I understand that the 88 stock front ARD springs are 3.881" ID. There is a good assortment of 3.75" ID springs, which are about 1/8" smaller, varying in length & rates, Has anyone every tried to install? How well do they fit?
For the 88 front the minimum coil ID is 3.25 and the maximum OD is between 4.75-5.0"
What springs are you looking at?
The stock 88 ARD spring has a free length of 12.31, rate of 205 lbs/in, the load height of 7.87, so at ride height it sees an approximate 910 lb load.
As you look at springs, about 910 lbs will be used to support the Fiero and targeting a 7.37 load height (1/2" shorter = 1" ride height reduction) you can determine the needed free length based on new spring rate to lower your car 1". Free length = desired load height + 910/Rate. If you want to lower the car more, remember that the springs are nearly 50% between the bushings and ball joints, so .25 reduction in load height = 1/2" reduction in ride height.
Thanks for sharing the info. I'm looking at standard 3.75" ID coil-over springs made by King, Eibach etc. They come in a variety of lengths from 8" - 24" and rates from 200lb/in. - 800lb/in. The 3.75" ID is very close to the stock spring ID of 3.881". All one would have to do is adjust the height by trimming an end with a cut-off wheel.
Amida, did you have any luck getting the 3.75" springs to work? I'm looking for some 725 lb / in springs. I'm modifying the LCA so that's no big deal, but I don't want to have to modify the crossmember / upper spring hat, so if the 3.75" springs fit that would be awesome.
Amida, did you have any luck getting the 3.75" springs to work? I'm looking for some 725 lb / in springs. I'm modifying the LCA so that's no big deal, but I don't want to have to modify the crossmember / upper spring hat, so if the 3.75" springs fit that would be awesome.
Jeez, Steven. At 725 #/in I'd think the chassis would be the new spring.
Amida, did you have any luck getting the 3.75" springs to work? I'm looking for some 725 lb / in springs. I'm modifying the LCA so that's no big deal, but I don't want to have to modify the crossmember / upper spring hat, so if the 3.75" springs fit that would be awesome.
I began to mistrust the info in some of these threads. What car is this 3.75"-3.881" I.D. for???? I measured my '88 front coil I.D. and it was 3 7/16", or 3.44" . What a waste of time that was looking at the coil charts. 725lbs. sounds really stiff for street front springs, but I don't know what is ideal for road racing. Maybe someone can share some info on that; as far as ideal spring rates for different applications.
doNOT go so stiff on a 88 front or rear unless it is a pure track car only run on super smooth tracks even then 725 is too much 3 1/2 times stock
you want just stiff enuff not way too stiff to work
I take it you haven't measured the motion ratio on the front of an '88 Fiero.
It's 0.53. No joke. A 725 lb/in spring up front works out to a wheel rate of only 200 lb/in. There are production cars with higher wheel rates. It's actually a little lighter than I wanted to run, but I'm limited by shocks. Since the shock is in the middle of the spring it needs to damp a 725 lb spring despite the low wheel rate. I'm looking into adapting some Bilstein motorsports units to try to address the issue.
With a wheel rate of 200 lb/in I'd be at only 1.8 Hz for the front ride frequency. That's at the upper range for production sports cars. Not in the realm of race cars yet. That said, my Fiero is basically a dedicated track car these days. The only time I drive it on the street is to and from the track, and for testing.
I'd prefer to be at 2.2Hz front / 2.4Hz rear, but that would require 1170 lb/in springs up front and 755 lb/in in the rear. If I can adapt the Bilsteins up front that may be doable. For the rear, 755 lb/in that goes beyond the capability of the basic Konis. I don't want to shell out the $$$$ for 2817s. This is still a budget build.
quote
Originally posted by sspeedstreet:
Jeez, Steven. At 725 #/in I'd think the chassis would be the new spring.
The wheel rate is only 200 lb / in. I may need to brace the crossmember, but we'll see.
[This message has been edited by Steven Snyder (edited 06-18-2013).]
Originally posted by fieroguru: The stock 88 ARD spring has a free length of 12.31, rate of 205 lbs/in, the load height of 7.87, so at ride height it sees an approximate 910 lb load.
