kcaalarcon

has anyone ever considered or actully extended the length on the rear lower control arms? from my understanding the longer your control arms are the less they vary as suspension depresses so you dont have as bad of roller steer as with the shorter arms when they are set at more of an angle then stock. which would also allow you to have the arms at a steeper angle and increase forward bite?

BMR Tech

The control arms on the 3rd Gen and 4th Gen are about as long as they should ever be. They really need to be shorter to square the wheel in the wheel well. What exactly do you mean by "roller steer" are you talking about oversteer, roll rate, or something else? The length of the control arm will not impact the oversteer or roll rate.

SlickTrackGod

I actually purposely shortened mine to induce roll understeer. you have to get the static and dynamic angles of the car correct through testing- every car rolls differently and corner "set" ride heights vary so you need to check your cars attitude with inspection o-rings on the shock shhafts. (Zipties work decent too)

SlickTrackGod

company tech experts on public forums trying to answer questions.

ill handle this. just sit and watch

it WILL impact oversteer and understeer.

Twin_Turbo

iTrader: (25)

as the car rolls and one side goes into bump, that side has the LCA at a different angle and as such the resulting horizontal component is different, in other words, the axle will not be perpendicular to the centerline of the car and will cause a roll over or understeer depending on the angles and length of the arms. A shorter arm has a bigger angular effect on the horizontal component. The angle of the LCA @ static height is of influence here also, the more angled down, the bigger the resulting horizontal shift (longest being arms horizontal) Arms starting out angled down will migrate to horizontal, arms starting out horizontal will migrate to aiming up and resulting in a gain towards shorter with compression, the other will become longer. Now figure in that ruding roll the other side has the suspension raising and doing the opposite and you can see where it becomes interesting

STG, you are confusing tech expert & sales person

SlickTrackGod

My bad. you are correct, I too posted bad info. See, i admit when i am wrong

SlickTrackGod

Kcaalarcon- your are correct with the reduction of change becasue obviously the arch of the longer arms would not change angle as much in 30" as it would in 15" length with 4" travel.

With that said. there is really no room to properly move the the LCA chassis mount forward so as to run a longer arm. Also in my opinion, these cars benefit greatly fron roll induced understeer if setup correctly becasue the cars are notorious for being tail happy off corners. Roll induce understeer keeps the rear end tighter coming off a corner.

SlickTrackGod

I'm availiable for hire...

....just thought i'd throw that out there.

Twin_Turbo

iTrader: (25)

do you do the dishes and vacuum and all?? ....

kcaalarcon

if i where to take the time to extend them i would make the mounting points very adjustable so i can tune it and do whatever i want with it to cause different affects. so depending on how its set up and the angles it could actuly make a slight handling difference. and just for the record, those of whom that have a welder and are good with it, almost anythings possible

SlickTrackGod

I have a welder and I do fabricate, so I understand that. it just that in my opinion you are doing this to reduce given tunability that exists if you know how to utilize it. I already stated I actually shortened my arms, not lengthened them. By lengthening them you are simply keeping them more parallel and thus more static at all times which helps take out unwanted rear steer if that is what you like. I personally like utilizing rear steer in a car and have done so very effectively. Whatch this video of my car near the end- just fast forward, the first 2/3rds is boring. You ge the feel for the nibbleness of this car coming back towards you. It steered like a jetfighter. Keep a leen eye on the rear wheel. As I slide through the corner you can slightly see the rear wheel turns inward as the car bites and leans @ 1:06. Replay it a few times from about 1:02-1:09 and you'll see it happen.

You also have to worry about reshaping the interior of the car's plastic molding to do the extending you talk about- if its not a concern then go for it.

