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#1063169 - 08/13/19 11:42 PM Shock Tuning - Calling MAP - Ride Quality  
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Travis Jones Offline
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So I have QA1 double adjustable shocks on my car, I know how to tune shocks for handling, but I am at a loss for ride quality.

I am running 550 in/lb springs in the front ( I may upgrade to 650's shortly) and 220# springs in the back.

Over typical Michigan roads over bumps I notice bounce and some vertical reverberation after a bump, does this mean I need more jounce/compression or rebound adjustment, or perhaps less jounce?

Given that I can change the characteristics of the shocks in a few minutes, I look to have a nice ride calibration with the shocks, and then when I hit the track, adjust the shocks and give her the business.


86 SS 6.0L LQ4, TBSS GEN IV intake, 92mm TB, 30lb injectors, Summit Stage 3 NA Cam, Stainless long tube headers, Stainless 3in exhaust, Microsquirt ECU, FABbot AR5 5-speed, Torsen LSD, QA1 Lvl 3 Suspension Kit, UMI Front & Rear Braces. Check out my build blog on Summit Racing's OnAll Cylinders https://www.onallcylinders.com/author/travis-jones/
#1063175 - 08/14/19 01:30 AM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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mmc427ss Offline
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75% of what we feel in the butt as ride quality comes from the rear suspension. Play with the rear shocks first.

Running 650 springs up front with Viking DA, 130ish rear spring and DA.
Run C6, R7 up front, C5, R6 in rear on the street most times. Drags much different settings and autox the numbers go way up especially in the front. Using a china marker the numbers for each venue are written on rad support at the fender corners. The marker being not permanent allows me to keep track of the settings and mark down the changes. Alignment settings, ride height, carb and ignition also kept there. Maybe someday will get a dry-erase board and hang it off the dash, not.

How does the car ride? Between the extra 150 lb up front and 650 coils, all rotojoint suspension, Delrin in #1,2 and hard poly the rest, 36 psi tires, poly engine mounts, 9 1/2 caster, and a lot of extra braces the car doesn't and will never ride like the nice ride parked out front. Doesn't need to have good NVH, it's a toy.

A friend has a 67 Camaro with Viking DA coilovers up front, DA in the back and sets C0,RO up front with 330 springs and complains all the time about ride. Global West rear leafs in the back are the big contributor to poor ride, no fix for that. Could go to a low rate rear factory spring back there but would wrap them up without traction bars. COMPROMISE.
Bob

#1063176 - 08/14/19 01:42 AM Re: Shock Tuning - Calling MAP - Ride Quality [Re: mmc427ss]  
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Travis Jones Offline
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Originally Posted by mmc427ss
75% of what we feel in the butt as ride quality comes from the rear suspension. Play with the rear shocks first.

Running 650 springs up front with Viking DA, 130ish rear spring and DA.
Run C6, R7 up front, C5, R6 in rear on the street most times. Drags much different settings and autox the numbers go way up especially in the front. Using a china marker the numbers for each venue are written on rad support at the fender corners. The marker being not permanent allows me to keep track of the settings and mark down the changes. Alignment settings, ride height, carb and ignition also kept there. Maybe someday will get a dry-erase board and hang it off the dash, not.

How does the car ride? Between the extra 150 lb up front and 650 coils, all rotojoint suspension, Delrin in #1,2 and hard poly the rest, 36 psi tires, poly engine mounts, 9 1/2 caster, and a lot of extra braces the car doesn't and will never ride like the nice ride parked out front. Doesn't need to have good NVH, it's a toy.

A friend has a 67 Camaro with Viking DA coilovers up front, DA in the back and sets C0,RO up front with 330 springs and complains all the time about ride. Global West rear leafs in the back are the big contributor to poor ride, no fix for that. Could go to a low rate rear factory spring back there but would wrap them up without traction bars. COMPROMISE.
Bob


Bob, we are in similar circumstances, It's much less about "NVH" as whole as it is tuning out this weird post bump bounce.


86 SS 6.0L LQ4, TBSS GEN IV intake, 92mm TB, 30lb injectors, Summit Stage 3 NA Cam, Stainless long tube headers, Stainless 3in exhaust, Microsquirt ECU, FABbot AR5 5-speed, Torsen LSD, QA1 Lvl 3 Suspension Kit, UMI Front & Rear Braces. Check out my build blog on Summit Racing's OnAll Cylinders https://www.onallcylinders.com/author/travis-jones/
#1063177 - 08/14/19 02:14 AM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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MC96 Offline
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Needs more high speed control. Which would be in the design on the shim stack, not in the tuning of the preload on the shim stack IE putting clicks in.

