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Old 06-02-2011, 12:06 PM   #1
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Default Tune With Camber Links

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?
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Old 06-02-2011, 12:45 PM   #2
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You are correct but what he is describing is a bit different. Camber is merely the orientation of the wheel to vertical. Obviously if you shorten the turnbuckle, the wheel tilts topside inward. What he is referring to is a bit different. Let's say you have 2 different camber link holes side by side in the shock tower. He is talking about moving the link from one hole to the next thereby shortening the overall length. You still need to fine tune the length to this new position to get the wheel camber you desire though. He is saying that you don't get camber by merely moving the tie rod end over a hole. It is a threaded adjustment.

There are a few things about that article that are wrong. First off the upper link length does affect roll center. Roll center isn't a static location. It moves with suspension travel. The shorter the upper link, the more the roll center moves with suspension movement. The longer the upper link, the less it moves around with suspension movement. As you compress the suspension, a shorter upper link will begin to point downward faster and faster than a longer one, even if they have the same orientation at the desired ride height and hence the same roll center at ride height. That would be the only time they are the same. The primary advantage that newer cars have over the older ones from 20+ year ago is that due to the longer arms and links, the roll center moves around less with suspension compression.

There are some other things wrong with the article that I won't get into right now.
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Old 06-02-2011, 12:56 PM   #3
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Quote:
Originally Posted by fredswain View Post
You are correct but what he is describing is a bit different. Camber is merely the orientation of the wheel to vertical. Obviously if you shorten the turnbuckle, the wheel tilts topside inward. What he is referring to is a bit different. Let's say you have 2 different camber link holes side by side in the shock tower. He is talking about moving the link from one hole to the next thereby shortening the overall length. You still need to fine tune the length to this new position to get the wheel camber you desire though. He is saying that you don't get camber by merely moving the tie rod end over a hole. It is a threaded adjustment.

There are a few things about that article that are wrong. First off the upper link length does affect roll center. Roll center isn't a static location. It moves with suspension travel. The shorter the upper link, the more the roll center moves with suspension movement. The longer the upper link, the less it moves around with suspension movement. As you compress the suspension, a shorter upper link will begin to point downward faster and faster than a longer one, even if they have the same orientation at the desired ride height and hence the same roll center at ride height. That would be the only time they are the same. The primary advantage that newer cars have over the older ones from 20+ year ago is that due to the longer arms and links, the roll center moves around less with suspension compression.

There are some other things wrong with the article that I won't get into right now.

I wouldn't mind at all if you got into it. This article seemed a bit "off" on some aspects --- that's why I wanted to post it. Get some other insight.
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Old 06-02-2011, 01:23 PM   #4
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The problem with nearly every article that I have ever seen is that while they try to get technical, they stay too general. Shock and spring threads/articles are a prime example. They'll state generalization like stiffen the front for understeer, stiffen the rear for oversteer and things like that or using a stiffer front spring and the front will carry better off of a jump. All that does is further mess a person up as they have some info but no knowledge. It's hard to educate people without giving up your "secrets". I have no team loyalties however so I don't mind.

I have yet to see an RC car suspension article that flat out tells you where to start tuning. Everyone says start with the tires. Understandable and somewhat wrong. You start with a set you know should work well for your conditions. The reality is that you first start tuning on the bench without running the car. The very first thing you start with, ALWAYS, is the springs! Real car performance handbooks state this. Real race car tuners know this and it's what I was taught when I started tuning RX-7 suspensions for road course events. The key is balance and you can't get it with generalizations or guesswork. Tuning a car is systematic. You must first truly understand what everything does and know how to use it properly. Once you know that, tuning isn't all that hard. It does require time and effort but you at least know what is happening when you make a change.

Spring rate balancing.

Any suspension has a natural frequency that it wants to resonate at. That is, the speed at which is will vibrate in an undamped state. To start tuning you must begin with absolutely no shock oil in your shocks. Springs only. Pick the car up and drop it. 5 or 6 inches is fine. Just drop it off the roof! Make sure you drop it level. If the front and rear bounce at the same rate, you have suspension balance. You may run into a situation where one end bounces much faster than the other. This is bad and what may happen is the car will porpoise. Think about how the animal swims and watch the way the car bounces. You'll see it pretty easily if you have it. FWIW: It is far easier to find an unbalanced setup than a balanced one.

