Jim,
I agree that lowering equally does not affect spring rate.
However, in reference to lowering unequally from one side to the other; Are we really getting in to corner weighting and/or wedge here? GM certainly does not do this. There are some tolerances on ride height set by the factory.
Also let's say that the weight is equal side to side. What happens to the handling then when a 350 pound person gets in the driver's seat?
I have lowered and tracked 2 C5's and have not noticed any handling difference, good or bad. Lower for looks.
Not contradictions here but questions only.
Dave

 

Well, I am no C5 tech, I had more then one person tell me what I was feeling is normal because I am unloading the spring. They also said since I had BASE suspension with a softer spring then the Z51 or Z06 setup that when you let out on the bolt you are letting out on the loaded pressure on the spring, because the spring is going back to it's natural state. I was also told that since the arc has changed on the spring, that in itself will also affect the handling of the car.


Help me understand why if a spring is under pressure my pushing down on it, lets say for example, by 3 inches and you let up on 1 inch of that pressure that you are NOT unloading the spring? Isn't that what you are doing by turning the bolts. If I remember correctly the service manual says the front and rear spring are under pressure, which would be down..?? and if you let the spring go up by taking out the bolt the pressure decreases?

I would like to know if my thinking is correct and if I am wrong, which I could be, I won't pass along any wrong information in the future.

thanks.

Whatever the case maybe. I would recommend that you mark and/or count the threads before you lower incase you don't like how the car rides.

Robert

 

Bluewasp,

In your hand held example, you let up the pressure on the spring by 1 inch by not pressing as hard. I think that's where the analogy unravels, as the 3200 pounds of corvette is held up by the 4 springs, before and after lowering. The car can't "let up" on the spring - it weighs what it weighs

Unless I'm missing something really funky in the C5 design, the load on the springs is about 800# per corner, regardless of ride height. A lot of other suspension variables can change with ride height, but mass is not one of them

Thoughts?

Rob
01z06

 

Hey, this is getting into a very good discussion! :yesnod: First , Dave, Yes , a 300 pound persion's weight will be distributed more on the left side suspension, but some will also be on the right side. Using algebra and considering the stiffness of the corvette, I estimate that the 300 pounds will be about 200 on the left and 100 on the right with most of the weight on that weight on the rear of the car.

From my experience, I lowered the front and rear exactly the same amount(1 inch). The reading before I lowered it were a bit higher (1/16 inch) on the left than tey were on the right. After I finished, the left side was still 1/16 inch higher than the left. I weigh about 200 pounds and after the lowering I thought the car was very solid in its handeling. MY allignment is set to factory specs. except for the Camber which is -!.2 in the front and -1.0 in the rear. I handles like it was on rails, and I have lots of miles on road courses with no handeling problems.

Robert, Rob(rjn) is correct. The car stills weighs the same as it did before the lowering, and all that weigth is attached to the springs, so assuming you lowered all cornors the same amount, it is impossible that you unloaded any of the springs. An interesting note is the the Vette spring is loaded be raising the end of the spring, and not pushing down on it as in your example. But you are correct that by easing off on a spring you are unloading it.

By lowering one side more than another, you are letting one end of the spring suport more weight than the other side. This is called weight jacking in NASCAR terms, and I don't think it is a good idea with our road cars. That type of jacking would greatly "loosen" or "tighten" (NASCAR terms) the car in turns, depending on which way you were turning.

If you get the car lowered equally on all corners and have a good alignment, your car shoud handle very well assuming there are no other mechanical problems. Have FUN with your tinkering, I do. :D

 

Well that is what I thought at first too, before I lowered my car, but someone explained it to me and it change what I thought. Let me see if can explain it how he did. In short he said that since you are allowing the spring to move up you are taking that extra 1 inch or however much you lower it off the spring. You would have the load of the car + the pre-compressed load. I understood it as since the spring is compressed at, for example, 500 pounds and you add the car its now at 3700 pounds of spring pressure and if you lower it 1 inch then you take pre-load pressure off the spring. also changing the spring rate of the spring since the arc of the spring has changed.

Another way to look at it would be when you change the height with the bolts the spring is flatter then if it was at the stock height. and since the spring is flatter then it would be at stock hieght. The spring has MORE pressure on it at the stock height..... Thats why the car is higher.. The spring itself is pushing the car up, with the bolts bushing down the spring adding to the pressure on the spring.

