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my '67 sits lower on one side and i also would like to raise it up about 1-1/2' in the back. i know what the IRS looks like and all but i don't know if it can be adjusted for right height. is this possible? thanks in advance
First I would be sure that the bolts at the spring ends are both the same length measured from the bottom of the leaf to the top of the nut. If they are the same length and there is different ride heights, I would suspect a leaf is weak or broken. If these inspections are OK then you should be able to adjust the ride height. I do this by remembering that longer is lower. This means the longer the distance from the spring leaf to the nut the lower the ride. Conversely a shorter length will raise the car. It also raises the car more than the changed length. I have sometimes used a double nut on each bolt to retain the nuts since the adjustment may not be able to use the cotter pin holes. I have been able to adjust my ride height and have the bolt distance be the same or really close to the same length.
If you jack the car up under the centre of the rear spring and the car sits level from side to side the front springs are OK . A weak front coil on one side will raise the apposite rear corner .
You'll be hard pressed to get any significant adjustment of the rear ride height with the original type trailing arm to spring bolts. The pic below is what they looked like.
Take a look at your AIM, UPC 4, Sheet B5 and perform the "D" measurement on both sides. It will tell you if your spring is within ride height spec regardless or tire size. Midyear rear leaf springs do wear out and replacement may be in order. If you get to the point of wanting to replace the spring, do a search for Eaton Detroit Spring.
you know, i should have noticed that the wheels are literally hanging - albeit upside down - from the bolts attached to the leaf springs. common sense tells you shorter bolts will raise the car. thanks for all the tips and info, guys.
First I would be sure that the bolts at the spring ends are both the same length measured from the bottom of the leaf to the top of the nut. If they are the same length and there is different ride heights, I would suspect a leaf is weak or broken. If these inspections are OK then you should be able to adjust the ride height. I do this by remembering that longer is lower. This means the longer the distance from the spring leaf to the nut the lower the ride. Conversely a shorter length will raise the car. It also raises the car more than the changed length. I have sometimes used a double nut on each bolt to retain the nuts since the adjustment may not be able to use the cotter pin holes. I have been able to adjust my ride height and have the bolt distance be the same or really close to the same length.
Hope this helps.
Steve
Steve, being a surveyor and quite well-versed on geometry, i have to ask...how does the raised height differ from the bolt length? common sense tells us that a 10' bar, secured at one end, raised 1' in the middle is raised 2' at the other end, but i would think that the bolts on this suspension are close enough to the wheel that it would not make a big difference. am i missing something?
Steve, being a surveyor and quite well-versed on geometry, i have to ask...how does the raised height differ from the bolt length? common sense tells us that a 10' bar, secured at one end, raised 1' in the middle is raised 2' at the other end, but i would think that the bolts on this suspension are close enough to the wheel that it would not make a big difference. am i missing something?
I do not have the explanation for why this is. It probably is related to the spring and how it provides lift. I suspect that the tighter the spring is (spring length shorter) the more it raises the car. I have been using this information for many years of dealing with leaf springs & simply wanted to share it. I do not use stock bolts since there is not enough threads on them for when I adjust the ride height on my Vette. I pull a trailer with mine & load the back with items that a slung on the back of my Vette so do need the adjustment to the ride height.
The reason is quite simple. The spring wants to arch excessively unlike the way it looks while the car is sitting on it causing it to flatten out. The downward force that the spring naturally is trying to do is allowed by using longer bolts resulting in less upward lift on the rest of the car.
The reason is quite simple. The spring wants to arch excessively unlike the way it looks while the car is sitting on it causing it to flatten out. The downward force that the spring naturally is trying to do is allowed by using longer bolts resulting in less upward lift on the rest of the car.
I get all that, but I am not sure we are talking about the same thing. My point is that it would seem that a 1" shorter bolt would raise the back of the car 1". The bolt is almost directly under the end of the half-shaft, therefore the difference in bolt length from stock will result in an adjustment of equal amount....or so it would seem.
03-09-2017, 06:04 PM
1967 IRS question