Each end of the car has a natural suspension frequency. This is what you are trying to balance. You want them to go up and down at the same speed. The faster they bounce, the higher the suspension frequency. Typically high frequencies are used for smooth surfaces and lower frequencies for rougher. Off road cars will typically use lower suspension frequencies. There is no one right answer as to what it should be though. Overall balance is most important though so always go for balance first with attention to overall rate second.

Typically you'll find that many cars have much higher front frequencies and that the front of the car will spring up very quickly in relation to the rear. A couple of things can be done to fix this. Since I like to default to whichever end is slower, I'd find a way to run a lighter spring in the front. You can also try moving the lower location to different spots. Farther out gives you more leverage and hence a higher frequency for the same spring. The upper location lets you fine tune. When you achieve balance, it's obvious. When you have an unbalanced car, it's obvious. It does take trial and error to get this right but the nice thing is that you don't have to run the car to figure it out. I have many different spring rates and have sat there for a long time trying to get a spring combo, shock mount location that achieves balance.

Many people like to run the lower shock location as far out as possible. Again this is another one of those areas that too many people give too general of information on. I find a combo, regardless of where the shock locations end up, that achieves balance. Balance always gets priority. With patience you can potentially figure out all the different spring combos that achieve balance with every shock location. You'll be there a while.

Only after you have a balanced setup do you add shock oil. I start with 20W front and rear. Now you need to drive the car. If the front and rear bounce around too much on the springs then go up the next weight. Let's say the rear end settles down and isn't bouncing around on the springs and the rear isn't so stiff that the wheels are starting to bounce on the track. It's perfect. Leave it alone. Let's say the front is still spring bouncing though. Keep going up in oil weight until it doesn't. You can adjust this a little bit as typically you have a range to work in so again, there isn't always 1 right answer but there is one correct range you should be in. Typically on a rear motor, 2WD car you'll have a front oil weight higher than the rear assuming of course your spring rates are balanced. You're done with springs and shocks for now. Next it's on to roll centers, and then tires.

This is obviously a very different way of doing things but it is how real race cars in the real world get setup and I can absolutely say it works in the RC world equally as well. The only difference in the real world is that you aren't typically adjusting shock oil but are instead adjusting internal dampening to give the desired shock and rebound settings. On my RC10, I have blue springs in the rear with the next to outer lower and upper shock locations with 40W oil. In the front I have green springs on the inner lower location with the middle upper location running 60W oil. It's perfect. I know it's an old car but it will outdrive most new cars at the track since most of the guys at the track are setup wrong. If you don't have a balanced front and rear suspension frequency, every little bit of tuning you do from here on out is a bandaid.

Start playing around with this little exercise to get an idea of how it works and I'll add to suspension tuning later on. Keep in mind this technique works regardless of whether the car is 2WD, 4WD, rear motor, or mid motor. It doesn't matter and the end result is always the same. If the TLR22 guys that are running rear motor would use this technique when they try the mid motor setup, they'd find the spring rates and dampening is completely different between the 2 setups (as would be the roll centers that work well) and that many of them may actually like it.
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Old 06-02-2011, 02:29 PM   #5
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You have made the most sense from anything I've seen thus far with set up.

I have to clean up my car from Memorial day weekend this evening. I'll clean out the car and begin messing with the suspension.

Just to confirm, you simply remove all the shock oil, reassemble the shock (leave the pistons and everything alone) --- and start from the highest tensioner point on all shocks? (You know... where you can put more pressure on the suspension, or less).

You then balance out the car by adjusting those tensioners yes?
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Old 06-02-2011, 03:09 PM   #6
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Your spring tension is adjusted to whatever ride height you desire but you must perform all of these tests with full electronics installed including battery as they are all vehicle weight.

The goal of spring and shock tuning is to balance the car and tune them to handle the bumps. That is all that you should be using the shocks for. They aren't tuning aids for better cornering although if you get them setup properly you'll find the car does turn quite well. Proper tire selection and roll center selection are used for cornering ability and vehicle stability. Shocks only absorb bumps and jumps.

