Soft Spring big sway VS Stiff spring smaller sway bar

I know there are two basic schools of thought on handling. The traditional method of choosing a stiff spring package and then tuning with sway bars versus going with softer springs and big sway bars. Recently it was said that the softer spring route has a narrower range of best performance. I would think that this is just the opposite. I can get that on a smooth track the stiffer setups would be great for all out performance. On a not so smooth track, like many, I would think that the softer setup would be an advantage over a greater range of operation. I do not understand the narrow range of best performance for the softer spring setup? I would think that under most circumstances that the softer springs would be an advantage. Can somebody explain this to me.

Also how would this relate to street performance cars?

Damon

We run that setup in our circle track cars. We have 20 or so extra shocks to choose from (for 4 cars) and a shock dyno at the track in the trailer.

The shocks we use have a massive amount of rebound. You could do a pull up on one before it extended out.

The idea for us is with the rule of a 5" static ride height, the car compress with the soft springs, it seals the nose to the smooth track, and nearly doubles aero downforce.

It is completely perfected with a pit crew of 3-4 guys collecting, recording, and analyzing data input every time the car comes off the track.

Herb Adams was an engineer that once worked for Pontiac. He was instrumental in the development of the Trans Am. He believed in the theory of moderate spring rates and large anti sway bars as a path to decent ride comfort and great handling. I agree with his methods. Look at it this way: The car will ride nice in all conditions, but when you push the car in a turn, the anti sway bars come into play. Its sort of like having a hidden talent that only works when you need it.
Going the route of the stiff spring/smaller anti sway bar, you have a car that will ride rough all of the time. This combo may be better for competition since the stiffer spring rates will lessen the chances of the suspension bottoming, but for the street, it certainly isn't my style.

I like the soft springs and heavy sway bar for the streets. Ride on the streets is great, and still handles great. Did that with my first handling car, a '71 Sebring. Any handling requirements like road course, major autocross, then heavier springs are required, then a heavier sway bar also. Not to mention proper shocks.

I'd say there are three schools; soft spring-big bar, moderate spring-moderate bar, stiff spring-soft bar.

The soft spring-big bar approach has a narrow range of performance because the pricipal is, as autoxcuda pointed out, the spring rates are so soft that aeroforces as low as 60 mph will begin to push the nose of the car down. These rates are so low that they are only effective on a smooth surface race track. On a street car they would be bottoming out and causing issues. In the case of the stock car shown above, these would be wheel rates as low as 150#. When your springs are that soft, shock control of the motion becomes hypercritical and requires valving requirements that are not going to be found in an off the shelf offering. As pointed out, the race team about has a dyno to select the best shocks based on their combo of springs/bars they are using at any particular track. That is far and away more work and effort than almost any street driver will be willing to put in.

By comparison, 150# wheel rates are down around many of the stock size t-bars that mopars came with. I don't know about many guys here, but I have bottomed out almost every stock sized offering in a mopar in regular street driving, even teh "big" Hemi bars. To use combos like this on the street requires very large sway bars to be effective, and honestly, there are not large enough offerings out there to really go this route on a classic mopar. As Hochkis pointed out in another thread, they are looking at a 1.5" diameter bar for this approach to even get to the moderate range. That is huge.

I agree with the Herb Adams approach that the moderate rate combo is the best allaround approach for most street cars. BTW, during the Herb Adams era, Pontiac also developed and marketed the Radial Tuned Suspension. This was nothing more than aggressive alignment specs to take advantage of the new radial tire design. But, it tweaked a lot of parts counter jockeys and car owners for the better part of a decade. But I digress. In any case, this is why, finally, we are seeing a migration in the mopar world towards 1.0 and bigger bars, whch are fairly moderate rates. Combined with the widely available sway bars of 1, 1.125, and 1.25, we have finally hit the point Pontiac found in the 2nd gen F body around 1974.


The higher spring rates are necessary when you start driving very aggressively because there are a multitude of forces at work. Not only do they resist the obvious bump and roll, but there is also anti-dive at work here as well. Stabbing the brakes going into the corner really shift dynamic loading and it can easily overload the average shock absorber, so you need rate to hold things up. Racing at speed alos increases the load of dips and bumps, so significantly higher rates are need to resist bottoming on less than smooth surfaces because of the speed. I'd also make an arguement that calling competition style anti-roll bars "soft" ma also be a bit of a misnomer. They may appear a bit softer compared to some springs, but they still are pretty stout. In this approach, I might even argue that mopars come up short. A 1.22 t-bar is the biggest occasionally available t-bar around. This is entry level racing performance, but in a mopar, you're maxed out. Its easy to see why there has been a steady migration towards chevys at the nation's oval tracks. As Mitch has pointed out in multiple posts, the radical transition loads placed on a car in an autocross has led him to constantly increase t-bar sizes to the 1.24" he has now, and, unfortuantly, he is maxed out.

Now, that isn't to say everyone out there needs a t-bar that is an inch and a quarter in diameter. But, I think almost anyone would benefit from the overall moderate approach because it uses readily available parts that can be matched with a decent, but cost effective shock, such as the widely popular RCD Bilsteins, without breaking the bank of getting into super trick shocks.

Brake dive is another issue worth mentioning that comes with a lighter spring.

Great info, TC!

Thanks Wade.

The whole soft spring/big bar set up has only really gained a lot of momentum in the last decade as the nascar boys have tried to work within rules and improve aero. Some of their sway bars they run are up to 2.5" in diameter. Yes, they are tubular, but that still is a huge honking bar to put under a car.

Another draw back to the big bar approach in a street car is that cornering on less than smooth roads, a big bar can actually cause the inside wheel to lift and create some skittish handling characteristics.

I've liked Herb's thinking ever since I read one of his books 30 years ago. I'm getting it. Thanks for the info guy's especially TC@HP2

To me shocks are a big deal. Have not heard much about Fox or King shocks i guess due to the costs? Just what is an awesome shock for a street performance E body? I don't mind spending extra coin on shocks that are worth it.

Damon

I now know why King and Fox shocks are not talked about. They don't cater to the street crowd. I was used to seeing talk about them on Truck forums and thought they might do something for the car hugging crowd too. Nope!

Damon

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I now know why King and Fox shocks are not talked about. They don't cater to the street crowd. I was used to seeing talk about them on Truck forums and thought they might do something for the car hugging crowd too. Nope!

Damon

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Not true. Ridetech Shocks are made by fox and are the best on the market....for now.