coil over question

recently aquired a 39 ford coupe w 12 bolt rear end w 4 bar and coil over rear suspension. front end is dropped axle and buggy spring. car drives well except for a little bit "pogo stick" from the rear. i need to change the rear x-member. if i lean the coilover's in at the top and or cant them some front to back will that get rid of the "pogo effect". thanks steve

 

try it, but it sounds like the shock part of your coilovers might be a bit wore out.

 

Ya also may have to heavy a spring,,,, Are your coilovers adjustable?

 

You can slightly change your spring rate by leaning them in. You need toi find a shop or circle track racer in your area that has a spring rater. Once you know what rate of spring you have than you can decide how much more or less spring rate you want. You can buy springs in 10 lb increments. try pro shocks, they used to have a chart in there cat that would give you the amount of spring rate change per degree of angle if i remember right. i also was told that any coil over setup has a tendancy to be a little choppy.
hope this helps
chuck

 

yes they are a threaded body for adjusted any ideas how much a 1/2 inch of adjustment changes the spring rate, if any??

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Speedway Motors, Lincoln Neb. catalog has the chart for angling coilovers. There is no spring rate change caused by moving the spring up or down the shock, you are just changing the location of the spring, UNLESS you have the shock fully extended and are compressing the spring. You can figure out the spring rate you now have by taking the car to a public scale and weighing the rear of the car. Back at home jack the car up until the spring is fully extended, no weight on it. Measure its length. Set the car back down and measure the compressed length. An example: if the back of the car weighs 1,000lbs and the springs compress 2" then the spring rate is 250lb/in. 'Course there are progressive coils, which voids everything above.

 

Although there appears to be quite a bit of adjustment on coilover shock bodies there is a lot less actual useful adjustment than you might think. As bobw indicated if you have it adjusted up all the way to get the desired ride height and the shock is topped out that is a bad situation. The reverse is of course true as well. Once you get more than just a little way away from having the shock in the center of it's travel at static ride height you risk damaging it and maybe your teeth as well as it hits the stops. Erring a little on the side of more up travel than down is a good idea. Erring on the side of less up travel isn't.

For sure you should use the longest shock that can be possibly mounted up in any given situation 'cuz the longer the spring the lower the rate you need and the more travel and better ride you'll have. As far as the "pogo" effect goes as some pointed out it sounds like the spring rate is too high or the shock damping is either worn away or adjusted too low. You can lean 'em over and that'll decrease the rate but it will simultaneously reduce the damping effect as well so it might not get you much of anywhere at all. If the car is slammed down pretty good and the shock is short and you can't change the length for whatever reason you'll likely just have to live with a choppy ride although getting some proper damping in there would help quite a bit. Had a friend change from 10" rear springs to 14" springs at a lower rate. Ride height remained the same but the ride was transformed. Luckily the mounting setup allowed the use of the much longer coilover--a luxury a lot of lowered cars don't have.