Fred,

Thank you for doing this research! I appreciate your findings on alternate spring sizes. Looks like there are a few more options out there I was unaware of.

Here are the pistons I'm running:
http://www3.towerhobbies.com/cgi-bin...FVSEARCH=89353

With the AE bronze 5.90 springs in front and the silver 3.30 in the rear, are you sure you've actually got suspension balance and instead didn't exactly double the front effective rate over the rear? I was pretty sure. I pushed the car down and watched all 4 come up at the same time. I did a drop test and it looked fine. Took a little spin and it looked balanced. These are the springs that come with the car at kit build, and as Chris said

"As far as spring and shock mounting locations they both only made one change from the standard FT setup. They both ran brown springs in the front and green in the rear, just like the FT setup. They both mount their rear shocks at position 1-I just like the FT setup. They both mount their front shocks in the O position on the arm, just like the FT setup. The difference was that they both moved the front top location to the 1 position instead of the 2 position, just like I found in my test. My tests conclusion gave me the exact same springs and mounting locations as the Ryans! In the end it proved to me that the testing I did was spot on."
--

The bronze and silver came with the kit. I assume that balance is pretty achievable with this set up.

You said the fronts are mounted all the way out on the bottom. Where are the rears mounted?

The bottom of the front's springs are mounted on the outter hole. The top I had brought down 3 hole (I believe from the stock set up). This did in fact prove too much on the front - which is why I ended up bringing the collars down, and while this did improve performance -- the front end did still felt a little heavy. Not as bad, but a bit.

But with this change on the front tower location i can tell you this..... I had 150% improved cornering ability. I ultimately (last night) decided to bring my front spings up 1 notch each and left the bottoms on the outer hole.

This just doesn't add up to me without the front of that car being insanely heavy compared to the rear which I know it's not.

I also had moved the rear suspension from the kit's recommended starting point down 2 holes. I have the bottom of the rear shocks on the inner hole.

I do feel like the car is a bit off balance, mainly due to the feel in the air over the tripple, but it's just so planted now in the turns....

this may be the first thread i have read word for word... keep the information coming guys.

Ok cool. Thanks man. I won't. :cool:

I had said something in 2 previous posts that may have sounded contradictory so I want to clear it up. I'm surprised no one called me out on it although I'm sure someone will find a hole in this explanation too! Earlier in the thread I stated that the shock collar adjustments do not change spring rate, which many other have also stated. Later in another post I said that tightening the shock collars has an effect on spring rate. This may sound confusing but the problem is in the way we need to think about things. Having an effect on and changing aren't necessarily the same thing.

I'm fond of using analogies to try to get a mental picture going but sadly they don't always help! :lol: So here comes another one anyways. Once you get your effective (also known as dynamic) spring rates figured out where the front and rear of the car bounce in harmony at the same time, you've got it. The effective spring rates are the same. However what about the shock collars and the effect of tightening them down? Think of the shock collars as the volume knob on your stereo. It changes intensity. It doesn't change the station. You've already got it. You are merely turning the volume up or down but it's still the same thing you were listening to. You've just got more or less of it. Visualize your shock collars in the same way. You are just adjusting the amount (volume) of your suspension to your liking. You are getting more of the same thing or less of the same thing. Suspension tuning is basically the same as making sure each speaker in your stereo is playing the same station (assuming of course they can be setup to play different ones) and that each speaker is playing at the same volume level.

Did that confuse anyone even more?

I did some more experimenting on my slash yesterday and I have a problem. I do not know the rating of the springs other than they are in the 2lb range. I am running 45WT oil in the front and 40WT oil in the rear. The truck is still bottoming out over almost everything however I do not want to go much thicker because it looks like it is starting to bounce over the bumps. Should I get some stiffer springs and run lighter oil?

It would be valid to try. Changing the pistons inside the shocks to increase pack would also be something else try to. If a setup isn't working somehow, don't be afraid to try something else. You can never be truly certain if it works or not until you try it.

Do you have a 2WD or 4WD Slash? The reason I ask is because a good friend of mine just bought a 2WD Slash and I may help him tune it over the next month or so.

Actually Fred this clears a lot of regarding the shock collars. That anology was actually very good! I'm not in much doubt anymore my car is not balanced. Remember - the initial place I had all this gave my car balance. The only changes I have made have been bringing up the front suspension 1 hole on the tower and messing with the collars.

So you know how some stations come in on 2 different stations? In our area, 103.5 came in on 103.9 as well. Same thing with my stuff. I moved the shocks up a hole. Same radio station, same song, just a different selection on the dial.

It's time to get into tuning with camber. This is a pretty intense topic that has been written about extensively elsewhere so I'm going to suggest that anyone interested do an online search for roll center and the effects of changing it. You'll find tons of information. This is still going to end up being a very long post though so grab a drink and take your bathroom break now. When searching for roll center aricles online, try to stick to more tech oriented articles rather than online threads discussing the topic as threads can get confusing if you weren't involved in the whole thing. What I will talk about is some generalizations and things to look for in regards to roll center tuning.

