Re: AMC Handling

[Tom Jennings <tomj@xxxxxxx>]

There is understeer built into the rear leaf setup; the front spring  
perch is higher than the rear shackle pivot, so there's a geometry  
change when a spring gets compressed.

Recurving the rear springs flatter, with taller shackles to achieve  
the same height will undo this. You will absolutely need to add a  
panhard etc to counteract the side slop, especially with tall shackles.

Lowering blocks between the axle and spring will drop it safely,  
easily, and cheaply; however it increases axle wrap-up, so you'll  
need a "traction bar" setup or equiv. I was gonna use flat stock to  
sneak beside the spring front pivot bolt and a braced bracket bolted  
under the spring U-bolts for the far end.

Braking forces will make the rear axle oscillate (shudder) by  
wrapping the springs up (reverse of a drag racer's problem :-) so the  
traction bars are required with lowering blocks.

I did this on my '79 AMX I used to autocross; but I broke the car  
before I ever got the panhard and bars built. Instead of taller  
shackles, I made 2" blocks and bolt extensions for the shackle  
chassis mount. There's very little force on them, hence the factory  
pair of 5/16" studs.

I may go back and do all this to my 70 hornet.



On Dec 29, 2005, at 11:35 AM, Sandwich Maker wrote:

> " From: farna@xxxxxxx
> "
> "
> " You'll also need to tighten up the rear springs. Either add a  
> leaf or
> " use one of the short "half leaf" bolt on stiffeners. Also add a  
> panhard
> " rod or Watt's link to control sideways movement -- yes, even with  
> leaf
> " springs. A nice four link would be even better. A 1/2"-3/4" sway bar
> " would be a good idea also. You don't want the rear as stiff as  
> the front
> " though, it will handle funny then!
>
> the rule of thumb for camaros, with a generally similar geometry to
> '70s amcs, is fronts 50% stiffer than rears.
>
> " One more thing -- get wheel weight down! Weld Draglite wheels or  
> similar,
> " and lighter calipers. I've been exploring the lighter caliper  
> bit. There
> " are aluminum replacements for the 82-83 style Concord/Spirit GM  
> calipers,
> " but they state "for off road use only". They are ISCA certified for
> " racing though. Speedway carries them (www.speedwaymotors.com). I  
> wonder
> " why not for street use when they are cetified for road racing and  
> circle
> " track? That's got to be harder use!
>
> that just means they're not dot [or whatever] certified for road use.
> racing use is harder, but they get more maintenance.  snow/salt
> corrosion isn't a problem for instance.
> ______________________________________________________________________ 
> __
> Andrew Hay                                  the genius nature
> internet rambler                            is to see what all have  
> seen
> adh@xxxxxxxxxxxxxxxxx                       and think what none  
> thought