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Discussion Starter #1
Well I have been working on a design for a buggy with portals. I keep getting stuck on the suspension. The buggy must be at or under 6' tall with 40s on mog9s. How much uptravel do you think a rockcrawler and extreme use rig should have. I want to be able to do just baout anything with the buggy.

So how much suspension uptravel is enough? How are most buggys set up? How about desert trucks?

Thanks for the info...
 

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Up travel and down travel are generally just as important.

for desert racing more uptravel is nessasary bacause they need to be able to absorb big bumps

ex: i put a coil spacer lift on my tacoma and i can drive through dips and over speed bumps and whoops a lot faster without bottoming.

the same is not true however for rockcrawling. the downtravel keeps your rig stable at the lower speeds so it is important to have.

if you want all around performance (high speed and low speed) ask GOAT1 what his ratios are (uptravel/downtravel). From what i have heard and seen it domintaes every where (high speed and crawling).
 

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Uptravel and down travel are equally important, If you get an equal ration, you can actually set the truck up so that your CG will lower relative to the axle, or stay the same. If you have all down travel, you will increase your CG under hight articulation, and if you are all uptravel, your CG will lower. This will apply in most suspension geo. but is very dependant on spring rates, and how well you can balance the trucks suspension. You will also need to know things like if you want to build the truck for climbing, descending, or fairly level ground, as well as high speed and crawling.

So what do you want to do.I assume you want a well rounded truck, but that is up to you. If you do not want to change springs etc, for trail types, you should go with a static level ground setup, and then choose your spring rates acording to you desire for high speed or crawling. You need to be honest with yourself here, or you will not get max ability out of your truck. Come up with a percentage of use for the truck, and base it off that.

IE
Rock crawling %
High speed (bajaish) %
High speed (rocks) %
Trails with climbs (extreme) %
Trails with descents (extreme) %
Dare i say it, MUD %

this should give you an idea of what you need
 

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Discussion Starter #5
Well I will throw some more info in on this one for puff dragon....

IE
Rock crawling %

-Most likely the biggest thing. I would say over 50% there. If I am going to build this buggy I want it to keep up for at least a few years. With the sport changing so much I know this is hard. I also want to have a suspension that will handle a rock crawl comp if I decide to go that way.

High speed (bajaish) %

-I find myself doing this more than I should :D I would say this is a big part too. I like being able to run to and from the trails at a greater rate of speed than normal. I would say 25%

High speed (rocks) %

-I don't really do this...yet. I find myself thinking that a lot of climbs at the comps require a little bump and momentum.

Trails with climbs (extreme) %

-I think that I mentioned this above.....I don't really know what percentage though.

Trails with descents (extreme) %

-Same as above.

Dare i say it, MUD %

-Very very little! But I do run a lot of snow....

So far I am trying to use a 16" travel coilover or ORI strut. I want to get at least 6" uptravel. Do you think that this will be enough or should I push for 8". I am also planning on running air bumpstops if I use coilovers to help with the higher speed stuff.

Wheelbase is going to be 101"

The link configuration for the front suspension is also giving me fits. I am leaning toward running an inverted wishbone on the bottom and upper links outside the frame on top. The wishbone will attach at two points at the frame, and one point at the axle. That link will be on the bottom. I am leaning toward doing this so that I can get more uptravel from the wishbone. If I do it the regular way the motor really starts to get in the way.

Its only on paper right now though so I can change it.
 

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Take a look over at my thread in the Mercedes Forum on my link buildup which is still in progress and should be buttoned up next weekend. http://www.pirate4x4.com/forum/showthread.php?s=&threadid=110032 Also more pics can be found at my project link in my sig.

I am building mine with very little uptravel as I plan to do mostly rockcrawling and climbs. I would say it has about 2-3" pure uptravel, but will have more as far as articulation goes. I also plan on possibly an airbag or hydro setup to raise the ride height of the rig for when I highcenter it.

