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Old 07-30-2009, 05:51 PM   #1
Tankrust
 
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Discussion of suspension tuning methodologies

I think it is a good idea to discuss the two different suspension tuning philosophies and how they are being employed by current aftermarket Camaro suspension developers:

More bar/less spring

vs.

More spring/less bar

Both have advantages and disadvantages. In my experience, more bar/less spring setups tend to be more "streetable" for a car used as a daily driver. Straight line ride quality does not become stiffer with larger swaybars. You will tend to lose some independence of the suspension however. These cars tend to do better on smoother race circuits. Increasing swaybar size does not reduce weight transfer during braking and acceleration (dive/squat).

More spring/less bar setups tend to ride more stiffly. Well designed dampeners are more critical for making high spring rate setups comfortable for daily driving. Full suspension independence is maintained. These setups tend to track more predicatably in bumpier cornering, with less tendency for the back end to "step out" over bumps. Higher spring rates also lower the weight transfer (dive/squat) encountered during braking and acceleration.

Input regarding staggered tire fitment from the suspension developers would also be great. I think everyone here is interested in instrumented testing results (skidpad, slalom, track times) and comments from all suspension developers so we can make an informed upgrade decision.
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Old 07-31-2009, 07:30 AM   #2
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I second this request. This is probably the best suspension post I've read here. Can we keep this from becoming a sales pitch for a particular system?
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Old 07-31-2009, 10:16 AM   #3
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A short answer would be, with the 20s it more bar and more spring and more damping. They are monsters to control.

After almost 1,000 miles of daily driving my bone stock 2 SS gthe one thing that is bothering me more than any other is the jitter in the steering wheel over certain types of ridges in pavement. These smalll imperfections should be a non-event. They bring a shudder or jitter all the way to the steering wheel becuase the wheels and tires take so much to control. Upgrading the radius rod bushes will help. On the Xa equipped Camaros I have done this is not an issue so we know that more coil and more damping will imporve this. More coil and more damping and radius rod bush upgrades improve this.

In the rear, the rear end stepout is my biggest nit to pick. This is a fuintion of the sub-frame twisting independently of the body. Increasing coil, damper or sway bar do nothing about this and may make it worse. The only solution is to make the rear sub-frame bushes more stable and restrit the movement of the rear cradle.

I don't know how much detail you want to get into. Let me know if you were looking for more information.
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Old 07-31-2009, 12:32 PM   #4
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I have noticed the front end jitters as well. It is particularly evident on roads with deep ruts or on camber changes mid-corner. I wonder if an increase in caster would take care of the tramlining? The very heavy wheel/tire combo will be difficult to get under control without completely killing on-center feel and making the car slow to turn-in. I have heard that those who have bumped up the front tire size to 275's have noticed a decrease in steering feel.

Does Pedders have plans to offer an adjustable caster/camber plate solution? If so, do you plan on using spherical bearings/pillowball mounts? A higher durometer rubber top mount with more static camber than stock would also be appealing for those that don't want the additional NVH associated with full metal camber plates. How much camber were you able to get on the front end with the factory camber adjustments?

Have you taken video of the rear suspension carrier during testing to verify that it is twisting?

Thanks for the all the info Pete. I know you are still in the development stages but there are a lot of people who will be getting these cars ready for track duty in the near future. I see lots of potential sales for whoever can get some published performance numbers.
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Old 07-31-2009, 02:39 PM   #5
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The rear sub-frame issue was found by GM when they were building the GS Camaro. The track solution they developed were Delrin they cut. That would be too harsh for street use and perhaps even too harsh for sub-frame longenvity in a race car. Our solution will be tested by Riley Tech. It is derived from our street parts bin as are all our Camaro bits.

The all new design for the strut mount does not make a camber plate an easy part to design. We did the Mutang camber plate in about five minutes. We can generate -2 degrees with the OEM size slot in the clevis. A couple of mm will move that to 3.5 withj not change in NVH.

There is no caster adjustment possible on the OEM front cradle for the Camaro. Where the G8 has a slotted hole for castor adjustment the Camaro has a round hole. Pedders will have a castor adjustment solution for the Camaro very soon.

