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Discussion Starter · #1 ·
Looking to get my ride height dialed in on my 70 sportsroof. Fronts are easy with coilovers, but the back sits about 2-3" higher than i want it. I have 4.5 or 5 leaf (can't exactly remember) mid-eye leaf springs and want to avoid blocks. I have found a local shop that I trust that can de-arch the leaf springs.

Two questions
- Will this process change the spring rate?
- Will the geometry change of the leaf spring cause it to ride differently than it does now? By this, I mean that leaf spring eyes are generally re-positioned to change ride height...reverse eye, mid eye, etc... In the de-arching instance, the eyes remains in the same position, but the leafs themselves will have less curve/sit flatter. It would appear to me, that this could potentially cause a rougher ride, but i will defer to the experts on this.
 

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Looking to get my ride height dialed in on my 70 sportsroof. Fronts are easy with coilovers, but the back sits about 2-3" higher than i want it. I have 4.5 or 5 leaf (can't exactly remember) mid-eye leaf springs and want to avoid blocks. I have found a local shop that I trust that can de-arch the leaf springs.

Two questions
- Will this process change the spring rate?
- Will the geometry change of the leaf spring cause it to ride differently than it does now? By this, I mean that leaf spring eyes are generally re-positioned to change ride height...reverse eye, mid eye, etc... In the de-arching instance, the eyes remains in the same position, but the leafs themselves will have less curve/sit flatter. It would appear to me, that this could potentially cause a rougher ride, but i will defer to the experts on this.
Doesn't change the spring rate.
Shouldn't change the leaf spring geometry such that the RIDE itself is different. (unless afterward you started bottoming out)
De-arching will change the roll center. The handling will change. Whether you'll notice I don't know.

ex-Global West GM
1991-1995
 

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Discussion Starter · #3 ·
so if i understand this correctly...lowering a vehicle 2" whether it's by change in eye location, using blocks, or de-arching all modify the roll center the same way as it's just simple geometry. However, using blocks to lower said vehicle provides negative effects through an increased moment arm between the pinion and bottom leaf spring mount.

Are there any negative implications like this associated with lowering via de-arching vs eye location change? I am probably over-thinking this and the answer is..."probably, but such a small difference, you won't notice"...

Thanks for the input @GT289. you were one of the "experts" i was hoping would weight in. :cheers:
 

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so if i understand this correctly...lowering a vehicle 2" whether it's by change in eye location, using blocks, or de-arching all modify the roll center the same way as it's just simple geometry. However, using blocks to lower said vehicle provides negative effects through an increased moment arm between the pinion and bottom leaf spring mount.
Exactly.

Are there any negative implications like this associated with lowering via de-arching vs eye location change? I am probably over-thinking this and the answer is..."probably, but such a small difference, you won't notice"...

Thanks for the input @GT289. you were one of the "experts" i was hoping would weight in. :cheers:
Kinda somewhat answered in my original post but........ there is a difference whether it was lowered via eye location or via de-arching but I doubt
you'd notice the difference on the street. Twist imparted to the leaf pack would be different, depending upon where the eyelets are located. You may get
some roll-steer change too. You can alter roll steer by lengthening or shortening the shackle length- therefore, you may see a roll steer change from a
change in eyelet location because inadvertently the shackle length has effectively been changed.

ex-Global West GM
1991-1995
 

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Discussion Starter · #5 · (Edited)
You may get some roll-steer change too. You can alter roll steer by lengthening or shortening the shackle length- therefore, you may see a roll steer change from a change in eyelet location because inadvertently the shackle length has effectively been changed.
100% makes sense. It did not click until i read your post. I always thought shackle length solely contributed to ride height and i did not understand the relation between eyelet location and "modified" shackle length. Thanks for the help!
 

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No problem. Vintage Mustang not horrible. Stock shackle length pretty close. Pinto not so good. Measure the bump steer with a tape measure and the roll steer not much better....

ex-Global West GM
1991-1995
 
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