Originally Posted by berry50 (Post 9757708)

I think my question may have been mis-interpreted. I have read and understood the whole thread. And, i do get the theory behind Fred's set up technique. Apart from ONE question that i can't work out.

On a 2wd rear motor truck (in my case an SC10), i seem to need stiffer rear springs (due to more weight at the rear), to get a correct spring balance. Now, my simple question was, how come one all the SC10 set up sheets i see, including the AE team drivers, everyone runs stiffer front springs if having balanced front and rear works better?

Maybe i'm reading too much into this set up, but i just can't get my head around that.

Originally Posted by fredswain (Post 9221853)

Here's one thing to try. Figure out approximately where your center of gravity is. Just use a finger on each side of the chassis and try to pick the car up. Move your fingers farther back if the front end is rising first. You'll probably end up somewhere near the center of the battery in location. Once you find it, >>>>push down with 1 finger on this spot. The front and rear of the car should both go down at the same time if it is balanced.<<< Do this on springs only as shock oil can change this a little bit.

Originally Posted by Oso Negro (Post 9757268)

Well said! Don't let these people bother you!

I've tried your method and I am a true believer. I'm becoming one of the fast guys at my track thanks to you and expect to get even better in the short term. It's all thanks to you!

I've been racing on and off for over 25 years and I never quite understood how it all fit together 'till now. I've quit twice out of frustration in that time because I could never get over the knowledge hump and find consistency day to day, week to week.

Most of the guys at my track copy the settings of the factory guys because we host a lot of big events. We end up getting setup sheets specific to our track all the time from the winners.

I am proud to say that thanks to you I no longer need that crutch. My buggy is outhandling my competition and it is just a matter of time until my skills catch up to what my buggy is capable of giving me.

Bottom line, it is working for me!

Originally Posted by kc_nitro_rc (Post 9762131)

Raced my SC10FT for the first time Saturday night. Setup was basically what they recommend. Went up to 35wt oil in all 4 shocks after my 1st qualifier. Truck felt really good.

Came home Saturday night and had some time to play. Dumped the oil out of the shocks and tried Fred's method of spring tuning. Using the recommended red front & gray rears I pushed one end down at a time to see if they would rise equally. The front definitely had more spring up. Tried it again using blue fronts & green rears. (This is one of the Maifield's setups.) Again, front sprang up quicker.

One thing I will say is that when I had 30wt or 35wt oil in my shocks using the AE recommended setup the truck 'bounced' equally front & rear and rested level.

Another note, scaled my truck- 9 ounces on each front tire & 17 ounces on each rear giving me about a 35/65 front to rear weight ratio.

Fred, I want to tell you that changing camber link locations has always changed the way my cars steer.

Originally Posted by kvrc (Post 9762935)

So with the scale numbers you listed your short course truck weighs 3.25 lbs.
That tells me either your scales are way off or you are leaving the battery and body off when scaling. You need to do all testing with a track ready car.

Originally Posted by berry50 (Post 9757708)

I think my question may have been mis-interpreted. I have read and understood the whole thread. And, i do get the theory behind Fred's set up technique. Apart from ONE question that i can't work out.

On a 2wd rear motor truck (in my case an SC10), i seem to need stiffer rear springs (due to more weight at the rear), to get a correct spring balance. Now, my simple question was, how come one all the SC10 set up sheets i see, including the AE team drivers, everyone runs stiffer front springs if having balanced front and rear works better?

Maybe i'm reading too much into this set up, but i just can't get my head around that.

Originally Posted by jrspruitt (Post 9755594)

I believe the reason for that is the mechanics of the front suspension. It seems like it would be the other way around, because of the weight differences. But the front shocks are mounted farther inboard on the lower A arm, which causes the actual spring rate to become a fraction of its actual rating. If the shock was mounted on the outer hinge pin, it would be a 1:1 ratio with its actual rating, but the farther inboard it goes, the more leverage the arm has on it, so if it was mounted in the middle of the A arm, it would be a 1:2 ratio or half its actual rating. Where as the rear shocks are mounted farther to the outside of the arm. The shocks also tend to be more up and down, compared to the front, which also plays a roll. When the shock is laid over more, the beginning part of the compression stroke, there is more movement of the A arm for a given amount of shock compression, than near the upper bounds of the A arm movement, so its a little bit like a gear reduction issue. As the A arm movement increases in regards to a given amount of shock compression, there is less force needed to move the shock, so you need a higher rated spring to get the effective final rate you need That's my understanding of it at least.

Originally Posted by Sarinexia (Post 9200772)

How To Tune With Camber Links
“It’s all about positioning”

Camber Link Length:
Link length is adjusted by altering the mounting positions on the shock tower and/or hub of the vehicle. This adjustment is not used to alter the tire’s camber setting! Instead, once you’ve settled on a camber setting (-2 degrees, for example), the link will be readjusted to maintain -2 degrees of camber after the position change.