Ive got my nose in some pretty advanced shock stuff through a few different friends of mine. Slow bleeds, with a hell of a nose on the graph made possible with cut bands.The shock has like .020 of no valving in the transitions of directional travel, like a too small of bolt in the mount that adds a bunch of compliance over racing surface roughness, then really slow bleeds through the low speed of the shock, and not much change into the transition to high speed.


86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
#1063181 - 08/14/19 02:29 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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SSLance Offline
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First thing I would try Travis is to take rear rebound to full soft. The weird after bump bounce you are feeling is the rear shock trying to hold the suspension compressed.


Lance
1985 Monte Carlo SS Street Car
#1063213 - 08/19/19 07:45 AM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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MAP Offline
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Hi Folks,

Thanks Travis, but I'm hardly the expert on shock tuning! Others here have done much more.

One thing I like about adjustable shocks like your QA1 and/or what Lance has, is the ability to tune over a very wide range of dampening characteristics from a single shock. The interesting thing is that adjusting for more or less dampening, doesn't give a linear response in the ride quality one might expect, because, after all, we're calling on the shock to deal with many resonances at the same time, like vertical wheel resonance, sprung mass/spring stiffness resonance (both common and difference modes when dealing with sway bars btw,) plus the sad bowl-of-jelly behavior of the A/G body chassis. Unfortunately, the odds of a single shock giving optimal dampening for all these resonances is almost vanishingly small.

Then too, we have the matter of valve divergence...

I know I liked the Bilsteins back in the day, and even Monroe Formula GPs before that, but it was little more than a matter of dumb luck that they worked passably well with my modified '78 Malibu and my modified '81 Grand Prix.

At least you have the advantage, Travis, of starting with great shocks. However, it's quite likely that a single shock will never satisfactorily dampen all significant modes. In that case, you'll need to start tuning individual resonances, most likely by changing stiffness, hence things like playing with body bushings and the like. Now we know why the OEMs use limitless CPU modeling time and why they hire so many PhDs! But as a humble home enthusiast, I'd start by making some radical changes to increase chassis stiffness, so we can move those pesky resonances deeper into the stopband of the suspension motion transfer function. If we could get effective stopband attenuation for exciting chassis resonances, then we'd only be left with a 4th-order system at each wheel, at which point a single shock can usually do a pretty good job! (Sorry to talk shop but it's the only way to get the idea across with precision.)

By the way, this explains why using stiff tires and stiff springs creates endless NVH problems for our A/G body: the higher suspension resonant frequencies, and now just talking about the two resonances associated with our 4th-order system, bring the chassis resonances closer to the suspension passband rather than the stopband. Unfortunately, that's the exact opposite of what we want, so the lesson remains: stiff tires and stiff springs need a stiff chassis, no matter what kind of shock we use.

HTH,
MAP




Last edited by MAP; 08/19/19 08:24 AM.
#1063220 - 08/19/19 09:28 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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MAP Offline
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Hi Folks again,

Good shocks definitely help, but they do almost nothing to tame the chassis. The Bose project sound folks certainly understood this.

But let me come out of shop talk mode and bring this down to earth. I will use an analogy that most can relate to, but please understand my aim isn't to be sexist. My guess is that this picture will register better than speaking of 4th-order wheel systems coupled to a transmission line of a chassis.

What we tend to do with our A/G bodies is hang stiff tires and stiff springs and stiff bushings, on a floppy, loosy-goosy A/G body chassis first conceived in the 1960s. For NVH, it plain doesn't work.

It's like putting a bikini on Rush Limbaugh and hoping the results will look like Kim Kardashian. Or, lipstick on a pig. Or, turning a sow's ear into a silk purse. (Or, insert jarring juxtaposition of your choice here. Btw, absolutely nothing disparaging intended against RL or KK.)

HTH,
MAP




Last edited by MAP; 08/19/19 09:38 PM.
#1063225 - 08/20/19 01:10 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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Hunter79764 Online content
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MAP, I'm guessing you will get a lot more pushback from giving us all the mental image of Limbaugh in a bikini than you will from comparing him to a Kardashian...

So does it follow that a stiff chassis and soft suspension and tires is good for "comfort" with some level of performance? In other words, is there any reason NOT to pursue a stiffer chassis, besides cost and weight that I'm sure drove the original decisions to make the G body out of Al Dente spaghetti?


