Outcast Outcast Squat - Good or bad?

Magnus_CA

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Hi All,

Been running my Outcast on grass and asphalt the past few times out and I noticed the back end likes to squat when accelerating and at/near full throttle. I know that this is to be expected to some extent when accelerating but I wonder if this desired behavior at a high rate of speed. It really surfs on grass. I've upgraded my springs to tekno oranges and plan to install some aftermarket shock oil soon but I'm not sure how much anti-squat it will provide. I was also considering lowering the rear spring collars to bring the back end up quite a bit.

So is squat good or bad and if it's bad how did you tune it out?
 

Buck

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You need squat on any vehicle to maintain proper traction under acceleration.
There does come a point however when there is too much, especially on a 4WD vehicle because the weight distribution is too uneven which results in not getting enough front wheel 'bite'.
Ways to combat this;
Lower rear shock collars, so that when the truck is at rest, the back end sits ever so slightly higher than the front.
Throw some 1000cst (or greater) shock oil in...and set your rebound to max. Normally when bleeding the shock after filling, you despress the piston half or almost all the way before you screw down cap. Don't do this.
I set mine at about 95% rebound, and the truck is very quick to return to its nuetral position after rapid weight transfers.
Downside is your damping over rough terrain may not be as pillowy, but for aggressive maneuvers that induce a lot of pitch and yaw - the truck will self level more quickly and be inherently more stable.
I am using Tekno yellows all around, with more viscous oil and the truck's attitude under accel and decel is very predictable and stable.
 
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Magnus_CA

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Thanks for the reply. Suspension tuning is such a mystery to me. A couple questions about what you wrote...

Q1:

Normally when bleeding the shock after filling, you despress the piston half or almost all the way before you screw down cap. Don't do this.

Are you suggesting I leave the piston arm extended when screwing the cap down? I think this contradicts what the manual says to do right?

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Q2:

I set mine at about 95% rebound...

What are you referring to and how do you measure it to be 95%?

Thanks.
 

Stanleybb50

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I've grown to like squat. Well - I should say I go back and forth with liking loose suspension one day and the next liking it firm.

So - I decided to just have a lot of trucks now! Haha - some soft and some hard. (TWSS). :)
 

Buck

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Yes, contradictory for sure.
I did it the way the manual says, and there was zero rebound.
Truck is too heavy for no rebound (especially with stock springs).
To get 90% plus rebound, put the cap on (piston all the way out with shock oil all the way to the top but slightly concave in relation to the top of the shock body), and turn slowly about half way (slowly!), the shock will bleed. Then, push the piston up ever so slightly (5-8mm), and tighten the cap down fully.

You need to depress the piston a little to remove the remaining air in the shock and to avoid hydra locking it...and because you don't want the shock to 'explode' back to full rebound. In theory, how far you press the piston in before fully tightening will dictate how far it will come back out once fully depressed...so in the example above it will rebound slowly to almost all the way out save for 5-8mm after being fully depressed.
You may opt for more damping or less, but I think on this truck with the short wheel base the weight transference is rapid...a lot of rebound helps to counteract that rapid (and potentially destabilizing), shift under aggressive maneuvers.
 

Magnus_CA

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Really excellent explanation. Thank you. I'm going to give your method a go. I'm draining my shocks now.

I think it will be easy to tell if I've filled them right. There was plenty of fluid in the shock from the factory assembly but they have very little rebound...maybe a quarter inch. I'm sure I can do better. We'll see how it affects squat.
 

Buck

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You will definitely need to top up the fluid level a little in order to achieve more rebound. Ultimately the amount of rebound is determined by the amount of oil displaced before locking down the cap...
 

Buck

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So how did it go?
Did you get them set up with more rebound?
What CST did you use?
 

Magnus_CA

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So how did it go?
Did you get them set up with more rebound?
What CST did you use?