You can use whatever pistons you like inside the shocks once you get to the shock oil stage but just make sure they are all the same. Typically I'll start around the middle. On Team Associated shocks I'll start with a #2. Keep in mind that after you have everything completely balanced on the car, if you find you need a stiffer spring rate in front after driving on the track, you MUST also stiffen the rear to keep the balance the same! Springs must be changed/adjusted as a full set and not only as front and rear. Only shock oil can be adjusted differently at each end and even then it won't vary too much. You won't have 10W at one end while 60W is at the other. You get the idea.
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Old 06-02-2011, 08:13 PM   #7
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I have all of my electronics installed (including the battery).

I have emptied out the shock fluid (25wt in front, 25wt in rear).

I'm now on straight shocks.

I apologize as I'm like a child on this subject as I don't seem to fully understand. I understand the concept of dropping the car 5 to 6" off the ground and getting the spring rate the same around the whole car, but If it's not the same... how do you make it the same? How do you adjust it? I was just going to tighten down the spring tensioners as needed in the front and the back. Is this how you find the optimal balanced spring rate?
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Old 06-02-2011, 08:32 PM   #8
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i think what he is saying is that if one end is not balanced with the other you have to change the spring itself in order to achieve this balance.all the rc manufacters sell option springs for there vehicle.the only place i can see where i would differ on his knowledge would be that there have been times for me when i needed to loosen one end or the other of my car to get it to track to my liking.an example would be a situation where the track is relativly smooth but really slick.i dont know the technical lingo for it but i can tell you wwithout question that under these circumstances putting really lite oil and lighter springs in the rear allowed the car to place more weight on the outside wheel around corners and not spin out.hopefully this guy will elaborate more on this subject,im just a avid racer with no real 1;1 car tuning experience.
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Old 06-02-2011, 11:18 PM   #9
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Correct. The spring collars are only adjusted to get a level ride height. Once you have them set to give you that ride height, forget they exist. You are done with them. Another way to see suspension frequency is to set the car on the table, floor, etc and then push one end down all the way. Let go and watch how fast it rises. Now do the same at the other end and again watch how fast it pops back up. On my old JRX2, the stock springs were so far off from each other that the back would gently rise but the front would snap up so fast that the wheels would come off the ground. Many of the issues of that old car that were dealt with in subsequent versions of the car were actually bandaids that wouldn't have been necessary had they have offered a better match of springs. Anyways back to the suspension...

If you get different suspension frequencies between front and rear, and you most likely will at first, the only way to change this is to change springs at one end, change shock mounting locations, either top, bottom, or both, or all of the above. When I started spring rate balancing on my old RC10, even knowing what I'm doing and what to look for, it still took me several evenings to finally get a good combination figured out. Now that I know the car and it's shocks, I can get pretty close just guessing so it doesn't take as long anymore. Always strive for balance. When you start to make some changes and play with some different springs, you'll start to figure this all out. It's always easier if you see it.

If you ever run into a situation where the car needs to become unbalanced in the shocks/springs to improve handling, you are actually experiencing a different problem that is using the unbalance of the shocks as a form of bandaid to mask the real problem. Cornering issues can be dealt with using roll centers, ride heights, and tires. Sometimes a sway bar is even necessary. Sometimes at one end and sometimes at both. A prime example of when to use one is when running a low roll center, as most off road cars do, but the shocks need to be very soft. A sway bar is almost always a must in this situation. Typically a high roll center works better with a higher ride height and softer suspension, and softer tires. A lower roll center works better with stiffer shocks, stiffer tires, and a lower ride height. A higher roll center has a greater resistance to body roll which means the shocks have less of an effect in controlling this. With low roll centers the car has less resistance to body roll which means the shocks will need to be stiffer to offset it. The lower your roll centers, the more likely you are to require a sway bar. I was going to get to all of this later on. One part at a time. Once you had the spring rates balanced and had shock oil figured out, then I was going to get into the rest.
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Old 06-03-2011, 10:11 AM   #10
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Very interesting. I wasn't aware the collars were only for determining what ride height you want to be at. I always thought they were to stiffen or soften the suspension. So far this has been a very educational thread for me!

