Slow Motion Shock Tuning Video's

Just wanted to share some of my shock tuning video's with you from Wednesday night.

All video's have the shock settings, two step RPM, and boost information overlayed at the top of each video in red text.

All numbers are clicks from full tight. So R13C8 would be 13 clicks from full tight on Rebound, 8 clicks from full tight on compression.

Aside from the Run #1 (which was lower RPM/Boost) in the video, all of these runs resulted in spinning. But you can really see from the shock settings how it changes the way the tire is being hit, and how far it's traveling/rotating before spin starts.

Run #1 and Run #2 has the EXACT SAME shock settings, just more RPM/Boost on the launch. You can clearly see by how hard it smashes the sidewall, that "hit" changes with power of the car even on the same shock settings.

Explains a lot why one car to another can't use the same shock settings, even if it's the same brand shock.

Still tuning... but just thought I'd share. It's AMAZING what you can see in slow motion. Really the 2nd run and 5th run both just felt like it spun right at the hit... but that is not true.

You can see run 4 was ALMOST there. Turned about 1/2 or 3/4 of a tire rotation before it spun. Run 5 was with the tighter shock, and you can see I went to far. Car spun nearly right at trans brake release (not enough hit).

Enjoy... I will try to keep this up to date as I continue to learn/make the car leave on more power.

https://www.youtube.com/watch?v=jr1VILyS7WE&feature=youtu.be

As you are seeing and most find it hard to believe...........is that rarely does anything EVER spin "at the hit". Now what it does 2 tenths out is an entirely different matter.

Your goal, especially with radials is to get a shock setting and power level that maintains the hit. What I mean by that is to watch your videos and see how much the sidewall of the tire bulges at the hit. THEN you want to maintain that bulge for as long as you can. This shows the amount of "hit" on the tire and how well your setting maintain that hit. If you squash it hard, but then the sidewall springs right back, it will smoke the tire every time if you have power

What I'm still struggling with to learn is this.

1) How does compression effect hit. What I see now is that the rim doesn't bounce back into the body at all when the sidewall recovers. It appears to launch the body up. But I don't know if too tight of compression doesn't let the sidewall come back round again (get up on the tire). Is the body launching up taking the tire with it?

2) How does front shock rebound effect hit? If the car is out of travel at the front, and spins after, it means full weight transfer as soon as possible. However, does that mean tighter shocks will always make early spin worse, or can it help by delaying the full weight of the front brakes/wheels from being applied to AFTER the spin is starting.

Rear compression doesn't control the "hit" at all, because the suspension is separating at the hit........AFTER the initial hit is where the bump or compression comes into play. If the extension is soft and really lets it hammer the tire and flex the springs and tire HARD and you have the bump stiff, the shock won't settle easily, which will make the car "hop" on the tire and springs, because the shock is fighting those two things. Its a balance. You want to control the hit with extension and then "hold the hit" with the bump. So this tells you that when you adjust one side, you will also likely need to adjust the other to maintain a balance of action and reaction.

Keep this in mind.........on high HP big tire cars that run "shock boxes", we run the extension tight and the bump is locked up on the shocks and then softens the bump as you go out, to absorb the track. So the tight setting both ways really controls the housing and the hit. Obviously YOU can do that, so it's balance. This also tells you though, that really tight extension and loose bump won't work, nor will really loose extension and tight bump. For all intents and purposes, forget what the body does and watch what the tire does. The body is hooked to the springs and will do as they dictate........so if you control the tire and housing, the body will take care of itself

"You want to control the hit with extension and then "hold the hit" with the bump. So this tells you that when you adjust one side, you will also likely need to adjust the other to maintain a balance of action and reaction."

So does this mean with looser extension (more hit) the shock needs to be tighter on compression to hold the tire down? Or looser to absorb the inevitable bounce back without launching the car? (Or is somewhere in between depending on the symptom?)


Monte what do you think of the 4th run? Close on tire sidewall hit or do I need more?

How about front shocks.

Thanks a lot by the way for taking time to respond so far.

Excellent info guys. Thanks for sharing!