The front wheel jitter is best addressed with damping, coil rate and radius rod bush upgrades. W have found th ZETA and ZETA II chassises to respond very well to negative toe. I personally have run up to 1/4" total negative toe with excellant results in a fully Pederised G8 and in some testing on the Camaro. Certainly there will be some loss of tire life in exchange for amazing turn in. There is virtually no loss in straight line stability well into triple digits. Removing the castor bias may alter the jitter as the wheels would strike the road imperfection more squarely. I run no bias in my fully Pedderised G8 and think that when the castor adjustment becomes available to the public with a good solid suspension the Camaro will be the same.
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Old 07-31-2009, 06:13 PM   #6
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So far, there has been 2 different testings, and lets just say, and I really do not know, but lets just say the outcomes were the same; neutral steering. Now neutral steering can mean different things to different poeple. But again for assumptions and simplicity, lets say that both setups obtained the same goal of neutrality.

With that said, those that have been around with Pedders a while, will know that we frequently will do things in steps. To us, it was important to be able to meet our goal without a full system and without our custom adjustable sway bars with adjustable end links. A professional driver rated our setup a 9 out of 10 and under a race track environment, as witnessed on the video. We obtained the goal of understeer when desired, and oversteer when required. The professional driver was seriously happy with the setup. We were not. Yet we did obtain our goal, and know what we have done will seriously satisfy 95% of our customers. We did learn a huge amount without a full system, which may lead us to offer a different setup in the rear, that will be dependent on your style of wheel and tire. For simplicity sake, tire side wall construction and aspect ratios, for maximum complement to a suspension, will make a very serious difference in handling characteristics, can can require a different damping and coil rating. So we will fine tune a second rear Xa setup for the rear to get the maximum out of a totally different wheel and tire package.

We are doing this because we need to support the communities desires for for extreme rear tire variations from the monster biggies, to the sleeper don't mess with me thru the twisties tires or I will eat you!

Now with all this said, I hope no one thinks that we are stopping here. Our tests again were just first steps. Within the next several weeks, we will be testing our vehicles with our new sway bars, rear cradle bushings, then a systematic approach to all bushings. The evaluations will take several thousand miles of driving, and now that Pete has finally taken delivery of his SS, the fun can really begin!

So to conclude, we will have a variety of setups and the knowledge and experience to back each one up with experience and recommendations. This will eventually lead to the ultimate Pedders eXtreme Xa Track II system.

Right now, however, Pete needs more hp!. So soon we will be able to test with 600hp at the rear wheels. More on this later.

I have received a lot of emails and phone calls that I have been unable to answer. The reason is I spent this week working on a killer project that will eventually help a very large amount of kids. Pedders has teamed up with WD40 and SEMA to build a killer Camaro, along with a hole bunch of very well known suppliers that are also SEMA active. Barrett Jackson is also involved. This Camaro will be in a lot of car shows, in the GM booth at Sema, and will eventually end up at Barrett Jackson in January(?) for auctioning to the highest bidder. The money earned will go to the SEMA non profit helping organization that will turn around and give to to some very needy organizations that will give very needed help to a bunch of young boys and girls.

I will be eventually making an official post on this, but for right now, hear is what she looks like:





By the way, she was dropped 2 plus inches front and rear. Ride quality is seriously good and the handling is off the charts. She does not link driveways, however. She s currently running on stock wheels and tires, but will very soon have custom Forgelines with 275s up front and yes, 315s in the rear.

Plus I learned a hole lot about the Camaro this trip, that I will be sharing with all of you. So watch for future posts.

mike
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Old 07-31-2009, 07:23 PM   #7
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that looks sexy.
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Old 08-01-2009, 09:21 AM   #8
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Very nice Mike!!
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Old 08-02-2009, 03:03 AM   #9
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that looks sexy.
Yes it does! If I had not gone with Rally Yellow I would have gotten the Imperial Blue
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Old 08-04-2009, 04:45 PM   #10
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Spring Rate or Sway Bar

Quote:
Originally Posted by Tankrust View Post
I think it is a good idea to discuss the two different suspension tuning philosophies and how they are being employed by current aftermarket Camaro suspension developers:

More bar/less spring

vs.

