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Ride height Questions


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I searched through all the threads on this topic and I’m still confused.  I just picked up a 70ss and I’m going to back rallies that are 15x8 5bs front and rear.  245/60 and 275/60.  The car currently has air shocks. If I let all the air out, the wheel well trim is 24 1/2” to the ground (see picture). The front is at 28”’.  What should the stock measurement be? I’m guessing closer to 25” front and rear.  The last picture of car has air shocks pumped up. So the front springs need to be replaced or coil overs.  Car is heavy…BB AC Windows. Any advice would be great…pictures even better.
Thanks

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Just measured mine flat surface garage, 25 on the front is what I have... I have 60# in the shocks but I'm not saying that is factory, just my setting. Pic 1 is rally wheels BFG's Pic 2 are aluminum racing wheels drag radials rear. BB,AC,no load leveler installed pretty much stock configuration 🤣

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Modified.jpeg

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Thanks …your stance would be perfect for me. Now to figure out what front springs I need to bring it down from 28 to 25.  I’m thinking stock springs for a BB, AC pwr window car would be fine. Finding that seems to be a challenge…any one have a part number ?

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1 hour ago, Joselk1 said:

Thanks …your stance would be perfect for me. Now to figure out what front springs I need to bring it down from 28 to 25.  I’m thinking stock springs for a BB, AC pwr window car would be fine. Finding that seems to be a challenge…any one have a part number ?

I’ve got the same set up… ‘70, big block, AC, power windows (I’d think this additional weight wouldn’t be much of a determining factor, if any). 

I’m the guy who tries to bang round pegs into square holes and routinely uses butter knives to remove screws, so my mechanical knowledge is - shall we say - a tad limited. That said, here’s the front and rear spring codes per my Build Sheet. Plug these (‘GQ’ front, ‘BM’ rear) into the Interweb and see what you find. 

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There's something in the GM heritage archive files too that has spring rates, I seem to recall. Heading out for the evening, I'll look later. 

You can look here though in the mean time, you may find it, or if nothing else, there's a boatload of great info here.

https://www.firstgenmc.com/forums/index.php?/resources/gmheritagearchiveinfo/

 

EDIT: I had a couple of minutes. Here are the spring tables from the archives. Something to look at when matching spring rates against replacement springs.

 

1970 front spring.JPG

rear spring 1970.JPG

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My Monte carlo has an air ride suspension with 2 inch drop spindles. I just set it to a stance that I like. A little higher in the rear. 

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Took measurements on Barn Find Monday before I started replacing the entire front suspension. 

The front was 25" and the rear were 24 1/4".

The rear was rebuilt 2yrs ago with stock replacement coils, gas shocks, f -41 boxed lower arms, sway bar and upper arms with new bushings. 

I will again take measurements after I'm done with the front makeover. I found what springs the factory installed and then used the chart above to find the closest spring to that. 

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I ordered the Moog replacements. There was a post by MCfan a few years back, showed his ride height (stock height ) with Moog 6330 front and 5379 rears.  I ordered them yesterday along with Viking shocks. I want stock ride height with 275/60/15 in the wheel well without trimming.  

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FWIW, My 72 Custom has a 454 with A/C and a 4L85E trans that is a bit heavier than a T-400. (plus power windows, locks, EFI, etc. Point being, it's 'heavy' as you mentioned in your initial post)

I ordered the same rear spring - 5379

For the front, I went with 5536 springs, which by Moog's description is for 454, HD, with Air Conditioning.

Part number 6330 says it's for a 454, without air conditioning.

Tomorrow, I'll get a good side shot of the car as it sits. Granted, the 5536 appears to be a stiffer spring than the strongest 'CQ' spring on the factory chart above, but the car rides just fine, and sits good. The springs have seemed to settle down a bit after a couple of years, since installation.

Below are screen shots of the spring rates, installed height, etc.

 

moog 5536.jpg

 

 

moog 6330.jpg

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16 minutes ago, Joselk1 said:

Looking forward to that side shot tomorrow.  Can use measure center of wheel opening trim to ground please…thx.  

Ok.

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On 5/12/2023 at 6:28 AM, DragCat said:

Just measured mine flat surface garage, 25 on the front is what I have... I have 60# in the shocks but I'm not saying that is factory, just my setting. Pic 1 is rally wheels BFG's Pic 2 are aluminum racing wheels drag radials rear. BB,AC,no load leveler installed pretty much stock configuration 🤣

Stock.jpeg

Modified.jpeg

We have twins. 

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So this is what I come up with Gary. The car has a little more than a quarter tank of gas in it now. 

The tires are: 

Front:  225-60-17 which is 27.6" tall  (roughly equivalent to: 225-70-15 or 215-75-15)

Rear:   255-55-17 which is 28" tall    (equivalent to: 275-60-15 or 235-70-15)

Ground to center of wheel trim is a little different on both sides of the car for whatever reason, but an average measurement is: 

Front: 26-3/4         (the front is a bit higher than the back in actuality by 1/8-3/16, depending which side you look at)

Rear: 26-3/4    

At least in this car, the lighter weight front spring (6330) would drop the front end even more (too much, for me). Adding gas does tend to drop the rear a bit, and I'll be filling up soon once I run a little more of this old gas out of the car. 

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An update for everyone. I installed the moog 5372 coils into the front of Barn Find. Finally on the ground again. She is at 26 in in the front now. Was 24 before the rebuild. 

The rear has the moog cc501s. 

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Looks good, they'll probably settle down a little as time goes by. Initially,  mine seemed like the front end was too high, but looks better now.

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