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2 stage pistons...Do they work?

2 stage pistons...Do they work?

Old 11-22-2011, 08:45 AM
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Originally Posted by mattnin View Post
I am not the one who made that assumption symmetricon.

You may be right, RC shocks might require faster rebound than bump but I'm not so sure about that
Warning: Possibility of in-cohesive rambling ahead. You have now been appropriately warned.

I've been occasionally skimming this thread since it started and was convinced I'd stay out of this latest scuffle. Oh, well...

Since everyone else is throwing in credentials along with their opinions and thoughts I'll start there. As I sit here on lunch break I would need a half dozen hands to count the springs, swaybars, and shocks that lay around within 5 yards of me (verifying a swaybar at the moment for a 2013 Chrysler sedan). I've ridden dirt bikes since I was 7 and snowmobiles since I was 5 all the while helping my father who runs a side business out of the garage tuning and rebuilding shocks the local powersports dealer as well as travelling for a year or two tuning shocks for one of the Ski-Doo racing teams in Snowcross and winter x-games. Now my wife has to deal with this gear-head that can't leave well enough alone. lol

Now to my 2 pence. Everyone is right, just not in the right areas for some.

Mattnin, most of the stuff you have posted has either come from an oval or street car shock tuning manual. As a general rule, the smoother the surface the higher the rebound to compression ratio will be, so onroad and oval should have more rebound damping as you have stated and shown graphs for. It has been mentioned that for pressurized shocks you need to increase rebound damping to balance the shocks natural tendency to extend. This is a VERY large influence especially on lighter rigs like dirtbikes, snomobiles, and atv's.

I really wish you luck testing upside down dual stage pistons, but using examples from completely different forms of racing (not even including scale) and labeling them as truth for all when you admit you aren't an expert/engineer in the shock tuning realm is what really rubs myself (and I assume others) the wrong way.

Another thing that has been completely skipped over (as far as I can tell) is high speed damping vs low speed damping in full size. This is another reason why the pistons you've shown have rather low compression damping as this is strictly the piston you are looking at, not the complete shock. Low speed damping takes care of most weight transfer and rolling bumps while high speed greatly increases compression damping when hitting the face of jumps and other high impact instances like whoops where you don't want the chassis to bottom out and kick the vehicle completely off the surface of the track.

While these focus more on bump and jump handling as there is no left/right transfer on a bike, here are some examples I am personally very well versed on:

Shock tuning for a standard trail riding snowmobile or dirt bike is completely different from that same vehicle being raced in snowcross or supercross and is the closest resemblance you will find anywhere to offroad RC racing. My ktm200exc for the trail has pretty close rebound and damping ratios. Without actually measuring them I'd say its close to 1.2:1 compression:rebound. This is more on the aggressive side for single track riding and while my wrists would probably appreciate less shock when hitting a stone or root, it makes it much easier to power through whoop sections. Other 'less agressive' brands are probably along the lines of 1:1 or less. Now take a dirtbike meant for a supercross track and you approach or go over 2:1 on the compression/rebound ratio (not including high speed vs low speed damping).

My favorite example for shock ratios has to be Blair Morgan (may he recover as much as possible from his spinal injury). He ran almost NO rebound damping so that he could spring from jump to jump and triple through rhythm sections on snowcross tracks most could only double double through. Both he and Tucker Hibbert used this to dominate most snowcross events.

Now that I'm done typing I have no urge to see if any of that makes sense, so glean from it what you may...
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Old 11-22-2011, 09:51 AM
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Thank you Krio, all good points!

Matt do me a favor and move on from the quoting and such pointed at me. i dont mind you posting information but i have not said anything towards you since i said i would stop. lets move on and agree to disagree ok?

As i get older i realize that you have to accept people for who and the type of person they are. on the internet is is difficult to do that because everyone is so quick to point fingers and in general very rude. i was born in the 70's and have seen the evolution over the years and in reality it is sad. half of the things that people say to me on the internet would never happen face to face, and that is generally why i say what i say because i fear no one or anything (with exception to my wife) and would repeat anything i say to anyone at anytime (PM sym and sour and ask them what i do on a daily basis!!).

Matt i expect a very thorough report on your findings when you start tuning!
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Old 11-22-2011, 09:58 AM
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Originally Posted by Krio View Post
Mattnin, most of the stuff you have posted has either come from an oval or street car shock tuning manual.
My last two examples have been from 1:1 motorcycle racing shocks and 1:1 buggy and baja truck shocks though.

The motorcycle shock needed about 1.5:1 rebound/bump damping. The baja truck needed 3.9:1. So it does appear that the lighter the vehicle is, the closer the ratio needs to be.

I also don't claim to be right concerning these RC shocks. As matter of fact, at best I am usually only 50/50 right on everything I do which is pretty poor. I don't know if our RC cars need more rebound shaft rate than bump and I have never said that in any of my posts. I do know that the only examples I have been able to find where rebound is faster than bump in 1:1 scale is in the front drag race strut, and in 1/10 scale using tapered pistons, RPM pistons, and the RCSHOX designed pistons. I haven't been able to find any other shocks with less rebound damping than bump otherwise. If anyone else can show actual examples with numbers and data of shocks designed with less rebound than bump damping to please post them because that can help not only me, but anyone else who is interested in this type of technical conversation.