I guess in short you're saying the only adjustments your making to spring rate is:
a. change the springs themselves
b. change the locations of the shocks on the towers

Ill make this a bit easier (so if you want you can reference my manual) -- I'm running the RC8be.

http://www.hobby24.no/ViewFile.aspx?ItemID=16246

Check out page 23. This diagram clearly shows the shock towers.

In the front there are around 7 adjustment settings and on the rear about 10.

If I have you right this is all you can do to adjust the spring rate to be equal. If you don't find that equalibrium you must change spings to a higher or lower freq. spring rate.
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Old 06-03-2011, 10:42 AM   #11
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Sort of. If you only have 1 set of springs then certainly finding the right combination using the available spots that you have is the best immediate thing you can do. Understand of course that a shock that is mounted farther out on the arms has more leverage while one mounted farther in has less leverage. There may be some circumstances where a certain track likes a farther out mounting position than another but you can't obtain balance with your available springs. In this situation you'd need different springs. There is no one right combination or one right mounting location that always works. There are combos though that achieve balance and finding these combos is what is important.

If you absolutely have to use only 1 set of springs, the important part is finding the mounting locations that achieve that balance front to rear. The reality is that if you are stuck with only 1 set of springs for the front and 1 set for the rear, assuming of course you can achieve balance with these, you'll probably only find 1 mounting location combination that works, maybe 2. The mounting locations to get there are of secondary importance. Balance always takes priority. Keep in mind if you have a combination that is balanced perfectly and all you do is move the bottom or top shock location over 1 measely hole, you will throw everything completely off! Knowing what springs to run is worthless without knowing where to run them.

I'd go buy a full set of optional springs if I were you so you can find the perfect combo for where you run. I just bought the full Team Associated spring kits for front and rear which made things much easier.

Whichever end of the car moves up and down slower than the other with no shock oil is the end you should try to balance too. In other words work on slowing the other end down. If you can't get it slow enough, then work the other end.

You'll figure it out. It's a neat learning process through trial and error and you'll fully understand it pretty quickly after playing with it a bit.

I know there are some people that are probably reading this thinking I'm a nut since you never see anyone tune this way. Too many people spend too much time on trial and error based on guesswork rather than logic. Sometimes these people never find a good setup. Other times they finally stumble on something that works well. It's not to say you can't get there through trial and error and just by knowing what your car is doing. My way is easiest and damned near foolproof regardless of car size or style. Keep in mind most people arrive at a bandaid type of setup that works well enough for them. One way is to have a big spring rate imbalance front to rear but then to use severely different shock oil weights front to rear to compensate. You may obtain a front to rear frequency balance this way BUT at the expense of cornering ability and/or dampening ability over bumps and jumps. This way makes it possible for the car to be balanced but not be stable! Then those people will try to bandaid other things to compensate. If you start wrong, nothing after that point can truly be correct.
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Old 06-03-2011, 01:28 PM   #12
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I have located the additional spring sets for the front and rear. Each come with 3 different springs. It's only 30 bucks, but I'll have to wait to get them ordered until next week.

So for the time being I'll be using the stock springs to find the correct balance. I'll do what you said and move them around accordingly and see if I can get that balance (or at least for now darn close to it). I'll work on that tonight.

Once I do get balance (or damn near) --- It should be time to add the shock oil. The oils I have to work with right now are:

25 wt.
27.5 wt.
32.5 wt.
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Old 06-03-2011, 01:37 PM   #13
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Quote:
Originally Posted by fredswain View Post
I know there are some people that are probably reading this thinking I'm a nut since you never see anyone tune this way. Too many people spend too much time on trial and error based on guesswork rather than logic. Sometimes these people never find a good setup. Other times they finally stumble on something that works well. It's not to say you can't get there through trial and error and just by knowing what your car is doing. My way is easiest and damned near foolproof regardless of car size or style. Keep in mind most people arrive at a bandaid type of setup that works well enough for them. One way is to have a big spring rate imbalance front to rear but then to use severely different shock oil weights front to rear to compensate. You may obtain a front to rear frequency balance this way BUT at the expense of cornering ability and/or dampening ability over bumps and jumps. This way makes it possible for the car to be balanced but not be stable! Then those people will try to bandaid other things to compensate. If you start wrong, nothing after that point can truly be correct.
I 100% agree with this statement. I've been into the hobby for a long time, but I've been about the "band-aid" treatment. If it's off here, counter act with this, or counter act with that. More shock oil here, more or less camber there. I've been hoping to gain some knowledge... good knowledge how to make a proper set up from start to finish. I'm really appreciating all of your good advice!!! I'm giving it a real "go" and i'll look forward to seeing how the new set up works compared to my guess work prior to this.

