L6969

I need some help on a decision picking a spring.

I purchased a very mint all original 87 350 tpi
iroc last fall with about 21,500kms on it. The only thing not original to the car is the Intrax lowering springs and 17” chrome replica rims. Eventually I will sell these. The Original springs, rims and tires I have btw.

The intrax are too low for me but the car looks killer. I will be replacing the chrome 17” with oe painted 17” reps. I will be using factory shocks and suspension.

Which of the springs would offer the best ride quality based on the above with stock shocks?

The Umi has a stiff rear rate with a soft front at 600/200.

Hotchkis has a softer all around rate at 600/140.

BMR is 620/160.

Pro kit is 714/177.

I don’t want to be too soft and feel floaty and too stiff and bouncy doesn’t make for a fun ride either. Not corner carving or dragging the car, just looking for a well rounded spring. If anyone has one of these springs on stock shocks would love to hear your thoughts.

Roc on!

Camaro51

Working in the industry ive talked directly to all of the above at different trade shows. They are all good places and all have great thoughts on why they make their suspension set ups the way they do. I chose UMI after talking to Ramey over there. In my opinion he has a great background with many years in short track racing and knows how to set a car up to be balanced and handle turns at all speeds. It may have been because he was the best at describing the hows and the why's in a way i could totally understand and it didn't sound like a sales pitch, but i chose UMI. and before i tore my car down to go super crazy i drove my 91 with the UMI suspension with their springs and it was amazing! My buddy following me through a turn told me he watched the car literally suck down to the ground as i cornered. It looked as balanced as it felt. with a firm but driveable ride. I would highly recommend any of the UMI parts.

L6969

if I was going to replace shocks definitely umi would be likely the way id go as well but I’d also be upgrading everything for better for performance to match. I’m just looking for stance and ride comfort with complete factory suspension and after a lot of debate it came down to who had softer springs rates all around that would pair better to oem shocks. Hotckis and bmr were two left. I wanted to pick BMR cause of the price but I’m leaning hotchkis cause the drop is only 1” vs 1.25-1.5” with bmr, is slightly softer and can keep me in alignment spec without having to do things like LCA relocation brackets, adj pan hard bars etc...

I want to keep the car totally original with two small subtle upgrades, 17” replica wheels and subtle lowered stance. I debated putting the oem springs back in but after looking at some photos of the car a few years back on those springs they still sit pretty tall for a 30 year old spring. Mind you the oe springs probably had 10k miles on them, 13k on the whole car as of today.

Camaro51

Dual rate springs and adjustable shocks tend to offer the best ride for street driving. You can dial in how stiff you like the car to feel with the shocks. For daily driving i tend to use a softer shock setting and for performance i dial em up a few clicks. If its strictly a street car. I would check summit or equivalent for lowered stock spring replacements and get adjustable shocks. You wont need a high performance spring to get the feel you are looking for on a street driver. And save a ton of money. And larger sway bars will limit body roll. Just my opinion...

L6969

i don’t disagree. Only like i say it’s a very original very low milage car that may see a tank of gas run through it the whole summer. Its more of a show and shine car than and drive and enjoy car so I would never reap the rewards of investing in better shocks and sway bars etc. The only other spring I see that’s 1” drop but no idea what the spring rates are is suspension techniques. The eibach 1” pro kit would definitely need after market shocks at 714/177 or I would of went with those since I can get them as cheap as the bmr and umi springs.

Camaro51

Theres a company called RareParts that makes factory rate iroc springs in stock height and 1" lowered. You cant buy direct as they are a wholesaler, but if you contact them they are nice people and can get you part numbers and some dealer names of who sell them. My bet they are the moog or acdelco springs you see advertised. They make high quality steering and some suspension replacement parts. I would say better suited parts for your build.

L6969

thanks I looked into them and theirs a dealer 1/2 hr from my place but they only seem to make a 706 or a 420 front spring and a 104 rear spring for the V8 cars. Definitely cheaper though.

