Lowering Spring Perches

I priced having my stock Konis converted and I found a lee expensive alternative with Spax purchased from Superformance. I am happy with the Spax and I have my original Konis that can easily be reinstalled. note the Spax install is easy and require no modifications.

 

I do have the 25mm or 1 inch front spring perch, works great, I didn’t have to get my front wheels align.
I’ll try to find pics later.

 

I did this modification to my car when I got it 16 years ago. When I did it I learned that you cannot use the same drop of spring perch on the front and on the rear for two reasons:

1. The motion ratio (amount of wheel travel relative to shock travel determined by the geometry of the suspension) is not the same front and rear. As a result it requires a smaller drop on the rear to achieve the same amount of lowering as on the front. From memory the difference of drop is 30-50% less on the rear to achieve the same amount of drop on the front.

2. If you put a 25mm drop lower perch on the rear it will contact the suspension arm.

I do not have exact numbers but I was able to install the 25mm drop lower perch on the front and a 12.5-15mm drop (I cannot remember the exact amount and have no way of measuring) on the rear. Perches were custom made for me by a machine shop again more than 15 years ago.

Lowering the car even a little does place the suspension in a different range of motion and there are bump steer considerations to have your alignment correct. Even if the car still drives straight a proper wheel alignment (ideally with the driver weight and half a tank of gas) is money well spent.

 

I was wondering if or what effect this modification might have on ride quality since you are effectively altering the neutral resting position of the shock. It will have less range in compression and more range in rebound. The Koni does have an internal adjustment but not sure which way you would turn it to compensate for this. I really have no complaints about how my car rides and handles. For street use it's pretty good for 1960's tech. So I assume the reason for this mod is purely cosmetics.

 

Zero effect on ride quality as the spring rate remains the same and the damper is no operating any differently. I have decades experience in chasing tiny ride variations on race cars and can tell you without a doubt that this is a cosmetic modification only to minimize some of the visible wheel well gap.

 

In 1990, FChat member “Steve Magnusson” designed low spring perches for lowering the car. In those drawings, he specifies that lowering the front spring perch by 1 cm causes a 1.7 cm reduction in car height. In the rear he calculates that lowering the lower spring perch by 1 cm causes a 1.4 cm drop in car height.

I am currently redoing the suspension bushings on my car and am concerned that after reassembly the car will be even higher than it currently is. I am currently trying to find a machinist who can manufacture Steve’s lowering perches. I am thinking about targeting a 1" drop front and back, which would translate to a little less drop than that given my presumably current sagging suspension.

Here is a link to a thread that includes photographs:

Lowering a 308 with original Koni shocks


Did the factory set US-spec cars higher than Euro-spec cars? I have heard of this being done by other marques to comply with USA headlight height requirements.

 

Should be an interesting mod on a car with the deep front air dam option like mine that seemed to touch everything on the stock ride height.

I finally took it off and bought a "regular" one from Ebay.

That was nearly 20 years ago and I have been fighting the urge to put the old one back on just for the cosmetics.

 

Hi Tommy. I have the regular spoiler, and I have to say that I think it looks just "right". I originally wanted to put on the deep spoiler, but my thinking of the aesthetics has changed over time. Regardless, they all look "good" !!
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I don't think there is a car in the world that looks better than a yellow black GTB

 

You're very kind Tommy. She's an all original 77 (other than the Eurioized front bumper !). I must admit I might one day purchase the deeper front valance, but I really do like the look of the smaller spoiler overall (and certainly easier when parking !). All the best.

 

It was a 77 yellow/black GTB that altered the course of my life forever when it drove past my house when I was a 13 year old back in 81.

Chassis 21277

 

Here is the story

https://www.ferrarichat.com/forum/threads/please-help-me-find-chassis-21277-308-gtb.342117/