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Tune With Camber Links

Old 05-31-2012, 09:56 AM
  #946  
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I've done a little more reading and thinking on this whole RC thing...

The way I am seeing it right now is that the RC "position" (the convergence point from those imaginary lines), do not correlate to a raised or lowered RC.

The way I am understanding it now, is that a raised RC is increased resistance to roll (high RC, high resistance).
And the way to get more resistance is to angle it in on the inside so it pushes against the opposite side (I'm not sure if that sounds as clear as it does in my head though).
So more angle on the upper link will also increase the camber change during suspension travel.

This way I can see how through a suspensions travel, the difference in angle between the lower and upper link can reduce, causing the RC to lower (less resistance).


Any of this correct?

I suppose with my new understanding of it, I can see why it would be important to have a closely balanced RC front to rear, one end will roll a lot more than the other if they are too far apart.
But would be impractical or not suit real world needs to have them the same.
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Old 05-31-2012, 02:20 PM
  #947  
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The spring balancing was intended to get the suspension frequencies the same from front to back. This helps avoid porpoising and other stranger wavelets that might hit the chassis as a result of the differing frequency from front to rear. As Fred always stated: the shocks are for absorbing bumps and jumps. If you follow through on this, the setting of the springs should be fairly simple and the damping needs should be obvious when you start your testing. From there, you start paying attention to how the car handles through the corners. What I have found at that point is that it should be relatively small adjustments to get a pretty decent handling car. My track in my back yard is pretty loose, low grip. I tried and tried to set the car up to make hard traction in the rear end. Finally, I surrendered that and went to short camber links in the rear. It lets the rear end slide out under power in a controlled manner and I can carry a lot more speed around the track without having to work as hard to do it.
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Old 05-31-2012, 05:39 PM
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If you are replying to what I said above, I probably should have been more clear.
When I mentioned balance, I was on about roll centre balance.
As in to have the front and rear roll at a similar rate.

Also, I do have one question about roll centre, does the resistance increase if the link is adjusted too far either way?
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Old 06-03-2012, 09:47 PM
  #949  
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To Fred or any of the other big-guns in this thread:

I've managed to find a great spring balance with as similar a shock angle as possible. After racing today, the back end is bouncing when I punch it down the straight, and feels like it donkey-kicks a bit coming off of jumps. The rest of the car in almost all other areas of the track feels great. I just need to calm down the rear a bit.

Inside the rear shocks are the #2 Associated pistons, as well as 27.5wt oil. I originally started tuning with 35 weight oil and stepped down in 2.5 increments. In my head, I'm thinking I need to put in the piston with the larger holes and stick with the 27.5wt. I know you're supposed to compensate for the larger diameter holes with heavier oil, but the behavior of the rear end can be pretty dramatic.

The question is, would this calm down the rear by increasing the rebound rate and reducing the amount of pack when going off a jump? If I'm wrong PLEASE correct me.
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Old 06-04-2012, 05:12 AM
  #950  
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Is there a 4wd diff tuning guide in this thread? I can't find it.
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Old 06-04-2012, 05:19 AM
  #951  
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I would think heavier oil if ur springs have nice balance .
I know its not the same but in my scte I worked on it for about 3hrs trying to find 2 different balanced spring set ups . Went with the lightest set first and omg it feels awesome as long as I'm smooth on the throttle bumps felt great , jumps did also ( its a long line SC track w no big jumps). I went with 4hole stock pistons with 32wt in front and 27.5 in rear in even when dropped with oil it still has same frequency and don't bottom out on table if dropped under 2feet. I went from being about a sec off pace last race to having the fastest top 5 laps this weekend . Now I just need to make the other 12-15 laps that clean . Lol
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Old 06-04-2012, 05:34 AM
  #952  
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Why heavier? There was heavier in them and the performance was not as good.
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Old 06-04-2012, 06:51 AM
  #953  
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In regards to pack and the effect of hole size and oil weight in the shock, there is lots of bad info on the internet and no clear explanation as to what the difference truly is other than to say combo X has "more pack" while combo Y has "less pack. Here it is in layman's terms and keep in mind that this may go against what is stated somewhere else online.

Pack is based on the speed of the shock oil passing through the holes in the pistons. A smaller amount of hole area will lead to more pack and a larger amount of area will lead to less. There are some places online that get this backwards.

Let's say we has a shock that has 2 holes in it and it has 40 weight oil in it. Now lets say we have another shock just like it that has 1 hole in the piston but 1 hole but 40 weight oil in it. Lets assume the holes in the piston are all the same size. Keep in mind this is an example only and the numbers chosen are for illustrative purposes only so don't get overly caught up in if this is completely accurate or now. It's the mental image I want to convey.

We would logically think that twice the oil thickness going through half the area would equal the same amount of resistance. However the shock with the single hole and the thinner oil will pack faster. It all has to do with the hole area. The movement of fluid through this smaller area has to happen twice as fast as the shock that has 2 holes. I know the viscosity of the oil is different but it still doesn't change the fact that the oil still has to go through a certain place in a certain amount of time. You'll hit a certain point where the shock needs to move so fast that the flow through this hole ends up being turbulent and can't move fast enough. This will cause the shock to just not keep up with the demand and it will pack. It won't compress as far as necessary in the time demanded of it. This may or may not be a problem though.

