Rear Spring Arch

[Ron G.]

Re: Rear Spring Arch

Mark - As I mentioned in a prior reply that I am in possession of a NOS 1963 rear spring. I bought it many years ago from Dave Bartush, and if I remember correctly he said it was an NOS spring for a 1963. If you are privy to the differences for the 1963 application and how it differs from the 64 - 74 spring, could you post it and pics would be great. I am also in possession of some original paint that was used for all the rear springs for 63 - 74. It was 200-L weld thru primer from Ionoklad Corporation. Thank you. - Ron

[Gary B.]

Re: Rear Spring Arch

Ron,

An obvious key difference between the 63 spring and the 64 and later springs is the 63 is a one-stage spring with all leaves curved, and the 64 is a two-stage, with leaves 1-6 curved and 7-9 straight.

Gary

[Mark M.]

Re: Rear Spring Arch

Ron as Gary said the 63 had all 9 leafs arched and its rate was singular at 196. In the Podcast with Franz Estereicher he said the 63 is basically like the 64 up design except as we know the top 3 leafs. There were a number of suppliers of corvette spring parts around the Detroit area but Ontario Steel Products acquired by N Amer. Rockwell 1968 did most the manufacturing of them because of their small line capabilities. Franz mentions ways they produced the springs from GM specs and I would guess they all must have followed them. The paint or rust inhibitor application methods seem to have differed. 63s had (not sure of correct material name) tactile 400c applied to tension sides and whole pallets of them were dipped in this dry to the touch oil. 64 up had ioniklad ? 200 j applied to tension sides and edges with a wallpaper brush or sponge. As Franz has mentioned this material was a water based high zinc paint, they plagiarized from the heavy truck industry. Cold galvanize paint seems similar. Ron I guess the spring you have could depend on when it was made as it could be a different supply source in later years. I don't know if the rear leaf springs had this issue as much as the front coils had when they came from as Franz put it a GM service wing. So the 64-74 originally would show zinc paint hand applied on bottom and sides of leafs. 63 used a light drying oil. I've heard never to use petroleum base oil on spring steel as it will weaken it. Ron if you post some pictures, some members here may help find any issues. Could you give the free arch measurement of that NOS spring as it's been discussed how to in this thread?

[Ron G.]

Re: Rear Spring Arch

Gary,

Yes, give me a little time and I will get you that info. I have spoke with Franz in the past at length about how the coating was applied to the rear spring. While we both agreed that it was the aforementioned paint that I previously mentioned, we did have different thoughts as to where the paint was covered on the spring. First let me say that I know how knowledgeable Franz is, and I have much respect for him and the information that he has brought to our hobby, but after several conversations with line workers where the springs were painted, this is what I have been told and I say it confidently because I have backed it up by observing midyear and early sharks that were believed to have been untouched chassis'. The factory spec was for only one side to be painted. However, when I purchased this NOS 1963 spring 35+ years ago, it was coated on one side only with the Ionoklad 200 - L weld thru primer. One of the line workers said that they were to only paint the tension side, but after sometime in 1964-1965, it was easier to just dip the whole leaf as it took less time. My observations of the early midyears is that one side was only painted, but sometime after that after looking at 65, 66, & 67 cars is that it looked like both sides of the spring were painted. I have been wrong before, and maybe I am now, but speaking with someone who actually did the job and then looking at what I believe were unrestored springs, I would have to stick to what I seen. Franz does not agree with me that the later car's springs were totally painted, but just one side. When I was restoring one of my cars in the early - mid 80's, I researched and purchased 95% of the actual coatings/paints for the entire car from the same suppliers that GM purchased them from. Again, I could be incorrect, but seeing and speaking to people who did the job is difficult for me to think otherwise. - Ron

[Gary B.]

[Mark M.]

Re: Rear Spring Arch

This paint detail is something new to me and hearing Franz speak of it has me considering a credible source. We know there were a number of suppliers and a minimal spec. They usually do whats easier and hand applying to each leaf seems slow. One or all sides who knows with a number of years suppliers and workers involved. As I mentioned before, I recently dug out 2 original 9 leafs in good shape. One has all the signs it's never been apart before and the seller said it came out of a C2. I recently took it apart and all the tension sides have the gray paint. The tops don't except one has a pea size dot. I'll post pictures soon. I do have access to other springs but it will take time to see if there's any help from them. The low mile 69 spring I recently pulled out had the gray on the bottoms but I don't remember if the tops had any. I wasn't looking for it than. So both one and all sides painted are possible.

[Gary B.]

[Mark M.]

Re: Rear Spring Arch

So be it. Thanks for the help

[Mark M.]

Re: Rear Spring Arch

Since the subject of springs is aroused again, I thought a mention of the Eaton Detroit spring we put in the 69 L36 car was due. After a few months of the car sitting and driving on the new spring, it was hoped to see it settle some. It's the 9 leaf and the car seems to sit an inch or more too high still. Their spring also required longer mount bolts, 5/8" more if I remember correctly. The car handles well. My guess is this spring will take a few years or more to sit at factory height.

[Gary B.]

[Duke W.]

Re: Rear Spring Arch

Some structural materials have a behavior called "creep". When placed under load for a long time, even below the elastic limit, they permanently deform. Most elastomers are good examples. Steel is not and has very low creep characteristics including high carbon tempered "spring steels". Springs can "sag", but that is usually due to overloading, or corrosion removing enough material to reduce the spring rate.

If steel had significant creep characteristics the Golden Gate Bridge would be sagging and the Empire State Building would be shorter than when new.

If a new spring increases the ride height significantly there's little chance the ride height will return to normal unless the spring is overloaded for a long time or looses significant material due to corrosion or any other cause. The problem is the spring design. Just because it has the same number of leaves as the original doesn't mean it's the same.

It's something you have to take up with the manufacturer, specifically their engineering organization, not "customer service".

Duke

[Mark M.]

Re: Rear Spring Arch

I agree the eventual creep (fatigue) will probably take more years than I have to wait. It took most of the 52 years of the original spring to sag were it is. The new spring starts out 5/8" higher just in the additional thickness. I'd like to see where it is after a few hundred miles and I'll take measurements against the AIM. The next course is use the new bottom spring with the rest of the original as many have suggested or another spring all together. The car doesn't look bad but the inch or more high isn't where it should be if it's settling isn't in the near future. The trailing arm bolts are original and the cushions are Bair's. 47K miles on car with as built most all original chassis parts.

[Gary B.]

Re: Rear Spring Arch

Mark,

It’s easy to get GM rubber cushions: GM 3831586. From gmpartsdirect.com for $6.38 each, plus shipping. I wonder how the cushions from Bair’s compare. Changing cushions is a relatively easy swap.

Gary