Raising rear end height - Page 2 - Pontiac GTO Forum
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post #11 of 22 (permalink) Old 05-07-2018, 12:25 AM
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Problem is in your name, boy.
A man would have said I didn't realize this would damage my car, thanks for the heads up instead of getting all butthurt and throwing a pissy fit.
I will make sure not to give you any advice in the future JNYBOY.
Lift it however you want, at least I gave others a heads up on air shocks and the damage they will do to their goats.
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post #12 of 22 (permalink) Old 05-07-2018, 06:15 AM Thread Starter
 
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Gentlemen,

Please go back to your neutral corners. I regret that my question started this exchange.

The suggestion of using beefier real coil springs gets my vote.

Thank you all for your inputs, explanations and experiences; let's stop this thread and get out their shopping for Mother's Day Cards.

NoAngelBuddy
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post #13 of 22 (permalink) Old 05-07-2018, 09:32 AM
 
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Air shocks no good. Otherwise some good advice in this thread.
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post #14 of 22 (permalink) Old 05-08-2018, 12:03 PM Thread Starter
 
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Pinion Head,

Thank you for your reply. I ordered a pair of Moog 5235 real coil springs (they were designed for 1965 283/327 station wagons). The install height is the same and the ends are the same as the original 5237's. ( The "ear" shaped retainer at the bottom is what I have at the pigtail end; "ear" was a perfect description.) The 5235 free height, spring rate and load are all higher. I took some "before" height measurements and after installing the new 5235's, I'll record and post the delta's.

I heard others speak highly of CSS KS and I checked them out; the cost was >3x more than the Moog. I'll probably go with the CSS, if I don't get enough height from the 5235's or if the ride is exceptionally harsh.

NoAngelBuddy
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post #15 of 22 (permalink) Old 05-09-2018, 06:42 AM
 
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Originally Posted by Noangelbuddy View Post
The 5235 free height, spring rate and load are all higher. I took some "before" height measurements and after installing the new 5235's, I'll record and post the delta's.

NoAngelBuddy
I took a look at the specs (5237 vs 5235) and it appears to me that you may very well get your desired 3 or 4 inches of rear ride height. But a lot of that ride height gain is going to be the result of the much higher spring rate of the 5235's; a little over 30% higher to be exact.

So, as an old road racer that has monkeyed a LOT with spring rates for the purpose of tuning handling characteristics, I feel compelled to tell you that without a commensurate change in overall front rates (via higher spring rate or larger front anti-roll bar), you're going to change the cornering dynamics of the car significantly. It is going to have a much higher propensity for oversteer; "tail-happiness" in laymen's terms. I realize that all the drag racers on here are going to say "...so what?", but I just wanted to make you aware of the probable effect on everyday driving. And yes, I agree the rear ride stiffness is going to go up noticeably as well, but maybe not enough to be objectionable.


Last edited by denrael; 05-10-2018 at 06:23 AM. Reason: Corrected percentage difference in spring rates.
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post #16 of 22 (permalink) Old 05-09-2018, 07:49 AM
 
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LOL Back in the day I had air shocks on my 81 Trans Am. I found that if I put the shocks all the way up the car would spin out all the time. It was frigging dangerous!
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post #17 of 22 (permalink) Old 05-10-2018, 06:57 AM
 
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Just playing around with the numbers, it looks like the calculated (repeat calculated) difference in ride height, new Moog 5237 vs new Moog 5235, on your '65 would be 4.75". Of course if your original rear springs have sagged, the difference could be greater than 4.75".

Incidentally, in the process of doing the calcs, I discovered I had fat-fingered (actually, fat-figured ) the percentage difference in spring rate in my post above. But everything I said WRT to handling changes still applies... 30% is still a significant rate change, particularly when applied to only one end of the car.

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post #18 of 22 (permalink) Old 09-03-2018, 04:47 PM Thread Starter
 
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Raising Rear End Height

I was admiring the elevation the Moog 5237's added to my GTO and thought I would post some empirical data.

Before changing the old rear coil springs I took three measurements (rear edge of the quarter panel, center of the rear wheel and rear edge of the door) on the passenger side and marked the locations with blue painters tape for the "after" comparison measurement points. The "before" heights were 33 3/8, 37 1/4 and 39 1/2 (rear edge of the quarter panel, center of wheel hub and edge of door respectively. The "after" heights were 39 1/4 (almost a six inch delta!), 41 1/2 and 41 1/4.

I suspect my rear coil springs were probably far worse than other cars to begin with. The first owner put monster coil springs in the front (which I suspected came from a truck) that dramatically raised the front of the car. It was so high gas jockeys (remember those kids before self serve?) would peek under the car to see why it was so high. The ride and handling were awful and after driving it cross county to get home, I restored the front suspension with new OEM coil springs, shocks, etc.; no longer was each tar strip a teeth jarring experience and it did wonders for improving tire life.

I have not put the car on the road yet so I can't speak to ride comfort, but I really like the look at this point.

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post #19 of 22 (permalink) Old 05-21-2019, 09:09 PM
 
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Originally Posted by Noangelbuddy View Post
I was admiring the elevation the Moog 5237's added to my GTO and thought I would post some empirical data.

Before changing the old rear coil springs I took three measurements (rear edge of the quarter panel, center of the rear wheel and rear edge of the door) on the passenger side and marked the locations with blue painters tape for the "after" comparison measurement points. The "before" heights were 33 3/8, 37 1/4 and 39 1/2 (rear edge of the quarter panel, center of wheel hub and edge of door respectively. The "after" heights were 39 1/4 (almost a six inch delta!), 41 1/2 and 41 1/4.

I suspect my rear coil springs were probably far worse than other cars to begin with. The first owner put monster coil springs in the front (which I suspected came from a truck) that dramatically raised the front of the car. It was so high gas jockeys (remember those kids before self serve?) would peek under the car to see why it was so high. The ride and handling were awful and after driving it cross county to get home, I restored the front suspension with new OEM coil springs, shocks, etc.; no longer was each tar strip a teeth jarring experience and it did wonders for improving tire life.

I have not put the car on the road yet so I can't speak to ride comfort, but I really like the look at this point.

NoAngelBuddy
NoAngelBuddy, would you mind throwing up some shots? I am swapping out the rear springs on my 66 lemans, currently not sure what they are, but with 275 tires out back, I sit 1.5" lower at the hub than in the front...and they are a newer spring. Ordered Eaton and moog 5235. Was told by moog 5237 was shorter than their stock 66 spring, counter Intel to what you claim with how much altitude you got! I never trust them, only people who've installed.
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post #20 of 22 (permalink) Old 06-08-2019, 03:12 PM Thread Starter
 
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Rear end height

Dave,
Just took a few photos and trying to post them (a first for me). Attached just one since there may be a size limit. Let me know if you get this and want more.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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