I do hear what you are saying about front links with a portal axle. If drawings are giving you fits, wait until you start building ;)
 

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So cruiserrg, you feel uptravel should be limited for rock crawling. I find the trucks with little uptravel tend to be very tippy in the rocks. My opinion is that you should be about 50/50 on the rocks. case in point, your off camber, and you start to climb a rock with your front left tire. As you start to compress that front left tire, half way up, you fully compress the front left suspension, from this point the body will roll drastically, more than it should, untill you reach full droop on the right side at which point, the truck will either lift a tire, roll over, or force to rear suspension to take up the slack for the front. All this time, your CG is getting higher and higher. Now in an ideal situation as I see it, your front left would reach full compression almost at the exact time your droop side maxes out. This gives you a neautral CG, and keeps the truck stable. This can be done with spring rates instead of travel, but will lead to heavy rate springs that are not favorable to rock crawling. Your travel and spring rates are very critical, to make the truck perform at peak performance in the situation it was designed for, and should be directly affected by each other, meaning, that the spring rate is calculated using the uptravel required for the application as well as a few other factors. One up side to very little uptravel, is that you can maintain alot of height from the body of the vehicle to the rocks, this may be desirable in some situations, but I would think it would be better for MUD, to keep the frame and junk out of the mud to decrease potential snow plowing of mud and water. Anyways, there are alot of factors, and I dont claim to have the correct answers, but I pay alot of attention to vehicle setups, and how they perform on extreme trails, as well as alot of testing of different setups on my own trucks, so i feel i have a good grasp of what does what.

FLAME AWAY
 

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Yes droop can happen when the other side is on the bump stop, but it will increase your CG. Again, there are alot of factors, but even 40/60 would be a good number, and maybe 30/70, but anything less is not desireable in my opinion on the rocks. It sounds like cruiserrg is at around 16/84 or so, based on a 16" of travel, but i would assume he is going for more drop, bringing him to 10/90. But again, just my opinion, and I am not knocking your setup cruiserrg, just making an observation.
 

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Puff,

I agree with your point about the suspension bottoming out going over a rock, but here is where I am building my rig different. In the situation you describe the raising of the CG doesn't happen until the axle hits the bumpstop at the frame or the suspension bottoms out. I am building mine to have direct uptravel (both tires traveling up) to about 2-3", but this will not be where articulation stops. I plan on having center bumpstops at my links where they converge at the axle this is where the 2-3" uptravel will stop. The key is frame bumpstops will be much further up. This should allow for the axle to articulate much further than the 2-3" up travel as the links pivot around the center bumpstops. Hope that make sense.

Now this is all theory until my rig is built, but I believe I will achieve the desired effect with the center bumstops.
 

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Ok cruiserrg That is sorta what i thought you were doing, but I addressed it like you were not, to make a point untill you said some thing, I would say your design is right on. Sounds liek you have thought it out. Actually I jsut finished a cent bump stop setup on a truck today. It has about 7" total compression, but more articualtion travel than you can shake a stick at, that will be maintained by the springs.
 

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Puffdragon said:
Ok cruiserrg That is sorta what i thought you were doing, but I addressed it like you were not, to make a point untill you said some thing, I would say your design is right on. Sounds liek you have thought it out. Actually I jsut finished a cent bump stop setup on a truck today. It has about 7" total compression, but more articualtion travel than you can shake a stick at, that will be maintained by the springs.
Not a problem, as the point needed to be addressed.

Glad to hear your center bumpstop worked, validates what I am designing. It's also is necessary to do on my rig as the link are very close to the engine do to the MOG portals and lowrider chassis. ;)
 

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FWIW, I also used the center bumpstop on the rear of my rig when I put the K5 tank in (rear, between the rails). When I shortened the wheel base and frame, it forced me to have the tank over the rear axle. To keep the axle out of the tank when dropping off a shelf, I built a smallish cross member at the front edge of the tank, with a bumpstop that extends far enough down to stop the axle within about 1" of the tank. That gives me 6" up travel on the axle, but around 10"+ at the frame for articulation. Works great as far as I'm concerned...
 
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