Camaro51

Yeah i talked to them at a trade show. He said the iroc-z models had that higher rate. Since he does parts for the OEM's i kinda felt he knew what he was talking about. So will it be too stiff for you? Thats hard to say. Its factory spec but the iroc-z did ride a little stiffer stock than an RS. The softer rate spring may sound too light but keep in mind theyll more than likely be stiffer than what you have now as they arent 35 years old. Hope i didn't complicate your decisions more? Just didnt want to see you spend more money than needed.

vinny R

I purchased a set of these, your post did not mention them so I figured it would be worth a look if you have not made a purchase. https://www.foundersperformance.com/...v=7516fd43adaa

I copied and pasted the description below of the spring rate. I could not find actual numbers but as you see these are "progressive rate" springs. From the research I did these are supposed to give you that stock ride until they start to bottom and then the rate increases the further they compress. You can't beat the cost, especially from FP, and these are German made steel so we all know that usually means quality. I have not installed mine yet as there are other mods to go along with these. I see you just want the look. Hate to throw another choice at you but if you research this forum you find some good feedback on others that use these Vogtland springs.

Vogtland compound Spring Rate. As the distance of spring travel reduces, the performance demands of a spring drastically increase. Derived from racing, the Vogtland compound spring consists of two different spring rates. The initial rate provides the proper pre-load necessary for proper suspension function during all road conditions, and the final rate is designed to provide the appropriate vehicle balance for neutral steering characteristics. Each spring is calibrated for every specific car model, and provides a balance between performance and comfort. more details on - https://www.carid.com/vogtland/30-mm-x-30-mm-sport-front-and-rear-lowering-coil-springs-mpn-959212.html"

L6969

actually looked into those. A few things turned me off to them. First was that I’ve read people saying the wheel gap in the front is bigger than the rear even after settling and cutting a half to full coil off the front was necessary. Also found that the ride drops by about 1.5” which puts me in a spot to start adding things like adjustable pan hard and lca relo brackets etc... to get the alignment specs dialed in. So while they may be $150 cheaper they will certainly cost more in the end. Finally, I read the thread founders put up on here and they never came back to answer anyone’s questions and they never posted spring rates. Actually it’s hard to find that info but I’ve read 550-600 upfront and 150 to 170 out back as estimated guesses. So they would be potentially a tad stiffer in the rear than the 140 hotchkis and about the same in the front as hotchkis. But when a company won’t transparently list their tech specs and claim to be better than their competitors who list their tech specs the old voice in my head says don’t bother with companies like that. .

QwkTrip

iTrader: (22)

I think the Hotchkis rear spring is 100-140 lb/in to be specific. Not a constant rate spring.

vinny R

I thought that to be odd myself that they do not post those specs. The German companies seem to be all about tech.
As for the wheel well reveal I am interested to see where my car settles with these. Right now I have stock springs, I still have the paper tags on mine, and my rear wheel well reveal is more than the front, and I have a taller tire on the rear? These are 30 year old cars so I think the suspension settle will be different on each car so when installed who really knows where you settle out. I have read in these threads where lowering springs where installed and the car actually sat higher. This probably will not be your case as you have lower springs already. I got mine from a member here for $100 and already had installed the adjustable panhard bar. I am actually thinking of just installing the rear springs and not the fronts to see if it levels me out. I am surprised that you did not need the adjustable panhard bar already considering the drop of the springs installed on your car.

L6969

that is also my understanding

L6969

I bought the car with those springs in it last September and definitely should have an adjustable pan hard bar and lca relo brackets at minimum. I also believe by visually looking, the alignment is maxed out in the front from where the stock camber plates are adjusted too so I wouldn’t doubt new caster plates would be a good addition as well to the intrax spring.

mind you I’m 350/ac/all pollution control still installed so my front end is heavy as it gets a non ac car would do better with these intrax springs upfront. I believe the netted about 2.5”
drop and they’d sit closer to 2” with a less heavy front end.

QwkTrip

iTrader: (22)

I had Suspension Techniques springs on my car for 20 years and it was a mild drop. Also, I think shocks are more important to ride quality than the spring rates.

I never had an issue with progressive rate springs when my car was stock, but it freakin' hates progressive rate springs now that the car is highly modified. I've had three different sets and all were a disaster with the car going any which way but straight under throttle. I mean it was scary. Constant rate springs fixed it right up.