Let's go back to the first serious off road r/c car, the original RC10. True there were cars before this but it was the RC10 that really caused offroad racing to explode and evolve into where we are today. Car design has changed over the years and typically it is because track design has changed.

The original RC10 was built with no preconceived notions. The designers looked at real offroad buggies and designed the car around them. There was no other real good frame of reference. The original car had short suspension arms, higher roll centers, and sway bars. To say those cars had lots of roll stiffness built into them is an understatement but they had to since the shocks were typically set much softer than they are now. The tracks of the day were smaller and tighter than they are now with more bumps and small jumps but without the large fast monster double and triple jumps we have today where you can be airborn for 30 feet. The tracks were also much looser and traction was lower. The motors of the day were also much slower. Car design and track design go hand in hand. If you take that original car and run it against the modern stuff on a very fast blue groove track, it'll probably get it's butt kicked. Conversely if you take a 22 and run it back on these older tracks, it would probably get it's butt kicked in return. You need to design a car for your particular track conditions. You also need to tune for it. So where am I going with this?

The current generations of cars have very long suspension arms and run very low roll centers compared to the cars of 20 years ago and it all ties into current track designs which are faster with more grip. Car design and balance also determines what type of roll centers you'd want to run. Roll centers are not static locations in space. They move around with suspension travel. The more the suspension moves, the more the roll centers more. The lower a roll center, the wider it's range of movement is in space compared to a high roll center. The longer suspension arms have the advantage that their geometry doesn't change as much as a shorter arm does with travel. In other words, the car's roll centers don't change as drastically or as quickly with suspension movement. That is the main advantage to long arms and is the reason they've gotten long over time.

Generally a car with a lower roll center will be more stable at high speed. The chassis reacts slower to transients. A car with a higher roll center will generally be less stable at speed but will respond faster to transients. They will also be less forgiving. Modern cars with their lower roll centers feel easier to drive as a result. They feel more stable and this is important for high speed straights and big jumps. The wide track and longer wheelbases over the older cars also help this. However low roll centers come with a price. It makes it harder to turn. We've seen the front wheels on 2WD buggies get wider in later years to help get some front end grip back in cornering. Coincedence?

In general with a low roll center we are distributing our weight more evenly on both the inner and outer tires which will make them want to slide more and in a more controllable manner. A higher roll center will distribute more weight towards the outside tire in a corner putting more downward force on it helping it to dig in harder. However when the tire lets go, it lets go more abruptly and less predictably. If you aren't fast enough for this to happen, then it's really not a concern. Modern cars are fast though. Very fast. And tracks have more grip.

On a looser track, you can run a higher roll center since you are going to lose traction and slide easier anyways. You are trying to get some weight back down on that outside tire to help with grip. With a higher grip track you'd want a lower roll center so that when your tires slide, it's more predictable and controllable.

A rear motor car like a 2WD buggy, has an awful lot of weight out back. When the back goes around, it can be pretty abrupt. Running a lower roll center can help keep this controlled better. It will definitely make it much more predictable. On a higher roll center with all the weight back here, when the back loses traction, it may just completely snap around on you. Obviously there isn't just a high and a low roll center. There is a whole range and I'm using generalizations here to get the point across. You'll gradually transition from one extreme to the other as you work your way through the range. It's all fine tuning.

Now let's say we have a mid motor car or even a 4WD car that has better balance without the extreme pendulum effect, the car is inherently easier to control at it's extremes. You don't need to run as low of a roll center. All you'll end up doing is drifting all over the place. You can run a higher roll center and maintain control far easier. Everything is a balancing act though.

Now keep in mind if you are running a certain roll center at one end, start by setting it about the same at the other. For a 2WD rear motor buggy, I'd start by setting it very low. If you have problem pushing through the corners, raise the roll center in the rear a bit until it's balanced the way you like it. Don't necessarily be content there though. You should try to then raise the roll centers all around and drive it again. You'll know where to finally stop when you are finding the car too touchy in the high speed sections.

Shock and spring stiffness also play a role. The lower your roll centers, the more the shocks and springs control the lean of the car. The higher your roll center, the more the suspension itself controls this and the less of an effect the shocks and springs have on it. Remember I said the old cars had softer shocks and springs to deal with the bumpy tracks of the day. They also had higher roll centers to control lean to get cornering ability back up.

The lower your roll centers, the more important having a stiffer set of springs or thicker shock oil becomes since more forces are applied to them in corner. "But Fred, you said to adjust the shocks and springs only around how the car handles the bumps and not it's cornering ability." Yes I did. Hopefully your setup will all work out but what happens if your conditions require a fairly soft suspension setup but very low roll centers? If this happens then you need another way to control roll and that it with sway bars. Not all cars have them but some do. It's not to say you always need one either but you might. You might not need them at each end either. Perhaps you only need one in the rear or only in the front. Then how thick of one do you need? These are all very hard questions to answer but the best thing to remember is that if you need one, make it as light as possible while still getting the job done. Don't automatically assume you'll need one right off the bat though.