The bolts pull the spring down adding to the weight which = pressure on the spring. By lower the car you are taking off that pressure on the spring making the spring HANDLE less weight + the weight of the car. The weight of the car isn't the factor really since it doesn't change in our case. The pre-load weight/pressure put on the spring is what changes the height of the car and the amount of load and weight on the spring when the car is on the ground.


Hence you are UNLOADING the spring!!!

Since the car is lower and the spring is "flatter" the rate of the spring has changed which cause my loose feeling...

That is kind of what he said, and it makes sense to me.


???????????????????????????????????????? ???????

Robert

[Modified by Bluewasp, 10:44 AM 11/26/2001]


[Modified by Bluewasp, 10:49 AM 11/26/2001]


[Modified by Bluewasp, 10:52 AM 11/26/2001]

 

I know the weight of the car doesn't change by turning the bolts... :) That much I am pretty sure of. I am talking about the weight of the spring compressed (amount compressed = weight need to give said pressure) plus the weight of the car.

I also know that you should put the height of the car, the same on all sides. Anybody should know and understand that both sides, as in both sides of rear and front have to be at the same height. For one thing it would look stupid and it would cause problems. When I lowered the car I didn't just start turning bolts and praying that it would come out right. I turn each bolt 20 1/4 turns, I can't remember if I turn it 20 or 18.. But that doesn't matter. I know I did it the same on all sides, and measured with a yard stick. My car was the same all around. I think the front might was .1 to .2 of an inch lower. A yardstick isn’t the most precise measuring instrument. ;) Just wanted to make that clear. :) :) :)

I sent a e-mail to my friend who told me that I was unloading the spring and waiting to see what he has to say.

I can understand both point of views and I really don't know what is right now!!!!

I think we need to get a firm answer on the affects of doing this mod to our cars.

peace!
Robert



[Modified by Bluewasp, 10:41 AM 11/26/2001]

 

Another way to explain.... Those bolts are putting 500 pounds of pressure, for example on the spring at STOCK height and you take out the bolts and you are decressing the pressure on the spring at the new lowered car height, and since you have less pressure you NOW have LESS weight NEEDed to achieve the NEW Lowered hieght and pre-loaded spring pressure. Which makes the spring softer or whatever, but it changes the way the spring springs! :D

And you are UNLOADING the spring when you turn the bolts...

am I correct??????




[Modified by Bluewasp, 11:04 AM 11/26/2001]

 

Robert, You can prove which statement is correct with a simple experiment. I know that you believe that if a spring changes shape its loading has changed, since you used that as an example.

So, get under your Vette and measure the curvature of your rear spring (or its loading) by measuring vertically the distance from the center of the spring to a line running between the two lowest points of the spring. Then make what ever adjustments ot the rear adjusting bolt that you wish and after settling the rear suspension by driving a mile, then remeasure the same vertical distance between that you did before the adjustment. You will find that the spring is in exactly the same curvature (or height) as before. Since the height of the spring hs not changed, the loading has not changed. This is a simple experiment , and if you really want proof, then do it.

If you don't want to do this the at least ask the other person to give you a way to prove that the spring is actually being unloaded by lowering. :cool:

 

Message edited by me to keep on topic at hand.
No, argumentative tone was intended, sorry
:)

I never said I was a C5 Tech or suspension god. I am someone that lowered their car as per the C5 Tech section on this forum. I posted a message saying my car was loose after the fact. The car height on sides are the same. I was then told the reason for the car being loose is that I was "unloading" the spring, which made the spring softer.

Check out this thread.. in there i said the car was level, as in same all around. About 20 1/4 turns all around. In that thread you will notice 1 or 2 posts where people are telling me I am "unloading" the spring.
http://forums.corvetteforum.com/zerothread?id=178485

Thanks for your help

Robert




[Modified by Bluewasp, 6:02 PM 11/26/2001]

 

OK, I think I see where you're going here...at the risk of further clouding the pool...

