I purchased a beautiful 57 Pontiac hardtop. The previous owner installed new front springs. They are way tooooo stiff. The car follows every wave in the pavement. Current suppliers all sell the same large wire diameter coil springs. No information is provided on spring rate. There are front coils on eBay but they are listed as 57-60 which is erroneous. Can anyone tell me the wire diameter of the original spring. Does anyone have an original set for sale.
The wire diameter on my 57 (US) Star Chief seems to measure around 0.657" (its tough to get in there on the car with calipers). CPR seems to list them, but no specs: https://www.pontiacparts.net/product/1957-front-coil-springs/ Eaton Detroit Spring will also make springs to order, at stock or modified heights: https://www.eatondetroitspring.com/findmyvehicle/
Look up (coil spring specialties) in Kansas, they can give you exact stock specs and make whatever you want.
Difficult to know just what springs you have, don't rule out the shocks. My Coker radials are very rough riding & a swap is planned. Any spring rate under 350 is pretty mild & a 50's Olds spring is super similar. https://www.jalopyjournal.com/forum/threads/replacement-springs-for-a-50-olds.1349556/#post-15861944
Thanks for all the info. The 0.657” wire diameter is approximately what I’m measuring on mine so it’s something else. The old BFG radials could also be part of the problem as well as the shocks. I ***ume your springs are 1957 originals not replacements?
Espo.com is another spring source. Edit: I haven't bought springs from them but CPR (California Pontiac Restoration) has always been a reliable parts source for me. Last time I looked they also have an inventory of NOS parts - you never know, maybe they have some original springs on hand.
Look up the Moog coil spring PDF file online. It lists them by coil size, rate and free length. Once you know what you need, go shopping!
I am pretty sure those front springs on mine are original. I am second owner, PO did not do much to the car. I am replacing the rear leaf springs but thats another story. If your springs have been cut to lower the front they are going to ride somewhat stiffer.
Car has dropped spindles so coil cutting would not seem to be necessary but who knows. This Pontiac is an older restoration maybe 20+ years ago. Definitely p***ing on the Cleavage thing
Jon, where did you find drop spindles for your 57’s King pin set up, or did you switch to Chevy Tri five ball joint system?
Dropped spindles were offered by Fatman Fabrication. Southern Rods and Parts acquired Fatman Fab ***ets This system has the kingpins like the original.
How do I find your thread on the 56 wagon? I cranked the adjusters all the way until they bottomed pushing that upper mount as far to the rear as it would go and the lower mount to the front. All I was able to accomplish was zero degrees caster and a little negative camber.
The 57 Pontiac still had kingpins, which has limitations in setting caster angles (need to check for bind...). See below for front spring numbers from Pontiac Master Parts Catalog, which differ by style, transmission, etc. My car is a convertible (2867) with the Hydramatic, which probably has heavier springs due to the heavier/boxed frame. Aftermarket wheels could also potentially effect things, as originals had close to neutral (0.75" positive) offset.
Yes, difficult to get any Caster with Kingpins. one advantage of Ball joints. Can the control arms be shimmed?
Caster situation gets worse. Best I can get on the driver side is 1 1/4 degrees negative caster. The upright actually leans towards the rear at the top as would be expected in a suspension set for positive caster; however, my Longacre alignment tool reads negative caster on the 40 degree swing. A close visual inspection shows the kingpin is not parallel to the upright(front or side view) so poor workmanship on the dropped spindle could explain the discrepancy. I’ve done steering geometry modifications on ball joints cars even going so far as to move ball joints to achieve 6-7 degrees positive caster but this thing is going to require some as yet undetermined modification to achieve ZERO caster.
I'm just thinking out loud here, but if you were to shim the front of the upper control arms and shim the rear of the lower control arms you might be able to increase caster while keeping the the pivot pin geometry parallel. The shim thickness would need to differ top/bottom due to the different mounting bolt spacing on the control arm shafts. EDIT: This might also add a bit of "anti-dive" geometry to the front end. Again, need to test without the springs/shocks to make sure there is no binding. Let us know what you find. Below is an example of what we are dealing with (55 Pontiac).
You guys were correct about shimming the control arms. Decided to reverse the adjuster in the lower control arm in an attempt to get more forward movement of the spindle. Loosening the upper control arm bolts revealed that cranking the upper and lower adjusters to their maximum positions had put a lot of twist on the control arms. I put a 0.110” shim under the front of the UCA. Haven’t gotten to the LCA yet but when re installing the lower spindle bolt it was obvious that the bolt holes in the LCA weren’t parallel with the spindle bolt. Good news. A quick check showed + 1 degree caster and negative 1/2 degree camber. Started out looking for a softer ride and ended up improving the caster. Maybe get a little anti dive action here.
You do know that you adjust caster and camber with the upper trunnion right? By turning it, it threads the top of the spindle forward and backward, while moving the spindle in and out as you turn it.
In measuring the control arm mounting bolts, it looks like my UCA is 3.75" OC, LCA is 8.5" OC. (I think control arm bolt spacing may differ across years/models) Did a little trig and for each 1* in caster change you need 0.065" shim (about 1/16") up in upper front, 0.148" (just over 1/8") down in lower rear. Should make sure there is enough bolt length for full engagement...
If you’re shimming bolts on a king pin car you need to remove the spring so you can make sure there’s no binding through the suspension travel. These are not like ball joint cars that allow that kind of movement. You will quickly wear pins and bushings out if you try to twist them
After placing shims under the front of the upper control arm mounts and under the rear of the lower control arm mounts and cranking in the maximum spindle adjustments, the caster is +2 1/2 degrees. The camber is -3/4 degrees. The eccentric is in the least negative position so -3/4 is the best camber achievable. The upper and lower control arms were shimmed to match the angle of the spindle bolts and relieve the twist on the control arms. Before shimming the control arms, I measured +1 1/2/ degrees of caster. After adding the shims and relieving the stress on the control arms, I measured 2 1/2 degrees. Now back to the original problem of the stiff ride. Thanks for all the help.
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