Advanced Suspension Mods

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Wow Charlie that last one was incredible. It's gonna take a few reads to get that to sink in! Thanks for all your input! This is a hobby for me too, just on a much lower and slower level Haha, I'm not tossing a thousand dollars into a new suspension setup every couple weeks :p Your words are not taken lightly and keep me motivated and pointed in the right direction(I think lol), thanks!

[Die-Laughing]

That gives me a better idea.. I completely forgot about bumpstops and I wasn't aware how important they are. It sounds like bumpstops will be very useful to me. What is the proper way to setup a bumpstop? It sounds like I should put the car together in the lowest setting and make my bumpstop that length and then add preload to get the height where I want it. I guess this is where your spring rate & length comes into play. It sounds like I didn't completely fail with my 200#F / 175#R setup. I cheaped out on shocks but, I'll have to make due.

[Zanzer]

[Advancedynamix]

Charlie it came off real easy with a punch,but It wont pass over the welded portion at the top of the rod.Remember these are the Cabriolet Gas Adjust.

HMMM, I wonder if yours are different than mine, because mine were welded to the shock iirc.

[Advancedynamix]

what determines the firmness of the spring? I thought that was the rate of the spring. I figured the lower the rate, the softer the feel.. The higher the rate, the firmer the feel. I want it to be firm but, not 350# firm like the ebay civic coilover springs. I can see how the rate of the spring would affect sag & height but, to me it seems like length of spring and adjustable sleeve would have the biggest role in height. If I relied on a really low spring rate to lower the car, it seems I'd have a really soft feeling low car.

I went with 200# 10" spring in front and 175# 8" springs out back. I plan on adjusting my height with the adjustable coilover sleeves. I'm looking for low street stance. I don't expect maximum comfort and I don't need it to be most efficient on the race track.

Good question, and it's simple.

Spring rate rises as the spring is compressed. That means that a 150lb spring takes 150lbs to compress 1", but the rate will rise from there. Your car will only compress or "sag" the spring until the spring pressure equals the weight placed on that spring. That will be your dynamic or working spring rate. If you have 120lb springs on your car, the dynamic spring rate will be the same as if you had 150lb springs on the car. the difference is that the 150lb springs will sag 2" and the 120Lb springs will compress 3'', but the end result is a 175ish lb dynamic spring rate (these numbers are just for example purposes and not factual figures).
On an adjustable spring style of shock, you are relying on the sag of the spring to give you adjustability. For full adjustability the car should rest lightly on the bump stops with the adjusters at their lowest setting (while still holding the springs securely, NO SPRING FLOAT!) To raise the car you add prelaod to the spring, which will compress it and effectively raise the rate of the spring. This doesn't make the car stiffer, it simply raises the ride height until the rate exceeds the weight placed on that spring, then your suspension has been handicapped. Not all springs react equally, so the progression at which the rate rises depends on the spring itself, which is why I can't provide actual numbers for this stuff.
Now, when the base rate of the spring exceeds the weight applied to it by the car, the suspension will be stiffer, but for most driving conditions (race tracks included) this is a terrible mistake and only hinders the suspension. For years, I have seen road racing teams (even on a professional level) effectively eliminate the cars suspension by putting heavier springs on the car and heavier sway bars until the cars suspension is almost rigid. This is not the best way to tune suspension and it has been proven on many different platforms, that working suspension will keep the car on the track at much higher speeds than solid suspension.
That being said, your spring rate is directly proportionate to the weight of the vehicle and the lever ratio of your suspension. Higher initial spring rates will just sag less to get to the dynamic weight (the pressure that is actually holding the car up). This pressure only changes if you change the weight of the car or the lever ratio of your suspension system.
To control the attitude of the car under driving conditions, it is best to use shock valving and/or bump stops. This is why springs only cost about 100 bucks a piece for top of the line racing springs, but shock absorbers can climb well over 10,000 dollars a corner for top of the line components (don't believe me? Look up a set of used Penske shocks on ebay, now imagine what these teams pay to have Penske custom make shocks for them). Shock absorbers are where the magic is in a cars ability to do what we ask it to do in any situation. Getting the dampening right, that's the ticket to success. Springs simply hold the car where you want it, and sway bars make up for a compromise between performance and versatility.
Progressive wound and multiple rate springs are good for a wide range of driving conditions, but bump stops are a less expensive way to accomplish the same task.


Also, My car's fastest lap times have been with 150lb rear springs and 200lb fronts. I have tried all the way up to 250lb front and 200lb rear, with bad results on every track that I tried higher rates on as well as on the skid pad. I have tested with 2 different types of street tires (nakang ns2 and Federal Formoza) as well as 2 different "R" compound DOT race tires (Toyo Proxes R888, and Yoko A048 ) and Bias ply racing slicks (Hoosier R35). I have put over 20K track miles on the car, in various configurations and I have access to a several skid pads for testing. I've used up over 2 dozen tires in 2 years on the track alone. This is my hobby, but I take it pretty serious (all the while having a blast of coarse, ). The R&D that has gone into the stuff I post is very extensive, but it's not written in stone so if you find something that works better for you, I encourage you to share. These cars are magic on the track when they are set up properly.

