Steering and Handling Discussion.

[bradley300]

Originally posted by Flyin-Low
As you mentioned in the first post, you are yet to see an ATV with zero bumpsteer, but doesn't Polaris claim exactly that with their front design on the Predator (maybe the outlaw too?).

Might have to check out that setup as well. I'm curious as to how it works.

-Martin

you are correct, the predator and outlaws have absolutly no bumpsteer with the PRO steering system. this creates its own problems tho, and shows bumpsteer (in small amounts) isnt all that bad.

with the a-arms and tierods on the exact same arc, they are the same length. so when you turn the wheels both tires are turned at the exact same angle. do this with any other quad and you will see the inside wheel has turned more than the outside. this helps the inside wheel dig and in turn, the quad turns more precise than the PRO system, that has no bumpsteer what so ever, but in turn, does push in the turns more so than other quads in its class

[400exrider707]

Originally posted by bradley300
you are correct, the predator and outlaws have absolutly no bumpsteer with the PRO steering system. this creates its own problems tho, and shows bumpsteer (in small amounts) isnt all that bad.

with the a-arms and tierods on the exact same arc, they are the same length. so when you turn the wheels both tires are turned at the exact same angle. do this with any other quad and you will see the inside wheel has turned more than the outside. this helps the inside wheel dig and in turn, the quad turns more precise than the PRO system, that has no bumpsteer what so ever, but in turn, does push in the turns more so than other quads in its class

Thanks for the info bradley, I am not too familiar with the polaris setups. Also the act of the inside wheel turning more than the outside is known as ackerman.

[F-16Guy]

Originally posted by 400exrider707
....Also the act of the inside wheel turning more than the outside is known as ackerman.

I was waiting for someone to bring that up. By angling the spindle arms to point so that the two imaginary lines meet at the center of the rear axle (bearing carrier), you create an effect that causes the front wheels to follow parallel arcs around a common center point of a turn, which eliminates tire scrub. Another thing I haven't seen mentioned is roll center. If you look at your front end, you'll most likely see that the upper a-arm frame mounts are farther out toward the spindles than the lowers, and that the upper a-arms are slightly shorter. This causes the upper and lower arms to follow two different arcs, which creates a little bit of negative camber as the front suspension compresses. This helps keep the contact patch of the front tire squarely on the ground as the body of the ATV rolls while you're negotiating a corner. By altering the relationship between the lengths of the upper and lower arms and their mounting points, you can control the amount and progression of the camber change. You could also potentially cause a positive camber change, but you won't see that much since it's not very desireable under normal conditions.

[drsnugfit]

Originally posted by 400exrider707
Good questions and good observations on your part. This is really tough for me to say not seeing it in person. It could be a number of things contributing though. First question for you, were the epic arms by any chance +1 forward, I've noticed this has quite a negative effect on the handling of the R's. This would definitely cause the "pushing" in corners as you described. This could also be from poor castor setup. Whether the arms are adjustable or not for this I'm not sure. As far as the movement of your wheels, good observation. This happens on all atv arms. What I find odd however is that your longer arms moved more. This should be quite the opposite actually. The shorter the physical length of the arms, the more they have to travel up and down to get the wheel to move a set distance. Longer arms have to move vertically less to get the wheel to move the same distance, as the wheel is further from the frame. 1 inch is almost negligible however. Another question are you using the 4:1 wheels still? I'm assuming you are. Now I really cant say for sure as I don't know the design intent of the epic arms, but there could be a few different things going on here. First, nonparallel arms could cause this. Using nonparallel arms can be used to an advantage to gain camber as your wheels cycle through their motions. Using unequal length arms could also cause this. (Please don't confuse my term "unequal length" arms, as I've yet to see an ATV that used the same length top and bottom, it just means that one arm is not cycling as much as the other arm. Adjusting Camber could cause this too, as you are effectively taking length or adding length to the upper arm by doing so. It is possible your new arms are non adjustable or adjusted so that the arms are "parallel" and "equal length" Meaning they are following the exact same cycle pattern, they remain parallel throughout the entire cycle of the suspension.

From the sounds of it your epic arms were either designed poorly or poorly setup. No offense I don't know your abilities or how the arms are built, and I certainly don't want to step on anyones toes, yours, or epics! Suspension setup could have also played a role in how these arms performed, so there really are too many variables for me to give you a definite answer. Your leagers have to move throughout the wheel travel, they might just move little enough for you to not notice or its possible they are losing camber throughout travel so that the top of the tire is doing all the moving and the bottom stays planted, which isn't good either. Having camber remain constant is good to have, or even slight camber gain would be good too. It really depends on rider preference and type of racing. If you're faster with a narrower quad then you have obviously nailed a better setup, whether it be rider input, suspension design or suspension setup, or a combination of the three, something is right now. Let me know if anything else needs explaining, I realize some of this may be confusing. Please don't be afraid to ask, because if someone doesn't understand something, then chances are other people don't understand it either.

awesome thread, so much info, with regards to 450Rs with +1 forward arms and pushing into corners, I have +1 arms and have noticed it doing this, other than change the arms is there anything i can adjust to try to either stop it pushing in or lighten the effect a bit.?

Thanks.

[bradley300]

a + 1.25 swingarm will ballance it back out.

the stock swingarm is .25 inch too long for the a-arm design, so adding +1 foward a-arms, your just adding to the problem of too much foward weight, so a +1.25 swingarm should ballance the weight evenly, or as close as possible

someone correct me if i'm wrong, i'm not 100% up to date on 450r's

[400exrider707]

Originally posted by bradley300
a + 1.25 swingarm will ballance it back out.

the stock swingarm is .25 inch too long for the a-arm design, so adding +1 foward a-arms, your just adding to the problem of too much foward weight, so a +1.25 swingarm should ballance the weight evenly, or as close as possible

someone correct me if i'm wrong, i'm not 100% up to date on 450r's

In theory it sounds like it would work, but even at that, I was still disappointed in +1 forward arms, they just push no matter what, or at least push a lot more than +0 arms. The only way we could get the front end of the quad in question with +1 forward arms to bite better was with brand new holeshot MX tires on the front and with the front end sitting nearly 1" lower than the rear end, which is a terrible idea, we just wanted to see what had to be done to get it to bite like it did when it was +0 forward.

Magazines have done test with the +1" foward or +.5" foward and the only quad they noticed a benefit in was the banshee. Other than that they said all other atvs handle worse with the +1 or +.5

[400exrider707]

Originally posted by FoxHondaRider
Magazines have done test with the +1" foward or +.5" foward and the only quad they noticed a benefit in was the banshee. Other than that they said all other atvs handle worse with the +1 or +.5

I have also read this from the owner of Ishock.

yeah dirt wheels did a test with it, Hydrodynamics (iSHOCK) said it was worse, there were a few others too.

[bradley300]

Originally posted by FoxHondaRider
Magazines have done test with the +1" foward or +.5" foward and the only quad they noticed a benefit in was the banshee. Other than that they said all other atvs handle worse with the +1 or +.5

that is assuming that you dont extend the back end to match