Grand National suspension kit?

[litlv6]

Hey everyone. i'm new here and i'm curious to have some opinions on the suspension i have ordered. A little about the ride. 1986 Buick Grand National. It has a chip, 2800 redstripe stall, cottons 200r4 trans, auburn posi, and the usual Turbo Buick gauges. i ordered a Hotchkis full suspension kit with springs, upper and lower trailing arms and lower trailing arm supports, also front and rear sway bars. also have a new set of bilstein shocks on the way. :smoke: Should this setup work well with a G-Body or will it feel like an unfolded lawn chair when i hit a corner? Thanks for any input.... I know how to build a car that "hops" like Hell but new to tryin to set up suspension for handling, and or making a car launch straight. some pointers would be nice

[Hotchkis]

Hi litlv6 - You made a great choice on the Hotchkis full kit. It will make a HUGE difference. That system works really well and is quite popular.

Check out this Hot Rod Magazine story (http://www.hotrod.com/projectbuild/1987_chevy_monte_carlo_suspension_install/index.html)

Since that story was written we've unveiled a new Extreme Rear Sway Bar (http://www.hotchkis.net/7888_gm_gbody_extreme_sport_rear_sway_bar.html) for that car with adjustability and more articulation.

One of the major magazines is prepping a G-Body build right now with our system, so you'll be seeing it soon.

[litlv6]

Hi litlv6 - You made a great choice on the Hotchkis full kit. It will make a HUGE difference. That system works really well and is quite popular.

Check out this Hot Rod Magazine story (http://www.hotrod.com/projectbuild/1987_chevy_monte_carlo_suspension_install/index.html)

Since that story was written we've unveiled a new Extreme Rear Sway Bar (http://www.hotchkis.net/7888_gm_gbody_extreme_sport_rear_sway_bar.html) for that car with adjustability and more articulation.

One of the major magazines is prepping a G-Body build right now with our system, so you'll be seeing it soon.

thanks for the input. i'm pretty excited to get to installin it. should be startin on sunday, i'll post the results when i'm finished..... :enguard:

[Hotchkis]

Yes, please let us know what you think, and post photos!

[406 Q-ship]

Be aware that the GN's are hard to get to track through corners well due to their power delivery, they seem to be all on or all off for torque which makes for an interesting ride. Tuning on the wastegate or better yet a electronic wastegate controler that applys power smoothly. My .02

[litlv6]

Be aware that the GN's are hard to get to track through corners well due to their power delivery, they seem to be all on or all off for torque which makes for an interesting ride. Tuning on the wastegate or better yet a electronic wastegate controler that applys power smoothly. My .02

thanks for your .02 :idea: thats actually an idea that hadn't crossed my mind...... electronic control wastegates are little pricey i believe. I'll check into it for sure though thanks

[Samckitt]

Hi litlv6 - You made a great choice on the Hotchkis full kit. It will make a HUGE difference. That system works really well and is quite popular.

Check out this Hot Rod Magazine story (http://www.hotrod.com/projectbuild/1987_chevy_monte_carlo_suspension_install/index.html)

Since that story was written we've unveiled a new Extreme Rear Sway Bar (http://www.hotchkis.net/7888_gm_gbody_extreme_sport_rear_sway_bar.html) for that car with adjustability and more articulation.

One of the major magazines is prepping a G-Body build right now with our system, so you'll be seeing it soon.

I don't see how the Hotchkis rear sway bar will make that much difference over what came on the G bodies stock from the factory. The lower control arms move with the rearend, why not make it so the ends of the swaybar mount to the body/frame? Seems to me like that would work MUCH better than hooking it to the control arms.

[Norm Peterson]

I sort of see what's going on with the 'Extreme' design.

Think of it as being a way to utilize a relatively large OD thinwall tubular sta-bar without adding the kind of roll stiffness that endlinking the same bar directly to the chassis would. Attaching it midway along the control arm introduces a ~0.5 motion ratio (1/4 stiffness), which will likely vary a little as the suspension moves and the link and control arm inclinations change. Roll stiffness-wise, only the effect matters. Compliance-wise, I think it leads to a fractionally higher rear RC and a little bit less axle roll (under)steer, relative to the OE sta-bar that is bolted only to the control arms.

It probably needs to be paired with closed-section LCAs, since the offset link attachments will apply torsion directly to them at their midpoints.

I haven't run any stiffness checks yet.


Norm

[novaderrik]

I don't see how the Hotchkis rear sway bar will make that much difference over what came on the G bodies stock from the factory. The lower control arms move with the rearend, why not make it so the ends of the swaybar mount to the body/frame? Seems to me like that would work MUCH better than hooking it to the control arms.
you mean like maybe using an F body rear sway bar setup?
this is exactly the idea that a few aftermarket companies came up with a few years ago, but of course they had to think up cool names for the bars in order to make people think that they didn't just look under an F body and say to themselves "that looks like a good idea".

[Samckitt]

Didn't know the F body has that setup. I saw it under a late model Trailblazer.