I let them drain overnight and picked up some washers to replace the stock ones. I'll fill them tonight and report back tomorrow.
 

Magnus_CA

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So how did it go?
Did you get them set up with more rebound?
What CST did you use?

I used 40wt up front and 35 in the rear. My results were...puzzling.

I followed the method as you suggested and when I was done I had one perfect rear with 90% rebound (which I was shooting for), one rear with next to no rebound, and two fronts with a slow 25% rebound. The difference in behavior between the two rears was night and day. I started to wonder if (at least) my rear shock was defective. I topped it off and experimented with different bleeding techniques but could not reproduce the performance of the other rear.

I start to make some progress when I was more generous with the shock oil. I removed the bladder and filled the cap halfway with oil and then installed the bladder and dripped more oil into the cap. Then I screwed the cap onto the topped off cylinder halfway and used your bleeding technique. This produced rebound similar to the other rear but the piston won't travel as far towards the cap. I can feel the pressure build up as the piston approaches the cap. The shock shaft was exploding downward, which I don't think is good.

While I was messing with my shock oil experiments I had youtube on autoplay showing various shock filling methods. It's interesting that not only are the bleeding techniques varied but the desired rebound behavior is varied as well. Some people wanted max rebound, some went for different rebound between the front and rear, and some wanted no rebound at all (which I think is what Arrma wants us to do). A lot of these youtubers were into competitive R/C! There's obviously a lot of black magic at work here.

I suspect the bladder and cap design is inferior. The bladder is hollow, which allows air to collect behind it, and the bleed valve sits below where the air collects. I don't know how the air is supposed to escape.

I'm not sure where I go from here. I think the only way I can produce a consistent result across all four shocks is if I shoot for zero rebound, which just feels wrong.

Needless to say this experience has been a frustrating one. Wah.

-Edit-

I think what I'm experiencing is hydrolocking, which Buck mentioned above but I had no idea what it was until just now. I just read about a different approach that seems promising...BlackDragon from rcshortcourse.com suggests filling the shock with oil and threading on the cap completely. Then you're supposed to unscrew the cap and bleed oil until you can push the shaft all the way in without hydrolocking. I might try bleeding a little at a time rather than all at once, which should maximize the rebound. I'd be happy with 50% across all shocks at this point.
 
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Buck

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Wow.
Ok, well first thing I can say is check the bladders...some other post made mention of the fact that the bladders were different across two of the rear shocks.
That could make a diff as one may be thicker/firmer than the other.
I would not recommend removing the bladder and filling oil behind it...you need air in there to keep the bladder firm...and also to allow it to depress slightly under full shock compression. Remove the cap, and wash it along with bladder. Dry them well and put the bladder back in, this should re-create a nice proper seal.
I had no trouble getting all of mine to rebound at about 95%.
Admittedly, it took a few cap on, cap off and refill episodes to dial them all in the same, but I did not run in to the issues you noted above...
It sounds to me like to much oil is bleeding before you fully tighten down the cap.
It is possible you are screwing them on a little too much before depressing the piston a few millimetres.
I only screwed the cap on about a third of the way...let it bleed a little, depress a few mm's, and while holding in that position then fully tighten the cap (at least get the bleeder hole past the point where it can still bleed before you let go of the rod. Tighten fully, and then when you push the shock all the way in, it should rebound to about 90%!
 

Magnus_CA

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Wow.
Ok, well first thing I can say is check the bladders...some other post made mention of the fact that the bladders were different across two of the rear shocks.
That could make a diff as one may be thicker/firmer than the other.
I would not recommend removing the bladder and filling oil behind it...you need air in there to keep the bladder firm...and also to allow it to depress slightly under full shock compression. Remove the cap, and wash it along with bladder. Dry them well and put the bladder back in, this should re-create a nice proper seal.
I had no trouble getting all of mine to rebound at about 95%.
Admittedly, it took a few cap on, cap off and refill episodes to dial them all in the same, but I did not run in to the issues you noted above...
It sounds to me like to much oil is bleeding before you fully tighten down the cap.
It is possible you are screwing them on a little too much before depressing the piston a few millimetres.
I only screwed the cap on about a third of the way...let it bleed a little, depress a few mm's, and while holding in that position then fully tighten the cap (at least get the bleeder hole past the point where it can still bleed before you let go of the rod. Tighten fully, and then when you push the shock all the way in, it should rebound to about 90%!

