OKAY, here it is...I have been researching my tail off about "handling" suspension pieces for my '86 Regal. Thus, I have figured that the best way to find out what is the "best of the best"/"money not-so-much an object" handling suspension pieces on the market, is to ask the people who own these cars, and have tried the different parts out there.
I have looked at the great tech articles, regarding suspension, on this site, which have been a help, but I want the members' feedback on this one. This may be a long discussion, I'm hoping, in order to get the most detailed and helpful suspension experiences/knowledge out there. We own the cars, we buy the parts, we bolt them on, and so on and so forth.
So, here are my main questions:
-lowering springs (1" to 1 1/2" MAX): Hotchkis, Eibach, custom Moogs, custom Eaton Detroit Spring, other high-end springs???
-shocks: Bilstein, Koni, Tokico, other high-end shocks???
-front upper tubular A-arms: Global West, Hotchkis???
-B-body spindles: what B-body model years are best for 12" conversions???
-boxed rear trailing arms (adjustable uppers for correct pinion angle): Hotchkis, Metco, SouthSides (?), other high-end boxed trailing arms???
-sway bars (1 1/4" max up front, 1" max out back): Hotchkis, Herb Adams, ADDCO, other high-end sway bars???
-bushings (front end/engine/tranny/body): PST, Energy Suspension, Global West Del-A-Lum, other high-end bushings???
-disc brake upgrades: Baer, Stainless Steel, Wilwood???
-chassis braces
-wheel and tire sizes
Thank you for taking the time to read this message. Hopefully, we can make this a lively and informative discussion. I will be adding my recommendations after I post this introductory message.
Lou
Now, this is what I think is a great high-end, daily-driveable, corner-carving suspension:
***NOTE: My car is factory-equipped with the 307 V8. Therefore, front spring rates/loads, front right-hand bushing types, etc. may differ between my car and Turbo Regals.
-Hotchkis 1" lowering springs (I have these on my car, and like their overall performance...not too stiff, slight hint of a road-racing car feel)
-Bilstein shocks (I have these on my car as well, and I also like their overall performance...they complement the Hotchkis springs very well...I had KYBs with the Hotchkis springs, but they are not as durable or stable as the Bilsteins)
-Global West front upper tubular A-arms/DLAs (Hotchkis is inferior?)
-Metco rear trailing arms
-Herb Adams sway bars
-PST polygraphite bushings (less squeak/minimal deflection)
-Baer Track (front), Touring (rear) disc brakes
-various Kirban/GM/Poston's chassis braces
-COMPLETE set of polygraphite/urethane body bushings
-wheels and tires: I have 17" x 8"s, 4.5" backspacing, 5 on 4 3/4" bolt pattern all around...Nitto NT-555s 245/45 front, 275/40 rear...fronts rub slightly at the bottom rear of the inner wheelwell where it meets the frame at full steering wheel lock, and hit inner fender/outer wheelwell lip very slightly on large dips/bumps as a result of 123k mile rubber bushings...rears rub the frame very slightly in hard cornering as a result of body roll, and the 275 is NOT recommended on an 8" wide rim, rather a 9" to 11" wide rim, ideally a 9.5" wide rim (source: Nitto/BFG) if you can get 4 1/4" of backspacing...the Nittos have a 300 wear rating, and GREAT sticking ability in hard cornering...pretty good in rain...pretty cheap through Discount Tire Direct (www.discounttiredirect.com)
The following recommendation is different from what I have on my car, but I may well revert to in the near future for zero rubbing issues and proper driving stability and safety...
FRONT: 17" x 7" w/ 225/45/17, 4.5" backspacing, 5 on 4 3/4" bolt pattern...(remember, 12" conversion pushes wheels out 1/2" or so, and may limit wheels to 5 on 5" bolt pattern, I believe)...OR, 17" x 8" w/ 235 or 245/45/17, 4.5" backspacing, 5 on 4 3/4" bolt pattern...but then again, RUBBING ISSUES!!!
REAR: 17" x 8" w/ 255/45/17, 4" backspacing, 5 on 4 3/4" bolt pattern...OR, 17" x 9.5" w/ 275/40/17, but then again, it's hard to find a 9.5" rim with the ideal 4 1/4" of backspacing to limit rubbing issues...5 on 4 3/4" bolt pattern
Hopefully, this will spark some discussion on this subject...
