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Discussion Starter #1
Hello All,

On my 65 coupe, I am kind of struggling where to start figuring out and issue where the car feels unstable above 45-50 mph...

I don’t have any serious vibrations or anything like that, but when I am on the highway or backroads, the car feels like it is constantly floating or wobbling side to side, particularly towards the left. I am constantly having to correct with the steering wheel.

It has newer tires on it that I keep around 35lbs. The previous owner had air shocks installed in the rear. I thought that those might have been under inflated, so I bumped the shock pressure up from like 40lbs to 70lbs. That seemed to help a little, but it still feels unsettling to where it is not enjoyable but a little unnerving to drive.

Y’all always have such good input and advice - thanks in advance!
 

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Most of the time such issues are caused by one or a combination of factors including: a. improper wheel alignment, b. poor quality tires, c. worn suspension components, d. chassis mis-alignment due to previous accident, etc., d. dragging brakes, e. loose wheel bearings, etc. Rear air shocks don't help, either.
 

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Discussion Starter #4
Yeah, I am not familiar with air shocks or their advantages/disadvantages- so I was wondering about that...
 

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Yeah, I am not familiar with air shocks or their advantages/disadvantages- so I was wondering about that...
Typically used as a "fix" for worn out leaf springs. The problem is that the upper shock mounts were never intended to support the weight of the vehicle and, over time, will metal fatigue and end up cracking then ripping away entirely.
 

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Discussion Starter #6
OK,

Thank you for the points to look into.

So if I was to replace front springs/shocks and rear springs/shocks, any suggestions for budget friendly daily driver or modest performance parts? It is a mustang after all and I’d like to drive it like one ?! It’s a 65 A code...
 

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Here is a recent thread on front suspension upgrades:

 

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+1 on the suspension being old and tired in addiction to the air shocks. When I was young and stupid, on a back country road that I would drive home from high school, I would haul butt (guess 80 plus mph). I would have to drive in the middle of the road at high speeds since the car lifted and swayed side to side like I was floating on a cloud. I have a different 66 now, same thing would happen......high speed sway. Total suspension replacement and a steering box rebuild, she is pretty tight. Far far far from a sports car of today, but 100% more stable at high speeds. I did not go with a kit, pieced mine together. Eaton rear improved handling leaf springs (GT) and Scott Drake "GT" style coils. In addition, I did upgrade to a larger sway bar. Good luck.
 

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OK,

Thank you for the points to look into.

So if I was to replace front springs/shocks and rear springs/shocks, any suggestions for budget friendly daily driver or modest performance parts? It is a mustang after all and I’d like to drive it like one ?! It’s a 65 A code...
Depends on how budget friendly you are looking for. On the low end, KYB GAJ shocks on all 4 corners, Eaton GT springs on all 4 corners. The Eatons are pricey these days though (as are all springs) as the price of steel has gone up. Maybe cheaper springs would do you fine, but I use the Eatons and they seem to be good to me.

If you want a little higher end, change your shocks out for Bilstein Street-valved shocks. They are pricier but have significantly less "bounce" to them than the KYBs.

When you're doing this, make sure that all of your other suspension components are in good shape - all bushings good, no rot, everything properly lubricated, etc. Then finish up with a good alignment set to -0.5 to +0.5* camber, +2.5 to +3.5* caster, and 1/16" to 1/8" toe-in. Shouldn't have any problems after that.

FWIW, my '66 fastback cruises at 90+ MPH on the Eaton springs, Bilstein shocks, and exactly those alignment specs. I never have to worry about any weird darting unless the wind gets really strong from the sides of the car.
 

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Shocks are one of the areas you don't want to go cheap on. You could probably get by with some cheaper coil/leaf springs, especially if the car is stock and a daily driver. Though I'd want to get some nicer shocks that are going to make it comfortable, especially if you're driving the car every day. The cheaper shocks might be ok at first but if you're putting a considerable amount of miles on them I don't think they'll last very long.
 

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I conmpletely replaced my front suspension on my 66 convertible. All new upper an lower control arms with roller perches, springs shocks, tie rods, your name it. Swapped in a 1" front sway bar and a shock tower brace and monte carlo bar and what a difference! Wasn't cheap but i wanted to drive this car numerous times a week and It goes wherever I want it to.
 

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Warning. If you rebuild the suspension like others have suggested (and the steering) you'll find yourself driving the car much more often!!! LOL.
 
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