I agree!! Great info guys!

Cool, well timing info for me. I just got a set of DA shocks for my car. I plan to hit the track next week.

I have not looked at the videos and was just answering in generalities. But to answer your question........if the extension is pretty loose, it is going to "throw" the housing hard and hammer the tire. With this scenario, if the bump is too stiff, the reaction is going to be too stiff as compared to the action and can make the car "hop" on the springs or on the tire...........Now, how to fix it? and the answer is, it depends. If the tire really NEEDS to be hit that hard, you would need to soften the bump a little to let the housing "settle" easier and keep it from hopping. Most of the time though, the tire should not need to be just pounded into submission at the start and in that case you stiffen the ext. Seldom do you need to just hammer the tire, especially when you have power. You want to control it smoothly. When the car "feels" smooth and slow, is usually when it's fast. When it leaves like a dump truck hit you in the azz, the settings are off.

A radial has a VERY stiff sidewall, so if you actually see it bulge, you are hitting it pretty hard. If you HAMMER it and flatten it out, it WILL spring back, because you will NOT have enough power to hold it there, I guarantee it. So the goal is to bulge it a little and keep it there.

Power is another consideration. If you make a decent pass and decide to go back and "stand on it" power wise, you will most likely need to stiffen the extension. Because more power, will hit the tire harder with the same settings. This is where guys miss it. They go back, hit it hard, it knocks the tires off and they think they overpowered the track. Usually not the case. Usually they overpower the shock, hammer the tire and it bounces back and spins. A more power hit usually requires some attention in the front as well. Hit it too hard too fast, top the fronts quick and it will spin the tire

A certain track surface will maintain a certain g-meter reading, as it relates to your car. Learn to tune by the g-meter and keep detailed logs. When you look at the track, note the condition and determine the Gs you think it will hold, you put in the tune that produced that number in the past. I can usually tell you within a hundredth what our car will 60ft before we go to the line.....provided I have read the track right. I have 1.20 tunes, 1.15 tunes, 1.10 tunes, 1.05 tunes and so on. Each of these will require shock changes to be optimum

Cool videos!! Thanks for sharing... I am always trying to learn more about how everything in the suspension works together to launch the car! Thanks Monte for the technical help!!

Most guys buy some shocks, throw them on there, get some general settings from a buddy and never touch them again. That doesn't work. Where your buddy runs his settings on his shocks means nothing to your car and where it wants them. Optimizing a setup is WORK and frankly, most guys are too lazy to put in the time, nor have the knowledge and equipment to do so anyway. Now that may sound harsh and a dig at people but it is not meant to be that way at all. Most are ok with "good enough" and we see a proliferation of that when you get those inevitable responses of "my C-body rears and 90/10s work fine" whenever the shock selection threads come up. Working "fine" is a relative thing, depending on who you ask and what you are trying to do with the car.............Many guys WANT their car to 60ft better, or think it SHOULD 60ft better, but when you start rattling off changes and it may need this, or this and try this, they generally run out of patience pretty quick if they don't get instant results.........Like I said......it's WORK

Love this thread thanks again for good info dizuster and everyone contributing!

Never thought about focusing on the sidewall as a gauge for the "hit". That is good stuff right dare!

Dizuster and I just went through this my car. Using the Go-Pro we saw the housing bounce. My theory was to tighten the compression. The more I tightened it the worse it got. Then we attempted to loosen the front rebound to help it pitch rotate. We ended up with a car that went from running inconsistent 1.32-1.36 to 1.45. We rethought it. Tightened the front rebound, tightened the rear rebound and put the rear compression back in a reasonable starting area one click tighter than what we had been running. The result is a string of 1.29's. Is there more in it? I 'll bet there is. But now with a balance between rebound and compression at least it's consistent.I would have attempted more this weekend but I broke the car.
Doug

Very interesting!
Thanks, Don

my question on this subject is, how much effect does tire pressure( in my case 14X32 slicks) have in shock tuning, to me higher pressure would keep the tire from mashing as much and lower pressure would allow the tire to mash more with a given shock setting, or is this a small percentage of the equation.

bump just for some re-reading.