Thanks for the vote of encouragement regarding testing the pistons upside down. It feels like searching for a little known secret in racing, whether I am right or wrong.
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Old 11-22-2011, 10:01 AM
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Originally Posted by mattnin View Post

Thanks for the vote of encouragement regarding testing the pistons upside down. It feels like searching for a little known secret in racing, whether I am right or wrong.
thats exactly what leads me to all of my creations..."AN EDGE"
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Old 11-22-2011, 10:52 AM
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double post
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Old 11-22-2011, 10:52 AM
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Originally Posted by mattnin View Post
My last two examples have been from 1:1 motorcycle racing shocks and 1:1 buggy and baja truck shocks though.

The motorcycle shock needed about 1.5:1 rebound/bump damping. The baja truck needed 3.9:1. So it does appear that the lighter the vehicle is, the closer the ratio needs to be.

Thanks for the vote of encouragement regarding testing the pistons upside down. It feels like searching for a little known secret in racing, whether I am right or wrong.
That motorcycle was an street bike from what I could tell, and my defense on the baja trucks are that they don't have to take any jumps, but strictly deal with sharp stutter bumps and cornering.

I'll try to find some graphs for supercross, etc as I personally think they are the best and possibly only comparison in full scale auto racing when it comes to RC cars and similar track types.

Here's another way to look at it:
When you need to stop the chassis from moving (landing a jump) you need stiffer compression than if you are stopping the tire from moving (stutter bumps). While the displacement of the tire relative to the chassis may be the same when landing from a jump and hitting a large step, the force required to keep the chassis stable is completely different. Lets say you are on level ground and hit a log in baja. The relative velocity of the chassis to the ground is 0 and you want as little of that force transferred to the chassis as possible. Low compression takes care of this and assuming the chassis is high enough to clear said obstacle you are good to go. When landing from "X" feet in the air the relative velocity of the ground to the chassis is not zero, so you need to transfer a lot more force to the chassis to get that relative velocity back to zero without bottoming out.

On most rc tracks there are tons of jumps most tracks have gone to high clay contents and are a pretty smooth surface. For RC there are always jumps so most damping with standard pistons deals with landing and cornering with little emphasis on stutter bump/whoop handling. Having dual stage pistons (face up) gives you all the jump landing damping you need while giving up a little on initial chassis roll entering a corner and splitting whoops 50/50 as ideally you want less damping in both directions, but at the very least you are keeping the tires in contact with the ground more with the quicker rebound. Is it perfect? No. Is it a better compromise than giving up jump landing (that all tracks need) to obtaining a more stable car through bumps (that most tracks don't have)? I think so and it's just my guess that while you will handle whoops better than dual stage upright and standard pistons you will give up too much on jump landings to make up the difference. Go back 20 years to when tracks had like no jumps and where whooped out loamy places and it would probably be the completely opposite scenario and "upside-down" dual stage pistons would probably be dialed.

Last edited by Krio; 11-22-2011 at 11:20 AM.
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Old 11-22-2011, 03:01 PM
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Originally Posted by MantisWorx View Post
you guys are forgetting one MAJOR issue and that is spring force. on a 3500lb truck with springs that relate to over 1000lbs of force of course you will need more damping on the rebound to compensate for that, our tenth scale springs are nowhere near that type of force therefore, it simply is not the same our springs do not "Spring back" near as quick or with as much force as a 1:1 car. and most of the 1:1 cars use progressive springs and valving that also controls the fluid rates on the inside, we dont have that luxury.divide everything by 10 and see what happens. and once again guys try them first and THEN come back and comment, right now you are all just quoting paragraphs with no real experience. i have actually tried it during testing and it simply doesnt work as well as quicker rebound and this holds true even to this day. i am currently tuning my dex210, there is a washboard section on the back corner and with my 4 hole 1.1/1.2 20wt combo in the rear it keeps bucking the rear up and is not stable at all where as on my SC i can literally punch through it and gain positions over anyone who is not running the pistons. so i opened up the lower holes to 1.3 went down to 17.5 fluid and it now floats through like its supposed to! so in effect what did i do, i quicken up both but i quicken up the rebound more. i will say that yes if your rebound is too fast it can definately be counter productive there is no argument there. if you look at the video on my homepage there is a shot of the buggy going down the straight from the rear, it actually has too much rebound.
http://www.youtube.com/user/Mantiswo.../4/vGop6ZpNMQ8
there is another shot of the car coming straight towards you and on that shot i slowed the rebound down via smaller rebound holes and you will notice on that shot the the car floats. so right there we have some proof of what the effects are.
another video on my channel shows a 1.0/1.1 combo
http://www.youtube.com/user/Mantiswo.../3/E3P-0GBUaRs
this was during some prototype testing and these pistons were designed for a smoother track. as you can tell the truck bounces around ALOT it was controllable but with the slower rebound all you see is air under the tires and that means less traction!

