backbone

[duckSol]

Originally Posted by kennysabarese ok, ok you convinced me. Race version it is! Just gotta watch my budget, I'm waiting for my tune to come in, and I want a Backbone, ProBeam and new Tires and Wheels

Charlie Brown once told Snoopy, good things come to Dogs who wait Snoopy was not impressed

Start where the rubber meets the road. "it's where the rubber meets the road" is an old line form a 1960's tire commercial. Still true.

In order of priority;

1. Tires - Many will agree, the RSA's need to eat asphalt preferably in a large open area or SOLD to a Ricer,

2. Probeam,

3. Tower brace & Backbone.

When the midship flex is taken out, there will be added effects and compounding of existing unfelt effects to the front suspension & tower that should be addressed when stiffening of the mid frame structure from the DDM Backbone.

Each, 2 dramaticly & 3, will have its own effect on handling and ride.
Personally, I think the ride improves due to rapid recovery from bumps but some may not like that and equate it with rough ride as there is more feel to the road surface and road imperfections.

When all is said and done IMHO, CAR will handle like CAR was intended to handle but does not from the factory because of GM keeping production costs down while at the same time providing a time proven design for us to easily modify and inexpensively make better like some of us did when teenies.
For those who ask why mod, CAR the next best bet is the new Nissan 370Z with a tower brace that twists but supposedly comes back to original shape
or a Porsche at $170K that is a performance car only in the eyes of Motor Trend or Rode along and got Tracks in my drawers

Keep these things in mind.
Just got off the phone & DDM is busy getting ready for Texas, so I don't know if the next round of DDM prototype IC charge pipe and re- TUNE will happen this Thursday or not.
You may want to hold off on a tune, and do the 1,2,3 I mention above.
There is more, see title,

[rob the elder]

We need a tin head to do a quick NASTRAN model and give us an order of magnitude difference between the two brace designs. I suspect that the end result will show that 95+% of the benefit is gained with the street model and going to increased thickenss will only be seen as having an impact in extreme conditions.

If you think your way through the problem, its not constant loading that causes most of the handling challenges, its dynamic and impulse loads at the corners that causes the rapid changes in geometry of the car that cause the problems with handling. Stated another way, grandma can drive around a nice smooth corner. Look at NASCAR

Where grandma and a lot of roundy round drivers get in trouble is when driving over rough roads or quick and frequent changes in direction that upset the chasis feel and the driver's ability to appropriately feel and predict what and how much input the chasis can accept without departing from controlled flight as they say just before the crash.

My personal experience goes like this. While going fast on the freeway or on smooth, even mountain twisties, the car would only get upset during transition from one direction to another. Its the time constant of the chasis based on a lot of factors but think of it as stiffness and damping. If the chasis always reacts in a consistent and predictable manner, then the flexing and motion don't cause as much of a driver challenge because it's predictable and consistent. Over time a driver can learn to accurately predict how much control input the car will accept without departing controlled operation.

Take the same car, again in my personal experience, and put it on the freeway on ramp at very high power levels and acceleration, make the ramp undulating with non-uniform roughness and you end up with non-linear inputs to the chasis. In my case, this resulted in the rear end doing a "dutch roll" motion that was inconsistent due to the nonlinearity of the input and the inability of the chasis to stabalize and react in a predictable manner. It caused me problems because I could not accurately predict what the car was going to do next because it was not reacting in a predictable / consistent manner. Mostly due to lack of stiffness in the rear end.

I added the DDM beam to the rear support member and the rear end meandering around unpredictably under non- linear inputs went away.

But since there is no free lunch, the energy input that used to show up in the rear end while very much dampened out by the new stiffness provided by the DDM beam was transferred forward to other parts of the chasis. So now what was a very disconcerting dutch roll in the rear end has become a kind of "head shake" where the center and front end of the car tend to react to the transferred non-linear loading on the rear end. The car is much easier to drive close to the edge of traction and control but is still not perfect.

I believe that the center brace will greatly stiffen the center of the car as it is designed to do, and personally I believe that the street version has more than sufficient stiffness to do the job for any but very extreme conditions.

By that I mean either rapidly changing loading with low roughness - like a high speed slolom course that puts a lot of smooth but constantly changing - and even reversing - loads on the chasis. Add in heavy braking loads followed by max power acceleration and you get an idea of the challenges the mechanical system has to operate through. My personal opinion, to be confirmed by modeling, is that the difference in stiffness between the street version and the race version will turn out to be so small that short of full on track racing you will never see a difference.


Alternatively, driving slower on a rough and irregular surface can also stress the chasis. IMHO street driving can be as challenging for the chasis as track driving, because you run into all kinds of conditions that would not be allowed on a track. Like other cars going the other direction, pot holes, broken pavement, ice, oil spots, metal grates, etc.

I chose the street version because the cost / performance to me appeared to justify that decision for my driving. Most of the loads my car sees are WOT going straight ahead anyway

[duckSol]

Rob nailed it.

I have held all three backbones and in the simplest of terms:

Stock - like it is made from a TIN CAN I am over 50 and could put it between my legs, sticking up and twist it 90 degrees or wrap it around my leg or use it in a beer can sculpture!

Street - has much less
flex, would take at least a six pack to to do a fraction of the above and I would hurt the next day and it wouldn't be from the six pack.

Race - designed to ELIMINATE flex mostly from the V 8 conversions! No matter what the twist torque from an after market motor of say 640hp, the windshield most likely WILL NOT crack!

