Mid Short Long arm Wheel Travel Arm length?> - JeepForum.com
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Unread 01-02-2012, 04:16 PM   #1
Timido
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Mid Short Long arm Wheel Travel Arm length?>

Is there an Ideal arm link for certain wheel travel? How much travel am I going to have with a 4" spring?

I remember someone saying 2x the wheel travel. I am running 35" tires 4" lift springs and am going to be installing poly 3link 4 link rear 4" stretch with a 1" skid. I would like to take advantage of as much belly clearance as I can.

Thanks. Tim

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Unread 01-02-2012, 05:09 PM   #2
Scooter402
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Lift springs do not dictate wheel travel. Spring height will, to a point. But there are many more factors in play dictating wheel travel than just arm length and spring height. There is the amount of bind in the suspension as it travels, there is the total length to the spring...the spring rates, the sprung and unsprung weight of the rig. Long story short, yes, long arms will travel more than factory "short" arms. But there are many other things to consider when trying to calculate wheel travel. The easiest way to do it is to disconnect the shocks, remove bump stops, and use either a hoist or ramp to get max travel before any binding, then get shock length/set bump stops from that.
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Unread 01-02-2012, 07:00 PM   #3
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Your #1 constraint will be using standard springs. Run 12" travel shocks unless you want to unload the springs. And as for arm length vs. travel, a "stock" length arm (let's say 17" lowers) can fully utilize 12" travel shocks IF the suspension is setup correctly and you're using appropriate springs. Your most ideal situation is to have the arms as flat as possible at ride height, aka your axle as far back as it's going to travel throughout the suspension cycle at ride height. The more angle you've got at ride height, the more jacking you'll experience during droop. At about 2.5-3" over stock my lowers (17") are at about stock angle (2-3*) at ride height....all with superior clearance and geometry. At full droop with 10" travel shocks, the axle is still visually centered in the wheel well while it's slightly back of center at ride height. I'm also using Poly frame brackets but did it a bit differently in order to retain the best possible clearance, well-knowing that longer arms wouldn't do one thing for me except decrease clearance.
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Unread 01-03-2012, 11:58 AM   #4
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imped for those of us who have done the "poly" front and are moving onto the rear how did you massage the rear mounts exactly? have been debating going poly for the rear or just doing completely on my own. the poly brackets do make some compromises but im not sure id really notice. my front arms are 30" and i considered them mid-arm length. they would, by comparison, seem quite long compared to 17." ive stretched the front 5 inches and have 16" coilovers so to me it seems about right. id be worried, however, of using arms much shorter then this in the rear. sorry op im only hijacking because it might have bearing in this thread topic.
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Unread 01-03-2012, 01:14 PM   #5
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I didn't do a thing to the frame brackets. I just set up the axle brackets at the right width and angle to match the ~25* frame end so that the JJ's were neutral and inline at ride height. With shorter arms like mine, there really aren't any compromises if you're setting it all up from scratch--the clearance is great, the separation is good, you don't experience any tub or frame clearance issues with shorter arms, and as long as you setup the separation at the axle correctly, the squat results will be excellent. I'll likely be using Poly's brackets for my front 3 link and will probably end up with longer arms than I did in the rear--probably ~22" lowers--which will work out great with the 12" travel shocks and 3" springs I use up front. That'll be awhile though because I'd like to push the front out at the same time, which will cost some $$$.
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Unread 01-03-2012, 03:16 PM   #6
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I will have to get a tape measure out and start eyeballing where the link mounts would look right. Your setup looks like the poly mount is about as far back as it can be. Right now I am have a stock 03 shovel hanging below a 1.5" suspension bracket. (total about 6" hanging below the frame) 28" long arms 13" stock upper arms. Imped are your rear shocks outboard or stock location?
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Unread 01-03-2012, 05:13 PM   #7
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Quote:
Originally Posted by Timido View Post
I will have to get a tape measure out and start eyeballing where the link mounts would look right.
Look or work? It's all about what travel you want to be able to use/can potentially use. That determines arm length (to an extent). Unless going to CO's of 14" or more travel, you don't need some long-*** arms.
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Originally Posted by Timido View Post
Your setup looks like the poly mount is about as far back as it can be.
You bet. I wanted those mounts tucked as far back towards the tire as possible while allowing me to run the lowers at the length I want. That's where they ended up with the axle positioned where I wanted it, about 1.5" further back than stock. Those mounts and the lowers hardly ever hit anything, which was a goal.
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Originally Posted by Timido View Post
Right now I am have a stock 03 shovel hanging below a 1.5" suspension bracket. (total about 6" hanging below the frame) 28" long arms 13" stock upper arms.
Am I reading that right? 28" lowers and 13" uppers? Have you seen what that does to your pinion angle through the suspension travel? Time to fix that man, along with the poor clearance....
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Originally Posted by Timido View Post
Imped are your rear shocks outboard or stock location?
Outboarded.

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Unread 01-04-2012, 08:35 AM   #8
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I know my geometry is messed up that's the plan to fix it. This all helps alot. I hope the poly front mounts. Have enough frame seperation.
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Unread 01-04-2012, 10:12 AM   #9
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Quote:
Originally Posted by Timido View Post
I know my geometry is messed up that's the plan to fix it. This all helps alot. I hope the poly front mounts. Have enough frame seperation.
Frame separation is a bit ambiguous without knowing arm length. If you're using a pre-made combo upper/lower bracket, then its location is largely dictated for you based on the IC you're trying to obtain.

Separation at the frame brackets is really nothing to pay much attention to. What's important is where the arms form their intersection (IC) passing through the bracket into space.

Less separation at the frame bracket will usually create a more stable IC as your suspension moves and your COG changes in relation to terrain. The closer your upper and lower arms are to being equal length makes frame separation even less important.
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Unread 01-04-2012, 10:33 AM   #10
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Quote:
Originally Posted by Timido View Post
I know my geometry is messed up that's the plan to fix it. This all helps alot. I hope the poly front mounts. Have enough frame seperation.
It's adjustable--tons of people use those particular brackets (and home-made variations) with great results. Research for a while and you should feel very comfortable with how you'll handle it.
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