unsprung weight - Chevy Impala SS Forum
 
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post #1 of 10 (permalink) Old 04-05-2002, 12:54 AM
AdioSS
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How can we reduce unsprung weight on our cars?

I pull that big ass HO rear swaybar off my car when I put the rear QA1s on and I believe my car handles better now than before! The shocks set on 5 are stiffer than when I had the bar attached with the stock shocks. While I still had the bar in the trunk, it did seem to corner just as well as before. Could this be due to me pulling however much that bar and all teh brackets and stuff to hold it on combined with the stiffer shocks? I had the shocks set to 12 in the shop and when I pushed down on the bumper, it would barely move. I then dropped them down to 8 and it was still too harsh for me. (I'm still used to the FE1 suspension on my Caprice.) I took some corners tonight with the shocks on 5 and it handled GREAT!

I'm kinda afraid to totally pull my front F-body bar because when I did that on my Caprice (for drag racing) it acted crazy! You could turn the wheel and the entire car would lean several degrees. I'm thinking of just swapping my stock bar back on and dialing the shocks up to 3 or 4. I'm betting that would get close to good and it would redue more unsprung and total vehicle weight.

Maybe I'm just rambling again, but sometimes when I do this I get onto something. Somebody save me from this madness! [img]8.gif[/img]
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post #2 of 10 (permalink) Old 04-05-2002, 07:12 AM
amickracing
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Ways off the top of my head...
Get stamped steel 15 inch wheel, That would have to help the weight out a bunch. I believe someone is making a tubular lower control arm in the near future, that may save some weight. Possibly drilled rotors and or lighter caliper rotor combo.

About running with no sway bars... I believe George (SSMOKEM) is running HAL's w/o any sway bars, and has no complaints about handling.

P.S. This rambling stuff is kinda fun lol
post #3 of 10 (permalink) Old 04-05-2002, 10:24 AM
bryante
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Unsprung weight sucks, but there's not much that one can do about it on our cars.

After all, the axle is the heaviest component in the back, and I don't see anyone offering an aluminum housing for it Up front, there's also not much opportunity to drop significant amounts of weight.

The components at the extremities of the suspension are the most critical, and in our case that's obviously the wheel/tire package, brakes, spindles, and knuckles. Wheel weight can be reduced by throwing a lot of money at aftermarket wheels, but I don't see a lot of other opportunities for reducing unsprung weight.
 
post #4 of 10 (permalink) Old 04-05-2002, 11:25 AM
AutocroSSer
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What Eric said [img]smile.gif[/img]

Also : if you're looking to delete the swaybars (for weight reasons) but improve the handling, look into stiffer springs....quite a bit stiffer. Keep in mind this will probably hurt (by a good bit) the ability to launch the car in a straight line. Possibly/probably to the point of making the car all but unstreetable.

As a "wild guess" (and I'll emphasize again, this is a GUESS and may be totally off!), I'd look at something in the 1000 lb/in range in front and 250-300 lb/in range in back for spring rates WITHOUT swaybars.

Don't know of anyone who has gone this route yet on a B-body, but it'd be interesting to try....

Shocks are NOT intended to support the weight of the car! Hell, one look at the flimsy pieces the shocks bolt into will tell ya that [img]smile.gif[/img]. They ARE intended to DAMPEN the weight shifts in transient conditions (i.e. dampen the spring motions).
post #5 of 10 (permalink) Old 04-05-2002, 01:08 PM
Mark Ekberg
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What about coil over shocks for the rear. Then you can get rid of the spring and the bar?
post #6 of 10 (permalink) Old 04-05-2002, 04:09 PM
bryante
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I don't think that getting rid of the swaybars should be the end goal. I think that Ed's in the right ballpark with his spring rate guesses, and I can only imagine what that would do to the ride quality (my 750/220 setup is a bit on the stiff side). I can't think of a good reason not to run swaybars except for the unsprung weight issue, and that could be fixed via a Bill Harper-style rear bar mounting.

Also ditto what Ed said about shocks. It's important to note that shocks will only slow down the rate of roll in a cornering situation - sit in the corner long enough, and they'll eventually let the car roll over to its "natural" state (which, without swaybars, means that you're dragging the door handles). Shocks should only be used for damping the mass of the vehicle, and not as a substitute for inadequate roll rates.

I'd love to suggest that we build up a suspension FAQ, but I think there's enough good info out there already. I'd really suggest starting with Caroll Smith's line of "... to Win" books (yea, I know I'm sounding like a broken record).
post #7 of 10 (permalink) Old 04-05-2002, 05:50 PM
AdioSS
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It was just an idea [img]smile.gif[/img]

I pulled the HO bar off because it has destroyed my stock LCAs. I had used bumper shims and longer bolts to keep it from pulling through, but they have started to pull through! I am "patiently awaiting" my J&M extended control arms so I can put either the HO or stock swaybar back on.