And yes you can hear the local guys were hating on me because we all talked alot of smack and then I went out and put my money where my mouth was and walked all over all 11 of them that day. We've all been friends since- seriously.

kcaalarcon

i can understand how you are utilizing the rear steer to your advantage and how in some cases you prefer it. but will the wheels always toe in? and wouldnt they also toe out at times? which again depending on the circumstances can be good. but from my basic understanding having more angle on the arms can create more forward bite? and thats where i was going with the longer arms is you can angle them more and not have as dramatic rear steer but still have some. cuz if you have to much angle on the short arms when the suspension compresses it can really displace the wheel. i apoligize if im making it seem like im not agreeing or saying anyones wrong, im just trying to get a better understanding of the concept from people who most likely know alot more then i do

SlickTrackGod

Let me break in down a little what you said because a couple of things you are saying are contridicting to me, maybe that is where we are not understanding weachother. You say "longer arms so you can angle them more". A longer are will not angle as much, it will stay more static, or level so to speak. If one side is obviously mounted lets say 4" off the ground- and you take a 15" long arm & a 30" arm to compare travel and angle- the rear mount of each parallel to the ground static(4" also)- mow move both upward in travel 2"- the 15" arm will be at about 10*, the 30" arm will be at about 5*- so the longer arm has less angle change in travel.

As for angle and forward bite- this is mainly the job of the torque arm length. The LCA angle if inverted will cause wheelop, or if it is angled down will cuase "shock loading" on the tire sidewall on initial thrust and then rebound upward in recoil- both are bad. You want the arm to be parallel in max thrust forward motion for drag launch if that is what you seek.

Now with rear steer, the arms will generally favor just a tad towards inverted (1-2* at most when the static chassis is loaded with driver weight) You want them mostly parallel- but every car is different with spring rates, swaybar rates, damper rates, overall roll weight leverage, and tire grip coeiffeiocent- Iknow it seems confusing- but this is where you need to do some testing on your car for individual wheel travel. THis is done with shock travel indicators (sould simply cut and tie little zipties) onto the shock shafts and ground them out at static height. drive on a smooth skidpad one turn direction and gently stop the car- then check how much that shock body pushed the ziptie up the shaft from the static shock body height. With these indicators. you can figure out how much the inside and outside suspensions are compressing in a corner, and thus set the inside LCA to be parallel (at its horizontal max geometry length in ariculation) so as to keep the axle rearward furthest at max roll. The outside wheel you do the revese. You want the outside LCA to be inverted as much as possible to lull the axle forward on that side of the car as much as possible so as to actually change the "thrust angle" of the axle- note I did not say change toe becassue toe remains constant on a soild rear axle car.

Note in the first paragraph my 15" and 30" trailing arm comparisons. When they each come upward in travel 2" and I said the 15" arm will change to about 10*/ 30" arm changes to about 5*- also note that the parallel static distance of the 15" arm changes to about 14 3/4" with 2" upward arch (about a 1/4" change aprox for explination sake), whereas the 30" arm will shorten parallel geomety by only 1/8" in articulation swing. This shortening is what pulls the axle forward on that side of the car as the body leans. If thisis done incorrectly, one arm can go downward aand the other parallel as cause an awful roll oversteer where the axle steers outward drving the *** end of the car very loose in mid corner as you are trying to get back onto throttle inputs- a very bad thing and the car will always be tail happy.

Now you can understand why I try to preach to all the people I see on this board that buy LCA relocation brackets. They all seem to think that lowering the LCA to the lowest hole is the cure for forward bite. It is a bandaid fix for wheelhop and a poorly sprung and dampered rear suspension- and they are creating a poorly handling car in corners by doing so. The only proper way to fix wheelhop is to increase the spring rate and shock dampers accordingly so as not to invert the suspension at max thrust(You do not start further downward to fight the unpward thrust- you control the thrust movement) and then you load the rear tires more with a shorter TQarm. 99% of people use relocation brackets wrong. You want them to be very close to parallel at static height. If you get wheelhop, then lower them one notch until it goes away. If the angle is getting too low to eliminate wheelhop? you have other problem with poor rates.

83RDRACR

Extending the length of the arms requires a lot of fabrication. I made mine 23 1/2 inches center to center compared to the 19 inches of the stock lca's. A new crossmember was made and adjustable front brackets. This was part of a larger mod to build a custom 3 link suspension but you can see in the pics what work was involved.

As you can see the crossmember was positioned at the rear of the door opening below the "C" pillar. All of the forward thrust of the tires is transmitted through the LCA's so they and their mounts have to be very strong. The xmember is 2x4 .125 mild steel, the brackets are 3/16 and the heim joints are 3/4 chromemoly.

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