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1063227 - 08/20/19 02:22 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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SSLance Offline
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Eh, I'm pretty happy with my soft chassis and "stiff" suspension. Putting delrin in every suspension pickup point had little to no effect on ride quality but greatly enhanced handling, the same with stiffer springs and better shocks. Now, I can turn my shocks up and make my car ride like a go cart...and this would upset the ride quality purists for sure...but it's also super easy to soften the shocks up and air down the tires to get a very nice street ride with all the same parts.

In my experience, a very large part of the ride quality factor comes from rebound in the rear shocks. The abrupt stop limit up on extension AFTER a bump has compressed the rear is what Travis is feeling I'm pretty sure. Softening the rear rebound so the shock will extend easily after a bump takes this feeling away.


Lance
1985 Monte Carlo SS Street Car
#1063231 - 08/20/19 03:27 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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mmc427ss Offline
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Agreed, soften up the rear, leave the front alone until you ride tune the rear.

On Delrin for the 16 suspension pivot points, have had Delrin at those points now for almost 20 years, wouldn't go back to rubber or poly, nobody can tell the joints are solid from ride quality, impact on ride is minimal. Noise yes, but engine and exhaust mask that.
Bob

#1063235 - 08/20/19 08:40 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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MAP Offline
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Hi Hunter,

I admit I didn't think through all the implications of that image! I just tried to think of something shocking that would leave a lasting impression, something that purely technical talk almost never does.

But about what you said about the chassis, I absolutely agree. I can't think of a good reason not to pursue a stiff chassis, with one strong caveat, however: crashworthiness. The front end needs to be engineered to be stiff but highly "foldable." Stress-concentrating depressions in key triangulating members can ensure this to a significant extent.

Lance, I certainly appreciate your point of view, and this is a good time for me to remind folk that I seem to have an unusual hangup about ride quality compared to most hotrodders. But my hangup seems to be closer to the car consumer norm than the exception, otherwise, I wouldn't have the opinion that most new car designs have stellar NVH. This is also a good time to mention that NVH will have little or no effect on lap times and other metrics of maximum acceleration in a road-race scenario, and especially when the track surface is smooth. But NVH is felt every second that the car is driven over non-smooth surfaces, which is to say, essentially all the time the car is driven on public streets. To be honest, Lance, in the context of an all-out performance car, your SS succeeds amazingly well. But I could never tolerate it as a daily driver. And again, I blame GM for this, not you.

Best,
MAP

Last edited by MAP; 08/20/19 08:42 PM.
#1063237 - 08/20/19 08:52 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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You just didn't like climbing out of my race seats right MAP? laugh lol... It's all good. Different strokes and all of that.

I realize that I pushed my car a bit too far trying to get the last few tenths of a second out of it and I found the limit of it in it's current configuration. Although I enjoyed surprising a lot of people with what it could do on track, I'm also enjoying backing that off just a touch to make it more daily driver friendly for my standards. Still trying to find that happy medium, I'm getting closer and closer all the time.


Lance
1985 Monte Carlo SS Street Car
#1063238 - 08/20/19 09:11 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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MAP Offline
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Hi Lance,

I don't think you pushed your car too far! You thoroughly achieved your aim, and that's highly commendable! But I'm sure you'd be the first to admit that ride comfort wasn't high on your list of goals for that car.

It's like my speakers at home: collectively, they're the size of several large refrigerators. Performance is off the charts: that's why it was the worldwide reference speaker system for my former employer. But as a commercial product, it would be a complete failure. The public wants small, light, and portable, with performance usually in last place. I took that list and essentially flipped it completely around.

So, we just have to acknowledge that our goal may be far off the beaten path. But being far off that path doesn't render the goal any less noble or worthwhile.

Enjoy,
MAP

Last edited by MAP; 08/20/19 09:12 PM.
#1063260 - Yesterday at 03:10 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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Hunter79764 Online content
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I'm also on the oddball side of the hotrod spectrum, as ride comfort is high on the list, stability next, and turning corners quickly is relatively low. For whatever reason, noise doesn't bother me in the least so the rattling and squeaking is fine, but I like the feeling of driving the living room couch at 100 mph with only a light touch needed on the steering wheel... I'm fairly certain I'd need a new pair of britches if I took a lap in the passenger seat of Lance's car...


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1063264 - Yesterday at 11:05 PM Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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MAP Offline
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Hi Hunter,

It's amazing to me that the Bose project sound would have made Lance and you equally happy. It's all about having it all. And it takes an active suspension to make that happen. But Hunter, if you want good NVH but aren't that concerned about handling, why not take the easy, cheap way out and do what the factory engineers did - that is - use skinny, tall, soft tires with the lowest possible speed rating? Soft tires mask a whole multitude of suspension shortcomings and give great NVH. Plus, unlike performance tires, they give you plenty of advance warning when they're getting close to their limits.

