MaRKS aka loooseC....I applaud for your focus on this endeavor.....my favorite above all others (R63MazD)...a bit biased i must say(b/gt in the grosh) . What is the guiding principle for the shock placement(both ahead of the axle) ? Stay Warm!!!
In reply to 759NRNG :
I could not mount behind the axle because of the Panhard apparatus on the passenger side is in the way. I could mount them on top of the axle but the shocks are 20" long and would stick out the top of the bodywork by quite a bit. I want to keep the weight low in the car and as far as I know there is no disadvantage to mounting in front of the axle, so that's where they go. adjusting rebound will be difficult, though.
Dunno how much more fab work you're up for, but I was thinking there might be a solution to both your spring rate and adjustment access problems, in bringing back a bellcrank setup. You could put pushrods where the shocks are now, a 90deg bellcrank where your shock upper mounts are now, and run the shocks toward the back of the car, putting the end mounts on the rear upper tubes. Then you can adjust leverage on the bellcrank to get the effective spring rates where you want them, and not run any risk of messing with your big-money valving setup by changing actual spring rates on the coilover.
In reply to GameboyRMH :
Yes,that would work and because of the long travel shocks I now have, I would be able to use a better motion ratio than I had. But, would it be worth it for the small benefit of easy adjustment? I don't think so.
In reply to 759NRNG :
With the pushrod suspension, my wheel rate (spring rate at the actual wheel) was 365 lbs/in and the balance was good. I measured how much the shock would move if the wheel moved up 1 inch (.8129" shock movement) and punched that number into a suspension calculator and it told me to install 550 lb/in springs, so that's what I did. Something is wrong, though, it feels stiffer than before. I suspect my measurement, using just a measuring tape, were not accurate enough. I am going to do it again using a micrometer.
LC couldn't quite hear what the issue was with the diff locating bracket....other than binding on the DS? What is the fix?
In reply to 759NRNG :
I didn't use cone spacers on either side of the Heim joints so they push against the bracket holding them on. It's an easy fix that I will do when I move the top link over to the passenger side a little bit
In reply to SkinnyG :
Surprisingly, no. the spring rate and wheel rate match only when the shock moves the same amount as the wheel over a bump. This almost never happens except with correct geometry on a pushrod style suspension. In my case, when the wheel moves up one inch, the shock moves slightly less, the exact number I need to figure out to order the correct springs.
Do the new shocks have enough adjustment for the softer springs, or were they valved to the springs you ordered?
In reply to SkinnyG :
I asked Jerry from Penske (the guy who tuned them) if they will be good if I go to 450 lb/in springs and he said there is enough adjustment for that.
Ok I slept thru shop class again sorry SkinnyG....Loose C the P ways kinda next to nuthing eh?? Bare with me....are 250-300lbs/in springs way too soft?? What is this suspension software thingy you're using?
In reply to SkinnyG :
The rear springs are 12" long and 2.5" diameter so they will not fit on the front unless I switch those to Penske as well. And if I do switch coilovers on the front, the 800 lbs I have up there is not going to require 550 lb/in springs. I have been using an Excel file somebody gave me to calculate wheel rates but after looking at other formulas for calculating wheel rate, I think the Excel file is for independent suspension only. Look at these formulas for calculating wheel rates: http://www.truechoicekoniracingservices.com/worksheet.pdf
http://eibach.com/us/p-101-suspension-worksheet.html
My shocks are straight up and down, 31" apart and my track width is 48"-what wheel rate do you come up with for my car?
Using that Eibach formula, the effective one wheel bump motion ratio would be a 0.65:1, so you'd need a 565lb spring to match the 365lb wheel rate you used to have. BUT a two wheel bump will have 1:1 motion ratio, and now the 565 is too much - in fact, 1.5X stiffer than what you had.
On my Locost I chose spring rates of 140lb/in to give me a wheel rate of 140lb/in, and added roll resistance with sway bar. This keeps the ride and ground contact still reasonable for a street car. For the "wheel rate should equal half corner weight" crowd, my corner weights are about 400lbs on each rear wheel, with me in it. Except I chose spring rates based on suspension frequency, shooting for low-mid 2cps.
But that's just me. I look at what you do, what you've built, and I am in awe. I look forward to every update. I feel like a two-bit hack in comparison.
In reply to SkinnyG :
That explains a lot. If I understand correctly, I must have had a 365 lb/in wheel rate in one wheel bump before, with a much softer roll resistance. I will have to find a compromise setting but I have contracted with Ron Sutton Race Technology and he says he will have an answer on Tuesday. I suspect I will be putting in 400 lb/in springs without a sway bar or maybe 300 lb/in springs and add a rear sway bar. I appreciate the compliment, I hope I am better at this stuff than when I started 6 years ago.
While on the tractor digging stumps I got to thinkin' bout Pinks' rear shock dilema. Had the previous design, bellcranks and MC bits been thoroughly exhausted....without more mental gymnastics on your part?? I guess I'm asking, had this execution met it's engineering/fabrication conclusion?
In reply to 759NRNG :
Yes, in the rear of the car, I went as far as I could with them. I needed more suspension travel to keep the rear tires on the ground and the only way to get that with the MC shocks was a big increase in spring rate then change the motion ratio where the tire moves 2.5" for each 1" of shock travel. The problem with this is that such stiff springs (if they were even available) would overwhelm the shock valving.
In reply to Crackers :
It is true that buckboards do not make good EM vehicles but that isn't what I am saying. A super stiff spring does not mean the ride is stiff. I had 650 lb/in springs on the car but the wheel rate was only 360 lb/in due to the action of the rocker arms. In order to increase the travel of the suspension, I would have to change the motion ratio of the rocker arms and increase the spring rate to like 850 lb/in to keep the same 360 lb/in wheel rate I have.
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