Tech Question - Hudson Street Rod

Hello Mike ,

I am asking for help with a problem I am having on a 1930 Hudson Street Rod. I mounted a Ford Mustang rearend on the original springs, and the springs flatten out with the weight of the car, no arch.

With the spring flat the rear shackle hits the fender and wont let the spring work as it should. I had the springs re-arched and was told they may or not stay arched, they didn't last.

The local shop here thinks I should order new main leafs two Inches shorter to the rear.

Would this work? Please advise me on the best way of fixing this problem.

Thank You.

Jake

Jake,

Now let see if we can solve your problem.

In 1930 Hudson used 4 different 2 Inch wide springs on their vehicles, one 7 leaf,two 8 leafs and one 9 leaf. All the springs measured 23 29/32" by 30 25/32", or an eye to eye length of 54 11/16 Inches. The springs were designed to carry loads in and around900 Lbs. At this weight the springs still had 1 Inch of arch in them.

Too bad you did not know the year of the Mustang suspension that was used in your car. 1964 through 1973 Mustangs used 36 different 2 1/2 Inch wide 4 leaf springs. Two different divisional lengths were used, 22 x 31 and 21 7/8 x 31 1/8. However, the eye to eye lengths were the same, 53 Inches. There was a very wide range of design loads ranging from a low of 500 Lbs. all the way up to 730 Lbs. And loaded heights from 1/4 Inch reversed to a positive arch of 3/16 Inch.

1974 and up Mustang springs are also 4 leaf 2 1/2 Inches wide. But they measure 21 x 29, or 50 Inches long eye to eye. Their design loads ranged from 589 Lbs. to 750 Lbs. And at these loads they had a positive arch ranging from 1/2 Inch to 3/4 Inch.

I think your problem is more involved than the length of the Mustang springs.

The width of the Mustang springs are wider than the Hudson's, 2 1/2 vs. 2 Inch. Also the length of the Mustang springs are shorter then the Hudson's, 53 and 50 Inches vs. 54 11/16". And finally, the carrying capacity of the Mustang springs is quite a bit less than the Hudson springs, 500 to 750 Lbs. vs. around 900 Lbs.

With the Mustang springs being1/2 Inch wider than the Hudson's how did you mount the Mustang springs? Also with the Mustang springs being either nearly 2 Inches or 3 Inches shorter than the Hudson's depending of the year of the Mustang springs), was the rear hanger moved? If not, the shackle has to be being pulled forward - not going backwards.

With the vehicle weight difference between a Mustang and a 1930 Hudson and the weight carrying capacity of the Mustang springs, the springs are just not strong enough.

The cure is new springs heavy enough to carry the weight of the Hudson. But in order to design the springs correctly, we will need answers to some questions. To make sure the springs really are from a Mustang download our measuring form, and send it to us.

-Mike