Have you looked into Kirban's GNX (reproduction) rear suspension? It's definitely pricey, and that's before you buy the exhaust system that goes with it. But supposedly it's the only exhaust that will work with the suspension. Total cost is $2545! The new issue of GM High Tech Performance has an article on it and the install.
According to that article in GMHTP the exhaust is included, since it is the only one that fits. That is part of the cost, so if you also need an exhaust, then it is less expensive. Unless I am mistaken, which could happen.
Brian
Yes, I am aware of the Kirban GNX reproduction suspension, however, that is more for straight line acceleration than cornering, I believe. I have seen the article in GMHTP; very nice write-up. However, I'm thinking more along the lines of a road-racing type suspension...not too harsh, but something that gives confidence in high-speed cornering, off ramps, etc....basically a street road racer, not some Trans-Am setup, or competition road-racing pieces.
As a result of some further research, I have become aware that hollow sway bars measuring 1 1/8" front and 1" rear MAX are ideal for the street, along with rubber bushings which do not bind as urethane and graphite do, and not solid bars, or larger diameter (1 1/4" front especially) hollow bars...Del-A-Lums in the front control arms may be too harsh with the stiffer Hotchkis spring...everyone has said that the frame braces, front and rear make dramatic improvemnets...Baer Track (front) and Touring (rear) braking systems are ideal for the street...and the "squeaking" and "binding" tones of poly bushings, even the somewhat quieter graphite bushings, may not be so necessary with the frame braces, stiffer springs and shocks...maybe quality high-durometer rubber replacements are ideal...definitely boxed rear arms for stability and minimal flex.
I'm really interested in determining if the higher durometer rubber bushings (front end/rear arms) are better on the street in terms of quietness, road-shock absorption rather than deflection and a teeth-chattering ride...I'm really thinking that stiffer springs and shocks, coupled with decent sized sway bars, with rubber bushings is ideal for the street...I'd say that poly bushings are a good idea if your running stock rate springs and shocks, stock sway bars...what do you guys think?
I have the article right here - and here is the summary of their data:
60 ft. times before GNX:
Hi - 1.93
Lo - 1.89
Avg- 1.906 (five runs)
60 ft. times after:
Hi - 1.95
Lo - 1.81
Avg- 1.87 (six runs)
I am data driven when purchasing upgrades, and the data says that for the money you get very little improvement. I think the reason to buy this would be more for show purposes than anything. You could probably do as well with boxed control arms and airbags for much less money. It sure looks cool though.
On the subject of wheels, for great info call Jeff at Group A Autotrends in Mesa Arizona. He fits 18x8's front and 18x9.5 with 265 40's and 295'40 without any rubbing. Heith Elmer has had both in 17 and 18 inch versions.Jeff uses Simmons Wheels with custom back spacing's but gets it done. I think he can even fit a 315 40 in the rear. Hope this helps some. jeromy
I don't like polyurethane bushings on a street car. My friend and I put them on his camaro and I installed them in my lower rear control arms in my Regal. The bushings always squeaked. I replaced my lower control arms with the boxed Hotchkis arms (polyurethane with grease fittings). They tightened the rearend up on my car and no more noise. I also run KYB shocks and they work very good on my car. I was wondering if the BellTech drop spindles (2 inch) in the front and springs (1.5 inch) in the rear would help? Or would some of the performance springs that lower the car about an inch work better? Anyone have a source or manufacturer for purchasing different durometer rubber bushings for our cars?
Thanks, Craig
guys----i have a couple gn's and a gnx-----and if any of you have ever driven a stock gnx and a gn with similar mileage AND TIRES you would easily see that a gnx will greatly outhandle a gn---and i don't mean just in a straight line----the ladder bar/panhard system attached to the frame is a big improvement over those two upper sheetmetal links holding the axle to the flexible body that is squirming around on the frame----if you have ever compared the gnx suspension to that of the F body camaros and firebirds you will see it is almost the same---and that suspension design is one of the reasons those cars handle reasonably well----one of my gn's has one of the reproduction gnx systems on it and it also has 16 inch wheels/tires, bilstein shocks,full body bushings,seat brace,upgraded springs (stock springs in the gnx had slightly stiffer springs in the LF/RR position)----up front it has the Moog heavy duty idler arm, hollow sway bar, and heavy duty Dana intermediate arm----this car handles extremely well on road courses and will run circles around a stock gn and the rear suspension is a big part of that-----heck even NASCARS that i have seen use ladder bar/panhard suspensions and they don't race in a straight line...........