[litlv6]

ok install is finished, however its rainy here and i refuse to drive the car when its rainin. :help!: the auburn posi makes it a bit dicey with a 2800 stall and a cottons built 200r4 trans...... teeth chatter when you hit second lol.

ok so the rear sway is a bit larger in dia. as well as positioned differently than the factory. the lca's are fully boxed and since the g-bodies were never known for a RIGID 4 link it has a support bar that attaches at the lca's front bolt, and that bar carries up to the the upper cross member bolt to the uca. i bit hard to explain, i'll try to take a pic tomorrow but it basically triangulates the two of them so when your lca tries to pivot left or right it just carries that load to the uca and won't give. it really looks as if it will be very effective, it will have to be since the rear sits on 8.5 rims with a 275/50R15 in the back. i'll post results soon. here is a pic of the front of the lca with the lower part of the support.

https://static1.pt-content.com/images/noimg.gif

[Norm Peterson]

I believe that you're talking about something like these for the '68 - '72 A-body (that probably differ only a little in the shape).

http://www.umiperformance.com/catalog/images/large/4028a_LRG.jpg,

This particular piece of frame bracing is mainly intended to tie the upper and lower chassis side brackets together under heavy acceleration loading.

They probably do provide a little resistance against bending about the vertical axis, but this is likely to be a useful feature only if the LCAs feature unmodified polyurethane bushings. Which kind of brings us back to the drag strip . . .


Norm

[litlv6]

I believe that you're talking about something like these for the '68 - '72 A-body (that probably differ only a little in the shape).

http://www.umiperformance.com/catalog/images/large/4028a_LRG.jpg,

This particular piece of frame bracing is mainly intended to tie the upper and lower chassis side brackets together under heavy acceleration loading.

They probably do provide a little resistance against bending about the vertical axis, but this is likely to be a useful feature only if the LCAs feature unmodified polyurethane bushings. Which kind of brings us back to the drag strip . . .


Norm

norm, bein that i'm new on this sight help me understand this.... those braces you posted are alot like the ones on my gn. looking at them on the car to me it looked as if it would help with horizontal axis (left to right) flexing. because of the angle, if i tried to move the lca left/right with it disconnected from the rear that bar carried that load to the uca bolt which would have to bend for the lca to move left right. :help!: am i seein this wrong? a lil help if you would.....

[Norm Peterson]

As long as you still have both of the skewed uppers (as in most of the OE G-bodies) or the Panhard bar (OE in the GNX only), you should not get much lateral movement of the axle. If the axle does not move much laterally, there won't be much bending in the lowers to be resisted like that. Maybe there would be a few ft-lbs with the OE bushings, up to (I'm guessing about ten times more) ~50 or so with poly bushings. IOW, not a lot.

The lateral load does not divide equally between the uppers and the lowers. The rear roll center is essentially at the height of the UCA axle-side ends, so virtually all of the lateral load goes into them. Only a small portion goes into the lowers, assuming any sane combination of bushings in the various control arms.

I guess if you put solid Delrin in the lowers and something like soft foam rubber or Jell-O in the uppers that you could make the lowers do essentially all of the lateral location work, at least up until some upper "bushings" bottomed out, a tire rubbed, or the lowers or their bushings failed). And sooner or later everything from you to the U-joints would hate it.


As a general rule, you can consider the lowers in this sort of converging 4-link arrangement to be responsible only for fore/aft location of the axle ends. The uppers get two jobs of equal importance, one being control of axle housing rotation during acceleration/braking (obviously in combination with the lowers), and the other being lateral location of the entire axle while cornering (just the two uppers).


Norm

[T-CHRGD]

Check out www.scandc.com (http://www.scandc.com) if you want to get Really serious.
(sponsor link on the right)

Next best upgrade would be an SC&C stage 2 kit.

All the possible options will REALLY make your head hurt :hammer:

[litlv6]

As long as you still have both of the skewed uppers (as in most of the OE G-bodies) or the Panhard bar (OE in the GNX only), you should not get much lateral movement of the axle. If the axle does not move much laterally, there won't be much bending in the lowers to be resisted like that. Maybe there would be a few ft-lbs with the OE bushings, up to (I'm guessing about ten times more) ~50 or so with poly bushings. IOW, not a lot.

The lateral load does not divide equally between the uppers and the lowers. The rear roll center is essentially at the height of the UCA axle-side ends, so virtually all of the lateral load goes into them. Only a small portion goes into the lowers, assuming any sane combination of bushings in the various control arms.

I guess if you put solid Delrin in the lowers and something like soft foam rubber or Jell-O in the uppers that you could make the lowers do essentially all of the lateral location work, at least up until some upper "bushings" bottomed out, a tire rubbed, or the lowers or their bushings failed). And sooner or later everything from you to the U-joints would hate it.


As a general rule, you can consider the lowers in this sort of converging 4-link arrangement to be responsible only for fore/aft location of the axle ends. The uppers get two jobs of equal importance, one being control of axle housing rotation during acceleration/braking (obviously in combination with the lowers), and the other being lateral location of the entire axle while cornering (just the two uppers).


Norm

makes sense i guess. thanks for the input, i guess i was just overthinking it. i have a tendency to do that now and again. lol in my mind i was thinkin it had to do more than just the simple thoughts that came into my mind when i look at that particular part. seems as if it should be more complicated ....... lol

[litlv6]

Check out www.scandc.com (http://www.scandc.com) if you want to get Really serious.
(sponsor link on the right)

Next best upgrade would be an SC&C stage 2 kit.

All the possible options will REALLY make your head hurt :hammer:

thanks, that site does have some cool stuff on it for sure.. dont think i need to go that far into it yet, the new hotchkis set handles extremely well!!!! its a totally different car with that suspension vs. the progressive springs that used to be in the back and the factory sway bars.. A+ for Hotchkis!!