just tinkering with more ideas in how to reduce body roll in the car. i already have the 1-1/8" front bar and i know i could go a little bigger but i don't know how much more benifit that would give. reason #1, the only one left is 1/8" larger and #2, i'm still mounting to the same flimsy frame 'horns' in the front.
so here's my thought. i'm already running a spreader bar and electric fans so i have a little room to work with. what if i were to fabricate some type of bracket off the spreader bar flanges and mount a second, smaller and adjustable bar on top of the upper a-arm? hmmmm. what i'm thinking is a relatively small bar, about 5/8", from a yet-to-be-determined donor. i'd have to take the a-arms off and have a flange welded to recieve the end link and who knows what else but my only other option is some relatively major work to the front of the frame which would mean some work on the radiator for clearance just to put on a bar that is only slightly larger.

 

I thought you agreed in the last suspension post that extended spindles were the answer. The longer the spindles the higher the roll center the less roll in the corners.
If our center of gravity is 16 inches and a stock roll center is ground you have a 16 inch lever trying to roll the car over in the turns. Add a 1.5 inch taller spindle and the roll center raises to 4 inches above the ground and the lever trying to roll the car is only 12 inches. Less lean in the corners.
The negative side is the tires see more scuffing, the springs can be lighter , the front sway bar can be smaller.
The steering input also is quicker because when the car leans over the springs compress the bar torques and finally the wheels see the load. With a higher roll center the tires take more load while the springs and sway bar get less input.
Raise the roll center high enough and the springs and sway bar see no input, the car doesn't roll over but the tires take a beating.
Build extended spindles. Double click to enlarge.



[Modified by norvalwilhelm, 1:46 PM 11/4/2003]

 

Remember that extra 1/8" will add a lot torsional strength than you think. Just look at the crossectional areas of the two.....0.9940 sq.inches versus1.2272 sq inches. Thats only in the area.... the strength of materials calcs will make the difference even larger. If I brought my brain and memeroy to work I'd be able to do the calcs but alas I've been out of school too long and have dummed myself down a bit!

You might even find the 1 1/4" bar a little too stiff.

P.S. Box in the frame horns to gain the required strength.




[Modified by MikeC, 2:56 PM 11/4/2003]

 

Hey, what are you trying to do here, start another out of control discussion? I'm up for it.

I agree with Norval that a geometry change will yield the most significant results. However, I think that a larger sway bar and/or stiffer springs will help and it is the easiest step to take. Yes I know that it is more of a crutch rather than a solution but what spring rates are you currently running? Also, have you considered running a racing type sway bar? You know, the kind that is basically a torsion bar with splined ends to accept arms that connect to the a-arm? You can go pretty big and stiff with those and it would be a lot less work than an extra bar.

 

Clutchdust,
Have you considered "boxing" your front frame horns ala the Chevy power book?? NOT directed to anyone in particular BUT guys like Guldstrand have the knowledge AND the experience why NOT use their knowledge and experience. its FREE??? You will NOT get C-5 handling and braking out of a C-3. I have a highly modified race car (and it wins races) yet a C-5/ZO-6 street car is ONLY a few seconds a lap slower than my race car. ..redvetracr

 

yes, i agree that the taller spindles will be a major improvement in the cornering ability of the car but the extent of my thinking was just to gain negative camber under compression rather than gaining positive. i've been reading all these other threads trying to learn, not teach. i still have a pretty elementary understanding of suspension dynamics and have a hard time factoring in the 20 or 30 different variables that actually happen when a wheel hits a bump.
as for extending the spindle, i am still no where near a competent welder capable of doing this myself. and i figure i'd like to find a solution that doesn't involve cutting and welding since i don't trust myself because i know i'm not capable and don't know that someone i would hire would truely be capable. at the risk of sounding condescending, i think i will stress these parts significantly more than the average street driver. (if i decide to fork over the money to buy the pics from the photographer, i could show you a c-3 trying to roll 275-40-17s off their rims!)
in those same pictures it became glaringly apparent just exactly how much body roll i still have. BTW, burners, i'm currently running cut down 460# front springs and a 330# rear spring, konis, poly all around and the 1-1/8" front bar. i have a rear bar mounted but i'm not running because the car was too prone to snap oversteer.

 

clutchdust, why not mod the rear batwing mounts and set the diff about 3/4" higher. Just shim the pinion snubber with washers, easy enough. It''s a common mod on the older cars. That will raise the rear roll center too, concentrate on the rear too, not jus the front. The rear is even worse than the front.

I was thinking about maybe cutting out the floor, building a subframe for the tranny and the seats to sit on and then reinstall the floor. But, that''s a lot of work. I may just not do that. If I would do that I''d probably connect the birdcage to the body with solid mounts, I have urethane ones in there now (brand new)

 

why not just order some 750 or 1000 pound springs from a circle track outfitter and put those in.

I'm not sure i like the way the car pushes with too much front bar and you can't get a rear bar on with big tires to balance the car out.

A rear 5 leaf will give you 420lbs and a set of air shocks could stiffen it further to balance the car.

 

that''s like rigidly welding the suspension, what''s the use in that. Your teeth will rattlle out. No fun to drive. The trick is to get as little body roll as possible with the softest springs and sway bars. The trick in doing this is trying to get the CG as low as possible and the roll center higher.

 

i agree completely, but i assumed clutch trailers his car for racing only.

i gave up on putting a huge bar on front when i realized the the lower A arms can't take the load anyway. 550 lbs in front and 5 leaf 420 lb in back make for a brutal ride! I cringe when i go over repaired road and i have come out of my seat and head hitting roof in the old tunnel under Boston going the speed limit.

my philosophy is keep it simple but that doesn't give you sophisticated handling.

agreed

can you explain the rear diff mod in more detail?