As you look at springs, about 910 lbs will be used to support the Fiero and targeting a 7.37 load height (1/2" shorter = 1" ride height reduction) you can determine the needed free length based on new spring rate to lower your car 1". Free length = desired load height + 910/Rate. If you want to lower the car more, remember that the springs are nearly 50% between the bushings and ball joints, so .25 reduction in load height = 1/2" reduction in ride height.
FYI:
The front corner weights on my car are 655 lb for the front left and 595 lb for the front right. That's with a front-mounted 23-lb battery and power steering, but no spare tire, jack, or spare tire tray, and me (140 lbs) in the driver's seat. Let's call it 625 lb average for the front corners. Unsprung weight with 12" rotors and 17x7s is ~92 lbs based on my measurements. So the unsprung mass per front corner is 535 lb.
The motion ratio for the front is 0.53 based on my own measurements and your calculations from another thread.
535 lbs / (0.53) gives 1009 lbs of load at the spring.
Based on the photo it looks like you could simply cut off the tapered region and get a spring with a 3.5" ID on both ends. However, it would be really short... since the full length of the spring is 8".
At 700 lb/in, that spring would be compressed 1.44 inches, down to 6.5". That's ~2.5 inches of drop. Probably a bit too much unfortunately. However, with such a short free length compared to the stock spring, it may be possible to put a 1/2" spacer in there, especially if you modify the bottom spring perch to accommodate the 2.5" end of the coil...... or if you have a coilover shock with an adjustable lower sleeve with 2.5" diameter. Which is exactly what these are designed for on a Mustang -- stock upper perch, adjustable coilover lower. I'm going to try this. I need different shocks to handle that rate anyway.
I'm running 700 lb/in QA1 springs conical springs (8MB700) with custom Bilstien coilovers now. I had to cut the QA1 springs down to fit though, since my Bilstein coilover perches are ~1.8 inches higher than the stock lower perch. Annoying. I will probably end up ordering custom springs after all.
[This message has been edited by Steven Snyder (edited 11-19-2013).]
I'm running 700 lb/in QA1 springs conical springs (8MB700) with custom Bilstien coilovers now. I had to cut the QA1 springs down to fit though, since my Bilstein coilover perches are ~1.8 inches higher than the stock lower perch. Annoying. I will probably end up ordering custom springs after all.
Steven, given your experience with track testing, what spring rate would you recommend for ultimate street performance? The setup is on an '88 formula, 3800 sc, 8x18, 10x18, 12" vette rotors, Konis, stock sway bars, urethane bushings.
Originally posted by Amida: Steven, given your experience with track testing, what spring rate would you recommend for ultimate street performance? The setup is on an '88 formula, 3800 sc, 8x18, 10x18, 12" vette rotors, Konis, stock sway bars, urethane bushings.
I think my 700 lb/in front & 475 lb/in rear combination is fine on the street. It's stiff but not at all harsh. There was too much brake dive with 400. You will need to have your shocks revalved for anything above 200 lbs/in on the front or rear.
Pro Parts (http://www.propartsusa.net/) and Koni NA (http://www.koni-na.com/) can revalve your Konis. They will need the following information for each end of the car:
Spring rate Corner weights (with driver) Unsprung weight Motion ratio (for the '88 Fiero it's 0.53 for the front, 0.86 for the rear) EDIT: Rear is actually 0.95 to 1.01 depending on ride height, and increases slightly with higher offset wheels.
Make sure they give you dyno charts for each individual damper, at minimum with the following settings: full stiff, full soft, full stiff + 1 turn, full soft - 1 turn. That will hopefully get you close enough to match them left to right. Or ask them to just match them left and right on the dyno and mark the adjuster positions so you know where they are. It's not possible to match them without a dyno because, according to this guy the adjusters are non-linear near the limits and inconsistent from shock to shock. You can't just set both sides to "1 turn from full hard" and get the same shock forces.
You may be able to compromise with a lower rate having the front dampers valved to have more than the normal amount of low-speed compression damping (for braking), but highly digressive to still soak up high-speed bumps OK.
Now about the sway bars... What tires sizes are you running?
[This message has been edited by Steven Snyder (edited 11-22-2013).]
I think my 700 lb/in front & 475 lb/in rear combination is fine on the street. It's stiff but not at all harsh. There was too much brake dive with 400. You will need to have your shocks revalved for anything above 200 lbs/in on the front or rear.
