Thanks for the added information about your procedure of testing for the bumpsteer. I understand that as the spindle sweeps up/down the steering may be better in portions of that sweep arc. In this case, with the new shocks getting you lower, the bumpsteer deflection was more in it good part of the arc versus the bad part of the arc.
Thanks.
Peter,
Your very in depth explanation was great.
I understand the roll and COG of these cycle cars. What makes this worse is that all of the body roll control is transferred to the front suspension as the rear being a single contact point is no help against body roll in hard cornering as opposed to four wheels with the wider track width.
When I stated the “normal” setup of 2/3-1/3 I was referring to a more street driven non auto course weekend racing setup. We have some pretty big bumps on our roads here and with an 8:1 compression/rebound setup, our tires would be grabbing some air when going into pot holes or coming off of larger bumps.
With the 2/3-1/3 setup, I see how the M3W inner wheel would go down further with my setup than what you have in the M3W’s. But for normal street driving and conservative cornering, wouldn’t the 2/3-1/3 setup still give better overall ride comfort, but as we know, more body roll? Now this of course still relies on a good quality damping coil over. Trust me, I know the difference in quality shocks. Most late model CVO Harleys have lowered suspensions by 1” and the rear shocks are so harsh that it’s back jarring to say the least. Without air, they will support the bike, but the ride bottoms out a lot. Two up we run with around 40psi in the rears to get the non bottoming taken care of, but the ride is very poor. I upgraded to non air Progressive 440’s, but Ohlin’s are one brand people are using as well as Bitubo, Progressive and a couple other custom brands.
I’m trying to learn from some of you guys that obviously know their way around a car and suspension specifically. So I have some thoughts that I would like to run by you.
On the control arms and steering linkage, if you were to draw an imaginary line between the upper and lower control arm mounting points and then a similar imaginary line between the ball joints centers, shouldn’t the steering tie rod measure the same horizontally? So as an example you go up parallel from the lower control arm 3”, the tie rod should be the same length as it would intersect the two imaginary vertical lines. Is this correct? Because of the steering arm on the spindle allowing for the Ackerman steering, the tie rod would be slightly offset inward relative to the two imaginary lines.
Even though the tie might be the correct length as described above, if it’s not parallel to the lower arm, the vertical motion of the spindle would cause a fluctuation in toe creating bumpsteer. Is this correct?
Does the length of the control arms mean as much as long as the ratios are kept correct between the steering linkage and “A” arm length? Obviously the longer the arms the larger the sweep radius is, but I’m not sure I understand the how you find the sweet spot for their length.
Sorry to ramble, but when I have a possible chance to learn, I will always ask questions.
I find this very interesting and your way of telling the story is great.
