightened or filled properly I have stripped and re-filled them several times (using Motul 20wt fork oil) but they always went leaky on me again. Anyway the other day I stripped them down yet again to investigate further. I discovered the 2 rubber shock top seals both had tiny tears around the bubble part of the seal. It appears during full compression the sharp edge piston comes in contact with the seal which I guess cuts into it over time. Next time your shocks are apart run your finger along the side and the top of the piston and you will see how sharp they are.

It might also be caused by my current rear shock mount position which is the lower hole of the shock tower (to give me a bit more travel)

Just wondering if anyone else has noticed this or not.
 

zouz10

Well-Known Member
Messages
1,493
Location
Florida
I didn't notice this in my MCD yet b/c I have not taken the shocks apart yet. However, I had that exact problem on my baja! I finally remedied it when I changed the O-rings!
 

mylilmarder

Active Member
Messages
34
Location
Odenton Maryland
Leaky Shock

One way to help keep your shocks from bottoming in to add a piece of fuel tubing on the shock shaft at the bottom so when the shock compresses it does not and bottom out where the piston hits the top of the shaft seal. This is a trick that 1/10 scalers use.
 

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Excellent idea mylilmarder. Thanks for the tip.

The MCD shocks are a bit odd in that even at full compression there is still approx 7mm of exposed shock shaft hanging out from the bottom. What determines max compression is the physical contact of the piston top hitting the rubber seal. Not sure why they are like that but seems a bit strange to me.
 
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monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Please ignore what I said previously regarding the piston cutting into the rubber seal as further testing today revealed the true cause of my leaky shock problem.

I now honestly believe there is a fundamental issue with the design of these shocks and I will try and explain why. As I said earlier at full compression there is still approx 7mm of exposed shock shaft hanging out from the bottom of the shock and what determines max compression is the physical contact of the piston top hitting the rubber seal. The piston actually overshoots the housing if you were to remove the top of the shock and push it all the way in.

Heres a pick of the shock at full compression showing the extra shaft popping out the bottom.

IMG_1515.jpg



In this pic I have removed the top but inserted the seal pushed the shaft all the way in until it hits the seals bubble again illustrating the amount of shaft hanging out from the bottom.

IMG_1516.jpg



This is shows the piston overshoot at max compression.

IMG_1512.jpg



What happens is during a hard landing the piston pinches the rubber seal on a ring molded into the red shock cap causing it to tear. After pulling down all 4 of my shocks and turning the seals inside out I noticed this on every one as shown below.

IMG_1508.jpg

IMG_1511.jpg



So it looks like I will be forced to replace all 4 seals. To try and prevent this from occurring again I have done the following modifications. First I added a silicone shaft spacer as suggested by mylilmarder. This prevents the shaft overshoot so it now has a little space inside as shown.

IMG_1517.jpg

IMG_1519.jpg



I also removed the molded ring on the shock end so it can no longer cut into the seal.

IMG_1521.jpg



Hopefully these mods put a stop to this. It will be interesting hearing from others what there thoughts are as I truly think there a problem with the way these shocks have been designed or perhaps they just screwed up when they built mine and put the wrong sized shock casings on.
 
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MONAROMAN

Well-Known Member
Messages
485
Location
Sydney Australia
Mate mine don't get a chance to weep... Oh what I'd give to have weepy shocks :clown:

(sounds like a monty python skit - when we were kids we all lived in a rolled up newspaper...)

Seriously though, thats good work there mono, obviously a design flaw. I wonder if there are other shocks out there that may be adapted to the MCD's
 

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Haha [tragically]funny stuff. Trust me dude get a front bumper and brace up the front lower ball joints ASAP.

Actually I have 6 Baja5b shocks lying around the place not doing much so have often entertained the thought of modifying them to put on the MCD but the diameter is much bigger so is the length so theres no way they will fit and even if they did I would just be trading one problem for another.

Tried to do a temp repair on the seals using some super glue until Powerslide can supply me with replacements but seriously if your using your MCD's suspension to the max then I strongly urge you to check your seals for damage. I wonder how those hardcore UK racers are going and whether they are finding the same thing or not. Cannot believe im the only one having drama's but then again im kinda lucky like that...lol.
 
Messages
13
Location
isle of wight
One thing, looking at the first pic, is that rust on the shock shaft ?

If so that will quickly destroy o-rings and cause leakage. I noticed this as I recently got some new shafts, and they were badly rusted and pitted along there length. Needless to say the shop is replacing them and adressing the issue with their supplier(when they checked their stock, all the long shafts were as bad)
 

Kwakr

Well-Known Member
Messages
141
Location
Thornhill
im just thinkin out loud here....but anybody you know have the same vehicle??? Maybe get them to measure their shock shafts....try and compare....kinda weird that they are too big for the shock bodies...possible manufacturing error(???) and put tooo long a shock shaft in the shocks??
 

mcdracerunnerevo3

Active Member
Messages
30
Location
uk
hi, looks like the shaft/ shock body is wrong combo. possibly long travel shafts with the medium travel bodies. only logical thing i can think of. are they shafts and shock bodies that came with buggy? if they are some one must of had brain fart when they were building it:eek:
 

monotheist

Well-Known Member
Messages
174
Location
Melbourne, Australia
Thats what I thought but I measured the shafts and shock bodies and there all "long" according to the parts manual.

Just fitted up some Elcon replacements. See the post on the MCDRC forum for further info.
 
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