Pro Parts (http://www.propartsusa.net/) and Koni NA (http://www.koni-na.com/) can revalve your Konis. They will need the following information for each end of the car:
Spring rate Corner weights (with driver) Unsprung weight Motion ratio (for the '88 Fiero it's 0.53 for the front, 0.86 for the rear)
Make sure they give you dyno charts for each individual damper, at minimum with the following settings: full stiff, full soft, full stiff + 1 turn, full soft - 1 turn. That will hopefully get you close enough to match them left to right. Or ask them to just match them left and right on the dyno and mark the adjuster positions so you know where they are. It's not possible to match them without a dyno because, according to this guy the adjusters are non-linear near the limits and inconsistent from shock to shock. You can't just set both sides to "1 turn from full hard" and get the same shock forces.
You may be able to compromise with a lower rate having the front dampers valved to have more than the normal amount of low-speed compression damping (for braking), but highly digressive to still soak up high-speed bumps OK.
Now about the sway bars... What tires sizes are you running?
The tires are Pirelli 235/40/18, 275/35/18. Does it cost much for re-valving? What would be the spring limit for stock koni shock & strut ? Thanks.
Originally posted by Amida: The tires are Pirelli 235/40/18, 275/35/18. Does it cost much for re-valving? What would be the spring limit for stock koni shock & strut ? Thanks.
Which Pirelli tire? P Zero Rossos?
What drivetrain do you have? Your tire width distribution is only 54% rear. Unless you have a Quad 4, I can't imagine your weight distribution is better than 57% rear. Go to a narrower tire up front if possible, or wider in the rear. 225/275 wiill get you to 45%/55%, which still probably isn't enough.
If your weight distribution doesn't match your tire distribution you're going to have to sacrifice grip or intentionally screw up the weight transfer to keep the balance from shifting toward terminal oversteer. Start with the tires...
Anyway... If you run 700 lbs/in front springs and 475 lb/in rear springs, you'll probably want stiffer swaybars than stock. These springs rates won't give you enough roll resistance with wide, relatively sticky tires like those. Check here for stiffer adjustable swaybars: //www.fiero.nl/forum/Forum4/HTML/043365.html Unfortunately I can't yet recommend a swaybar stiffness because I haven't had a chance yet to add the swaybars to my roll resistance calculations.
IIRC, revalving and rebuilding is around $145 per corner, with parts. Extra cost ($100 total?) for dynoing. I haven't finished my shock dyno so I haven't dynoed my Konis yet, so I can't say for certain what spring rates they can accommodate. It's very unlikely that they will handle well with anything higher than double the stock spring rate.
What drivetrain do you have? Your tire width distribution is only 54% rear. Unless you have a Quad 4, I can't imagine your weight distribution is better than 57% rear. Go to a narrower tire up front if possible, or wider in the rear. 225/275 wiill get you to 45%/55%, which still probably isn't enough.
If your weight distribution doesn't match your tire distribution you're going to have to sacrifice grip or intentionally screw up the weight transfer to keep the balance from shifting toward terminal oversteer. Start with the tires...
Anyway... If you run 700 lbs/in front springs and 475 lb/in rear springs, you'll probably want stiffer swaybars than stock. These springs rates won't give you enough roll resistance with wide, relatively sticky tires like those. Check here for stiffer adjustable swaybars: //www.fiero.nl/forum/Forum4/HTML/043365.html Unfortunately I can't yet recommend a swaybar stiffness because I haven't had a chance yet to add the swaybars to my roll resistance calculations.
IIRC, revalving and rebuilding is around $145 per corner, with parts. Extra cost ($100 total?) for dynoing. I haven't finished my shock dyno so I haven't dynoed my Konis yet, so I can't say for certain what spring rates they can accommodate. It's very unlikely that they will handle well with anything higher than double the stock spring rate.
Steven, The car will be mostly street driven with occasional visits to the track. The tires are p7000 all season. The 2.8L will be replaced with a 3800sc with the stock 5sp. Thanks.
The stock 88 rear springs are about 145 lb/in, so 325 is over twice as stiff.
Koni struts were designed for the '84-'87 cars, which are about 175 ppi. They were not revised for the '88's.
While the struts are fine with the '88 springs, the factory '88 rear sway bar actually gives too much roll stiffness for them. My Formula exhibits a small amount of "fishtail" behavior coming off a downhill drift, indicating insufficient roll damping.