on this video the truck weighs more and has 1.1/1.2 holes with looser piston clearances and 25/20 oil as you can tell the truck is much smoother and has much more traction in all aspects. the truck on this video is over a second quicker per lap(1.7 on fast lap) than the other video my avg time was better than the quick time on the other vid.
http://www.youtube.com/user/Mantiswo.../0/MjlWBzWNjkE

so you guys that want to test slower rebound please take some vid its much easier to see whats going on than to just talk about it!
I have a set of your pistons on order, but just an observation to note. The third video difference in time may be more than just the shocks working though. The track appears to have more moisture in it.
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Old 11-23-2011, 11:31 AM
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Originally Posted by Krio View Post
I'll try to find some graphs for supercross, etc as I personally think they are the best and possibly only comparison in full scale auto racing when it comes to RC cars and similar track types.
I found a few shock dyno results.

Here is a trail riding bike XR 600 SM http://www.xrv.org.uk/forums/xr/7368...m-build-3.html


Here is an MTX dirt bike shock. http://www.dirtrider.net/forums3/sho...highlight=dyno



Here is a Fox Racing Evol ATV Shock http://www.maultechatv.com/techguide...Work/index.htm
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Old 11-23-2011, 01:25 PM
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Originally Posted by jmackani View Post
I have a set of your pistons on order, but just an observation to note. The third video difference in time may be more than just the shocks working though. The track appears to have more moisture in it.
not moisture but the track was raced on two days before on the newer vid, so there was less dust and more of a groove, same obstacles and rough track as it always is!
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Old 11-23-2011, 01:28 PM
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Matt, as said before, you're trying to compare 1:1 scale vehicles against our little 1/10 and 1/8 scale rcs. Our shocks are no where nearly as intricate as some of these race shocks of which you keep posting sheets from. Our shocks don't have are simple and trying to compare them is like posting a ferrari to a hot wheels car. that's the point that is trying to be made, so therefor you can't expect a 1:1 shock to work the same as a 1:10 or 1:8 scale when the components are totally different.
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Old 11-25-2011, 01:13 PM
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Originally Posted by MantisWorx View Post
Just finished building my 210¡ Im starting with 20/20 using the new sc spec, it feels good will start testing tomorrow aling with the garodisc. Im also running mm4, I thunk I can get it to work. Its a very well built and engineeres car, best ball diff I have ever built!
I've driven my 210 with your pistons for a while now. I've had Ass 25/20, but now decided to try 35/30. Handling and jumping is great, but the pack on landings is not enough.

A tip for you Mantis. Buy the shorter 52mm rear shock shafts, then you have no problems with the pistons hitting the caps. All you need is the stock rubber stops on the shafts. It does not effect the droop.
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Old 11-25-2011, 07:09 PM
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Originally Posted by HansÖ View Post
I've driven my 210 with your pistons for a while now. I've had Ass 25/20, but now decided to try 35/30. Handling and jumping is great, but the pack on landings is not enough.

A tip for you Mantis. Buy the shorter 52mm rear shock shafts, then you have no problems with the pistons hitting the caps. All you need is the stock rubber stops on the shafts. It does not effect the droop.

do you have the 4 hole or 6 hole? i finally got an entire day of running the car with 4 holes and ended up with 1.3/1.4 front with 17.5 wt and 1.3/1.4 15wt rear. plenty of pack and it never chassis slaps on any jump, very responsive, i like the car alot. except the damn clip came loose inside the dif.....
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Old 11-27-2011, 04:58 PM
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Originally Posted by MantisWorx View Post
do you have the 4 hole or 6 hole? i finally got an entire day of running the car with 4 holes and ended up with 1.3/1.4 front with 17.5 wt and 1.3/1.4 15wt rear. plenty of pack and it never chassis slaps on any jump, very responsive, i like the car alot. except the damn clip came loose inside the dif.....
6 hole. I didn't know you have different ones.
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Old 11-27-2011, 05:06 PM
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Originally Posted by MantisWorx View Post
do you have the 4 hole or 6 hole? i finally got an entire day of running the car with 4 holes and ended up with 1.3/1.4 front with 17.5 wt and 1.3/1.4 15wt rear. plenty of pack and it never chassis slaps on any jump, very responsive, i like the car alot. except the damn clip came loose inside the dif.....
On what car are you reffering to. I have never seen anyone run oil that "thin". Is it normal to run a lower weight oil using these pistons?
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Old 11-27-2011, 07:14 PM
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Originally Posted by HansÖ View Post
6 hole. I didn't know you have different ones.
the Durango SC spec pistons are 4 hole, i made them due to the request from a few team drivers. i think the 6 hole will be better in the rear and will test this week. for the indoor crowd they like the 4 hole better.

Ryno, you generally run as light as you can get away with. normally under 30 in most cases.
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