Rich,
Excellent point regarding the GNX rear suspension setup and its handling characteristics in a road racing scenario. Being able to precisely center the rear end, and place torque loads on the right parts (ladder bar, lower tubular trailing arms) in order to safely plant the rear tires on the road during cornering, makes the GNX setup a fairly smart choice, in theory that is. I guess that adding the fact that many NASCAR teams run the same type setup also bolsters the use of a ladder bar/panhard bar (essentially a 3-link) setup in road racing as well.
Also, I'd like to re-list my "ideal" G-body handling suspension setup...
-Global West front upper tubular A-arms with DALs (upper and lower)...boxed lower A-arms
-GW tie rod sleeves
-Hotchkis 1" drop coils all around
-Bilsteins all around
-ADDCO 1 1/8" front, 1" rear sway bars (hollow)
-rear seat, front triangular, fender braces
-full set of rubber body bushings
-Kirban GNX rear suspension with Global West rear lower tubular trailing arms with spherical bearings (frame side) and DALs (diff side) to eliminate bind
-Baer Track (front) and Touring (rear) disc brakes
-17x8 w/ 235/45 up front, 17x9.5 w/ 275/40 out back...5" b.s up front considering the tall spindle upgrade creates 1/2 to 5/8 of an inch more track width on each side...4.25" b.s. out back to center 275-wide tire between frame and qtr lip
...any more suggestions???
louis----i'd suggest a 5 point harness with all those suspension upgrades as I doubt the factory shoulder/lap belt would keep you in the seat of such a G force monster
I've got a polygraphite PST complete front end kit on my car and it seems to be pretty good. I've never heard any squeaks out of it. With that last post regarding the 5 point harness, I agree that with the car setup to carve corners, what about the interior? A car magazine some time back took a few cars out to see how they would do for some kind of all-around competition. They happened to have a GN out there that had some aftermarket suspension stuff on it, maybe PHR mag and it was their ad editor's car, and while they concluded the car seemed to be pretty good, they said, "The seats suck!" So it seems we've got a list to keep the car where we point it, but what about us? Other than putting a 5 point in and tightening down the belts so we can barely breath, what other options do we have to keep our faces off the windows?
A few months back GMHTP had Heaths cars in them. He was running a pretty bad suspension setup. I think he had Coreabu or Recarro seats. He also had a 4 or 6pt cage in them. You all seem to have left that out. A cage will stiffen the entire car up as a whole. I have a basically stock 87 Turbo T and am planning the road less traveled and make it handle. I plan to use Heaths setup as a base plan for mine. But my first step is going to be a cage.
I do suppose that upgraded seats are in order, with much-needed side bolstering, but a roll bar (cages include horizontal roof and dash bars) would be overkill in a street car. As much as my updated "recipe" for an ideal street road racer may imply that the car would be a killer g-machine, I actually think it would be a great HANDLING car, but definitely not up to the task of auto-crossing or competition road racing; I mean we are talking about almost 2 tons of steel here. Anyhow, in my opinion, and, as we all know, opinions are alot like belly buttons, everyone has one, adding a 4 or 6 point roll bar to a street car actually leans the car more towards competition (ie. track, ovals, etc.) than for spirited weekend driving, which is what I am after. However, Brandon, thank you for the advice, and while it seems you would like to emulate Heath's cars, I suggest adding a little of your own flavor to it. Good luck!
I am just getting ready to replace my front suspension, and add some beef to the rear. New tires are also in order. I was leaning towards the PST POLYGRAPHITE Super Front end kit. My front end is in very bad shape. I already have Bilsteins all around. I was going to get the 1 3/8" rear bar from ATR. Eibach springs all around lowered 1.0 front, 0.8 rear. I have some of the original MOCK Einke 16" GNX wheels, I found the BF Goodrich G-Force KDWS 245x16 50 ZR to be the best all around (dry/wet) tire I could find. I do not race, I use it for daily driving only. It has 184,000 miles on it and runs great with MSD 50's, PTE52...etc. I was reading everything above and thinking maybe the seat and frame braces would be a better place to spend the $, rather then the POLYGRAPHITE, and just go with the basic rubber replacement front end kit. I am open to all suggestions. I don't want to go broke however. I am looking at about 1500 - 2000 not counting the tires.
