Suspension setup questions....

[slaf]

Hi all !

I have few questions about suspension setup, hope you could help me...

1) How do I prevent my trucks from bottoming out. I hold them 3 foot high and drop them and I hear the chassis hittinng the ground.

2) Why when I hit a small jump the rear end go higher than the front end....I'm landing on the front wheels....

3) What effect on the truck if I change oil weight and spring rates ??


Thanks !!!!

[xdamxincx]

Hi all !

I have few questions about suspension setup, hope you could help me...

1) How do I prevent my trucks from bottoming out. I hold them 3 foot high and drop them and I hear the chassis hittinng the ground.

2) Why when I hit a small jump the rear end go higher than the front end....I'm landing on the front wheels....

3) What effect on the truck if I change oil weight and spring rates ??


Thanks !!!!
first off .. for us to make the best suggestion you need to tell us what kind of vehicle u have... as in make/model ... then you need to tell us what is done to the truck other than stock applications....ggg

without knowing what ur vehicle is the only question that can be answered correctly is number 2


you have to much spring pressure in the rear.. either take out a couple shock spring spacers or adjust the shock to where ur A arms are level in the rear....

[Grant Tokumi]

A quote from this thread (http://www.radiocontrolzone.com/forums/showthread.php?t=175643)
I have to respectfully disagree on the "limiting suspension travel to prevent bottoming out". I highly recommend NOT limiting the suspension travel in an effort to prevent bottoming out. If you limit the suspension, all that stress gets transferred internally and you will likely break something like an arm or shock tower. Imagine limiting the movement of your knee to bend no more than 90 degrees, and then jumping off something high. Once your knees lock at the 90 degree position, your knees will probably break. Not a good situation. So let that chassis bottom out.

If you must limit suspension for whatever reason, you can add spacers (fuel line works well) over the exposed portion of the shock shaft so that the shaft can't go all the way in. You still get some shock absorbtion, but once your start dropping the vehicle from tall heights, beware. Even going very fast over a tall speed bump can break things since the fronts will be compressing on impact.

Off jumps, if your front tires are hitting first, there is a good chance you are letting go the throttle too early. You want be on the throttle off the jump. But if you are talking about an abrupt jump like a speed bump in a parking lot, then I don't think there is not much you can do there, other than raise the ride height and/or (yikes!) limit the shock travel. :)

[racer234]

To prevent bottoming out you could bump the shock oil up. Go about 10 wt. heavier than what you have right now.

[slaf]

first off .. for us to make the best suggestion you need to tell us what kind of vehicle u have... as in make/model ... then you need to tell us what is done to the truck other than stock applications....ggg

without knowing what ur vehicle is the only question that can be answered correctly is number 2


you have to much spring pressure in the rear.. either take out a couple shock spring spacers or adjust the shock to where ur A arms are level in the rear....

Forgot to say that I have a MGT !

[xdamxincx]

Forgot to say that I have a MGT !

i would try rebuilding your shocks.. sounds to me like there is no oil in there ... u can try 45wt oil as a baseline...

[rocknbil]

Guys shock oil DOES NOT provide more suspension. It controls the SPEED at which the springs react. If you need to prevent bottoming out, the issue is with your SPRINGS.

1) How do I prevent my trucks from bottoming out.

This requires heavier springs, although a three-foot flat drop is not the same as coming in off a jump of even up to 6 feet. Because of the forward motion, the gravitational force is diffused a little. At any rate, if you're bottoming out on jumps, try heavier springs, but make changes EQUALLY all around, EXCEPT as suggested in #2 below.

2) Why when I hit a small jump the rear end go higher than the front end....I'm landing on the front wheels....

There are two good ways to address this, depending on what is happening. If it's on ALL jumps, see springs/weights below. If it's just on SOME jumps, you need to alter your approach.

Springs/weights: If this is happening on ALL jumps, think about what is actually going on. As you hit the bottom of the jump, your FRONT springs compress. By the time your rear wheels hit the jump and begin to compress, the front ones are "springing" back, lifting the nose a bit. But the front reaches it's apex (top of the "bounce") just about the time the rear springs begin to react, so now the whole vehicle is rotating FORWARD as it takes air. And over you go.