The preload of a spring ususally only matters in an unweighted state. To put this in terms I'm used to dealing with (kind of new to this corvette stuff :)), a macpherson strut assembly has a preload on it. It is defined by the lower spring perch position and the maximum shock rod length. On one of my other cars, there is 140# of preload on each front shock, which I could change by adding spring perch spacers, or moving the bottom spring perch (aka coilovers). This preload does not affect the car's handling as long as there remains more than 140# of weight on that corner, which is the case most of the time. If there is less than 140# (like out of a corner under throttle), the wheel is in the air. If there is more than 140#, the spring compresses further and the preload no longer factors into any calculations.

I've got to crawl under the car and have a look, but unless the bolt is acting some sort of moving fulcrum or something, then any preload in the nornal load axis shouldn't matter.

'course I could be wrong...

Rob
Tranverse leaf newbie

The only

 

Moneypit, you can tell by all the comments, back and forth, pros and cons, etc.,etc., that you're probably better off just leaving it stock...or else it might cost you bundle to get it back to the way it was designed to work. Looks are one thing, but replacing tires, bottoming out, etc. are another. Again, it's your decision to make, not mine. For me it's low enough...especially when I have to change the oil (without a lift). :yesnod:


[Modified by Mark S., 1:33 PM 11/26/2001]

 

Excellent rjn (Rob). The front and rear springs on our C5s are not preloaded. The only thing that flexes (compresses) the spring is the weight of the car, and as you pointed out earlier, the end of each spring is being deflected by about 800# of weight. And this 800# is acting on the end of each spring weather the car is 1" off the ground or 5" off the ground.

I appolige to anyone in this technical discussion who thought I was attempting to make detremental comments regarding their point of view. I was Not, but I was trying to state the facts and the truth of this matter. And I won't use the "yes Nod" :yesnod: face again for fear that it is thought to be a "LOL" face.

May all your lowering experiences be uplifting. :) :) :) :)

 

No problem. I just want the facts on the lower issue. I don't want to do something wrong and f-something up in the long run.! :D
robert

 

This the start of another topic/question. If the springs are not under pressure then why would I need to put a jack under the spring to keep the pressure inorder to remove it when I do my Z51 spring swap? I was told that GM shop manual for the C5 has a special tool listed in the manual to keep the spring compressed, but i could place a jack under it, unbolt and slowly lower???

Is this incorrect information? I need to get a shop manual and read it for myself! :yesnod:

thanks



[Modified by Bluewasp, 4:21 PM 11/26/2001]

 

About 30 minutes after I sent that last message, I realized I was wrong about the preloading. Robert , you are absolutely correct about that. With the suspension hanging as low as possible, restricted from going any lower by the shock absorber, the spring IS compressed slightly, which is called pre-load. Sorry for my blunder, and thanks for pointing it out.

I've had the front suspension completely off my car and, of course had to put a jack stand under the spring to bent it as high as possible as I slowly removed the shock absorber. The same goes for the rear suspension. You'll get no more discussion from me about the pre-load issue. Bye :seeya

Jim

 

No, problem.. I just wanted to make sure.

 

Ok, I think I found your problem here bluewasp. I had my car aligned yesterday by a real nice guy who explained a lot to me. He told me that when you lower the car it tends to toe out the wheels. So in other words the front of both tires in each pair (front & rear) tends to be pointing outwards from each other. This will cause abnormal tire wear on the insides of the tires. This is the case in front and in back. He also said that a toe out condition caused the car to "hunt", or dart back an forth. So I think you are right in your asertion that the car got very loose upon lowering, but it wasn't caused by unloading the spring, because the weight of the car was still the same on spring at all four corners, but you toed out in both the front and the rear which caused both the front and rear to "hunt".

I think that I may have finally put this topic to rest. This makes the most sense to me so far. Also, it was a qualified alignment guy who has been doing this for over 20 years that told me about the characteristics of a car when it is toed out, so I think you can take that to the bank!

How's that sound to you guys?

 

Saxn8r,

Where did you take your car? I'm about to get my 18 in. rims and tires put on next week and then will lower the car. I want to get it aligned to Z06 specs shortly there after.

 

Hey Rick!

I took it to Firestone here in Humble. I was very happy with the tech that worked on my car.

Corey

 

I have mine lowered to the max (shaved all bushings in front).
I have to take car a bit and DO scrape sometimes.
But it looks so :cool:

Michael