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Thread: Suspension setup help

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Old 08-02-2009, 07:59 PM   #1
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Default Suspension setup help

My setup:
front: stock three link with JSSuper bent lowers, Losi aluminum shocks w/ pen springs for droop and 70 weight oil, 6 oz of weight in CAC delrin NBL, 1.9 rok lox w/ stock foams

rear: 4 link rear w/ JSSuper lower bent links, Losi aluminum shocks w/ pen springs and losi blue coils and 70 weight oil, 3 oz of weight in CAC delrin NBL, 1.9 rok lox w/ stock foams

The problem: Too much torque twist even with 4 link causes it too flip if I try and bump it up and over an obstacle. Any one got any pointers or suggestions?
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Old 08-02-2009, 08:18 PM   #2
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1. Lower your overall COG (Center of Gravity).
  • One of the easiest things to do is lower you battery. In the stock setup it is placed on the chassis and sits pretty high. I moved mine to sit on top of the servo.
  • You used pen springs to limit your ride hight which is good. I also used pen springs, but switched to fuel tubing. I have my ride hight at about 2". I might go for a little less so that I can side hill better. I found that the pen springs gave way when going up a steep incline. I need the suspension to push the wheels into the ground and not lift at all.
  • Read http://www.rccrawler.com/forum/showthread.php?t=54791. This is a great post on suspension setups. You will be amazed a what tuning your links can do for your ride and performance.
2. Look at a different chassis. I felt that when I went to a skinnier chassis the drive line was more inline with the axle the effects of the torque twist were minimizized. The less bends in you drive line the more power you can get. Both of my axles are angled so that at the default ride hight the drive line is almost straight.

Since I am still learning about suspension I don't have a body on my crawler when I run it. This allows me to see how the various parts of the chassis, linkage, shocks, etc are working while I am driving. This makes it easier for me to spot issues and adjust them.
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Old 08-02-2009, 08:44 PM   #3
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Ok, lets start fromt he beginning.

You have taken a good approach to limiting the articualtion. However, If you are not running a droop setup, then pen springs arent really helping you. While they aren't going to kill you either, the best best idea is going to be some fuel tubing inside the shocks, on the shock shaft. They dont have the give that springs do, they are excellent at limiting suspension travel, and they dont rub the shock shaft which can wear it down and cause your shocks to leak.

Now from there lets move on to your wheels/tires. The very first thing you should do is pull all the weight out of the rear tires. The more weight they have in them the more they are gonna want to pull the truck downward when climbing uphill. Everyone seems to get the idea that COG is a stationary thing. Its not. COG is a variable that depends on how the truck is sitting.

Once you have pulled the weight from the rear end, then its time to relocate some of the other items in that are hurting you. Everyone seems to think the best thing in the world is to throw the battery on top of the servo... Yeah, great idea. Lets take the heaviest item on the whole rig and move it all the way to the front, and keep it up high. Brilliant.
The best thing to do with that battery is to get it as centrally mounted and as low as possible. I would rather mount the battery dead center of the chassis right on top of the tranny than I would put it on the servo.
Where should you put it... Well, that depends on if you have the skills to seperate the pack and move that weight where its usefull. It is true that by putting the battery on top of the servo that it eliminates it from the chassis, thus helping to stop the TT. However if you are able to, then split that thing up and mount 2 cells on each corner of the axle as close to the wheel as you can without interfering. Thats whats best.

Now, you need to relocate those electronics. First flip the tranny/motor. Then mount your ESC to the front 3 link, and your reciever to the rear 4 links.

Once thats done then its time for some fine tuning. 70wt oil is fine and great, however, if it were me I would lower the weight to 60wt on both front and the right rear shock. leaving the 70wt in the left rear.
Then, you need to so some spring adjustment to make that left rear stiffer so that it doesnt flex so easily. So either add pre-load spacers, or crank down the collar.

Thats about as far as you can go at this point. To stop anymore you are gonna need a 4 link up front and a new chassis.


Good luck
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Old 08-03-2009, 05:00 AM   #4
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Thanks guys for the responses. Chassis is a DMG NAT and my battery is 600 mah lipo that sits on the front 3 link. Electronics sit about as low as I can get them with the little room that there is. Fuel tubing seems the way to go I will have to get some.
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Old 08-03-2009, 06:28 AM   #5
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umm, if you already have a decent chassis kit, and have already moved your weight around and you are still having that much torque twist then all I can come up with is either your link geometry is all wrong, or you have one monster motor in that thing.

How bout some pics of your suspension...
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Old 08-03-2009, 10:50 AM   #6
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I have no torque twist with a stock chassis and links. My setup is esc and rx on the trans they weigh nothing. I have my battery pack split and run 3 cells on the front upper links and three on the rear uppers. My front tires all put together weigh about 5oz. and no added weight to rears except the beadlock mod to the stock rims. My opinion is pen springs is the way to go my front shocks have internal pen springs with about 3 coils cut off and blue outer spring they are mounted inboard the chassis and in the stock location on the axel. My rear shocks have the same internal set up but I run the soft silver springs on the out side and they are mounted out board the chassis and outboard the axel mounts. I also run 40 weight oil in both shocks.
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Old 08-03-2009, 05:54 PM   #7
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I am uploading pics now. Links are about 75% the length of the lowers. I made a set that is 70% the length as well. Motor is a HH torquemaster mini
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Old 08-03-2009, 06:26 PM   #8
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Belly height appears to be around 2". If you need specific pics let me know.


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Old 08-03-2009, 06:41 PM   #9
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Are you sure it's torque twist it may be those tires. if you dont have a real soft compound or grip the tires will bounse and cause you to flip. I think those are rc4wd tires and their compound is great for HEavy scalers but for a real light Mrc it would be bad!

Just a thought

The problem: Too much torque twist even with 4 link causes it too flip if I try and bump it up and over an obstacle. Any one got any pointers or suggestions?
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Old 08-03-2009, 07:51 PM   #10
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That was one of my thoughts too. I put losi blue inserts in there but switched back to the original might try going back to losi blues.
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Old 08-03-2009, 07:54 PM   #11
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Looks as if your not comping w/ it cause of the rear steer. So I'd stretch the WB. If your looking to comp this rig. Then I'd start by losing the rear steer. Try mounting your rear shocks so they dont lean towards the center of the chassis. Your shocks the way you have them now is allowing the chassis to lean/roll before they start damping. If they're more perpendicular from the axle then it'll have less tendency to TT.
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Old 08-03-2009, 08:18 PM   #12
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I cant believe I didn't see the rear steer at first but you might also check and see if your at perfect alignment ( front and rear ) a slight offset could cause your rig to flip or act as if you have torque twist. I've run the slat Irons and I am now runing the chisels and would definately suggest the chisels! ( with losi memory foams )
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Old 08-03-2009, 09:16 PM   #13
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O.k. I think I can pretty well see your problem...

1st, you have rear steer, which adds alot of weight to the rear of the vehicle, couple that with ALOT of weight up high and your gonna flip it every time.

All that weight up high is another reason you are getting so much TT. Want it to go away, move some of that weight.

Other than that, it looks as if your tires are really, really full of stiff foam. Which is going to cause alot of problems with traction.

I would suggest switching to some softer foam.
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