Rear bounces too much

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Paulie

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I'm really loving my Kraton!
I put in the Tekno orange springs and the front end stays pretty well planted, but I'm getting a lot of rear end bounce. It just doesn't want to stay planted. The terrain is mostly crusty snow and ice.
What do you folks think I should do to tune up the rear? Softer spring? Different shock oil?
 

Kauaiguy

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I'm really loving my Kraton!
I put in the Tekno orange springs and the front end stays pretty well planted, but I'm getting a lot of rear end bounce. It just doesn't want to stay planted. The terrain is mostly crusty snow and ice.
What do you folks think I should do to tune up the rear? Softer spring? Different shock oil?
Shock oil,use 60 or 70wt
 
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Paulie

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While I wait for shock oil in the mail, I'm going to change the hole settings on my shock tower and see what effects that has.
 

dpricenator

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I was just reading on pre-load and it's effects on the ride of a car. I ended up on a Lexus forum where someone said the following
"bouncy is really when the springs are stiff and the loads are high enough to compress the springs but the dampers are not strong enough to control the oscillations of the springs after they get compressed." This pretty much backs up the thoughts that thicker shock oil will help solve the problem. The thicker oil will help control the speed the shock will rebound after it's compressed.

Pretty sure we just said that thicker shock oil will help solve the issue. You can also play with the preload, but I usually just adjust it until my Arms are level to the ground.
 
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Paulie

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my big rock bounces also what else can be done to adjustment I'm not a shock builder
I changed the rear shock position on my tower to the lowest/inner most position. I will say that it has improved the rear end bounce tremendously on the high speed runs over crusty snow. I haven't tried any big jumps to see how that fares.
 
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Paulie

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Following up on this. I'm liking my new tuning, but as always, still working on things.

I rebuilt my shocks with https://www.amainhobbies.com/xray-delrin-v3-shock-piston-set-6x1.2-1.3-1.4mm-6-xra358033/p227265. I read in another forum that the stock Kraton shocks are 6 hole, 1.4mm. I used 80wt in front and 70wt in the rear shocks, but the rear kept bouncing still. I then changed the Tekno orange spring in the rear to a Tekno yellow. I figured I was getting too much rebound. I build my shocks dead with no rebound. Center mounting hole on each tower. I still feel like I could use a bit more dampening in front. Next time I rebuild, I will use a shock piston with smaller holes.
 

schoeds

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Following up on this. I'm liking my new tuning, but as always, still working on things.

I rebuilt my shocks with https://www.amainhobbies.com/xray-delrin-v3-shock-piston-set-6x1.2-1.3-1.4mm-6-xra358033/p227265. I read in another forum that the stock Kraton shocks are 6 hole, 1.4mm. I used 80wt in front and 70wt in the rear shocks, but the rear kept bouncing still. I then changed the Tekno orange spring in the rear to a Tekno yellow. I figured I was getting too much rebound. I build my shocks dead with no rebound. Center mounting hole on each tower. I still feel like I could use a bit more dampening in front. Next time I rebuild, I will use a shock piston with smaller holes.
I know, old post...

I suspect when you say "bouncy", you're not talking about rebound, you're talking about pack. I run a very similar setup, in fact the Delrin piston mod is originally mine, and I know for a fact the the rebound with 70-80wt is slower than a snail. Terrible for rough terrain, only good for softening mega air jumps.

Basically, your suspension isn't "working", so the bumps are kicking the truck into the air instead of being supple and soaking them up. You might as well have them filled with cement. Now, I'm not knocking this setup, as I run it stiff myself, but you're going the wrong direction to fix what's not working for you. This is why all race truggies run fluid in the 30wt-50wt range, to keep the tires in contact with the ground.

Now if you switch to a much lighter wt fluid without using softer springs, then you might get a nasty rebound. A real easy way to test rebound is to just drop the truck on the ground, high enough to make it bottom out. Does it bounce off the ground when it comes back up, or does it gently return to ride height? That's rebound....
 
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504_KRATON

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Following up on this. I'm liking my new tuning, but as always, still working on things.

I rebuilt my shocks with https://www.amainhobbies.com/xray-delrin-v3-shock-piston-set-6x1.2-1.3-1.4mm-6-xra358033/p227265. I read in another forum that the stock Kraton shocks are 6 hole, 1.4mm. I used 80wt in front and 70wt in the rear shocks, but the rear kept bouncing still. I then changed the Tekno orange spring in the rear to a Tekno yellow. I figured I was getting too much rebound. I build my shocks dead with no rebound. Center mounting hole on each tower. I still feel like I could use a bit more dampening in front. Next time I rebuild, I will use a shock piston with smaller holes.
I ran 70wt in all 4 and the back is still bouncy and a little too stiff for me. The 70 in the front is not viscous enough. I just ordered 100 wt for the front and 50 for the back. Ill report when I run it again. I will also be changing to a lower spring rate on rear coils and higher in font.
 
