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Thread: HD vs L suspension observations 101....

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    HD vs L suspension observations 101....

    Well, like over in the audio section, I have been pretty vocal about certain ideas, issues, concepts & theories. I get a lot of PM's about suspenion set-ups, my opinions, & recommendations,like I am sure many fo you do. So I was re-reading the Suspension forum these last few weeks, & also doing some research. I am not 100% on the part #'s yet, but the research is interesting.


    Everyone benchmark's the HD's handling against the Lightning Bretheren. So I started digging into trucks on the dealer lots, reading posts n various boards etc... I am going to the Ford dealer to do some parts searching today.

    1.) the shocks on the HD, for everything I can find are just plain old std F150 shocks. They are 1/2" longer than the stock L shock up front, & about the same overall length in the rear, but of course they are not bilsteins & aren't anything special at all. THIS IS THE #1 issue wth the handling differences of ouor HD's versus the L brethern.


    2.) There is NO REAR BAR.. duh we knew this.. but it is the #2 reason our trucks don't work like L's in the corners

    3.) the Front sway bar is, again as near as I can tell, a std/heavy duty {??} but off the shelf S-Crew bar. Different from a std or ext-cab, YES, but not different from a off the line S-crew. That is by visual & good 'ol open end wrench (in this case a cresent wrench) measuring of the bar. The Screw bar is larger, but that doesn't equate to stiffer.

    4.) Rear leaf springs: ok.. lots of debate.. I am working on exact part #'s from Ford.(Headed to the dealer after I post this) The rear leaf's are different from the '01-'02 HD's & the '03's that is for SURE. The '03 L & HD rear leafs are uncertain if the same or different part #'s. But the bottom line right now is that the '03 L & HD had a spec change for more payload capacity & do indeed, on average sit 3/4" higher in the rear. I am nearly certain that the rear leaf's for all the S-crews are different then the L's mainly from a vehicle weight stand point. I will edit this later when I confirm.

    5.) Overall vehicle weight, the HD weighs somewhere between 500-700lbs more than a L. someone may have the exact #... if so post it up please.

    So there are 5 key reasons why an HD doesn't handle like an L... 4 of which can be over come with GOOD sway bars & the L-Spec Bilstiens. The weight.. put YOU &/or the truck on a diet.


    So hopefully maybe Shanker can make this a sticky. I will post up Ford #'s later today or tomorrow. I hope.

    Rob W.

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    Stickied.

    On my 00 HD, my front springs have an SVT part # Tag on them. I have not paid close attention to the rear ones.

    Yes it has the regular old F150 shocks. I plan on upgrading mine to some Rancho's.

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    I'm currently running '02 HD coils on my ext. cab. They do not have SVT tags.

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    Good start Rob…

    Here is some basic knowledge of sway bars as I seem to get quite a few PMs about them.


    Front and rear sway bars or anti-roll bars are designed to reduce body-roll during turns. They have no influence on the suspension when wheels bounce in unison. They only come into play when they are twisted, that is, when vertical movement on one side of the bar exceeds the vertical movement on the other side, as when the body rolls or only one wheel goes over a bump. In addition to reducing body-roll, sway bars also reduce the adhesion limits of the side-by-side wheels that are being acted upon. This allows sway bars to be used as suspension tuning devices, and by varying the stiffness of the front and rear sway bars you can influence the oversteering or understeering characteristics of a car/truck.

    The HD trucks came with the same front bar as the Lighting, but no rear bar (I assume to keep cost down) as do most cars/trucks. This is also a decision based on assumptions about the driving skills of the typical owner. Understeer is the accepted norm in the U.S. and when the vehicle doesn't seem to be going where the driver wants it to go, he just brakes and turns the steering wheel farther -- an intuitive design considered defensible in court.

    Adding a rear sway bar not only reduces understeer, it also makes the car more likely to oversteer. – (for the rear end to lose adhesion and swing out when cornering.) That makes the truck more fun to drive (it turns quicker), but also more dangerous because it could lead to a spin-out. To correct for oversteer, the driver must stay off the brakes, add power, and turn the steering wheel in the direction of the slide -- a design considered indefensible in court, and one that could expose manufactures to liability.

    As a general rule, when a rear-wheel-drive car is equipped with both front and rear sway bars, the rear bar should have less stiffness/diameter than the front sway bar. Installing too large a rear sway bar can make the rear suspension so stiff that it will cause the inside tire to lift on turns, limiting rear traction. In a high speed corner, it will also increase the likelihood of "snap" oversteer.

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    Don't forget it is has a SHORTER wheel base as well, that is a big difference IMO. All I can say is the new L handles much better than the HD did, feel much safer/stable at high speeds and corners like a sports car.

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    I'm sure the spring rate for the front and rear are different in the L and HD! thats why the HD bounces over bumps and the L you don't really feel the bump. Also another key ingredent is that the L has a higher side wall on the tire than the HD that probably custion the bounce. This is what i've noticed in my dads L

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    Nick, the bounce is not the spring its the L-spec shock... the coils are identical... same part # same pieces.. extra weight of the cab & the shi*y HD shocks... thats the bounce. Longer wheel base exaggerates the problem.

    Rob W

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    i was just under my truck today it is a 00 and has 30,miles on it and when i was looking around on it. all the front suspension compents have svt on them and shock and springs do too. then i looked at my buddys lightning and the rear leafs look the same. just thought i would add some input

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    SmknHD
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    I have a stock suspensioned '02 HD with 80K miles. What are the advantages and/or disadvantages of the L spec or HD spec Bilstiens?

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    Stiffer ride with the L Spec. Majority of guys go with the L Spec.

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