Front spring interchange

40cpe

40cpe

Well-known member
I have a Posie's front spring on my '38 Deluxe and it rides rough. I'm looking to buy a stock spring and have found one out of a '47. They both are 2" wide and 40" eye-to-eye. Is there a reason that the '47 spring won't interchange with the '38?
 
Is there a reason you can't just remove a few leaves from your current spring? If the 47 spring has the same number of leaves it is most likely going to ride just as rough or worse.
 
JSeery said:
Is there a reason you can't just remove a few leaves from your current spring? If the 47 spring has the same number of leaves it is most likely going to ride just as rough or worse.
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Yup. Just a thought, have you considered that your problem may be related to your shocks? Are they stock or have you converted to tube types?
 
You can tell by looking if a spring will ride rough. The more arch, the softer the spring. Ever notice how flat the aftermarket springs are? Especially the monoleaf springs? The stock spring will be twice as soft as an aftermarket spring from my testing of springs on my spring calibrater.
I think the newer spring has a differences in eye diameters. I would measure along the bottom of the main leaf to get a true length.
 
The problem is with rebound after I hit a dip in the road. I have tube type shocks and have bought KYB shocks to replace the ones that came in the kit. It rides reasonably well on smoother roads (DUH!) but I've ridden in stock suspension cars and the ride is much more controlled. The Posie spring is almost flat and I agree with Andy that it contributes to the uncomfortable ride. I don't have a stock spring to measure the main leaf, hence my question on interchangeability. I'm hoping someone can tell me if the '47 spring will/won't work.

I have rebuilt stock shocks for the front. When the weather cools down a bit more I'm tearing the card down to install a rebuilt flathead, hopefully change to a column shift trans, do an engine compt clean-up, etc. and would like to fix the front suspension then.
 
Pedals mailed yesterday. I have never messed with the later springs but suspect they are 2" longer like the axles.
 
some parts listings list replacement springs for '35-'40, some list for '35-'48. His spring is 40" uninstalled, mine is 40" installed.
 
40cpe said:
His spring is 40" uninstalled, mine is 40" installed.
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That should give you your answer right there. At 40 inches uninstalled it will not be under tension installed. The car weight on the spring would flatten it considerably. You could add a pan bar if it doesn't already have one on the front and maybe use it.
 
JSeery said:
That should give you your answer right there. At 40 inches uninstalled it will not be under tension installed. The car weight on the spring would flatten it considerably. You could add a pan bar if it doesn't already have one on the front and maybe use it.
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Or get a shorter main leaf made. I would want to reverse the eye anyway
 
40cpe said:
Or get a shorter main leaf made. I would want to reverse the eye anyway
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That is true! I read you OP as wanting to use the 47 spring "as is". I normal get the main spring made locally. It cost in the $20 range and you get what you want.
 
Buy a main leaf with the reversed eye and build you own spring using leafs from and original spring. Make a 9 or 10 leaf spring and use the lipped Teflon liner between each leaf. I've done this with all my axle cars and always had a nice smooth ride.
 
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