The oil was bleeding out when I depressed the piston, so I didn't screw them on too tight. I'll try washing the caps and bladders and see if that helps.

How long did you let them bleed while the piston was in its depressed state? Or did you just depress slightly and then immediately close?

Did you check for hydrolocking?
 

Buck

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I depressed slightly and then screwed the cap down, I didn't wait too long if memory serves, but long enough just to let a little excess drain out. If you wait to long, the oil will start to work its way back down, effectively creating a pocket of air between the bladder and oil level. This will cause hydro locking. My shocks did not hydro lock...they fully depressed, and rebounded almost fully at an even/steady rate.
I even depressed both at the same time to ensure the rate at which they extended was the same, which they were.
Ideally, they will extend a little quicker when they first 'release' after being fully compressed, and then maintain an even rate until the end when they slowly stop moving.
Holding the shock body, fully depress the shocks down on a counter top or table, than lift both off at the same time and watch the rate at which they extend.
Like I said, it took me multiple times of openeing and slightly refilling (wash, rinse, repeat, lol), before I got them in sync.
People say rebuilding shocks is an art...don't know if I would go that far, but it certainly is not easy to acheive equal rebound (extension and rate) the same across both sides.
Truth be told I went through about 45ml's of liquid before all was said and done!!
First time I had ever done it...a lot of trial and error.
Watched a ton of videos and how-to's...everyone has their own way, and opinions about how much rebound is ideal or optimal.
Keep at it, all I can say is after a while you will get it bang-on...just takes a little practice and patience.
 

robl45

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I"m sorry, but this is idiotic, you are not setting more rebound, you are leaving air in the shocks. Good way to bend shock shafts.
 

Buck

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Instead of making disparaging remarks, why don't you offer your take on the matter?
There is nothing wrong with the method I have described.
Setting rebound is directly correlated to how far you depress the piston before securing the cap and a direct result of how much oil is displaced in the shock body prior to fully tightening it.
Fill shock with oil, exercise the piston and let stand for 15 minutes to remove air bubbles, screw on cap part way to bleed the shock, and then set desired rebound based on depressing the shock rod and tighten the cap.
There is countless articles and how to vids about the procedure.
I used this procedure and my shocks function perfectly, no bent rods, and good damping.

I"m sorry, but this is idiotic, you are not setting more rebound, you are leaving air in the shocks. Good way to bend shock shafts.
 

Magnus_CA

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So I had to give up on filling my shocks so I could reassemble her. I got good rebound on the rears, very close to 95%. The fronts were next to impossible to get more than 50% but I was happy to get them performing similarly. I noticed some of the holes in the pistons weren't deburred, which may have contributed to some of my trouble.

Regardless of not having the shock rebound all around I set out for my truck is running great. Between heavier shock oil, new springs, and a lot of work on my alignment my Outcast is handling like a beast. Thanks for all your input Buck!
 

Buck

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Awesome Magnus, good to hear!!
Feels great after some time and effort to get things running nice and smooth and to your liking with a noticeable improvement ;)
I am finding that every time I work on my truck I become more in tune (no pun intended), with finite adjustments and the impact they have on various aspects of performance.
Beast on brother!
And thank you for you all your advice and input regarding alignment and end point adjustment!
 

robl45

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The piston has holes to let it move through The fluid. The bladder may give a bit of rebound but any idea of setting it defies logic and equates to leaving air in the shocks.
 
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