I'm getting a go pro for Saturday. This was my 1st pass today. Hope the go pro helps me.

tire shake, not enough power down low, low air pressure tire wadding up?

More air pressure will make it shake WORSE more than likely. More air, puts MORE rubber on the ground by flattening the tire out. NOT something a car already shaking needs.

It needs WAY more wheelspeed early, or way less hit on the tire. Impossible to know without knowing some of the settings.

Many think slicks are EASY. Just throw them on, hammer it with power and away you go...........LOL!!!........if it were only that easy. More power equals more problems.

Prime example.........I have a customer with a big tire Corvette. With a 648 on nitrous, I had it 60footing in the low 1.0s on an ET Street tire. Getting after it REALLY hard and setting the tires on fire early.........Fast forward to now and they have an 865in motor on spray and a slick. Should be easy, right? So far is hasn't been 10ft cleanly. We can't get it on the tire. Even tried leaving on TWO nitrous kits at the hit and it just rattles the tires. I have the bar out as far as I can get it realistically, lowered the tire pressure, lowered the wheelie bars, tied the front down, stiffened rear shock extension and it STILL crushes the tire. Looking at moving the motor forward about 3" now to get some more front percentage

I'm at 9-9.5 air pressure on the 14.5x32 M/T.
I pulled power out and tightened the bottom knob 2 clicks after this pass and it spun pretty bad. Took one click out and removed more boost for the 3rd pass and it spun bad again but I think the track went away a little. Then loaded up and went home. I'll be back out Sat. to try again. Hope to get a go pro under there to have more info.
I have video of all three runs I'll load up to YouTube in a few and start a new post.

I think I had less then 5psi of boost at launch and for the first .5 seconds after the 1st pass.

Can't see the tire tracks at the hit in above pic, but what we can see is that at this point it has the tire paddling BAD.

If you square up the tire at the hit, you will NEVER hit it hard enough on out to stand it up. You MUST make wheel speed early. I suspect you are WAY soft early........Most turbo guys are

I added 200 rpm to the trans break launch number and it didn't shake anymore, but it didn't hook any more either lol

Removed 100 rpm after 2nd hit and still had trouble hooking. The track may have went away some. I'm going to try to get more data tomorrow.

I seem to have the best results by taking sweeps out of the top of the rear shock. I'm going to try 1 more sweep loose before the 1st pass tomorrow..

my struts fail your floor jack test so I might have them revalved this winter. There dbl. Adjustable Strange with the koni cartridge on bottom and the hex head on top. Has 2 flats from full right hand rotation on top, bottom is about middle of adjustment.

Has me confused good lol. I pull boost out and it spins more. It's goofy.

FastmOp is this after your gear change? It might need more boost on the hit

Monte: I am going to try my new boost controller next Friday. Previously with no boost contoller, it would initially hook on 5 lb but then start to spin 5 feet out. I realize the boost controller can help with this.

But, what would you suggest I set the rears at? They are Menscer dbl adjustable AFCO. The front's only have single Strange. Tires are 315 on 12" rims at 15 lbs.

Also, I am going to add 80 lbs of rear ballast this time (2 bags of fill dirt...I mean it is a truck!)

For me... there are a few things to consider on the launch.

1) The limit of how hard you can accelerate the car forward, is directly related to the traction available at that INSTANT in the run. Don’t think that traction is the same 0.1sec into the run, as it is 1.0sec into the run. It is NOT consistent through the run…

2) The traction available on transbrake release, is totally related to how hard you hit the tire. The harder you hit the tire (up until a limit of the tires ability not to deform), will give you the most initial traction. The more initial traction you have, the harder you can initially accelerate the car.

3) The traction available shortly after the car starts to move, is totally related to how much weight you were able to shift (through acceleration) to the rear tire right after the hit.



What I mean by these is this. The more downward pressure you put on the tire to plant it, the more traction you have. The more traction you have… the harder you can accelerate the car. The harder you accelerate the car, the more weight shift you have from front to back, causing more downward pressure on the tire… this added pressure from acceleration, allows you to accelerate the car even more!