I thought that Poly's were cheaper than rubber. Kevin posted that he paid a bit less for the rubber than polys.
I consider the polys to be a cheap substitute for rubber as they tend to bind and provide poorer handling in normal driving. The poly bushing will not last as long on the rear of the passenger side control arm near the downpipe as rubber either.
Mr. Nelson pointed out, correctly, that the Dur-a-lums are the best but more expensive.
I missed your link on the original post and this discussion took up on the mailing list instead.
Thanks to Scott S. for pointing out that we abandoned this forum.
Ian,
Regarding tires: I have seen the BFG KDWS 245/50/16 for $111 at www.discounttiredirect.com. I have purchased tires from Discount Tire Direct numerous times within the past 2 years and have been extremely pleased with the product and delivery time. The KDWS has an astonishing 400 treadwear, traction A, temperature A rating; the best I've seen for a performance tire to be used on a daily basis year-round...good choice!
The rear ATR sway bar is extremely beefy, so I would wonder if it would be detrimental to handling and/or straight-line accelaration. I would consider an ADDCO/Hotchkis hollow 1" bar.
Look at the Global West rear lower tubular trailing arms (they don't sell uppers) with spherical bearings (frame-side) and Del-A-Lum bushings (diff-side), which both eliminate the binding properties of poly bushings as well as the deflective properties of the rubber bushings. In my eyes, the GWs are the best rear lower bars on the market, considering bind elimination/minimal deflection/price.
Definitely go with the rear seat braces, front under-car triangulation braces, and front under-hood fender braces. These can be found through Postons and Kirban, or picked from some Gran Prixs and Monte SSs of the same vintage as your car. I recommend Kirban and/or Postons, where all 3 brace setups should run no more than $250.
Also, the front A-arm bushings should be replaced with GW DALs (use a GW bronze bushing for the right hand side upper A-arm [front or rear upper A-arm bushing?] to fight downpipe heat, as rubber/poly/nylon DALs would eventually melt and create a hazardous situation). The DALs do the same job as they would do in the rear lower trailing arms (ie. bind/deflection elimination). If buying the DALs, also purchase the adjustable tubular tie-rod sleeves from GW (worth the money, as they virtually eliminate play in the tie-rod adjustment). Use either Moog or TRW ball joints/tie rod ends/centerlink/pitman arm/endlinks (rubber bushings), etc. up front. These are available through Summit Racing Equipment or a quality parts store.
Try a 1 1/8" hollow front sway bar (any bigger creates "plowing" in cornering) from ADDCO or Hotchkis to tighten up the front end in cornering, as well as the Eibach or Hotchkis lowering springs (both good choices). I have the Hothckis springs and Bilstein shocks all around on my car and couldn't be happier with the car's stability and minimal ride harshness.
Remember, these are just my SUGGESTIONS, as they come from experience and research. I hope these suggestions help with your parts quest, and keep you within your $1500-$2000 budget.
Is it worth the money to replace the front upper control arms with the GW tubular upper control arms? It seems very expensive. I am also going to put the air bags in the rear, I can't seem to keep the tires from spinning.
sorry so long...
I have been checking out the suspension converstations since April, but I still can't seen to figure some things out regarding sway bars, bushings and front end set.
My 87 GN has the original suspension. And it is real bad. Mushy and bouncy.
I am on a tight budget, so I decided to only upgrade the bushings, springs, shocks and sway bars.
For shocks, I found the Bilsteins at www.hotchkis.net for $55 ea.
For srings, I found the hotchkis 1" drop kit at www.summitracing.com for $250.
My confusion now lies with the sway bars and bushings.
For sway bars: I found the global west front (1 1/8" or 29mm) for $210 and rear (1" or 25mm) for $190. And the hotckis front (1 1/4" or 31.75mm) and rear (1" or 25mm) set for $329.
My quesion with the sway bar is I read that the mid 80's f-body has a 36mm sway bar that bolts right on to our cars. Is this true and what year/model is this exactly? If the factory front sway bar is 32mm, that is the same size as the hotchkis. Does size matter? Is bigger better or worse? What about the rear?
Now for the bushings:
I found the energy suspension hyperflex Complete Polyurethane "bushing" set for $159.
