what are they? I also heard that going with a bigger front sway bar, and lower sidewall raises the spring rates?? What does a higher spring rate mean? Someone told me that since the car understeers from gm that raising the spring rate will only make the problem worse :confused: It makes sense to me cause I have both bigger bars, and lower sidewall and my car def understeers at the track :cuss What do you guys think? Someone give me a lesson in spring rates and suspension please :blueangel: Thanx guys :seeya

 

Wow where are all the experts :lol:

 

You should probably invest in a good book... and you probably shouldn't be modifying things until you have a clue. Seriously, you can make your car unsafe by just blindly "souping" it up.
The short answer to your questions are:
Sway bars don't affect spring rates.
Tires don't affect SPRING rates.
A larger front bar will increase understeer (decrease oversteer), this is safer for an inexperience driver.
A larger rear bar does the opposite. This can cause what is commonly called a "spin out".
Spring rates work the same (increase rear spring rate, get more oversteer), but if you increase both front and rear the same amount this doesn't affect over/under steer. Changing both bars works this way too (change both bars, the car corners flatter or not.. but doesn't over/under steer differently).
Z51 springs and bars are stiffer/firmer than standard suspension.
Gary

 

Okay...so I'm not an expert but here is what I can tell you from my understanding:

First Z51 spring rates: 660lb/in front and 327 lb/in rear

Now stiffer sway bar and side way raising spring rate. Kind of... Basically raising the spring rate means making it seem like a stiffer spring (say 675lb/in instead of 660). It doesn't actually raise the spring rate but has a similar effect. Why? Well the spring rate refers to the force needed to compress the spring. How does the car exert that force on the spring...by the weight of the car pushing down on it. Now say you have no sway bar and soft springs. This will allow the car to roll side to side as you turn. During a hard right..it will roll onto the left side wheels. Especially the left front. More of the weight gets planted on that spring and compresses it more than it was before. That tire now has to take more of the "load" of the car. So how does a sway bar effect that...well a stiffer sway bar will reduce the amount of body roll and thus reduce the force placed on a tire during a turn. Tires...same effect (not just height but also tire pressure). If a tire is soft and plyable (low air pressure/high sidewall) it will compress more than if it is stiff (low sidewall/high air pressure). It can have the same effect. How much effect...man it depends but it can all add up to 15-30 effective lbs of difference.

Now understeer...that is an issue in and of itself. The best case scenario is that all 4 tires have equal load on them as a car is cornering BUT what about when we accelerate? Only two tires are involved in that so it would be better to get as much pressure on the rear tires as possible. Softer springs in the back will allow the car to lean backwards when you mash the go pedal and give you better traction since more weight is on the rear tires. See the problem... to stiff in the back and the rear end wiggles/wheel hops and does all kinds of nasty things except go forward. Too soft in the rear isn't good for turning (drag racers will run REAL soft stuff in the back). So they try to balance those pieces. There are other issues as well. What about bumps and pot holes on roads. Too stiff and the car will literally hop around or break something. On the track that isn't as much an issue. Many track guys DOUBLE the Z51 rates. 1200lb front and 600lb rear. Finally remember what you have hear...a torque monster. You can move that rear end with the throttle if you want to. Get it hard in a corner and mash the gas and you can overcome a little understeer by sliding the back end around. GM would rather not have people spinning out on the highways and backroads due to a bunch over oversteer. Instead a little understeer is safer. On the track you can muscle it with the throttle if you want. To quote an old NASCAR driver, "Tight (Understeer) is when you see the wreck coming, loose (oversteer) is when you don't"

Help any?

--Bill
:crazy:

 

Impressive explanation. :cool:

 

:smash: :smash: :smash: :smash:
excellant explanation

 

So did you sleep at a holiday inn yesterday :lol: Actually you did help alot, thank you Bill. Now what is the relation bet shocks and under/over steer? I'm just trying to get the car to corner right without having to muscle it in ;) :seeya

 

I agree with you a 100% that is why, I am seeking the advice of my fellow forum members :yesnod:

 

I didn't make it to the Holiday Inn but I did have my Wheaties! :lol:

I'm just not the type to go around saying I am an expert on stuff like this. I understand the basics but there are people that can do this stuff in their sleep. Nothing worse than someone CLAIMING to be an expert but giving you bad advice/info. I'm just trying to help where I can!

Anyhow... shocks.... OH boy. You think sway bars and springs are black magic.....those are the wicked witch of the west! :jester
Compression, rebound valving...it's a huge explaination. I can give you some real basics here. Then I have to refer you to the books as noted above!
So you have a spring that is compressing and expanding. Say you compress the spring (hit a bump). If that spring is left on it's own, when it unloads (uncompresses), it will bounce up and down over and over and over again like a bungie cord until it uses up all the energy. A major part of the shocks job is to control the spring. Let it compress/uncompress once or twice but then get it back into control. If you don't the car is bouncing all over the place. Ever seen a car/truck going down the highway with the back end bouncing up and down....bad shocks. So that is one of the major jobs of the shock. It also assists the spring with taking some of the compression load as well. How much it helps with the compression, how fast it pulls the spring in during rebound (think your old Buick or pickup truck that takes a few bounces before it comes into control over a bump vs your vette) can be done a million ways. The main thing to realize is that the springs and shocks work as a pair. If one is TOO far out of whack with the other things go bad. Think about a shock designed to control a spring rate of 300lbs/in. When that spring was compressed it took 300lbs/in. When it unloads it will unload (a little less than) 300lbs/in so the shock has to control that type of unload force. It is designed to handle that type of force. Now take that spring out and drop in a 600lb/in spring. You have a HUGE increase in spring rate but the same shock. Now that spring unloads 600lbs of force on that poor little shock designed for 300. First you are not going to get the TRUE benefit of the 600Lb spring (but you will notice SOME difference) and secondly that shock will destroy itself quickly trying to handle that much of a change. So again...small changes are okay but big ones will not reap the total benefits and will shorten the life of the shocks. Even the Z06 which has 10% stiffer springs in the back than the Z51 option (10% 327 is only 32.7 lbs) required revalved shocks in GMs mind. Could you throw Z06 springs on a car with the Z51 option. Sure. Would it handle just like a Z06...not quite. Would I put Z06 springs on a stock car. Probably not without a shock change. It would be stiffer due to the springs but the effect would probably NOT be as great as you would expect. In the least case the stock shocks would lose some usable life. That's why the best packages are both springs and shocks. That being said....each race track is different and the pros will use different shocks and springs at each. It is an amazing science. Most NASCAR teams have shock specialists! One guy who is paid to setup shocks only!
If you are really interested I would tell you to grab a book. It is FAR more complicated than I present here. These are the real basics but I think it gives you a good primer.


--Bill

 

Thanx again Bill and if you want to be my shock specialist let me know, there is an opening in my team for next season :lol: How does free track time and board sound :D Off to the library I go :crazy:

 

No problem... glad to help. Tell you what...I'll take some of that 417rwhp in trade! :lol:

Someday soon I need to start upgrading.
--Bill

 

:confused: :confused:
IMO: the stronger the spring, the less the A-arm will move up and down. The less the A-arm moves up and down, the less the shock has work to do.
Or in extreme: put in a sold bar instead of the spring and the shock has nothing more to do. It will last 100 years. Keeping in mind, that you always have the same "outer load" on the spring, this is the weight of your car and this is not changed. right or wrong? Let me know.

Frederik


[Modified by C5 Frederik, 11:12 AM 11/15/2002]