fredswain

iTrader: (1)

Don't forget to balance damping and pack as well. The front and rear should still remain equal with oil in them, including when each end bottoms out. You'll find that you will not end up with the same pistons or oil in each end.

RC10Nick

iTrader: (9)

That's the process I always follow:

0: Set weight distribution, front kick, wheelbase, vla
1: push/release test w/no oil for spring balance
2: push/release test w/oil for oil balance
3: drop test for piston balance

A while back you wrote out a procedure for setting camber links. It was basically the following:

1: Set ride height to arms level front and back. Adjust front spindle height if necessary to level out ride height front to back.
2: Set links to longest length parallel to the arms
3: Test/tune links on track.

I've never really gone through this part of your method. Do you still recommend it? You've mentioned finding balance in your roll centers. Aside from how the car feels on the track, how do I know if my roll centers are balanced?

I like the tests for balancing the shocks because I can see what is balanced when I've gone through the procedure. With roll centers I really never knew what I could actually look at or measure and know I've found balance. Is there some kind of test or measurement I can make to help find balance in my roll centers?

dvaid852456

I've just read through this thread (or most of it any way)

What a great read. I am currently trying to apply this way of setting up my 4WD Touring Car.

I have done the spring balance test by using my camera on slow mo ( https://youtu.be/60OwElB87Zw) and settled on 2.7/hole 3 front and 2.6/hole 6 on the rear. From my previous setup I was on 2.8/hole 3 front and 2.6/hole 3 rear. When testing the previos setup the front had a higher natural frequency to the rear so I worked on slowing the front down with a 2.7 spring. To balance further I stood up the rear shocks by 3 holes and it is very well balanced now.

I'm about to set the oils tonight. I assume I do it in the same way. Compress the chassis and lift off and watch for frequency/settling at the same time?

I have the same question as above regarding RC. To find RC settings do I set the suspension arms level at desired ride height then set the longest parallel upper link and tune the front for steering aggressiveness(higher RC for more aggressive steering response and lower RC for smoother steering) and the rear for on/off power balance?(higher RC for more on throttle grip, lower RC for more off power and mid corner grip)

Finally set link length for RC change during chassis roll. (longer link for greater RC change and shorter link for less RC change)

The above are all generalisations but am I in the right ball park?

Pistol123

I beleive it is shorter top links for more rc change and longer for less. With longer the chassis will continue to roll.

One of Fred's comments was get the rc balance then try and raise the rc equally front and rear until it is too darty to drive.

dvaid852456

Ah yes I miss read my setup notes a shorter link will angle the upper link more as the suspension compresses so raising the RC and a longer link doesn't move it as much right?

I'm looking forward to a new, repeatable way of setting up my car. I've always started with a kit setup and made my own changes, one at a time based on what I believe I understand the effect will be from reading guides/forums and posting questions on here. I think the setup I have arrived at for my local indoor track will be pretty close but maybe a fully balanced setup will be even better as I always seem to be chasing my setup.

First tick was spring rates I had arrived at 2.8 in front and 2.6 in rear so not too far off from the more balanced 2.7 front and 2.6 rear slightly more stood up.

Great thread and thanks to Fred and those still willing to teach us

fredswain

iTrader: (1)

Does it understeer? Does it oversteer? Is it neutral (balanced?)

RC10Nick

iTrader: (9)

Right now it feels like it has a slight constant understeer.

fredswain

iTrader: (1)

You'll potentially always have a bit of on power understeer. These cars are just so powerful today that it's hard not to. That's why there's been such a trend with shifting weight forward or adding it up front. It's trying to keep the front end down. What you don't want is snap oversteer when you let off the throttle going into a corner. That's fine on loose dirt tracks with tight curves where sliding the rear end around point and shoot style is the fastest line but you don't want that on high grip tracks. It makes braking very unstable.

I start with low roll centers first, since it is the most forgiving, and then make a change at one end until the balance is where I like it. It may not be where you like it. From there I'll try to raise the roll centers at both ends equally until my times fall off. Then back up a setting. That gives a nice balanced car that is well compromised between grip and ease of handing.

I always start with as little anti-squat as possible. I only add it if I don't have enough forward grip on acceleration.

fredygump

iTrader: (1)

I've been trying my best to follow your tuning advice with tuning springs first, then tuning the shocks, etc, but I've struggled to get it to work on my mugen 7r. (It uses pivot balls.) The front always seems slow to rebound, even with the stiffest springs available from mugen (black, 1.6mm series spring).

I try to keep the pivot balls free, clean, and lubricated with teflon. But that doesn't fix it completely. Maybe it is b/c there is friction from two hinge pins on each side?

It is as fast as any other car on the track, but I feel there's something I'm missing.

I'm curious if you have any insight with pivot balls specifically? it seems to me that it doesn't matter what spring rate I put in front--the front suspension does not seem to be rebounding freely like the rear.

fredswain

iTrader: (1)

I bought a Durango DEX8 before Durango went under. I've never driven it though. I'm in process of converting it to a DESC10 short course truck since it should take more punishment with the large bumpers and full body. Parts are getting hard to find for them. I'll start playing with it and learning how to tune it at some point this year. The one thing that I have noticed is that at excessive droop that you get bump steer at the front. They put the outer steering link points at the wrong spot so that's something that I'll need to fix. I've been told that all pivot ball suspensions are like that. I suspect that whoever did it first didn't get it right and everyone since has just copied them. It looks easy to fix.

fredygump

iTrader: (1)

I'm interested in what you might find. In the mean time I'll be experimenting. I just re-built it, and I guess it's time to re-visit the suspension.

The Mugen has bump steer at full compression (toes out). I haven't tried to fix it. I think I would prefer bump steer at full droop rather than compression. Atleast at full droop you don't have much weight on the tires when it happens.

batryopratedboy

Fredswain, Freddygump, the issue there with bump steer is that as you adjust castor on pillow-ball suspension systems, it's moving the pivot position of the steering linkage up or down depending on the adjustment. Add castor, and it moves the steering link down... if the steering link is NOT PARALLEL then you're going to get bump steer.

That's to say, if you have toe-out on droop, add some spacers (or thread-out, just to experiment) the outside link to cancel it out. OR, reduce the amount of castor.

Remove the clips from the upper arm, slide it fore and aft and then cycle the suspension and observe what it does to the toe.

fredygump

iTrader: (1)

That makes sense. I just made a big change to my caster. I modified my upper and lower arms so actual caster angle (angle to the ground) is ~18 degrees now. I'm guessing stock adjustment is a range of 25-30 degrees? But now I have a range of18-30 degrees.

I'll have to revisit the bump steer, but right now I'm waiting for the snow to melt. I want to decide if I like the caster adjustment before I worry about it's affect on bump steer.

I'm making the changes because I drove a friend's SCT...I don't know the brand, but it's basically a frankenstein kit that uses an assortment of 1/8 buggy parts from other mfgs. The turning was so sharp that my usual steering corrections sent me over the pipes when I was trying to go straight. It was ridiculously touchy. This was driving on dirt.


I don't want that much steering, but I definitely want more than what I've got right now. And as I don't believe in JFM, I am convinced that the difference is in the suspension geometry. My guess is that it has a lot to do with caster, because caster is predetermined by the mfg, and has limited adjustability.

Tekno seems to be pretty good about listing their numbers--they have an option "10 degree" spindle carrier that results in between 20-22 degrees depending on kick-up. But they may be the only one that publishes numbers like this?

This summer I'll try to convince people to let me measure the caster on their cars.

30Tooth

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Jamarc

Pretty new to rc. This article is awesome!!