[Modified by turtlevette, 4:58 PM 11/4/2003]


[Modified by turtlevette, 5:05 PM 11/4/2003]

 

o.k. i agree with TT about the spring rates. i'm barely comfortable with the 460# i have now.
turtle, i do trailer the car to and from the track but i also drive it on the street occasionally.
part of what i'm trying to do here is to give a little more flexability as well. my thinking is the 1.125 bar works very well for the street but i could use a bit more on the track. so instead of having to change stuff out between track events, why not just have a second bar that i can disconnect/reconnect based on what i'm doing.
i'm still interested in changing that upper a-arm angle but due to the aforementioned distrust i have of mine and other peoples welding skills (you know no one is going to warranty their work), i'm trying to figure out a good way to mod the inner a-arm mounting location.
i'm still trying to wrap my mind around how the revised spindle/a-arm arrangement reduces roll resistance. i'm not denying it does, i just can't visualize it. still stuck on the basics, i thought roll was more a function of the springs/bars and our primary concern with the spindles was camber gain. i know that's not the way it works. it's like trying to comprehend how a cam works in an engine without understanding its relationship to the crank and piston. there's just alot to wrap your mind around.
turtle, your car would be much easier to make the mod that TT was talking about. the '80-'82 had a much different 3rd member than yours. gulstrand and others still sell the parts that can raise your third member up to achieve what TT is talking about. i'm afraid i'm not so lucky.
TT, can you give a better break down of how this helps so much? the thing i find so ironic is it seems like our discussions about our front suspension has been based on making it behave more like the rear. obviously, it's not without it's flaws but i thought it was much better sorted out for the performance application than the front just because it was designed around the corvette whereas the front was still a hold over from off-the-shelf chevrolet parts since the beginning.

 

The rear is terrible, the camber and toe are all over the place. Toe changes with suspension travel because the trailing arm has only 1 hinge point, therefore the wheel travels over an arc (seen from behind), this will give a different toe setting in all positions.
Camber, well, we all know about that don''t we. 6 link would be the solution there, no more erratic camber because of stub acle play. Also, the relateionship between upper and lower strut allow you to tailor the camber curve the suspension makes.

Raising the roll center is a very good way to minimize body roll. Roll isw caused by weight trasfer to one side (the outside in a corner) and if you raise the roll center this weight has to move over a "" taller"" arm (don''t know how to explain this properly but you know the concept of force and momentum where momentum = force over an arm length)

Raising the diff in your cars isn''t all that hard, I mocked it up and it only takes some welding on the mounting ears on the frame and the shimming on the front is no different from earlier years.

 

If you move the rearend up be very careful with the shimming up of the pinion. Remember the transmission has a downward tilt so the rearend must have an equal and oppostite angle. So it must be shimmed facing up. Our driveshafts are so short it is critical to prevent vibrations.

 

for me it''s not that much of a problem, I can adjust the rear mount on my tranny (I have threaded studs in thee that I can turn so it will raise and lower), I can set it so that the driveshaft is always dead straight from the transmission output shaft to the differential. 3/4"" rasied in the rear only requires a tiny amount of raising of the rear suspension mount.

 

Has anybody ever raided junkyards for other front suspension parts??? and tried say a mix/match..??? I know lotsa old A body folks use newer F body front end parts, including late 80's spindles to get the thing to handle better...and yes, I did that stuff with Global West...who when I contacted them in '95 or so, said they did nothing with old sharks....no help what so ever....
but the idea still in back of my mind....any clues??

GENE

 

For the front... I think I remember reading that our a-arms interchange with corvairs, and some of the big land yachts... I'll check the parts interchange manual. :cheers:

 

For 68-77's... top control arms are used on 68-82 vetts, 60-64 full size chevrolet (except taxi) and 61-65 corvair.

lowers look to be vette only... But if one of these spindles are taller then what we are using, should only be a ball joint or a slight tweak to get em to fit? Then again, might just be better off wackin the front end off at the firewall and throwing something else up there? :blueangel:

 

Twin Turbo when I installed my TKO I pushed it as high as possible, even going so far as to modify the tunnel where the shifter passess through the floor and the transmission still hung down about 3/4 of a degree. The rearend also pointed down about the same. This caused a vibration around 60-70. I measured the down angle of the transmission and the pinion then raised the pinion to be an equal amount above as the transmission was below. I also aligned the reared with the centerline of the motor/transmission and vibration free right up to 130 where I chicken out,
Running a straight driveshaft is also not good for the universal. They like a little movement to keep the rollers from flat spotting (Brinelling)

 

my tunnel is much wider and a large section on top is cut off. Also, the ZF-6 uses an internal shifter and isn''t that high in the rear. i think it''ll work out just fine.

 

The Tremec's also have internal rail shifters.
Tonight I hope to finish welding and test one of my coil overs on the rear. I intend to plot and accurate curve before installing the spring on the coil over of camber change which is very simple since I have a magnetic clamp on camber gage and also plot toe change. I already have the toe gage for the front and it will fit on the back.
I believe in the 6 link for holding a camber curve , for making quick toe/camber changes. I want to see if it holds toe to a minimum.
I have been having trouble satisfying myself with the coil over mounts. I have made 6 pairs, powdercoated and installed 2 sets, cut them off, ground the frame and trailing arm clean and started over.
Each set I find something wrong when testing so hopefully this is the final set.