The PST polygraphite complete "front-end" set for $219 for regular and $359 for super.
The global west del-a-lum - front upper "bushing" kit $117 - front lower "bushing" kit $129.
What is the difference between the energy suspension and global west "bushing" kits and the PST "front-end" kit? What is the difference between polygraphite and polyurethane?
www.globalwest.net
www.p-s-t.com
www.energysuspension.com
Many thanks-
In order to replace the front upper A-arms with the GW tubular pieces, you have to factor in the cost of the proper B-body (79 and up) or 2nd Gen F-body (70-81) spindle (these are getting harder and harder to find), calipers, rotors, pads, hoses, higher pressure master cylinder, lines, etc. etc. etc., which may run the conversion well into the $1000 range. Moreover, you will be amazed at the job just replacing the A-arm bushings with DALs and/or bronze/solid bushings (DP heat) will do, along with high-performance pads such as Performance Friction, along with PowerStop cross-drilled rotors.
Air bags have been proven to work, but why not try a lower tubular trailing arm like that from GW (see my previous post), so that you don't have to worry about air leaks or punctures. Tubular arms are also well-known to virtually eliminate wheel hop and aid traction tremendously.
"What is the difference between the energy suspension and global west "bushing" kits and the PST "front-end" kit? What is the difference between polygraphite and polyurethane?"
Shawn,
I can't answer all of your questions, maybe throw a guess out there, but I do know what the super front end kit from PST is. I believe (read: guess) that the polygraphite are impregnated with graphite to reduce/eliminate squeaks. They may even be polyurethane with the graphite mixed in, but just guessing. Another guess is that the bushing kits only contain bushings. The PST kits usually have more than just bushings. The super front end kit had all the ball joints and bushings, it also had two new tie-rods (they say it has two new inner and outer tie-rod ends, but includes the sleeves, so it's basically two new ones, you just put them together.) And I also think it came with a new idler arm, and it came with new sway bar bushings. So now all I have to redo, if I ever feel like it, is (maybe a new sway bar) a new center draglink and the pitman arm.
Louis,
There's nothing wrong w/ a basic 12" brake setup consisting of '79 - '96 B-body spindles & calipers, 1LE rotors and the GW upper arms. What I'm saying is don't assume you need to go SSB, Baer, Wilwood, to get outstanding braking.
On the arms, I am not sure if Global West's sale is over. If you price compare poly bushing equipped GW arms to the Hotchkis arms, which also have poly, I believe you will find the GW's are every bit as price competitive as the Hotchkis. The GW's have the cross bar with a downward travel stop (keeps the upper balljoint from reaching it's travel limit, strengthens the arm too) and a stronger press-fit upper balljoint.
Getting into the bushings, you will notice that people who have torqued the poly to spec have squeaking and / or binding. The graphite does not eliminate squeaking; it merely lessens it.
I have 16k street miles on Del-a-Lums and would use them again.
Poly *body* bushings tighten a car up quite well. I drove a friends car with them and for 170k miles it was tight as a drum.
As far as rear sway bar, when you button down the front of the car, and the rear, the rear will have a hard time articulating w/ a large rear bar, and this will cause oversteer. This list / forum has a bias towards 1/4 mile which is understood, but a big rear bar is not a handling thing on these cars.
Ian,
With the 12" brakes / GW upper arms, you are giving the car enormous braking and handling benefits. Yes it's worth it. If your rear suspension is stock, you would be well suited to box the control arms and put new bushings in. Wear on the bushings makes a perfectly fine car have a loose rear suspension.
There is nothing wrong w/ the PST or whatever KITS out there... (I hate the word kit) but a front end is simple. Upper balljoints, lower balljoints, outer tie rods, inner tie rods, tie rod sleeves, upper control arm bushings, lower control arm bushings, drag link, idler arm, and upper control arm shafts. Just ordering the appropriate CNR-88-C kit from GW eliminates a need for upper bushings control arm shafts, or bushings!
Matthew
Thanks, all.
My buddy has an 85 442 that handles amazingly. He flies around corners and there is no body roll. On and off ramps on highways are serious fun. That is what I am looking for. Belive it or not, all he did was cut the front springs for a 1 1/2" drop, and add the energy suspension Hyperflex system.
Between you guys and the folks over at www.turbobuick.com I think I have made up my mind.