Hope that clears things up.

[nitrofarm]

Charlie it came off real easy with a punch,but It wont pass over the welded portion at the top of the rod.Remember these are the Cabriolet Gas Adjust.

Just ground the dust seal caps down, adjuster sleeves fit like a glove now.

[Die-Laughing]

Die Laughing, stiffer spring rates will give you a higher ride height, not a stiffer one. Spring rate determines the sag. For a lower stance, you'll want less spring rate. After sag the rate will be the same. You're vehicle weight is what determines spring pressure, not the rate of the spring. An aggressive ride is more about shock valving than spring rate.

what determines the firmness of the spring? I thought that was the rate of the spring. I figured the lower the rate, the softer the feel.. The higher the rate, the firmer the feel. I want it to be firm but, not 350# firm like the ebay civic coilover springs. I can see how the rate of the spring would affect sag & height but, to me it seems like length of spring and adjustable sleeve would have the biggest role in height. If I relied on a really low spring rate to lower the car, it seems I'd have a really soft feeling low car.

I went with 200# 10" spring in front and 175# 8" springs out back. I plan on adjusting my height with the adjustable coilover sleeves. I'm looking for low street stance. I don't expect maximum comfort and I don't need it to be most efficient on the race track.

[nitrofarm]

Nitro, on the mk1 VW shocks you will need to grind the dust shield as it is not removable on the gas adjusts. On the Festiva gr2 shocks it must be removed, but if you cut the spring perches off at the welds then you can use the perches to help hammer off the dust caps. Atleast that's what I do.

Charlie it came off real easy with a punch,but It wont pass over the welded portion at the top of the rod.Remember these are the Cabriolet Gas Adjust.

[Die-Laughing]

Cool.. Well, I'll have to make it work. Thanks

[Advancedynamix]

Die Laughing, stiffer spring rates will give you a higher ride height, not a stiffer one. Spring rate determines the sag. For a lower stance, you'll want less spring rate. After sag the rate will be the same. You're vehicle weight is what determines spring pressure, not the rate of the spring. An aggressive ride is more about shock valving than spring rate.

Nitro, on the mk1 VW shocks you will need to grind the dust shield as it is not removable on the gas adjusts. On the Festiva gr2 shocks it must be removed, but if you cut the spring perches off at the welds then you can use the perches to help hammer off the dust caps. Atleast that's what I do.

[Die-Laughing]

Thanks for the tips & tricks Advancedynamix.. I ordered up a few items to do my coilovers.

In the front.. I went with inexpensive but, new MK3 front shocks that I plan to slot for camber and all the southwestspeed coilover pieces. In the rear, kyb's for a MK1 as well as the southwestspeed coilover pieces. I stiffened up the spring rates a touch from what you suggested but, I want to run it low with aggressive wheel fitment. I'm going to machine top hats and look into making rear camber plates. I'll document it in my build thread. Thanks again.

[nitrofarm]

Charlie would it be ok leaving the dust shield on and just grinding off the OD to allow the adjuster sleeve to pass over it?

[Advancedynamix]

Yeah, I wouldn't cut them unless your running it really low all the time.
On those Cabriolet shocks, you'll need to cut some (like .200" iirc) off of one side of the lower mount (the steel tube that the bolt goes through) of both shocks. If your patient, you can do it wit a hacksaw and a file, but make sure it's nice and square, or else you'll be putting extra stress on the lower mounting bolt. Put he short side toward the center of the car, so the shock body is offset inward. This is to allow the shock to clear when the rear suspension twists (articulates). I cut mine right to the rubber on the insides and then used spacers on the outsides. They haven't been contacting anything under there, but my car isn't slammed right now either.

[nitrofarm]

Charlie got my Cabrio shocks today I'm gonna try & do my Aspire rears tonight with the Black Magic 120# 10" springs. Should I just leave the "Bump Stops" the stock length and test drive it?

[Advancedynamix]

Thanks for the clarification Charlie. Next question: Isn't using the shorter shock on the rear beam the same thing as what off roaders do when using droop settings?

In a way, I'm using shorter shocks in a similar way that limiter straps or bumpers are used in off road. Off road systems tend to require more adjustment range, especially droop and ride height, than on road vehicles. The rear of a FWD road car (even dirt road, like in rally) doesn't need to droop very much. Now, for crawling around in trails, droop may be necesarry to keep the front from teetering and lifting the drive wheels. Tuning FWD suspension for slow pace rough terrain is new territory for me, but I'm looking forward to learning the ins and outs of this as well. I think Movin would be the go to guy for any questions in that realm.