Shock rebounding fast

[Dex_79]

1 of the rear shocks on my muraco was rebounding way faster than the other.
I gave all 4 an oil change and both rear shocks oil was very silvery in colour, the fronts was clear still.

After rebuilding the same shock is still rebounding noticeably faster than the rest.
Any ideas as to which part is likely the culprit causing this?

Thanks

 

[KnowAir]

Is the Muraco new? Has it always been this way? If so, perhaps a wrong piston, or complete shock was installed from factory? Or, either a broken piston, possibly a leak? The leak would manifest itself rather quickly I would think though by oil on the outside of the shock..

 

[Dex_79]

Is the Muraco new? Has it always been this way? If so, perhaps a wrong piston, or complete shock was installed from factory? Or, either a broken piston, possibly a leak? The leak would manifest itself rather quickly I would think though by oil on the outside of the shock..

I bought it 2nd hand.

Opened it up again this morning to make sure oil level was full and it was. No noticeable leak overnight. Didn't strip it down fully but changed the bladder and topped off again. Wondered if the hard springs I had changed to were uneven so changed back to the standard and it's still the same. Piston looked ok but could be worn around the outside I guess.

Once rebuilt it rebounds just a small amount like the other side without the spring on.

Possibly time for a new set of pistons

I rebuilt with 45wt in the back and 50wt in the front. Can't see this being the problem as the other rear rebounds nicely. As a bodge fix would building this side with 50wt even them out for now or would that be a bad idea?

 

[KnowAir]

I bought it 2nd hand.

Opened it up again this morning to make sure oil level was full and it was. No noticeable leak overnight. Didn't strip it down fully but changed the bladder and topped off again. Wondered if the hard springs I had changed to were uneven so changed back to the standard and it's still the same. Piston looked ok but could be worn around the outside I guess.

Once rebuilt it rebounds just a small amount like the other side without the spring on.

Possibly time for a new set of pistons

I rebuilt with 45wt in the back and 50wt in the front. Can't see this being the problem as the other rear rebounds nicely. As a bodge fix would building this side with 50wt even them out for now or would that be a bad idea?

It might even out with different fluid but, do the pistons first, maybe even the o ring seals too.
Sometimes the pistons warp or swell.. sounds crazy but I have a situation going on with a set of Losi Tenacity shocks I use on my Traxxas Hoss..
They fit perfectly, worked great for over a year, then suddenly one rear shock started binding up. Definitely not a bent shaft, dented shock body.. looks perfect inside and out. It only does it sometimes I'm convinced the piston swelled or warped. Sad part is, Losi only sells a complete rebuild kit for all 4 shocks.. I really just need a piston? Why buy all that? Heck, I'd even swing for 4 pistons but, not every piece for all 4 shocks. They even include plastic preload spacers? Cool right? The shocks have threaded bodies!? They don't even use spring spacers?

 

[Jeffwazz]

Also check that the piston is still in one piece - I tend to break mine

 

[Dex_79]

Had it out for a bash about with the kids today. Can't say you notice it in that situation at least.
Will order some hd pistons though and change them all out.

Only casualty today was the typhon 3s which I've truggified. The screw that holds the metal end of a rear drive shaft behind the u joint backed out so lost a wheel. Thought it was a bad 1 as it bounced away but 10 mins later once we got home and it's ready to rip again!
This thing a backflip demon with the muraco wheels on it!

 

[KnowAir]

Had it out for a bash about with the kids today. Can't say you notice it in that situation at least.
Will order some hd pistons though and change them all out.

Only casualty today was the typhon 3s which I've truggified. The screw that holds the metal end of a rear drive shaft behind the u joint backed out so lost a wheel. Thought it was a bad 1 as it bounced away but 10 mins later once we got home and it's ready to rip again!
This thing a backflip demon with the muraco wheels on it! View attachment 4266

That's awesome that you have the kids involved!! I tried about 12 years ago but girls don't generally care for these kinds of things. Was fun for about a month, then she was over it.

Our babies have left the nest. 29 and 24 years old now..

 

[Dex_79]

The typhon was a 6th birthday gift for our youngest . When I said RC car don't think the wife pictured quite what I ment . Needed to stick to wide open spaces to be safe to begin with. It's amazing how quickly he has got up to speed with it though. Wouldn't trust him near people all the same.

 

[Horatio]

1 of the rear shocks on my muraco was rebounding way faster than the other.
I gave all 4 an oil change and both rear shocks oil was very silvery in colour, the fronts was clear still.

After rebuilding the same shock is still rebounding noticeably faster than the rest.
Any ideas as to which part is likely the culprit causing this?

Thanks

Assuming no broken pistons, bladders or other parts:

Remove the pair of rear shocks. Remove the springs. Now compare the bound and rebound of the shafts in the shocks. Push the shafts all the way up into the shock body. Does one of them start to rebound all by itself?

If it does, it could mean you have more air in that shock. Refill it with oil, work the bubbles out of it by moving the shaft up and down with the shock cap off. Leave the the shock upright for an hour with the shaft at the bottom. Put a little oil into the cap, ready for when you attach it to the shock body.