[kennysabarese]

Originally Posted by duckSol In order of priority; 1. Tires - Many will agree, the RSA's need to eat asphalt preferably in a large open area or SOLD to a Ricer, 2. Probeam, 3. Tower brace & Backbone.

I have Eagle F1 GS-2 tires NOT RSA's. Does that change your opinion?

[rob the elder]

Originally Posted by duckSol Rob nailed it. I have held all three backbones and in the simplest of terms: Stock - like it is made from a TIN CAN I am over 50 and could put it between my legs, sticking up and twist it 90 degrees or wrap it around my leg or use it in a beer can sculpture! Street - has much less flex, would take at least a six pack to to do a fraction of the above and I would hurt the next day and it wouldn't be from the six pack. Race - designed to ELIMINATE flex mostly from the V 8 conversions! No matter what the twist torque from an after market motor of say 640hp, the windshield most likely WILL NOT crack!

WOW I love you man!

I need a copy of your duck! I want to put it on a pennant for one of my cars

[duckSol]

Originally Posted by kennysabarese I have Eagle F1 GS-2 tires NOT RSA's. Does that change your opinion?

Not of the RSA's.

Keep in mind I am responding from what I think I see as your view not my needs or wants.

I have the ones you have and I would not abuse them.
They are adequate and a good tire, but are a summer tire. I find them to be ok in the rain and snow by a very small margin of error.
Well satisfied with the wear and durability considering what I put them through in business travel balanced with my daily swings in testosterone level.

I intended to do as you but with this crap economy and an unplanned emergency purchase of 10 inch wide truck rims and tires, SLY rims & tires went out the window and into the crapper.
On top of that I cannot find a wheel WITHOUT 5 SPOKES I like.

More sticky would be nice but there are compromises and SLY is a daily driver for me when I am on the road for business so I need a balance that becomes a compromise.

I have a lead on some used 110 x 5 9 x 15 inch rims with drag slicks already mounted that will balloon out nicely and make a big mess, but those are for late April - early May if all goes as planned

[lil goat]

I was the first one to have a race version, it is the prototype actually. I was the one that talked with Dave on the reccomendation that the race works better for the GXP, it is because of the torque from the engine that the race was originally reccomended. Not sure you could tell much difference in cornering between the two. As none of us that I know of have driven both except Dave, maybe we should be a bit less insistant on what is best for who. I like to drift my car and went with the stiffest possible solution for that reason. There is no downside to the race version other than cost, so saying that someone should buy the street version because that is what you have is not very grounded in fact, bottom line buy what you can afford, either one will work very well. The race does deal with extended torque values a bit better on launch. I am at over 320 lb/ft of torque now, and that is going up with the meth injection so I am glad I have the race version. As far as the 1/8" being insignificant, the factory one is less than 1/8" as bad as it is trying driving without it, you may retink what an 1/8" of an inch can do. By the way if Dave did not think there was a good reason to market two different sizes he wouldn't. There is a thing in marketing known as "optimal price point". GM could have made the GXP a better car but not at the "optimal price point"

[mikep77]

Glad I saw this thread. I had ordered my backbone today, and went with the street version. Well after some reading I decided to call and change mine to the race version. When I called he told me that if you're planning to keep your NA and GXP stock, then the street version is fine. 2.4 turbos and superchargers along with Modded 2.0's should go with the race version.

[Critterman]

Well this is interesting, since I have the original prototype "street" version on my Stage III and Dave didn't have any issues putting it through it's paces, and mine is not PINK

I should add that my car had horrible torque flex with the stage II kit, left front would twist up and the car would squirt right, left, right in quick succession. It scared the $$## out of my wife. With the street I do not have a flex the front lifts uniformly and the back squats. If the rear walks out it is easy and controllable. It still is with the Stage III. Street is fine for me, but it may not be for you.

[LatinVenom]

I think any one with a V8 conversion would benefit greatly from having both of these suspension additions.

[JeffInDFW]

Robs post was very interesting reading, and I think he has some well thought out ideas. One other thing is, I do not care about cost. But I *DO* care about weight. The appeal of the "street" vertion to me would be that it is lower weight. However, with me being the typical man, I buy EVERYTHING bigger than it needs to be, so I am ordering the race vertion right now!

[carlintexas]

I get my race version this next Thursday at our DDM Mod Meet! The price difference between the two was so minimal...and not really knowing how they feel...I figured - better to err or the stiff side.

I think this threads great cuz it lets me see all those who have bought the backbone - and the positive comments.

Have you seen the front shock brace DDM puts on the stage III S/C? I may need one in starlight red to complement my turbo pipes.

[bigblau]

Just took my Solstice out of winter storage this week. Installed the race version of the backbone and immediately noticed the car has stiffened up considerably from before. It's like it's got a backbone now ...no more whishy washy stuff.

[lil goat]

I just thought of something I had sort of forgotten, I do NOT have the Pro Beam yet, they haven't made me a pink one. I think if you have the Pro Beam it adds enough stiffness on it's own that maybe the Street version is more than addequate, without the Pro Beam maybe the Race is a better choice, and it won't hurt anything if you add the Pro Beam later like I am going to do. Right now my Harley is sucking up all available funds like a sponge! It is very close to being done, after 6 years of modding.

(for the record I was watching Dave and Randy install Critterman's backbone when I made the smart comment that caused me to get a pink one)

[RevmanII]

Originally Posted by JeffInDFW . However, with me being the typical man, I buy EVERYTHING bigger than it needs to be

I'm with you Jeff. I went with the race.