More spring/less bar

Both have advantages and disadvantages. In my experience, more bar/less spring setups tend to be more "streetable" for a car used as a daily driver. Straight line ride quality does not become stiffer with larger swaybars. You will tend to lose some independence of the suspension however. These cars tend to do better on smoother race circuits. Increasing swaybar size does not reduce weight transfer during braking and acceleration (dive/squat).

More spring/less bar setups tend to ride more stiffly. Well designed dampeners are more critical for making high spring rate setups comfortable for daily driving. Full suspension independence is maintained. These setups tend to track more predicatably in bumpier cornering, with less tendency for the back end to "step out" over bumps. Higher spring rates also lower the weight transfer (dive/squat) encountered during braking and acceleration.

Input regarding staggered tire fitment from the suspension developers would also be great. I think everyone here is interested in instrumented testing results (skidpad, slalom, track times) and comments from all suspension developers so we can make an informed upgrade decision.
That is a mouthful. It is also an intelligent question. It's quite unlike most of the drivel posted as 'answers' so far.

You really lay out the pros and cons of both of those schools of thought very well. What I boil this down to is intended use.

The more bar, less spring setup tends to be a better all around package. The bar will provide good steering response and cornering feel without the brutal ride that achieving that same level of roll control would require with spring rate.

The big bar setup will tend to be a compromise in some situations. Bumpy corners (like the OP suggested) and if you are on the track, banging large curbs will cause more upset with the big bars.

The large spring rate, smaller bar setup will feel more stable under braking and will allow less weight transfer under acceleration. Essentially, the nose won't reach for the sky as much. That can be important for cars that have large power adders. Conversely, it will inhibit weight transfer so stiff springs may be bad for drag racers.

Given that discussion, I will now tell you that it is never black and white. There is no one correct answer. At Pfadt our philosophy tends to match our customer base. We know that as with our Corvette products, most of our Camaro products will be installed on cars that spend a significant amount of time on the street. These cars will probably hit an auto-x or an open track day or a drag race occasionally, but mostly they will be driven on the road. With that in mind we tend to add spring rate to the factory package (GM is notoriously conservative when it comes to putting spring rate in it's 'performance' cars, look no further than the Z06 Corvette for an example of a car that can use spring rate). We also like to put a lot of sway bar in our packages. It is the best way to get a car to feel lighter and more nimble. It also maintains very good street driving manners and wont make your car ride like a dump truck.

With the Camaro, the car has a long way to go. We look at that as an opportunity. The sways are the best balance tool that we have in our 'bolt-on' chassis tuning toolbox. We have developed a great bar package. With just a set of bars, the Camaro is transformed from a lumbering beast to nimble cornerer that can be thrown into a corner and steered with the throttle.

The next step is to deal with the spring rate (or lack thereof) in the car. We have developed some great drop spring and coilover packages that address that and still respect the fundamental balance we achieve with the sway bars.

To get back to the OP's original question, I will also address tires. I think it is crazy to require a tire change to achieve balance. At Pfadt we make our packages work with the factory tire setup. With that they will also work with and upsize tire package. We know from our testing that a 275 is about all you can reasonably fit on the front of the car, with that people are going to put a 295 or a 305 on the rear (some will even go 315 I would guess). To require a compromise in tire size to achieve fundamental balance is ridiculous. Our packages will all work with 'normal' tire packages. If someone runs something odd, that is where the adjustable sway bars will come into play. They provide the user tuning to balance out a car with different tires or different driving style.

Wow, looks like I wrote a novel here.

Hope this is useful. We at Pfadt race, drive and develop all of our suspension in house. It does not work until I say that it works. No 'canyon carvers' here, just racers. Stay tuned for all of the cool stuff we are working on for these great new Camaros.

-Aaron









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Old 08-04-2009, 06:39 PM   #11
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Quote:
Originally Posted by Aaron Pfadt View Post
That is a mouthful. It is also an intelligent question. It's quite unlike most of the drivel posted as 'answers' so far.