So lets look at the “stages” of a launch with some basic examples.

Stage 1 – Tire Hit
Car #1 - Lets say a car with 100% stiff rebound on the shocks (ie doesn’t move), has a given “dead hook” ability to accelerate the car at 0.5g’s forward. If you put power to the car on trans brake release to accelerate at 0.5g’s or below, you will not spin the tires. If you put power to the car on trans brake release to accelerate it above 0.5g you will spin.

Car #2 - Now let’s consider a car with a tuned shock. Let’s say you let go of the transbrake. The axle is thrown to the ground, planting the tire. This tire is pushed into the ground, and can now has more traction then it normally would, so it can now accelerate the car forward at MORE then 0.5g’s. Lets say it now has the ability to accelerate at 1.0g’s.

Stage 2 – Hit transition
Car #1 – As your converter starts to couple, and the car starts to accelerate forward, if you stay under the 0.5g limit threshold of spin, you will start to accelerate. As you accelerate, weight shifts to the rear of the car. Again adding more pressure to the tire. Lets assume that weight transfer gained you and additional 0.5g’s of possible acceleration + the 0.5g’s of dead hook tire traction, you can now accelerate the car 1.0g’s at this moment in the run.

Car #2 – Because this car has had the rear axle thrown to the ground on the hit, this added pressure from the hit already starts at the ability to accelerate forward at 1g. As the converter starts to couple, the car starts to accelerate. This acceleration can happen at a higher rate then Car #1, because the available traction from the hit was much greater. The harder you accelerate the car, the more weight shift you have. So now if you accelerate the car hard, you may gain another 1g of pressure from weight transfer, plus the 0.5g’s of dead hook, plus the 0.5g’s of tire hit. You can now accelerate at 2g’s.

Stage 3 – Acceleration
Car #1 – With a limit of 1g, you can continue to slowly add power as long as you stay under the available traction power limit.

Car #2 – At some point the suspension will run out of travel, and the “hit” pressure will be lost. This is a point where you are solely relying on your previous acceleration for pressure on the tire to accelerate you forward. If you failed to accelerate harder then the 2g limit during the Hit transition, and you have now lost your 0.5g’s available from the hit… you will only have 1.5g’s from your previous acceleration.


There are a couple other aspect to this that I have purposely ignored to simplify this. First of all… nothing actually happens in “stages” as I outlined above. There is a crossover of these things, but these are the BIG events that happen. Also chassis setup (instant center, anti-squat, etc) will effect the downward pressure on the tire. The point I’m trying to make though, is that it is good for people to understand the concept of downward pressure on the tire vs. traction vs. ability to accelerate.

Monte preaches “tire hit”, “wheel speed”, and “Getting up on the tire”. These are exactly what car #2 above is doing. Wheel speed is an indication of acceleration, it allows the tire to reform itself round after the hit, and also on a slick wheel speed (slightly spinning) can actually create more traction (and less motor load), then dead hooking.

But the bottom line is… You can see how the launch “feeds” on what you did early in the run, on what you can do next. If you don’t take advantage of the traction you have, at the INSTANT you have it… you will suffer later in the run because of it.

I sure am glad I raised an engineer.
Doug

Great stuff! Thanks for posting.

That slow motion is super slow What brand and camera settings are you using for that? Video taping, even using Super 8 film on cars on the starting line have really helped me over the years

My Saturday just got fubar. Will try to test soon at bowling green.

Diz, thanks for all the info. I hear what you are saying.

With all that in mind, do you have a baseline setup, or should I go with what I have? Of course, I can't find my log files right now to tell you what they are set at. My fronts were at full loose (Strange Single), but I changed them to +5 from full loose tonight.

Bada$$!!!!
Maybe one day I'll make enough power to need to learn more about this...best read in a long time...

On a slick tire car with power, you have GOT to spin the tire a little to go fast. Dead hook, or "stick" the tire early and it squares the tire up and NO AMOUNT of power applied after this will "stand" the tire up, until the car gets enough momentum that it stands up on it's own. That point is generally past 60ft, depending on how hard the car is moving.