I would like to continue learnign about how hard it would be to do the rear bar as Bill Harper did. I saw his pics and read his thread, but I still need more details.

This thread has given me one decent idea though. A guy on the local racer board does aluminum machine work. What suspension components would you trust would work if done in aluminum? Possibly the rear axle housings (thanks Eric)? Anything else I should ask him about?
post #8 of 10 (permalink) Old 04-07-2002, 08:49 PM
ToddsSS
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For those of you wishing to go sway bar delete. I think you could certainly set the car up to handle as good or better but I think the cost would get out of line.
Strange makes a coil over set up that will bolt straight into our lower front A-Arms using a special tapered spring (available up to 800lb rate). [designed for Cheveeles] For the rears you could delete the rear sway bar. Fab custom shock mount brakcets and run bearing mount compression and rebound adjustable shocks.

Front set up is approx $800.00 (I think) and rear shock AFCO or Carrera will run approx $450.00 each.

The biggest bang for the buck in unsprung weight are aftermarket wheels.
One trick to help Bill Harper has used (If you look real close at the pics of his suspension) you'll notice the rear shocks are mounted up-side-down. The boots protect the shaft in this position. (NOT all shock can [or should] be mounted this way).

Bars are a relatively low cost manner to reduce roll rate while still allowing a streetable spring rate.

With our 4-link style rear suspension, rates high enough to allow removal of the bar would be difficult to tolerate on the street (as Ed has pointed out.) Front of car can be done I think.

If the no rear bar is seriously pursued I think a long trailing arm suspension and coil overs would be needed to make it streetable and out handle the existing designs. (look at a NASCAR or BUSH series car or a 68 to 72 coil spring GM truck).
post #9 of 10 (permalink) Old 04-08-2002, 12:18 AM
Navy Lifer
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Following up on Toddd's observations:

The shocks on my car are (still) Edelbrock, which are built "inverted"--they have to mount that way to work properly, due to the internal release valve/port that is part of the design.

Bilsteins for the B-body are not built the same way internally, and while there is no specific reason for the position they mount now that I am aware of, with the shock body attached to the lower mount, it is possible, with some assistance from Bilstein, for the rear shocks to be inverted so that the shaft/piston is affixed to the lower (axle) mount. I would guess that the shocks mount as they do to give the piston shaft some protection from being struck by an object that might come up from the road surface.

Back to Cheston's basic issue of reducing weight, specifically unsprung, there is a ratio of weight spread for the moving elements of the car--the entire rear sway bar is not 100% unsprung, for example since it mounts to a part (the LCA) that is attached to the frame. I don't know the calculations to figure it out--maybe Eric Bryant can help. The use of lighter wheels is probably the one area you can make a bigger gain that anywhere else, at least on the rear. Front would be by going to a brake system with aluminum caliper, and, ideally, a 2-piece rotor with aluminum hat. Baer uses aluminum billet hubs for their B-body brakes, so there is another gain. The only other way to make serious inroads in this area is to go to a tubular control arm setup or by figuring a way to adapt Corvette forged alumninum suspension parts, which I would be concerned are not up to the task of supporting the weight of the car and its suspension loads.

I also think its wrong to assume that our cars MUST have a rear sway bar--if the front geometry could be made right, I opine that a rear bar could be eliminated. I'll say no more on this for now, but I'm working on something.....my lips are sealed for now.

As far as the "truck arm" Todd mentioned, I ran across an ad and website for a shop here in SoCal that advertises just such a setup. This is not an endorsement, and some may be offended or otherwise dislike the name and/or what you see at the site, but here goes:
http://www.hotrodstohell.net

A truck arm system would necessarily need a panhard rod or Watts link. So far I have not been in touch with these people, so I do not know if what they offer could be made to work on the B-body. They are doing a setup for early Chevelles, so the similarity suggests to me that it COULD be done. All it takes is money, I'm sure....
post #10 of 10 (permalink) Old 04-09-2002, 10:26 PM
AdioSS
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First off, the HAL/QA1 shocks would be almsot IMPOSSIBLE to adjust if mounted upside down. So there goes that idea.

I have the J&M extended rear control arms ont he way right now (I hope), so that is what kind of control arm I'm gonna be using. With the rear shocks set to 4 with NO rear swaybar, the SS rides and handles VERY WELL. I'm pleasantly surprised. When my control arms get here, I'll try the stock bar again, then maybe the HO. If I decide that NO bar works best for me, then it'll make it possible for my to use the Metco Instant Centers. [img]smile.gif[/img]
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