In general, a short camber link increases camber gain (the amount of camber the tire experiences through suspension compression), and produce more vehicle rotation entering a turn and more traction coming out of the turn. As the vehicle’s weight transfers and the suspension compresses in a corner, the increased camber angle of the tire will increase lateral thrust generated by holding more camber in the heavily loaded outside tire. The tire will have less rubber on the road and more cornering capacity when you add camber gain.

The opposite is true for a longer camber link. Lengthen the camber link by moving to the outer hole on the hub or inner hole on the shock tower, and this will decrease camber gain, which can make the car feel “lazier” and less reactive, while giving the car a more stable feel. Longer camber links are sometimes used on high-traction tracks to prevent traction rolling.

Formula: Camber link --
Short camber link =
+ Camber gain /---\ =
More vehicle rotation entering turns // More traction out of turn.

Long camber link =
- Camber gain \---/ =
“Lazier” Feeling – More stability


***********
Turnbuckle-type camber links allow you to adjust the length of the camber link while it’s still installed on the vehicle. This is done by a standard thread on one end and a reverse thread on the other. A small hex in the middle of the link makes it easy to spin the link with a wrench. A small grove on one side of the hex tells you what side the reverse thread is on.

***********
Changing the length of the link will change camber gain when the suspension moves up and down. Extra holes in the rear hubs and some shock towers give you different camber length options.


Camber Link Height:
Altering the camber link’s height (position vertically on the tower or occasionally on the hub) changes the vehicle’s roll center. This adjustment is most often tuned on the rear of the vehicle. Technically speaking, roll center is defined by the SAE as “the point in the transverse vertical plane though any pair of wheel centers at which lateral forces may be applied to the sprung mass without producing suspension roll.” ---- In other words: Think of roll center more simply as the point around which the vehicle’s chassis rolls in a corner.

So how do we apply roll center to vehicle tuning? All things being equal, when you move the camber link up the tower, the roll center is moved lower on the vehicle. When the link is moved down on the tower, the roll center is raised. In general, a high roll center (lower on the tower) is better for slippery or bumpy tracks because when you move the roll center really far from the ground level in either direction you introduce jacking, which messes with the ride height of the car, and you have a track width change that can either help or hurt your cornering performance.

For smoother high speed tracks, a low roll center helps decrease roll, and decrease weight transfer from left to right in a left hand turn and reduces the “tippy” roll-over feeling a car may get in high speed corners on a high traction track. Steering into the corner is increased as the car will “bite” more going in, but the vehicle will feel more stable coming out of the corner.

You can tune your over/understeer characteristic with roll center. Raising the roll center on the front or rear will make that end wash out first. So raising the rear will wash out the rear and make the car looser. Raising the front roll center will wash out the front first and make the car push.

Formula: Roll Center –

HIGH ROLL CENTER: (FRONT) >>>>>>>>> MAKES FRONT WASH OUT CAUSING “PUSH”.
HIGH Roll Center (rear) >>>>>>>>> Makes the car looser washing out the rear.
Camber link low on tower =
Roll center is raised =
For bumpier / slippery tracks

Low Roll Center: >>>>> Increases steering into corner
Camber link high on tower = >>>>> Increases stability coming out of corner
Roll center lowered = >>>>> Reduces roll over feeling
Smoother / high speed tracks

So basically with Roll Center you’re either looking for: (in the 2 extremes) ---
1. Stability – (Low Roll Center)
2. RESPONSIVENESS – (HIGH ROLL CENTER)

And with patience, trial & error based on your track you will find your sweet spot between these two by adjusting your camber link higher or lower on your shock towers.

Reference:

“How To Tune With Camber Links” by Stephen Bess; RC Car Action June 2011: (Pg. 97-99)
Question --------

“Link length is adjusted by altering the mounting positions on the shock tower and/or hub of the vehicle This adjustment is not used to alter the tire’s camber setting!”

I was under the impression to adjust + and – camber you simply bring in the link length or move it out. I’ve even seen instructional video’s showing this is how you adjust your + and – camber setting, but this article states this is NOT how you adjust camber, rather how you adjust HOW MUCH camber you have under suspension compression. So if this isn’t how you adjust camber, how do you adjust camber?

Originally Posted by john stu (Post 9764817)

im confused

HIGH ROLL CENTER: (FRONT) >>>>>>>>> MAKES FRONT WASH OUT CAUSING “PUSH”.
RESPONSIVENESS – (HIGH ROLL CENTER) how is washing out responsive"?

all i want to know do i raise or lower the links on the shock tower to get more steering and will shorter or longer links give me more steering

Originally Posted by kc_nitro_rc (Post 9776459)

Is it possible to downside the landing from that particular jump? Carry some more speed so your car is going more in a forward direction than down?

With all due respect I would go with smaller pistons in my shocks. Remember, springs & oils are for the bumps. Shock pistons are for 'pack'. Sounds like you will be needing more pack.

Did you try going up in oil weight until the tires started to bounce off the bumps? To light of oil and you still bounce on the springs, to heavy and the tires start leaving the track. Have you found the range of oils that work in between those two extremes?