Sturing en Handling Discussie

[Frank MB]

Omdat er op andere fora, zoals het volgende stukje van atvriders.com best wel gediscusseerd wordt over frame en arm geometrie, alsook de afstelling daarvan, wil ik kijken of we hier op het forum ook een mooie discussie op kunnen zetten en van elkaar kunnen leren hierover.
Dit is het eerste stuk van [url]http://www.atvriders.com Ik snap nog niet helemaal uit onderstaand stukje hoe alle lijnen getrokken worden, maar ik zal binnenkort even een paar armen tekenen in Inventor of dat iemand anders dat doet, zodat dit stukje iets duidelijker wordt.

Er staat ook nog een duidelijk stuk over camber en caster, dit is misschien ook interessant om erbij te zetten.

am going to use this thread as an open area for members to discuss steering and suspension and how certain pieces effect others. There has been an overwhelming number of people asking about wheel spacers recently, as well, more than a few talking about diamond J custom widening kits. I feel like it is unfair to not explain the theories behind these "add-ons" to people who dont understand them. We all had to learn at some point. Some people get offended when then realize that the inexpensive route isn't going to work and start looking for excuses to make it work. There will be no arguing of this in here, this is strictly technical information, with facts.

To start with, lets explain what a "perfect" setup is for an ATV. First things first, you have an atv frame with your basic dual a-arm setup. Dual a-arms are the way to go with front suspension. Using two arms creates four (4) pivot points. You have two (2) pivot points at the frame, and you have two (2) pivot points at the spindle. If you were to draw an imaginary line looking straight on at this, you would have a square, or a parallelogram, depending at what angle the arms are to the frame. This allows the spindle to remain at the same camber angle through its entire travel. This is only if both the upper and lower a-arm are parallel to each other. This would be the "ideal setup." However you can alter the mounting points at either the spindle or the frame to achieve a camber gain/loss through travel. You can do this by making the upper and lower arm unparallel. This is also quite common to see on some buggies and some offroad vehicles. I wont get into it to much more as of now, I want to keep this as basic and technical as possible.

Next area of focus is your spindle/wheel assembly. Your spindle is mounted to the a-arms, which holds the hub and then the wheel. To understand the ideal setup at this point, imagine a line drawn through both the upper and lower balljoints (or heims) that attach the a-arms to the spindle. You would want this line to travel through the pivot point of each. Now since most atv spindles are setup so that the upper balljoint is closer to the frame than the lower, your line should start from the atv and move away as it goes towards the ground, it will not be a straight up and down line, it will be angled. To make your handling ideal, this line should pass through the centerpoint of your contact patch on your tire. This is often why we see racers using an offset rims of 4:1 (see the FAQ section at the top of the page to understand wheel offsets). The 4:1 rim brings that centerpoint of the contact patch closer to this imaginary line, if not right on it, depending on setup. Having the centerpoint of the contact patch directly in line with your balljoint pivot points will create the least amount of effort to steer. Running a different offset rim like a 3:2 which is close to stock, moves this patch away from that pivot point line. This in turn puts more leverage on the "steering" Wheel spacers do the same thing, they essentially move the centerpoint of that contact patch away from the balljoint pivot points. This is why wheel spacers DECREASE handling efficiency. Sure they might make it harder to tip over, but at what cost? This is why I suggest to stay away from flipped/large offset rims and wheel spacers.

Last major important part of handling is your tie rod ends. You might say what the heck do these have to do with anything? A LOT is the answer. The location of your tie rod ends at both the spindel and the steering stem play a major role in bumpsteer. Bumpsteer is when your wheels steer themselves without input from the handlebars. It is caused from the suspension going through its cycles (moving up and down over terrain) and having improper location of steering linkages (tie rods and tie rode ends on quads). This is easy to demonstrate yourself is you so choose, it is always easiest to see this rather than read this on here. Jack your front end of your quad off the ground so the tires are not touching. Take one of your front shocks off. Now have the handlebars locked in a centered position (have a buddy hold it), now grab the tire/wheel and move it up and down. Watch as the front of the tire will point in and point out. This is the action of bumpsteer. I have yet to see a factory quad that came with NO bumpsteer. The cause of this on many quads is the location of the tie rod ends on the steering stem. To have NO bumpsteer, your tie rod ends must fall into these imaginary pivot point planes that we have been talking about. At the spindle, the tie rod end must fall on a plane with the balljoint pivot points (this one is generally hard to picture cause you only have an imaginary line instead of a plane) At the frame, the tie rod end pivots must fall on the plane of the a-arm pivots. As you can see on your quad, this is not the case at the frame. Your tie-rod ends are further inboard mounted on the steering stem. This is what causes bumpsteer for most atv's today. Kawasaki has tried combating this with their new frame design. By making the frame narrower in the front, it brings the a-arm pivot points in closer to the tie-rod ends on the steering stem, helping to rid of some unwanted bumpsteer. Laeger has also tried the same concept and as far as I know were the original company with the narrow frame. Many have heard of this, maybe not everyone understood the concept behind it, but it is the same, just bringing the a-arm pivot points in closer to the tie rod ends on the steering stem. The Diamond J custom kits, which seemed to die off for a while, but are back in question again, do the exact opposite of what Kawasaki and laeger have done. They widen your quad sure, but they drastically increase bumpsteer by moving the pivot point of the a-arms much further away from tie rod end pivot points, this creates a LOT of bumpsteer. You do not need to ride this setup to tell this, it is a simple mechanical design.



We will start here with this for now, anyone who wants to post questions/comments you are more than welcome. Also I know there are a few pictures floating around that will help explain a lot of this, if you are having a hard time visualizing. If anyone has any pics that they think will help, I ask that you do not post them in here as I would like them to go into each separate section of the original post, instead email them to me (send me a PM to let me know you emailed them) and I will post them up in this post, in an attempt to keep it clean, detailed and easy to follow. If not I will attempt to find more pics in the next few days and add them as we go along. Thanks.
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