To give you an idea where I'm running.. about 300 ft. of track. Usually a bit loose on the dirt (it's not high quality dirt... some small stones here and there). The Tripple section has a 3 foot launch and a 25ft (or so) distance to make the tripple. Not much time to line up for it after coming into turn 1. There is a double after that followed by a smooth table top. Otherwise a couple of small ones with an "S" turn that's a bit tricky, but that's it. It's a decent size track. Very nice. It's mid size for 1/8 and larger for 1/10.
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Old 06-03-2011, 02:54 PM   #14
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I forgot to mention how to tell if you have a good ride frequency after you've found balance. You can be balanced but not be good for your particular track. It's easiest to tell if you have too high of a suspension frequency (too stiff). What will happen is that when you first start tuning with a low weight shock oil, you'll find lots of spring bounce meaning your wheels will stay on the track just fine when smooth but the car will still bounce up and down on the springs, much like it does when driving with no shock oil.

Your goal is to get to a shock oil that stops this spring rate bounce, or minimizes it, without getting so stiff that the wheels themselves start to bounce off of the track. If you have too high of a suspension frequency you'll never find this point. You'll have spring bounce and then you'll get wheel bounce but you won't ever truly find the middle. You'd then need a lower suspension frequency. Any frequency equilibrium below this level could be used but for the most stability you want the suspension frequency low enough to effectively dampen the bumps yet high enough to conform to all terrain while not bouncing the vehicle around all over the place. Only you will be able to determine where this point is and it may be different from one track to another.

I have access to 2 tracks. One is outside, much rougher, with much softer loamier soil. The other is covered although not indoors, hard packed nearly blue groove clay that is fairly smooth with larger jumps but fewer bumps. The outside track wants a lower ride frequency than the harder clay track and entirely different tires. Basically everything. The races here alternate each weekend between tracks. They race at one track one week and the other the next week. You nearly always see the same cars show up week to week with exactly the same setup from the other track. I see people change 1 of 2 things but many times both. The first and most obvious is the tires. The other is tuning the speed control to change timing or to dial out some power. I rarely see people changing the suspension setups although a couple do. The same people typically win or place near the top week after week too.

I see one particular guy week after week changing his timing and esc settings between heats. He trys different tires and combos. Just looking at his car you can tell it is setup poorly. He probably doesn't know any better and no one has helped him learn. I actually think he's probably a decently capable driver but with a car that is setup so poorly it's very hard to drive smoothly.

A well setup car can make an average driver look good. A poorly setup car can make a good driver look average. A well setup car makes a good driver look amazing. A poorly setup car makes a poor driver a road hazard!
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Old 06-04-2011, 07:31 PM   #15
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Hi Fred,

I'm still working on the suspension to get balance, but I was approached with an interesting point from a buddy of mine. I'm sure after a few days he'll chime in on our discussion. Great guy.

He said he thought of the collars as tensioners to adjust spring rate, and not just used to determine ride height. So, when you're going off a jump, you can control how much spring rate you have by increasing collar pressure or decreasing it. It's usually about finding balance from the front to rear.

Although he does believe blancing is absolutley important, but only to a point with off road. Those collars are key to determine lift off. On the flip side, the shock oil is key for the landings. Not to say one is soley the determining factor over the other for take off or landings. They go hand in hand, but ultimately he felt these 2 things are their major functions. Cornering and stuff is just another subject, relative of course, but another factor aside from this.

For on road he agreed 100%. For off road he agreed mostly. Said it's not a bad idea and to give it a true go, but the collars and their function seem to be a bit up for debate. It kind of make sense the collars would provide increased or decreased recoil, don't you think?
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