TT MTA4 S50 conversion

[Krawlin]

Scenario two is much less confusing than my rambling sentences in scenario 1. In scenario two, you are going full speed ahead down a straight away on a track and about to enter a large, high speed sweeping corner, and again the corner goes to the left. Assume you are driving a car with a high center of gravity and soft suspension. As you slow down slightly to enter the corner and begin to input steering, the vehicle (and thus obviously the suspension) react, and you begin to turn through the corner. As soon as you input steering, the suspension reacts from the weight wanting to continue in the same direction, so the weight transfers to the outside (right side of the vehicle) and the chassis rolls (vehicle leans to the outside of the corner). The suspension is reacting to this by the car's left side (inside) suspension drooping and the car's right side (outside) suspension compressing. In this case, the bump steer would be toe out as the suspension compresses. So the as the weight shifts, the suspension reacts as the chassis rolls, and at the same time that the right side (outside) suspension is compressing, the outside front wheel is toeing out. This causes the car to under-steer, as the outside tires have the most traction, and the front outside wheel/tire toes out as a result of the suspension compressing and making bump steer show its dark side. You have to basic walk a fine line between losing it/spinning out and compensating for this bump steer, which is basically over correcting if the bump steer were not there.




So the point of all of that? Well, not much point other than just to spread the knowledge, because really we are just dealing with a monster truck, not an F1 car, and I think the only bump steer you will likely notice any ill effects from would be the rear bump steer, as you can't correct that by direct input to the rear wheels as you go. There are at least 2 digits worth of things you have to factor in here, and trying to make them all right would be like trying to polish a turd, because its just an MT and its suspension and tires are going to be numbing enough to the feel of the truck that you shouldn't notice much difference.

If you so much as adjust the camber on simple geometry pillow ball suspension like the MGT has you can affect bump steer at the same time, as well as camber rise, because you have to lengthen or shorten the arm (threading the pillow ball in or out of the arm counts as changing the length of you arm, as the pillow ball is 1 of the suspension's pivot points), and lengthening or shortening the arm changes the height difference between the upper and lower arm which affects camber rise, and changing the camber will affect the kingpin inclination angle which affects how bump steer changes throughout the suspension stroke at any given steering angle because kingpin inclination angle causes the arm on the knuckle to swing in an arc, which alters the plane of the steering linkage in relation to the lower arm throughout the steering range of motion and suspension's range of motion, etc., and things like this should be given some thought when trying to eliminate bump steer, and realistically unless you can completely redesign the suspension and steering geometry, you may not be able to get rid of all of the bump steer, in many cases though you could work with it as a tuning tool or a driving aide (Remember, bump steer is not always bad).

The simplest way to reduce bump steer to where it does not affect the vehicle or can even be noticed when cycling the suspension on the bench, is to play around with the height of the link at either end, now in the rear you can't adjust that since the bolt goes through the turnbuckle horizontally, but you can change the height of it at the knuckle, and in your setup you can shorten or lengthen the link and change it's mounting point on those CF link mounts you have to fine tune it. I will try out that lockout setup on my MGT now and post a picture later tonight and let you know if it works well on the bench (my MGT is in the roller and for sale stage, can't really run it).

Enough rambling, just thought I would throw some information out there since changes to suspension and steering geometry on our RC cars are often not given the thought that is given to changing the suspension and steering geometry on a 1:1 real vehicle, and 1 change can affect so many other things at the same time and not always in a good way, and even though we aren't dealing with an F1 car, the same things still apply. If you have a question about it, just ask, I'm no expert but I'll try to help as best I can, as I've had alot of experience to say that I've "been there done that", especially with trying to improve suspension/steering geometry, I own two Mugen MBX5 series cars (5R and 5T), so I know all about bump steer issues.



Just some food for thought.