Springs and things

I just finished doing this to my 67 fastback. I went with 620 springs, 5 leaf mideyes, 1"front sway, 3/4" rear sway, poly bushings....also go tht esuper starter kit and redid the steering while I was there. I went with 620s only because I have a big block and I wanted to be able to support the weight without extra bracing like my old GT springs needed. Yes you will need an alignment. The mid-eye leaf springs will drop you an inch in the back. Do you have the original shackles or aftermarket?

Great68, is that your car in your avatar? It looks good. Got anymore pics?

Damn!

what size wheel/tires are your car?? Are you going to swap them out or keep them?

Based on the pictures, the 1" drop coils and the mideye springs would look great, but that is my opinion others might disagree.

Original question: what is the difference between 620# and 750#, the ride harshness. It takes more force to compress the 750s than 620s, so bumps will be harder. But your handling improves because you remove body roll. I would tell you go with the 620s at the most.

Great68 said:

I have to replace a spring perch on my car and I got to thinking that if I am going to doing that I might as well go and replace the 36 year old stock springs I have and put in some performance springs.

Now, I know very little about suspensions and springs. I don't know what all the differences between springs available for my car are. I do know I do not want to do the Shelby A-Arm drop because that is more work than I want to do at this point.

I was looking at Mustangs plus and they have what look like stock springs, 620# springs, 750# springs, and variable rate springs. What is the difference? Which ones would I want? I am not looking to change the springs solely to lower my car, I want whatever will give me the best performance.

Also, what rear springs would I have to get to match the ride height of the new front springs I get?
And, would I have to get an alignment once everything is done?

Click to expand...

Just my humble opinion, but while you have the springs and perches out, you may as well do the shelby drop (hardest part is done). By doing this, you should be able to run some Negative Camber, which will really allow you to improve your handling! Here is an article that may change your mind on high spring rates as well:

Negative roll is a term used to indicate how the tire tilts in or out of the fender well during cornering. This is produced by suspension movement and body roll. Negative camber is when the top of the tire tilts in towards the engine away from the fender. Positive camber is when the top of the tire tilts out of the fender. Positive camber is found on most production cars. Positive camber causes outside tire wear and reduces handling by picking up the tire contact patch on the inside during cornering. This action reduces the amount of tire on the ground. The end result is understeer. Understeer occures when you turn the car to negotiate a corner but the car wants to go straight.

Negative roll is just the opposite. The purpose of negative roll is to keep as much of the tire’s foot print (patch) on the pavement as possible, which will increase traction. This is beneficial for cornering, deceleration (braking) and vehicle driving response. The side benefit will also be greater tire life. The easiest way to explain the concept of negative roll is: Suppose you are a down hill skier. Your head is the top of the tire and the snow skies are the tire contact patch with the snow as the pavement. As you make a turn you will naturally lean in towards the inside of the turn with both snow skies on their inside edge digging into the snow. If you were to lean the opposite direction you would fall head over heals.

So why hasn’t everybody picked up on this? Well a lot of manufactures have. Some production cars like the Mazda Miada have a negative roll system. They handle superbly without poor ride qualities generally associated with sports cars. This can be done because of negative camber gain. One major factor when using a negative roll suspension system, is that the spring rate for a negative roll performance application is less than if would be for a positive camber gain system. That is to say, the spring rate is less for a negative roll car to handle a corner at .95 g’s, as it would be for a car with a non negative roll or positive roll system attempting to handle the same corner at .95g’s.

This means a better ride without sacrificing handling.

Remember negative roll suspensions keep the tire contact patch flat on the pavement with proper geometry. Lighter springs allow the suspension to move which keeps the tire flat on the pavement. THE KEY IN RACING IS NOT HOW MUCH SPRING; BUT, HOW LITTLE.

To all those considering high spring rates, you may want to look into getting some negative camber, and using less lbs. springs. Then you have the best of both worlds IMHO.

In my case, I need the 620s to hold up the weight of my 429. So my road racing ability is already severely hampered by the big block.

Although the Neg Wedge issue is absolutely correct, the spring tension for the 620 is still a comfortable ride even with a small block. The extra spring tension will still give the car better handling

Nice ride

and BTW I like your sig on the other site, that was linked to in your sig on this site:

"The other day I passed a Honda dealership and a sign said "Zero Interest". My thoughts exactly"