The GOAL and I preach this to guys all the time on slicks, is to MAKE the car spin the tires. I don't mean shake your azz off, make it hop up on the tires and spin. That is NOT tire spin......that is shake INTO spin. What I try and have guys do is apply enough power early, to "set" the tire and suspension, make some wheelspeed early and have that wheelspeed become great enough to narrow up the tire and blow it off. More or less white smoking the tires. Then you back it off from there.

Most guys that complain about "blowing the tires off" are doing no such thing. Most are too soft, they square up the tire, it paddles and THEN it spins. Nothing on the planet, NOTHING, not even a top fuel car will knock the tire smooth off at the hit. All you have to do to see this is watch the super slo-mo of a fuel car during a race on TV. It hammers the tire initially, setting the tire and THEN either gets round or stays square. How to FIX it after the hit is one of the hardest things in the world to do on a fast slick tire car............Under powered and over tired bracket cars that just go out there and dead plant the tire and motor down through there are a different story. Very few have enough power to snap up on the tire and they use the dead hook thing for consistency, but that is NOT the FAST way down the race track.

1st, 3700rpm launch. This is the tire shake pic
https://youtu.be/_ir8fG4WmlA

2nd 3900rpm launch, 2 clicks tighter on bottom knob rear shock
https://youtu.be/ly5TI6MC528

3rd 3800rpm launch, 1 click looser on bottom knob
https://youtu.be/ly5TI6MC528

Do you data log? The reason I ask is because I'm suprised it can get up on boost that fast before the light comes down. Maybe part of the problem is inconsistent boost on the launch?

The other thing is if it spins right at the hit like that, I would be adjusting rebound (top adjustment), not compression (bottom knob). But without seeing either the data log, or a better slow video from the side, I'd be purely guessing which way to have you go.

Monte, do you consider a Hoosier quick time pro a slick? if not, than whats the method for quickest way down the track with these tires?

I have almost all the boost pulled out of it to not blow the tires off. It's only making 2-3 pounds on the break. 1st pass was more boost then the other two. I sat there on the last pass to make sure it built boost before I let go of the button.. the first pass had more boost then the 2nd pass and the 3rd pass had least. I was trying to tame it down to get it past 60 foot. Then I was going to poor the boost to it.

Yes I changed gears. It feels a lot stronger with the new gears. I also put the new motor in it this year.

FastmOp, what are you using for a boost controller?

Here will be my initial settings. The track will be ok at Houston's Royal Purple Raceway.

Weight: 3,500 lbs with 80 lbs rear ballast for about 53/47 weight dist
Front shocks: +5 from full loose
Rear shocks compression: +10 from full stiff
Rear shocks extension: +15 from full still
Rear tire psi: 17 lbs
Launch rpm on brake: 3200 lbs
Boost controller: 5 lbs at launch progressed to 15 lbs at 40 mph
Shift: 6,000

Thoughts?

AMS 1000, it's a CO2 on the waist gate system.

You had the MOST power on the first run you say......and that is the ONLY one where it was close to going...........what's that tell you

The fronts are probably going to be way loose for a radial at that setting..........and depending on how Mark has your rears valved, that extension may be too tight

Thanks Monte I will add 5 more clicks on the front and loosen the extension another 3 clicks?

I run a Hyperkontrol, well at least about to try it.

Otherdodge, you are a 76mm Air to air Intercooler right?

How much boost are you running now down track to net you 133mph in your sig?

This is a 408" right?

What tire?

How many total clicks on the strange fronts?

How loose is the converter under full boost?

Just confirming, but I would bet you can leave on near full boost... My car is 54/46, weighs 250lbs more then yours, and has a 116" wheelbase. Same rear shocks, same size turbo... Mine will leave on that power level no problem.

You had the MOST power on the first run you say......and that is the ONLY one where it was close to going...........what's that tell you [/quote]

You treed me Monte!

Exactly... Needs a bunch more power!

