68 custom coupe suspension - Impala Tech
Brakes & Suspension Conversion Questions & more

 
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post #1 of 3 (permalink) Old 07-26-2015, 09:13 PM Thread Starter
 
 
Join Date: Jul 2015
Location: iowa
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68 custom coupe suspension

my 68 had sad brakes,steering wheel play and swerved any time i hit a bump or groove in the road.very unsafe at highway speeds if wind blew.took it to a local mechanic and put steering box,complete front end rebuild and allignment,shocks and springs.it still swerves.steering and brakes are great.it has 15x8 corvette style rallywheels.they had spacer things in the front springs which were replaced with ss springs to keep the height for the front wheels.would this be causing the handling issue? sb 327 weighs less than big block would so....is the height gained from the big springs enough to cause the handling issues??? anybody am i better off dropping it with the right springs and 6.5 wheels? or is there another issue i'm overlooking???
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post #2 of 3 (permalink) Old 07-26-2015, 11:35 PM
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Heavier Springs will not cause any issues as long as you re-align the front end again after they are installed. Now this is if they are original or replacement springs that are recommended for your car. I put 396 Springs in my '67 283 car years ago and it went from a sagging 1 or 2 Inch under to a nice 1 or 2 Inch over. I also ran 14 X 6's in the front of that car and it all worked out great.

In my opinion, the 15 X 8's in the Fronts are too much. I ran 14 X 7's in the front of my '56 and did not like them. Went back to 6's and liked it a whole lot better.

If you still have issues, bring it to a good, well-known Front End Shop. Have them check the Ball-Joints, Idler Arm, Pitman Arm, Tie Rod Ends, etc as well as the Alignment.

Wheel Bearings too.

Bill

-Parting Out over 75 '58 to '73 Full Size Chevy Cars-

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post #3 of 3 (permalink) Old 07-27-2015, 06:24 AM
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Welcome to the Team Mike!

There are no special SS springs. The SS package was a set of bucket seats, four full wheel covers, and a pile of chromed pot metal SS badges. It (the SS package) was all show and no go.

Springs sag with time, even though the spring rate remains constant. So a fifty year old car with stock springs (selected by the weight of the car with what ever options where installed) is going to be sitting an inch and a half to two inches lower today than the day it left the factory.

The stock eight by fifteen C3 Corvette rally wheels can be used on the front of your car without any ill effects (assuming they don't rub) because you have the same front end that was under the C3 Corvette. From it's introduction in 1953 through the C4 introduced in 1984 the Corvette used a lot of full size Chevy (and the heavier D body Cadillac limo) parts in it's production. The big difference is that the engineers shortened the frame by removing the back seat. The Corvette wheels are neutral balanced that is to say the distance from the center mounting surface of the wheel hub flange to the outer rim, inside and out, is the same. Because of this the forces on the front end as you rotate the wheel are balanced.

If you used a same as only different aftermarket wheel that are not neutral balanced then as soon as you begin to turn the wheel the forces applied to the spindle increase with wheel arc that accelerates the movement taking up any slack in the front end quickly making the car jerk. This is because one side of the tire or the other depending upon wheel off set gets a greater lever arm to push or pull the spindle side to side. Using a wheel spacer or adapter only aggravates this affect.

So if your front end rebuild included replacing every part that wears (tie rod ends, all rubber bushings, idler arm, ball joints, steering arm end links, and the tie rod adjusters, rag joint, as well as wheel bearings) with heavy duty parts such as a police package or for a station wagon then there shouldn't be any slack in the front end.

There could still be play in your actual steering column as the bushings in the column wear out with use.

The only other source of free play would be inside he steering gear box itself (there is a nut on the top of the case that adjusts the end lash of the rack and sector gears) but if that is a remanufactured steering gear box it should have been adjusted properly before it was sold.

A lot of the vague road feeling in these old cars was designed into the car by the engineers intentionally and it wasn't removed until the mid eighties when the steering gear boxes were redesigned with bigger beefier shafts that don't twist. Read this article for further information on that subject.

http://www.hotrod.com/how-to/chassis-suspension/ccrp-0901-gm-steering-box-upgrade/

and another that is more of a how to than a why it feels that way:

http://www.superchevy.com/how-to/49838-bolt-on-late-model-steering/

and finally another discussion of the solution with useful part numbers and links for parts:

http://www.camaros.net/forums/showthread.php?t=30990

The final part of the puzzel is the actual tires you have. Tread design, tire construction, and the materials used to make the tire, greatly affect ride quality and handling. It is probably the biggest factor in the performance of your suspension.

Big Dave
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