The shock with the 2 hole piston and the 40W oil however may be able to keep up just fine. The speed of the fluid through the larger area is slower. At higher shock speeds it will be able to keep up better and will pack less. The difference in hole size will not be made up with the thicker oil at these speeds. The average speed of the oil through the holes in the piston is over a smaller range than that of a smaller hole/area in the piston. It will pack less as velocity increases. What if we used 3000W oil but no piston? We'd only have the resistance of the shaft moving back and forth and would have zero pack. The oil can't make up for it. This is the extreme example of no pack. The larger the total area of the holes in the pistons, the less the fluid needs to "move" as the piston compresses.

There are a couple of ways of looking at pack. Most people will say that on bumpier tracks with smaller jumps you want less pack and smoother tracks with large jumps you want more pack. In general this is true. What about a bumpy track with large jumps? It's a compromise.

Now remember how shock location on the arm and it's angle affects spring rate, it also does the same for dampening. I stated at the beginning that it wasn't uncommon to run a thicker oil up front than in the rear. Using the same pistons it's easy to see why. A local guy here swears by running more pack in the front and again it's easy to see why. If you've got a setup that requires a 3 lb spring in back but a 4.5 lb spring up front to balance due to arm mounting points, you've got 50% more static spring rate up front to equal the same wheel rate. Pack will respond in a very similar way. A higher shock oil may work up front or more pack. They each behave a bit differently on the bumps and I may change back and forth depending on what I need to car to so. I've gone more pack in the back but if the track is rough the car will get unsettled in the rear and won't take the bumps as well at that end. My current setup is using the true balance method with balanced springs, the same shock oil all around and more pack up front but again this changes with the track needs and the difference between them in terms of handling can be quite extreme even though on the bench it all balances.
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Old 06-04-2012, 06:54 AM
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It depends on HOW it's bouncing. If it's bouncing around on the springs, then you need to go up in oil. However if it's bouncing around on the tires (ie. tires coming off the track) then you need to go down in oil. In your case it sounds to me like you're probably having more wheel bounce. In that case I would try going down some in the back.

If you can't find the proper performance in oil (either by going up or down) then it's probably your spring rate. You might be running too hard of a spring rate.

Usually when it comes to pistons and pack, you're going to want to look how your landing, not how you're coming off the jumps.
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Old 06-04-2012, 07:08 AM
  #955  
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Originally Posted by darcness
It depends on HOW it's bouncing. If it's bouncing around on the springs, then you need to go up in oil. However if it's bouncing around on the tires (ie. tires coming off the track) then you need to go down in oil. In your case it sounds to me like you're probably having more wheel bounce. In that case I would try going down some in the back.

If you can't find the proper performance in oil (either by going up or down) then it's probably your spring rate. You might be running too hard of a spring rate.

Usually when it comes to pistons and pack, you're going to want to look how your landing, not how you're coming off the jumps.
Many Thanks to you and Fred for the reply!!

My truck is bouncing on the tires, not springs, coming down the straight. If I don't perfectly land a jump, the truck will donkey-kick a bit and the rear will come off the ground. As I said, moving down in oil weight systematically from 35 to 27.5 as suggested in this thread has helped, but the problem is still there.

Am I correct to assume that maybe its time to try a piston with larger holes? The #2 is in there now, a #1 would have slightly larger holes. Please keep in mind that my track has huge airs, is large, a bit loamy, and kind of bumpy. (you know, an actual offroad style track ;-) )
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Old 06-04-2012, 07:09 AM
  #956  
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Pack is based on the speed of the shock oil passing through the holes in the pistons. A smaller amount of hole area will lead to more pack and a larger amount of area will lead to less. There are some places online that get this backwards.
It is common to hear talk about the surface area of the piston being greater, which is the same as the surface area of the holes being smaller. Just thought I point that out since after reading through most of this thread, I have seen it referred to both ways, which both are correct.
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Old 06-04-2012, 07:13 AM
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@Hinecken

What it sounds like to me, you are referring to chassis slap(after jumps). if that is indeed the problem, try increasing pack, or going back up on your oil weight and try again. But then again, increasing pack may not be the right fix for the straights.

Is the truck bottoming out on the arms under full acceleration?
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Old 06-04-2012, 07:20 AM
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Anyone find spring / dampening balance on there TLR 22 (rear motor config / reg pack, no shorty). Just wanted to compare notes.
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Old 06-04-2012, 07:47 AM
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Originally Posted by Rob Phillips
@Hinecken

What it sounds like to me, you are referring to chassis slap(after jumps). if that is indeed the problem, try increasing pack, or going back up on your oil weight and try again. But then again, increasing pack may not be the right fix for the straights.

Is the truck bottoming out on the arms under full acceleration?
No chassis slap at all. Truck does not bottom under full acceleration. The faster I move down the straight, the less time the rear wheels are in contact with the ground.

Let's ignore the jumping for now, and just concentrate on the straight. That's really what I would like to correct. The straight is 120ft long and not so smooth if that's helps.

Again, thank you for your help. Truck feels great everywhere else.
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Old 06-04-2012, 08:00 AM
  #960  
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So I now retract my statement. U origionaly said it bounced around. ... now it does it on the tires . So on a scale of 1soft-10hard springs where would u think ur at? O and what hind of truck 2wd or 4wd
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