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Paulie

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I know, old post...

I suspect when you say "bouncy", you're not talking about rebound, you're talking about pack. I run a very similar setup, in fact the Delrin piston mod is originally mine, and I know for a fact the the rebound with 70-80wt is slower than a snail. Terrible for rough terrain, only good for softening mega air jumps.

Basically, your suspension isn't "working", so the bumps are kicking the truck into the air instead of being supple and soaking them up. You might as well have them filled with cement. Now, I'm not knocking this setup, as I run it stiff myself, but you're going the wrong direction to fix what's not working for you. This is why all race truggies run fluid in the 30wt-50wt range, to keep the tires in contact with the ground.

Now if you switch to a much lighter wt fluid without using softer springs, then you might get a nasty rebound. A real easy way to test rebound is to just drop the truck on the ground, high enough to make it bottom out. Does it bounce off the ground when it comes back up, or does it gently return to ride height? That's rebound....
I was talking about rebound. I put the stiffer springs on the stock shocks originally and the car was bouncing too much.
 

504_KRATON

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I was talking about rebound. I put the stiffer springs on the stock shocks originally and the car was bouncing too much.
Okay, thanks for that clarification. My understanding of springs and shocks are as follows. Very generally speaking, Spring rate supports the load, and shocks buffer spring oscillations resulting from compression/extension forces.
So, I want a soft rear and stiff front configuration. What would the 'seasoned' rc guy select.

Thanks,
504_K
 
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Paulie

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Okay, thanks for that clarification. My understanding of springs and shocks are as follows. Very generally speaking, Spring rate supports the load, and shocks buffer spring oscillations resulting from compression/extension forces.
So, I want a soft rear and stiff front configuration. What would the 'seasoned' rc guy select.

Thanks,
504_K

Your understanding is correct. It's like driving a 1 ton truck and 1/2 truck on the same back road. The 1 ton will bounce like crazy due to it's stiff spring rate and light load vs the 1/2 ton. But when you have a loaded 1 ton, the spring rate and load are a better balance.
I'm not seasoned by any means and my customization is still in progress. This is all subject of course, but I use the Tekno Orange in front and the Yellow in back. My battery is 570g. That would be the loaded weight with the addition of the weight of the RC car. I have been liking the way it has handled the jumps and terrain I ride on. Next, I will start to tune the shocks a bit better, but for me, the finding the right springs have made the most notable and easiest tuning.
I just cracked the shock tower off my rear diff, so I'm out for a bit on the bashing fun.
 

slpcrf450x

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You can have 2 situations that cause a similar bounce. Stiff spring with too thin fluid will cause the rebound bounce because the fluid does not provide enough resistance as the spring returns the shock outward. @schoeds was also correct with his explanation that too thick of fluid will cause bounce as well but in a different manner. If the fluid is so thick that it doesn't absorb enough of the rough terrain and transfer the energy to the chassis instead. You can also see some of this if the fluid is fairly thick and the spring is holding the suspension at the top of its travel. I ran into this a little bit with my Outcast. Softening the preload in the rear and allowing it to have a bit of sag helped dramatically.
By the way I am running tekno oranges on all 4 corners.
 
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ondaedg

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Want to rekindle this thread. I find that the rebound of these shocks is very slow even with Tekno springs. Will cause you to drift through a turn if you hit even the slightest bump because the wheels take so long to return to the ground. Anyone have any mods or piston/fluid setups that improve rebound while maintaining shock absorption over jumps?
 

nulli

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Want to rekindle this thread. I find that the rebound of these shocks is very slow even with Tekno springs. Will cause you to drift through a turn if you hit even the slightest bump because the wheels take so long to return to the ground. Anyone have any mods or piston/fluid setups that improve rebound while maintaining shock absorption over jumps?
Do the shafts move easily without springs? Might be a bent, swelled O-rings, raptured/swelled bladder, air......
 

dpricenator

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If the shafts move easily off the car, then possibly thin out the fluid in the shocks. I believe I am running 70 up front and 60 I the rear.
 

ondaedg

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Do the shafts move easily without springs? Might be a bent, swelled O-rings, raptured/swelled bladder, air......
I don't have any issue compressing the shocks. Nice and smooth. I'm going to tighten the shock collars down a bit to see if that helps. Would still be interested in hearing ideas on different piston/fluids they may be running.
 
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