Diz, yes 76mm, air to air.

It hit 14 at the top of third but mostly high 13's during the pass limited by the manual boost controller I had at the time.

It is a 389 (stroked 5.2. Was like that when I bought the truck, but wish it was a 408 because of the bore size for rings).

tire is a 315/60/15 Radial

For the front, it had been full loose on every run but will change it to about 10 clicks per Monte's advice.

The converter is a 3800 PTC.

I can probably get it to 10 lbs boost at the launch (never tried it). I was surprised that you could leave on that much boost from reading your previous posts! With some playing around, I will up the launch boost. My previous problem was initial stick but spin very soon after. I didn't realize that was a shock setting issue. I thought I needed to slow the boost down because I would be in full boost by 3 seconds.

I love this thread so much knowledge and insight thanks all for sharing....ive been learning a bunch


FastmOp what size spring are you running in your wastegate?

Great question. Think it was stuck. Testing soon.

Well I would say yours probably makes similar power at similar boost as mine. Pretty close anyway… So while I am sure that you could get this thing to leave on 5psi, and ramp in within 3 seconds… that will leave a LOT on the table.

On any halfway decent track, (even Wednesday night test and tune with the street cars running), mine will leave on 12~13psi 4,000rpm two step with absolutely no problem. We’re talking 0.02 60ft consistency over MANY runs, and MANY tracks with that tuneup. The boost is all in as fast as I can possibly get it in (boost controller ramp from 12psi to 16psi in 0.1sec, even though it usually takes around 0.3sec to physically do it). 1.41~1.43 60ft all day long.

Even on arguably the worst absolute JUNK unprepped terrible track I have ever been on in the middle of summer, mine would still leave on 8psi/3500rpm ramping to 16psi in 2 seconds. Only went 1.59 60ft… but it got down the track.

If you were honest with Mark about the power, he sets the baseline tuneup at 15R10C. That means EVERY ONE of his customers starts at that value, because he custom tunes the shocks for your car/power level.

That being said, I would do the following…

Put the car on the trans brake with NO 2 step, and see how loose the converter is at full boost (14psi). Whatever the converter stalls to at that power take 1500RPM off that for the 2 step. (say it goes to 5000 RPM, I would take 1500rpm off that number for the 2 step. So 5000-1500rpm = 3500 two step). Now set the boost controller to 10psi, and plug in that 3500 two step number in. Put it on the trans brake at 3500, and see if it will make 10psi at that RPM level.

If it makes the 10psi… you are good to go. If it won’t make that much boost, move the 2 step RPM up 200rpm at a time until it makes the 10psi you’re looking for.

Set the boost controller to go from 10psi to the full 14psi in 0.3sec.


Set the rear shocks at 15R/10C
Do you have caltracs? If so, put the bars in the upper holes, with zero gap on the drivers side, and 2 flats of preload on the passenger side).
Set the fronts in the middle of the setting to start.

Go up there and let it eat.

Make a few passes to make sure it will hook, but from there start adding boost/RPM on the launch. I have found that adding boost instead of RPM is easier to get the car off the line. Again, if you can’t make more boost without any more RPM, add 200rpm at a time to get the boost up 1~2psi on the launch. If you try to jump from 10psi at 3500rpm to 14psi at 4000RPM you won’t learn anything. Take slow steps… If you get to a point where you’ve added boost/RPM and it spins, don’t lower the power back down… click the Rebound 2 clicks tighter on the rears and try again… It may need the fronts tightened up too, but it’s really hard to say where to go without watching the car on video, or having someone pretty sharp watching the starting line.

The only advice I can give on the front adjustment, is if the truck “leap frogs” forward and spins, that would be an indication to tighten the fronts. If you’re watching on video, I try to get around a full turn of rear tire rotation before the car picks the front tires up off the ground. If you paint a stripe on the tire, and have someone even slow motion with the iphone, you can usually see this pretty easy.

But for the most part, since you’re just trying to get a handle on getting the truck down the track (not fine tuning), I would say the above tuneup guide will get you started.

Good luck!