I would like to know the answer to my question?

Thanx

 

I will try to explain to my best ability. I think on the LT it is more noticable than on a Honda. But bump steer is when you compress your front end the front of the tires point outward. And the opposite when you lift up on the front end the tires point inward. I have a racing buddy that just installed 400ex a-arms on his LT250r (with the help of some spacers) and now it is more noticable than when it was stock. We are thinking that because the Suzuki is more prone to bump steer than the Honda is because of the front frame rails on a Honda are closer together than a Suzuki. On a Honda the inner tierod ends are closer in realation to the bottom frame rails than a Suzuki. And once you widen the LT the bump steer gets worse. We are thinking that to cure the problem, we need to weld or bolt on extensions to the bottom of the steering stem to make the tierod ends be straight above the bottom frame rails. I'm not for sure if I explained myself well enough and if you need further explaination let me know. Or maybe somebody else has a better way to explain it.

 

Yeah I smell what you're cookin. I asked this question cause CT Racing's Allen Knowles said in an arcticle that the LT250Rs had tons of bump steer.

 

When you get the chance, go push down on your front bumper and look at what the front of the tires do. They should point outward and show you just how much bump steer the quad has. Our theory on the cure for bump steer is not yet proven, but it sounds good on paper. Just have to give it a real life test.

 

Your theory on reducing bump steer is both good and bad. It is true that the closer the tie rod ends and the a arm pivots are to the same vertical plane the less the bump steer. If you had the tie rods and a arms pivot on the same plane at both the outer and inner joints you would have no bump steer at all.

Your idea of making the flag wider to locate the tie rod ends over the a arm pivots would work to reduce bump steer, however, doing so will dramatically reduce the turning radius as well as make it a little harder to steer. The wider you go the less the wheels will turn because you get the pivot closer to the outermost point of its arc of travel. If it was that simple everyone would have been doing it long ago. There could be a happy median in there somewhere that might suit you ok. In other words move them out a little to trade some turning radius loss for less bump steer.

The real solution is to narrow the frame and make the lower arms wider to compensate. But that is a lot of work.

Another problem with the LT250r is that the frame is almost flat on the bottom. It does not angle up in the front section where the a arms bolt on like a honda. this effects handling in a big way when MXing in particular. It would not make that much difference in flat track racing. the angle allows the front suspension to more smoothly absorb the hits and especially the big landings. the more nose down the landing, the more the angle helps. And the biggest difference may be noticed in the whoops.

 

I didn't think about the turning radius being affected. I think one way to get back the turning radius would be to cutout some of the steering stops or cut them completely off and weld in your own that will allow you to turn the handlebars more. I think I would rather have less steering radius than a lot of bump steer. You can always use the throttle to get you around the tight corners! I don't like the idea of both tires pointing in two different directions.

 

The steering stops will not fully cure the problem either. When the tie rods are near the outside of the arc, turning the handle bars a lot has little effect on turning. It is moving the tie rod from frt to back instead of from side to side. And when the outer most part of the arc is past the wheels start to turn the wrong way.

 

The key word there is "reduce" and there is a trade off for reducing it unless the frame is narrowed. Moving the flag up the stem is another way to somewhat "reduce" the bump steer. There can be a lot of difference between reduce and eliminate. Any ever so small amount can be called a reduction.

Also the term "bump steer" has two meanings depending on who you are talking to. To some bump steer is the actual change in the toe measurement throughout the travel. To others it is what the rider actually feels or notices while riding because of the toe change. Simply changing the toe setting at ride height can have a big effect on the bump steer feel, but will not effect the actual toe change.

I am not trying to argue with anyone here. I simply want to get all the facts out in the open. Isn't that what this forum is (supposed to be)about, sharing usefull info? I wanted to reduce the bump steer on my Mojaves, but before cutting and hacking and welding, I drew it all up and saw that only minimal improvements could be made without big sacrafices unless the frame is narrowed. So I am now narrowing the frame and building some a arms accordingly.

 

Good thinking, I was just saying though.

 

Another side effect of moving the tie rods out on the flag is excessive Ackerman angle. I don't think there is actually such a thing as more or less Ackerman. I think you either have it or don't but say too much just for visualization. Ackerman angle is the angle difference between the left and right tire while turned. The inside and outside tires follow different radius arcs so the inside tire should be turned sharper than the outside. By spreading the inner tie rod ends apart, it will cause the inside tire to turn faster than the outside tire.

Changing the vertical position of the inner and outer tie rod ends will only reduce bump steer while the tires are straight. I also say reduce because it cannot get rid of it all together. The tie rods will still be longer than the A-arms and therefore will move in different arcs. By altering the angle of the tie rod, you can get those arcs to cross twice instead of just once. I am not saying this is not a useful solution, just that it cannot attain 0 bump steer. I don't doubt you can get it to where the toe-in is the same at two points such as full droop and full compression or ride height and full compression. When the wheels are turned, it changes all the angles.

It is very complicated to get rid of bump steer alltogether. The only was is to have tie rods that are the exact same length as the A-arms and at the same angle. Since the upper and lower A-arms are not the same length, the length is somewhere in between. If the outer tie rod end were at 60% of the distance from the upper to lower ball joint, the length of the tie rod would be (upper A-arm length*60 + lower A-arm length*40)/100. The inside tie rod end would be spaced the same percentage wise between the upper and lower A-arm mounts. You would need idler arms with short inner tie rods from the flag to the idler arms. The outer tie rods would also be connected to the idler arms.