Or, if handling is a bit higher on that list than I'm guessing, stay with tall and soft, but go wide. It's a great compromise.

Hi Travis,

Going way back to your original question, if you can't dial-out that resonance with the shocks, then I'd guess you're dealing with a chassis problem. The factory 15Hz longitudinal bending-mode fundamental (lambda/2) is a nasty one. If that's correct, then you've got some work to do to tame that resonance. Stiffer, rather than softer, is usually the way to go. I refer you back to my previous comments about pushing chassis resonant modes higher, and thus deeper, into the suspension stopband.

Q: Do you have some way to measure the output of an accelerometer? It would be great if you could pinpoint the frequency(s) of specific resonance(s).

Best,
MAP

Last edited by MAP; 13 hours ago.
#1063269 - 9 hours ago Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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mmc427ss Offline
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MAP, do you remember the Davidson bar from back in the old days?

The Davidson bar is a piece of 1x1 tube which attaches between the ends of the frame at the rear bumper shock mounts, Jeff D got the idea when he noticed only the fully optioned B-body station wagons, Roadmaster, Caprice got a piece of tube between the rear frame rails. Because the frame is longer at the rear on a wagon, GM (Buick NVH guys probably) felt this was causing NV in the wagons. Twenty years ago Jeff sold several nicely drilled and painted bolt in bars. He delivered mine at one of the NMCOA conventions we both attended way back then. Almost 20 years I've had that bar on now.

I find that piece of steel does have advantages.
Very handy to grab onto when working under the car on a creeper. Also you can hang a drop light on the bar.
Makes a great place to tie wrap the individual air lines from the air bags I use for the drags. At the track just slip the tie wrap down the tube and the air inlet is hanging there, no need to crawl under the car to adjust air pressure, no holes in the car.
But i think the real advantage is I believe it actually does reduce exhaust vibration/noise from the pipes. The rear tire exit of my tailpipes have a bracket rigidly attached to the frame just behind the #6 body bushing. Tying the rear frame horns together with that tube may reduce noise/vibration into the horns. And can't hurt by adding a little more rigidity to the frame.

Travis the UMI rear shock tower brace is a nice piece, put one on right after they released them for sale. Always thought there needed to be a frame reinforcement between the rails in front of the gas tank. Just a PITA to do with the body on the frame so I never did it. The UMI brace made that easy, 4 bolts and done.
Bob

#1063270 - 8 hours ago Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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MAP Offline
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Hi Bob,

I do remember the Davidson bar! I never tried it because it didn't seem to add rigidity in a particularly helpful way. And in my book, any added weight needs to do a very effective job of increasing rigidity, or it doesn't earn the ticket for the ride. (That said, I don't have proof that the Davidson bar isn't worthwhile?)

But I will share one piece of added weight I tried that definitely earned its ticket: the 1" x 3" x 1/8"-wall steel tubing I added to the bottom of the side frame rails. It made a very noticeable improvement. But if/when I get my hands on another A/G body, I'll definitely start surgery by getting the body off of the frame, and do my quasi unibody conversion. Not sure how I'll stiffen the side rails: either close the open sides of the C-channels directly, or close them by extending/coupling them with the floor. But either way, I'd aim for a big increase in the moment of inertia pertaining to the new cross-sectional geometry. A big increase in the perimeter stiffness of the cabin is not, thankfully, incompatible with good crashworthiness. In fact, it probably helps it. Does anyone recall the video that GM shot of a 1959 Impala crashing with a 2009 Malibu? The deformation of each cabin spoke volumes about good and bad design practice. Just wish we could benefit from airbags...

Best,
MAP


Last edited by MAP; 8 hours ago.
#1063273 - 6 minutes ago Re: Shock Tuning - Calling MAP - Ride Quality [Re: Travis Jones]  
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Hunter79764 Online content
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Hey MAP,
245/60-14's right now on the rear, a little skinnier but the same height on the front (can't recall exact size). I've tentatively planned on going with tall ball joints and leaving stock springs in the car with air bags to increase the rear when needed (road trips with tools and camping gear in the trunk is a common load scenario for me). Adding some frame bracing (Grand Prix bar, rear seat brace, and the aforementioned Davidson bar) were on the "Maybe" list, hence my original questions. the tall ball joints will require different wheel/tire combos, so 17's with relatively tall sidewalls were my thought.
I'm also still entertaining the full-redneck option of 32" All Terrain's and a slight lift, but that would be a completely different animal and completely different goals that don't have anything to do with the conversation at hand smile


Sometimes you just need a bigger hammer...

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway

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