front spring sag

[Bikerider58]

In Les Andrews Vol 1 book, checking the front spring for sag, one is to measure the distance between the middle of the bumper and floor. On page 1-275 these values are listed:


28-29 = 18 11/16 +- 1/2"
30-31 = 18 1/2 +-1/2"


On page 1 -279 the values are swapped between the year groups.
(28-29 is 18 1/2 and 30-31 is 18 11/16)


What is the correct measurement for the 30/31 year group?


Is arching the leafs as easy as explained in the book?

[1930 coupe]

Bumper height is not a very good way to check spring sag, because different wheels and tires will change bumper height.
Arching springs can be simple if you have all the proper tools and skills.
It can be a nightmare if you do not have the proper tools and skills.
Some people say to put the spring leafs in a vise and pull with a large wrench, usually all you get that way is a turned over work bench and a sore back.
I clean and bead blast each leaf, I use a hydraulic press to bend the leafs making a small bend about every two inches. Lay the leafs on a flat surface after bending, then push the leafs together until the ends touch the leaf under it and the spacing between the leaves should be somewhat uniform. Put the center bolt in and tighten it up and measure the length of the spring to see if you bent it enough. I like to over arch them about 1/2" to one inch in length to allow for settling after it is put back on the car.

[J Franklin]

I usually check the spring eye to axle distance to find spring sag. On a weak spring the parts are very close. I let the machine shop re-arch the leaves, it doesn't cost much.

[Larry Jenkins]

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When I got my 30 CCPU, it had what looked like a very bad sag in the front spring.

All it turned out to be is a broken center bolt.