With the shock in your hand (with an absorbant rag), when you attach the cap, don't fully tighten it until you've bled the shock by pushing the shaft slowly up into the shock body - don't let go of the shaft or allow the shaft back down - otherwise this will introduce more air until the cap is fully tightened. Listen carefully to any air/oil that escapes. Tighten the cap. Now move the shaft up and down.

Now do this for the good shock.

Compare the action now.

If there's still a difference, you need to replace the shocks or buy a rebuild kit.

 

[hobo]

I have a shock like that on my old v3 talion I have rebuilt it a few times and changed the piston and the orings still acts as though there's no oil in there the only thing I can think next is a new shock body

 

[Dex_79]

I have a shock like that on my old v3 talion I have rebuilt it a few times and changed the piston and the orings still acts as though there's no oil in there the only thing I can think next is a new shock body

Quickly becomes just as cheap to buy a pair from a breaker then lots of spares

 

[Horatio]

I have a shock like that on my old v3 talion I have rebuilt it a few times and changed the piston and the orings still acts as though there's no oil in there the only thing I can think next is a new shock body

If the shock oil comes out with silvery grey/metal particles, something, somehow is eating away at the shock body internal surface and the oil is blowing by the piston.

It's difficult to see how a nylon piston could wear a shock body, because on paper, the shock body is harder than the piston.

Pistons, if they wear from multiple severe impacts, can definitely work incorrectly. The precision holes - and the number of them in the piston - don't really matter if the piston is cracked and/or worn and oil is just passing the piston and it's fancy valving by.

 

[KnowAir]

If the shock oil comes out with silvery grey/metal particles, something, somehow is eating away at the shock body internal surface and the oil is blowing by the piston.

It's difficult to see how a nylon piston could wear a shock body, because on paper, the shock body is harder than the piston.

Pistons, if they wear from multiple severe impacts, can definitely work incorrectly. The precision holes - and the number of them in the piston - don't really matter if the piston is cracked and/or worn and oil is just passing the piston and it's fancy valving by.

Soo.. it's not normal to be emptying "grey matter" from my shocks when I want to change fluid weights?
I don't change fluids unless I'm tuning, repairing or "it leaked out"
I have to admit, I empty grey matter from my shocks most of the time..

After all, they are bashers if I were an avid racer I'd be more likely to keep up with such things. ✌

 

[Horatio]

I think

Soo.. it's not normal to be emptying "grey matter" from my shocks when I want to change fluid weights?
I don't change fluids unless I'm tuning, repairing or "it leaked out"
I have to admit, I empty grey matter from my shocks most of the time..

After all, they are bashers if I were an avid racer I'd be more likely to keep up with such things. ✌

Yes, I hear you.

I think shock fluid as it gets old and grimey can tend to go grey, but if it has metallic coloured debris, it means there are metal shavings in the oil.

A bit like 'that lawn mower' that has had the same oil in it for the past 7 years....

If it's not affecting what you do, no worries. For the avoidance of doubt, my post was specifically in response to the mystery the OP referred to in this thread. Not that we should all start keeping a colour log on our shock fluids!

To put this in super serious, technical terms, this will only be of interest to those that are unhappy with one corner of their rig being 'boingier' than the others....

Whilst I don't race much any more, I still like my rigs to be mechanically on point. Mint. Just right. Even my bashers, drones, aircraft and gliders.

It's just the way I like doing anything RC. It's probably a form of OCD.

I think I caught it from my wife.....

 

[KnowAir]

I think

Yes, I hear you.

I think shock fluid as it gets old and grimey can tend to go grey, but if it has metallic coloured debris, it means there are metal shavings in the oil.

A bit like 'that lawn mower' that has had the same oil in it for the past 7 years....

If it's not affecting what you do, no worries. For the avoidance of doubt, my post was specifically in response to the mystery the OP referred to in this thread. Not that we should all start keeping a colour log on our shock fluids!

To put this in super serious, technical terms, this will only be of interest to those that are unhappy with one corner of their rig being 'boingier' than the others....

Whilst I don't race much any more, I still like my rigs to be mechanically on point. Mint. Just right. Even my bashers, drones, aircraft and gliders.

It's just the way I like doing anything RC. It's probably a form of OCD.

I think I caught it from my wife.....

I think my lawn mower isn't "due" for a few more years..
I hear ya. Routine maintenance is the key to consistent and peak performance no doubt. Between lazy and..well just plain lazy I don't have a routine maintenance procedure. LOL
Thankfully I write OCI info in my wifes car owners manual, otherwise who knows.. my rickshaw daily driver has an idiot(me) minder to tell me when it's due..
One thing I don't suffer from is OCD.. plenty of suffering, just not that!!

 

[Horatio]

I think my lawn mower isn't "due" for a few more years..
I hear ya. Routine maintenance is the key to consistent and peak performance no doubt. Between lazy and..well just plain lazy I don't have a routine maintenance procedure. LOL
Thankfully I write OCI info in my wifes car owners manual, otherwise who knows.. my rickshaw daily driver has an idiot(me) minder to tell me when it's due..
One thing I don't suffer from is OCD.. plenty of suffering, just not that!!

If you and I weren't on different sides of the Atlantic, we'd definitely be good drinking buddies.

We might even get to do some RC.