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Author Topic:   Trailing Arm angle purpose???
dluna
Dirt Full Roller

Total posts: 42
posted March 29, 2002 04:32 PM
I have gained a LOT of knowledge so far just from this website. Another question I have though is: What changes when you move the trailing arm up or down. We have a 2-bar car and the trailing arm on each side is in the middle position. The mount only allows 3 positions. From the pinion angle discussion earlier, I took it that the more trailing arm angle (have it in the top position) the more forward bite. Why wouldn't everybody want their trailing arms to be in the top position if they will get the maximum forward bite? Is there a point where too much angle will cause a bind or something? Is forward bite more important on dry-slick or tacky (would you change the trailing arm position due to track conditions)? THANKS.

old racer
Dirt Full Roller

Total posts: 32
posted March 29, 2002 05:52 PM
Agressive angles can cause excessive roll steer during body roll. Steep angles will also offer very quick and hard inital bite but most find the bite runs out half way down the straight and now you are loose getting in. Everything is a compromise and there is nearly always an opposite action that occurs in all the adjustments you make.
You can get away with agressive angles on short tight tracks, but there are other ways to promote bite that are much more driver friendly. Best of luck.

HOTWIRE
Dirt Full Roller

Total posts: 40
posted March 29, 2002 08:24 PM
When the chassis rolls up on the left and rolls down on the right as in a turn the left link is shortened or has more angle from the axle to the mounting hole and the right link is lengthened or has less angle. This causes the left rear wheel to lead the right rear wheel giving the car more rear steer to help it turn better.

neverenoughbrew
Dirt Full Roller

Total posts: 56
posted March 29, 2002 10:24 PM
As the axle wraps on acceleration, the more angle you have in the trailing arms, the more they try to lift the rear of the car. With 58% to 60% of the cars wieght in the rear, this does plant the rear tires quite well. Now you do not need to run both links in the same hole. the one with the steeper angle will be planted harder. Steeper angles do create more rear steer(this is a loose roll steer condition) the axle will steer to the outside,loosening the car when you corner as indicated in the previous post. This can lead to inconsistant handling in the corners depending on how hard you drive in and when and where you set your car each lap and over bumps and ruts. This can be a good setup for a good driver though, but it is a little more driving by the seat of your pants. A previous post stated that more angle equals fast bite but you loose it quicker and by the flag stand. Well this also depends on your torque reaction device , pull bar length and angle, lift bar length, spring placement. Not to mention that even if it does fall off at the flag stand, I've done taken you off the corner and pulled away hard all the way to the flag stand, car is set up good and can drive two car lengths deeper into the coner than anyone else, unless driver loops it,your not gonna catch him, you just lost a spot. I would recomend installing 5 hole trailing arm brackets that are made that will allow you to raise or lower the trailing arms without changing the lead in the rear end. My driver has won UMP National Championship, he says the car he won it with was a piece of sh*t compared to our two bar car, never seen so much bite. Now don't get me wrong, I like a z-link on the RR to make the car more consistant, but look at all the 4-bar and z-links that clamp the LR. That is just making the LR a 2-link. It creates dynamic wedge. I really like two links all together and try to help anyone who has one out. E-mail me for some good additional info.

2nd2none
Dirt Maniac

Total posts: 193
posted March 30, 2002 12:14 AM
My 3 link car has 3 holes for both LR and RR trailing arms, does anyone make an adaptor plate that can be bolted to top/middle holes on my 3 hole bracket that will allow more angle? I guess it all matters on if the holes are inline with each other or if they are in an arc on the type of bracket

dluna
Dirt Full Roller

Total posts: 42
posted March 30, 2002 12:16 PM
check your private messages NEVERENOUGHBREW

millerlt3
Dirt Forum Racer

Total posts: 95
posted March 30, 2002 08:53 PM
I have always been told to try and not have any rear roll steer or have the car remain neutral as the body rolls over. With different length trailing arms you need the static angles of both LR and RR set properly so that during body roll the RR link length gain is matched by the same amount of LR length gain so that the rear end remains square during body roll. And this has always worked for me.

race8k
Dirt Forum Racer

Total posts: 98
posted March 31, 2002 09:59 AM
I think the reason you run unequal lenght trailing arms is to induce loose roll steer and to create dynamic left rear weight gain.

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