PotM GrandMarq.NET - Panther Headquarters Forum Index PotM
GMN Chat Room GMN's STORE!! GMN's Gallery Please!!
Results 1 to 4 of 4

Thread: ['02 MGM LS] Front coils to drop "1 with Bilsteins HD and rear HD air springs?

  1. #1
    Member
    Join Date
    Dec 2018
    Location
    Poznan, Poland
    Posts
    75

    Default ['02 MGM LS] Front coils to drop "1 with Bilsteins HD and rear HD air springs?

    My car somehow came with the P71, 700 lbs/in front springs. I restored the RAS with HD (stretch limo) rear air springs and there are Bilstein B6 shocks now all around (clocked 4000 mi on those), which are the firmer, sporty shocks.
    The front P71 springs are too firm and that's jarring. I figured I would just drop in 540 lbs/in rated front coil springs and be done with it.

    Being aware of the lift kit syndrome caused by aftermarket AC Delco and Moog springs claimed to be 'counterparts' of the stock HPP front springs, I bought Swedish-made Lesjofors front coil springs.

    Well, that's a bummer, now the car sits at least 2" higher in the front and won't sag down anywhere close to the front ride height that the P71 springs the car came with provided. I replaced these because the P71 springs are too damn firm for my setup.

    The Lesjofors compress and rebound PERFECTLY, but the front ride height is unacceptable, the car looks like a speeding motor boat and has been so for several days, even with speeding over potholes to make the damn coils 'wear in'.

    OEM NOS HPP-grade front springs are unobtainium. Well, they do exist. At junkyards I got no access to (I do not live in the States) and on eBay, for insane money (240 for a pair plus 250 for shipping). Don't get me started on custom springs from Eaton or other makers, their prices for shipping to Europe are INSANE (Eaton said SIX HUNDRED BUCKS for stock rated, 1" drop front springs, and 2/3 of the price is shipping!).

    I got these options:
    (1) push the money envelope down the rabbit hole and get NOS OEM HPP springs SOMEHOW;
    (2) try chopping one coil of the Lesjofors springs;
    (3) get other springs, I heard Moog 5660 that fit G-Bodies and Chevy S10 trucks provide a good spring rate and may lower the front end 1" below the stock height.

    I did consider the baking oven trick, but that's too nuclear and involves several risks (including death by forcibly ejected spring compressors...).

    The worst case scenario is to suffer on with the P71 springs. Argh.

    Now, the Lesjofors front springs (EW!) I got have 8 coils that I assume are active (the 1/2 of the 9th bottom coil has a closed and ground end). Hence:

    OEM HPP front coil spring rate: 540 lbs/in, minus one coil, should see an increase by 67.5 lbs/in or so, up to 607-ish lbs/in. This would be nice and provide a good match for my Bilsteins, bc the P71 springs I had are rated at 700 lbs/in (and were too damn firm).

    If I choose to go with the Moog 5660 (for G-bodies and S10 trucks), these are said to provide a nice 1" drop from the stock ride height. They are open-ended (infinite coil) springs tho; any recommendations for fitting them correctly on a 98-02 Panther?

    If you guys got any alternative suggestions for front coil springs that drop the car 1" below the HPP stock ride height, I'm very much open to hear (read) from you.
    '00 Mercury Grand Marquis LS, Silver Frost, the "Sharona": runs, drives and currently with mods in progress
    '96 Chrysler Grand Voyager LE 3.3 V6
    "You obviously have not been introduced to the ASTM Guidance for Profanity Gauging of Technical Services, Addendum#1, American English to Polish Scale Conversion, by which a repair done at a rate of 35 kurwas per 5 minutes means normal performance."

  2. #2
    Member tbear853's Avatar
    Join Date
    Jan 2021
    Location
    Virginia but I started life in Texas
    Posts
    105

    Default

    Just "food for thought" as I don't know your roads ... but if you cut a coil spring, it's overall spring rate increases.

    Example, say a spring has exactly 10 complete coils ... or "rounds". Let's say for example that spring will compress 2 inches if loaded with 1000 pounds. Each complete coil supports the 1,000 pounds and each one compresses 0.2 inches. Now you cut a coil off of the spring, you now have 9 complete coils. Each complete coil still compresses 0.2 inches, but only 9 remain so the spring compresses just 1.8" now per 1,000 pounds. One way to create variable rate springs is some closer coils that stack up and eliminate their cushion of space ... or their "spring" ... leaving the rest to carry increasing loads. The close coils are still there, but being stacked, the provide about as much "spring" as a solid block.