You really lay out the pros and cons of both of those schools of thought very well. What I boil this down to is intended use.

The more bar, less spring setup tends to be a better all around package. The bar will provide good steering response and cornering feel without the brutal ride that achieving that same level of roll control would require with spring rate.

The big bar setup will tend to be a compromise in some situations. Bumpy corners (like the OP suggested) and if you are on the track, banging large curbs will cause more upset with the big bars.

The large spring rate, smaller bar setup will feel more stable under braking and will allow less weight transfer under acceleration. Essentially, the nose won't reach for the sky as much. That can be important for cars that have large power adders. Conversely, it will inhibit weight transfer so stiff springs may be bad for drag racers.

Given that discussion, I will now tell you that it is never black and white. There is no one correct answer. At Pfadt our philosophy tends to match our customer base. We know that as with our Corvette products, most of our Camaro products will be installed on cars that spend a significant amount of time on the street. These cars will probably hit an auto-x or an open track day or a drag race occasionally, but mostly they will be driven on the road. With that in mind we tend to add spring rate to the factory package (GM is notoriously conservative when it comes to putting spring rate in it's 'performance' cars, look no further than the Z06 Corvette for an example of a car that can use spring rate). We also like to put a lot of sway bar in our packages. It is the best way to get a car to feel lighter and more nimble. It also maintains very good street driving manners and wont make your car ride like a dump truck.

With the Camaro, the car has a long way to go. We look at that as an opportunity. The sways are the best balance tool that we have in our 'bolt-on' chassis tuning toolbox. We have developed a great bar package. With just a set of bars, the Camaro is transformed from a lumbering beast to nimble cornerer that can be thrown into a corner and steered with the throttle.

The next step is to deal with the spring rate (or lack thereof) in the car. We have developed some great drop spring and coilover packages that address that and still respect the fundamental balance we achieve with the sway bars.

To get back to the OP's original question, I will also address tires. I think it is crazy to require a tire change to achieve balance. At Pfadt we make our packages work with the factory tire setup. With that they will also work with and upsize tire package. We know from our testing that a 275 is about all you can reasonably fit on the front of the car, with that people are going to put a 295 or a 305 on the rear (some will even go 315 I would guess). To require a compromise in tire size to achieve fundamental balance is ridiculous. Our packages will all work with 'normal' tire packages. If someone runs something odd, that is where the adjustable sway bars will come into play. They provide the user tuning to balance out a car with different tires or different driving style.

Wow, looks like I wrote a novel here.

Hope this is useful. We at Pfadt race, drive and develop all of our suspension in house. It does not work until I say that it works. No 'canyon carvers' here, just racers. Stay tuned for all of the cool stuff we are working on for these great new Camaros.

-Aaron









Hi Aaron,

To start, let me congratulate you on your Corvette successes. You all have done a very fine job on this.

As far as the Camaro, I do think we are in sink. Our references to split configuration is our testing related to just monitoring understeer and trying different tire sizes. I know that we both agree that oversizing tires in the rear adds to understeer. So my references to getting the same size tires really has to do with guys looking to upgrade. At the track, we did get neutral steering with just our coil overs. As you are doing, we are checking reactions to the Camaro in a systematic approach. As we did with our coil overs, we tried different setups, etc to monitor the changes. We will be testing the effects of our sway bars next week which may totally change our approaches. Doing this, however, is extremely time consuming, but gives all of us a great deal of information, to be able to max out on handling at each level.

We do know that guys are going to go all over the map on tire sizes. Because of this, we are actually going to offer 2 different coil/damping rates. One with higher spring rates with lower damping rates, and another set with lower spring rates and higher damping rates. This is due to the very serious differences or influences tires will have. this way we will be able to maximize on handling, for all tire combos that we will experience.

So I am looking forward to both of us supporting the Camaro. I think we both share the same vision as to what the Camaro can do, because what she can do in stock format is not impressive at all for any kind of performance driving.

Thanks so much for sharing!

mike
dms
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