Bilstein shocks - $55ea
Hotchkis 1" drop coils - $250 set
PST front end kit - $219 set
Energy suspension body bushings $107 set
Sway bar will be "wait and see"...
I sent Hotchkis an email asking them what their coil rating was and one to PST asking if they made body bushings for our cars.
Thanks-
Matthew,
Thank you for your suggestions. I am aware that a tall spindle upgrade using factory GM parts can give a G-body excellent handling/braking characteristics when used with a tubular upper A-arm. However, it has always been my mantra to "do it right the first time, and do it all the way", thus I would rather wait the extra time it would take to purchase the Baer 4-wheel brake upgrade, the GW upper arms, etc., etc. (ie. money, money, money!).
Also, when you compare the poly-equipped GW arms to the Hotchkis pieces you do get a competitive price, but I believe it is definitely worth the extra money for the GW DAL-equipped upper arms, because of the proven performance of the DALs, as you have stated, as well as that the GW arms have been known to create even more of a negative camber curve (not TOO much) to accentuate the gripping ability of a wide tire in hard cornering, as well as the obvious 12", 13" brake upgrade ability, etc., etc., etc.
As for poly body bushings, considering the binding properties of poly when used in rotational capacities (ie. trailing arms, A-arms), would there be a possible binding situation when the body is put under stress in relation to chassis flex (is it really a "binding" situation?)? Do/can poly body bushings squeak like poly A-arm or sway bar bushings? Maybe chassis braces (ie. rear seat, front undercar/underhood) can properly overcome the deflective qualities of rubber body bushings???
Shawn,
The Hotchkis spring ratings for 78-88 GM G-body 1" lowering springs are as follows:
600 pounds/inch front
135 pounds/inch rear
(these figures are taken directly from the Hotchkis website)
Does anybody know if hotchkis 1 inch lowering springs would be compatible with the Reproduction GNX Suspension?
Dan,
I would ASSume that using 1" lowering springs with the repro GNX suspension may entail dialing in a correct pinion angle, since a lowered car changes the suspension geometry in conjunction with the driveline angles. Thus, since the GNX suspension does not require the use of upper trailing arms (which, when using adjustable upper tubular trailing arms enables one to correctly dial-in the pinion angle to prevent pinion failure, etc.), this may be a difficult task, that is, being able to set a correct pinion angle on a car with 1" lowering springs and the GNX suspension. However, I'm sure that Dennis Kirban and his boys over at Kirban Performance have come up with many suspension "tuning" procedures that would be needed when using lowering springs with their GNX suspension. All in all, I do believe you should not have any problem using the Hotchkis 1" lowering springs with the GNX suspension. Kirban actually greatly suggests using a higher load rear coil (Hotchkis = 135 lbs/in...stock H/D coil = 115, 120???) to enhance the loading capacity of the rear suspension under acceleration/cornering, etc.
Contact the Kirban crew through www.kirbanperformance.com to confirm/add to what I have advised.
curious as to what the difference between 77 and 79 caprice impala spindles is, the cars are identical in all ways from what ive ever seen, does the hollanders say differently ? just curious. if i owuld have known at the time, i have scrapped a pair of 79 caprices and a 77 impala that I know of that i could have saved axles and suspensions off of,,,,
To get all the parts from Global West to convert to tall spindles totals to over $2000. Is this upgrade worth it?
I have a 87 GN, and I am restoring it....just did the body work and paint on the outside. Now I am looking for the perfect replacement suspension. I was looking into ATR suspension kit that brings springs, shocks, sway bar,clamps for front sway bar and end links.....all for $700.00. Can anyone tell me if that is a good price or does anyone have other suggestion as to where I can find a better price and is that the right suspension for my car without changing the comfort and performance????
I'm also looking for the complete bushing kit, any suggestions?
Thanks,
Enio
I put koni shocks on. I also put in a 1" lower moog spring in the front, and a 1/2" lower moog spring in the rear. I bought the PST super front end kit, but I have not put it in yet...
Hi everyone;
Obviously I'm picking up this thread a little
late, but the GNX comments were very interesting
to me.
I,m presently designing a Torque Arm/Panhard Bar
rear suspension for my Monte SS. I had the
opportunity to briefly examine an early-
production GNX, and am wondering if what I saw
caused problems in hard driving over uneven
roads.