    I've used up some CVPIs in my career, they were stiffer than my ''01 Grand Marquis with standard springs. Not long after purchase, I installed a set of the Bilstein HD shocks, they helped the '01 but it will still more easily seem to bottom on major high speed dips where the CVPIs didn't, but over all I love the ride. The CVPIs never seemed overly harsh, but they were department cars and at best had Ford PI shocks, I never bought Bilstein HDs for them.

    I can well imagine that the mix of Bilstein HDs with PI springs would seem harsh, un-needed on the highways here. Why I did add Addco sway bars too at both Frt & Rr and put AirLift red poly air bags in the rear coils for loading and towing duties (they are only used then, remain empty otherwise, I even plumbed them fo easy fast exhaust on compression). Cut PI springs and the Bilstein HDs will be harsher.

    I've cut coils on cars to lower a inch or two, I'm not averse to it.
    Last edited by tbear853; 07-30-2021 at 11:38 AM.
    No ... I'm not arguing with you ... I'm just explaining why I'm right ...

    Now go ... and whatever you do ... have a safe trip!

  3. #3
    Beater gonna beat sly's Avatar
    Join Date
    Mar 2010
    Location
    Lewisville, TX
    Posts
    22,493

    Default

    I think the stock HPP coil will actually sit lower than the CVPI stock coil. Definitely worth installing first before modifying. CVPI coils have a good inch or so lift over the rest IIRC.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  4. #4
    Member
    Join Date
    Dec 2018
    Location
    Poznan, Poland
    Posts
    75

    Default

    Well, it's been several days now and the "purportedly true to spec" (TEE HEE, HARDY HAR HAR) Lesjofors for my HPP still make it sit too high; eased down about 1/2 inch after hard daily driving, and it just won't drop lower. What a bummer.
    Unless a pal I got stateside actually pulls stock HPP springs from a junk yard, they are beyond my (and my wallet's) reasonable reach.

    The P71 ('cop') springs for the front have a relaxed length that is shorter than the relaxed length of the HPP front coil spring; in my case, the non-P71 spring is 16.25 inches relaxed and 11.5 inches installed. The front end sits well over 2 inches higher than it did with the P71 springs. However, like Sly said, the car will sit higher on the P71s than on the stock HPP springs.

    I assume the Lesjofors front springs are rated at 540 lbs/in. If they happen to be NOT to HPP-specs, they are 420-440 lbs/in. Cutting a coil will remove 1/8th of the coil number and increase the spring rate by 12.5% (1/8th), right?

    It is known from practice and by reference to the front suspension setup of B-body GM's (and Panthers have a 99% identical front suspension geometry) that any reduction of the relaxed front spring length gives twice as much drop on the front end.
    Example: if you got a 16.25" relaxed spring and you cut off one coil, which is roughly a reduction by 1.8939", you will get the installed height of (in this case) 11.5" -- and thus the front end height reduced by 3.78-3.79".


    These figures come from Moog's specs for the P/N 9046; assuming they are about the same for my horrible Lesjofors front springs, I can expect one coil removed to drop the car by 3.78-3.79". It is a big drop indeed; in my case there would be less than one inch of clearance between the tyre tread and the inward turn of the wheel arch edge of the fender.

    Of course, I will have to verify this by measuring the removed Lesjofors front springs and calculating how much I'd need to cut them, and the resulting drop (which means a temporary return to the P71s, GAH!).
    Last edited by SpitShine_PL; 08-02-2021 at 01:19 PM.
    '00 Mercury Grand Marquis LS, Silver Frost, the "Sharona": runs, drives and currently with mods in progress
    '96 Chrysler Grand Voyager LE 3.3 V6
    "You obviously have not been introduced to the ASTM Guidance for Profanity Gauging of Technical Services, Addendum#1, American English to Polish Scale Conversion, by which a repair done at a rate of 35 kurwas per 5 minutes means normal performance."

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
GMN Approved Links!


www.rockauto.com www.adtr.net