The solution for this is to stiffen up the REAR. Stiffer oil weight will SLOW DOWN the reaction of the rear, slowing down your roll. If this is still not sufficient, go with one step stiffer springs. The only time you'd stiffen the front specifically for a jump is if it's mashing the front suspension so hard the nose of the chassis bottoms out. You WANT the front to spring up, it keeps you level or in a nose-up attitude. Also this affects other things, see #3.

If it's only on SOME jumps: You just need to change your approach. Think about the explanation above, and what is happening. If you roll on some jumps, try this: At the precise second the front wheels hit the bottom of the jump, flick your brake as fast as you can. I mean as FAST AS YOU CAN, brake-throttle in one stab. What this does is dips the nose down prematurely so that as you ascend the hill, the nose stays UP. You may even get too much and roll over backwards, if this happens, give it a tap on the brake while you're in the air.

3) What effect on the truck if I change oil weight and spring rates ??

This is a pretty complex question but the gist is any changes to spring weight and oil weight affect the handling on straights, low speed corners, high speed corners, and the track surface you are on. The idea is to keep ALL FOUR WHEELS on the ground at all times, and distribute the weight as evenly as possible to maximize traction. A few guidelines:

On bumpy tracks, stiffer oils and springs will not conform as well to the track, losing traction. Use lighter springs and oils.

If the truck is "pushing" coming out of corners or high speed corners (that is, doesn't feel like it's steering enough:) Make sure you have a good STRONG servo to hold the corner (89 oz/in or better,) and if that's the case, try slightly heavier springs and oil in the REAR. That's right ,rear. If the rear is too light, it will cause the front end to lift when you get on the gas, reducing front traction!

For low-speed corners, if the truck has too little steering coming into corners or on low speed corners: Coming in, a little drag brake will shift the weight forward and get you more bite (search forum for "drag brake.") For the rest, slightly lighter oil weight up front, if that doesn't work, lighter springs up front. There are also camber/caster/toe-in adjustments you can make.

If you're "skitter" on high speed straights: lighter rear oil and maybe lighter rear springs.

If you are on "three wheels" on ANY corner (rear wheel lifts up) - your fronts are too soft, stiffer springs and oil up front.

If, from a dead stop, the rear end DROPS, this is called "squat." MAny believe this is a good thing and means it's "digging in." Think about it: the weight of the truck is still the same, so how can it be digging in? All that's really happening is it's removing more weight from the front, and is an indcator you are going to lose high-speed steering as mentioned above. If you're squatting more than 1/2 inch, stiffer rear oil and springs will solve it, or some different anti-squat A-arm mounts (I know these are available on AE's, not sure about other models.)

Any change you make to your suspension affects something else, and it always depends on the surface, tires, and most importantly (and often overlooked) how you drive. Like I said it can be pretty complicated. :D

[slaf]

Thanks for this loooonnngggg reply, it's really apprciated :)

[xdamxincx]

Thanks for this loooonnngggg reply, it's really apprciated :)


you know all that info is fine and dandy and all .. but something is goin on with ur shocks.. i asked if ur truck is stock or not u just said u had a MGT... so ur problem is ur shocks.. rebuild them like i said and adjust the rear and front arms to where they are arms level .. see if that helps.. then u can start to use that dictionary of suspension tuning written above by the other members....

so take ur shocks off take them apart check them out .. ur manual should tell u how to rebuild ur shocks.

[slaf]

I think that the problem is more my Proline 40 series tires. They are too hard, don't absurb any bumps.

Anyway, I'll rebuild all 8 shocks with new oil weight. But before I'll do some test with different springs.

Here's a pic of my truck...

[Fantom 15 gt]

Nice! Those wheels/tires realy suite the truck.

[HauntedMyst]

When you want to understand what your chassis/suspension settings do, consider getting the XXX Main TC Chassis Set Up Guide. Its a good resource to have with you and explains why and what changes do on your car. Even though it's written for TC's, the principles carry over to trucks and buggies.

http://www.xxxmain.com/bookz.shtml

[slaf]

Book looks interesting but oriented for touring cars....:(

[HauntedMyst]

Even though it's written for TC's, the principles carry over to trucks and buggies.

reread it again