1) Rear Steer- The PHB is non-level and also
non-parallel with the rear axle (about 5 deg).
The bar supposedly moves about 1/16" either way
during bump/rebound, and being mounted in bush-
ings it will likely push/pull the driver side rear axle forward/back. A little bit of this
forklift-style rear steer gets noticeable quickly-did it occur in the GNX? I'd rather not
go 8" out with my axle mount to match the chassis
PHB location if rod ends and a level PHB will
solve the problem. The only other way out is
mounting the shocks in front of the axle like the
F-bodies- don't want to go there, either.
2) Brake Hop & Oversteer- The GNX TA is very short, and pinned up front- not good under heavy
braking. The braking force applied to the rear
axle causes it to pivot on the TA and lift-which
is resisted only by shocks & axle weight. De-
coupling the front of the TA solves this by using
a 3rd link to direct axle braking forces into the
chassis. You get the best of both worlds- high
antisquat, and better stopping/cornering. Did
the GNX have any tendency to brake hop or
oversteer when braked into a corner?
If gas tank/exhaust clearances permit, I'll try
mounting the PHB chassis mount on the driver
side for better Roll Center motion. The "normal"
way works better for left turn oval track racing.
I'm undecided whether I'll mount the TA under
the diff like Mustangs, or duplicate the Pass
side mount of the GNX- Richard Clark's mention
of heavier springs in the the LF/RR position
suggests that offsetting the TA doesn't stop
chassis twist from driveshaft torque reaction
totally-darn! Hopefully the total package will
surprise the F-bodies down the straights and
in the twisties!
Hello,
This is my first post and I have been reading all of the previous suspension posts in order to gain a better understanding. However, I would ideally like to have my GN sit a little higher in the rear. Any suggestions for springs to acheive this effect? Also, are the Bilstein shocks good for both streetability and the occasional visit to the drags? Any help would be much appreciated!
Springs control the ride height unless you do some geometry changes. Check out this article in the tech area for some info on springs. Are you using the stock diameter tires? gnttype.org/techarea/suspension/springs
Steven, I don't believe getting the rear end higher will help with anything handling or traction wise... it does help melt rubber, though. :-)
Dean
Bruce Plecan posted this to the mailing list:
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The first thing the suspension needs is stiffening up the shell/frame. All the handing mods in the world are just going to aggravate the flex in the system. Making a noodle handle is very difficult. So First, all the body bushings needed replaced with polyurethane ones (and the GNX bushing added). Then add all the chassis braces. Rear seat, front crossmember, core support, fender. A full cage is the ultimate answer, but even it needs done right to truely get away from the noodle mode.
Next is keeping the tires in contact with the ground. Konis or Bilsteins. The others are limp or *too* stiff. Limp allows the tire to *chatter* (for the fancy guys, oscillate, ie poorly dampened motion). *Too* stiff means that with any road irregularity, a tire gets lifted off the ground, and cars corner on 4 tires better then three.
Now, you can get to brakes. With 12" front brakes, you'll want stiffer springs then using the 10.5s since there will be a serious difference in front tire loading on heavy braking. The 3rd Gen F Body springs with a loop removed seem to be a decent spring, IMO. Rears are a PITA. I went again for the 3 Gen F Body rears and then *adapted* them to fit. The BEST rear spring answer is converting to coil-overs, IMO.
If you go with the 12" front brakes then Global West Hotchkiss or Adams can supply upper arms, and they all give the same camber curve. The downside is the bump steer changes, for the worse, but with the heavy springs, isn't really an issue, IMO.
For the serious, then you might as well figure on mini-tubs, and frame notching just to be able to get as much tire as you can under the rear of the car.
Front sway bar is fine.
ATR rear is an option.
Best rear bar option is the HRpartsnstuff.
Rear discs brakes are a good idea, but serious launching means a transbrake.
Oh, and 285/40x17 and 225/50x16 BFG KDMS.
All opinion, and for free whatdja expect
Bruce
LOL
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Your springs may just be old and worn out. Mine were so bad that if I had only a few things in the trunk, it looked as though the rear tires were going to hit the inner fenderwell. I bought a set of variable rate springs from Kirban's. The rear on my car now sits just slightly higher than the front, so it has a little bit of a rake to it. Also I added two airbags, if you do that it can help with traction and if you really want the rear up in the air then just pump up the bags.