I may as well touch on tires here too since they play a role. It seems like lots of people like to run red dot tires and then just either use the standard foam or closed cell if they need it stiffer. By learning how to read your tires you can figure out what your car wants. I'm going to pick on some 22 guys here. At the tracks here I've noticed that some of these cars are showing greater wear towards the outside of the tires than the inside. This is a dead giveaway of a very low roll center. You have all that tread. Use it all! There are one of 2 things that can be done. One is to run more negative camber. Lean the top of that tire over a little bit to help get that tread wear more even where you'll use more of your tread. This may end up causing issues in handling elsewhere though if camber gets too extreme. The other thing to do is to raise the roll center a bit. This will help get the wear back in towards the middle. Keep in mind that very high roll centers wear the inside edges of the tires more but in certain circumstances this isn't always a bad thing.

Now what about foam or tire compound? There are a couple of 22's that have fairly even wear across the face but have most of the wear centered down the middle with less near the sides. These guys are running closed cell foam. As a generalization, a lower roll center wants a stiffer side wall tire while a higher roll center wants a softer side wall tire. I have a Losi XX that was given to me by a very good driver about 15 years ago. I haven't ever run it and haven't changed anything on it. I do know that he was a good tuner. That car has low roll centers and is running Losi silver dot compound tires with standard foam and it makes sense why. It needs it. He uses all the tire this way. The guys running low roll centers with the softer compound tires are compensating by running harder foam. Perhaps they should run a stiffer compound tire and instead run a softer foam. The wear patterns tell the whole story. You just have to know what you are reading.

Now since a higher roll center puts more downward force on the tire than a lower roll center car does, we want a tire that can get more compliant and can spread it's tread out better. Softer compounds do this. For a lower roll center car where the tires are going to scrub more, we need more side wall integrity which means a harder compound. The reality is that neither compount will really have an advantage in forward traction over the other. It's all about cornering and what your car needs. You don't want a tire that will fold over when it's trying to slide.

Now back to you 22 drivers. If you are running a rear motor setup, you'll want to run lower roll centers than the mid motor guys in order to keep the car controllable. You'll have entirely different springs and mounting locations chosen than the mid motor guys will to achieve balance and your shock oil selection may or may not also vary. The rear motor guys will also want to run a harder compound tire than the mid motor guys. In short, practically nothing will be the same!

I know this has been long and I've probably only opened the door for tons of questions and tons of clarification. The topic is huge though and even being general about it I've managed to write a small book. In short, to start out with, pick a roll center height and try to match it front to rear. Make small changes to help your cornering. Instead of changing springs or shock oil to help your cornering, change your roll centers at one end.

Something is telling me that this thread is about to explode with questions! Please PLEASE research the topic online first though!

The first post in this thread talk about were to place camber links to adjust roll center. On the shock tower the higher the camber link is mounted the lower the roll center. What about on the wheel hub? Is it the same?

On the shock tower, a higher mounting position is a lower roll center. At the hubs, higher mounting is a higher roll center. Keep in mind that camber link length plays a role too. As I said, roll centers move and change with suspension travel. The shorter your camber link, the faster it changes and the greater the total change. The longer your camber link, the slower it changes and the less your total change.

Does a shorter camber link give the same effect as a higher roll center and vise versa?

I have a 2WD slash.

In regards to camber link length, since our roll center isn't just one static point we need to establish that it moves over a certain range. Let's say we have 2 identical cars sitting at a level with the arms ride height. Let's say that the camber links are pointing at exactly the same direction as each other. Let's just say they are perfectly parallel to the arms. As the suspension compresses, these links move too as they have to. However one of our vehicles has shorter links than the other. When the suspension is at max compression, the vehicle that has shorter links will have them pointing at a much steeper angle than the vehicle with the longer links. At this point the vehicle with the shorter links has a higher roll center than the one with the longer links, even though at our ride height they were at the same point.

Now let's say we have 2 vehicles as above with the same setups sitting at level ride height. Now let's say they each have the exact same length camber links. One of them has it's camber links sitting exactly parallel to the arms but the other has the inside end of the links mounted a little bit lower which means the link slopes down towards the car a little bit. The one with the lower inner location has a slightly higher roll center. Now as the suspension compresses and the links move up, this one still maintains a higher roll center than the other one. The difference between them is pretty constant everywhere.

You could have a scenario with varying lengths and mounting points where one setup has the lower roll center at ride height but the higher roll center at maximum compression. There are lots of possibilities in this area.

Hopefully we'll play with that Slash in the near future. When we do, I'll post my findings and settings. Give me a bit of time though. My friend's wife is a bit controlling so it's hard to get my friend out for long periods of time. I am also about to change jobs in a week so I'll be on the opposite side of town soon. It may take me a while but I'll get to it.

Fred- not to argue with you, but roll center and its adjustment is also dependent on the vehicle. It is entirely possible to have one vehicle where raising the inner ballstud will lower the roll center and another vehicle that lowering the ballstud will lower the roll center. This again why its hard to generalize about vehicle tuning- every vehicle is different and its particular design must be considered when tuning.