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Measuring Ride Height - Checklist

2K views 11 replies 3 participants last post by  umangu 
#1 ·
Hi Guys,

I'm planning to do the Shelby drop and change the front springs as well as the rear leaf springs on my 66 coupe, 289. No A/C. Everything on my car is stock.

I want to measure the height and stance as it currently is. I quite like how it looks and don't want to alter it too much, lower it just a little bit maybe.

The problem is that all products out there tell me how they will change the ride relative to factory spec and I have no idea what factory spec is. My springs are still original and very saggy, especially rear drivers side. So I'm worried even 'lowering springs' might actually raise my height.

Please can you tell me:

1. Where to measure (ground to fender, mid-wheel to fender, ground to rocker panel etc).
2. Tire inflation (I have 205/75R14 tires at 32psi)
3. How to settle springs before measuring (bouncing car?)
4. How full should the fuel tank be?
5. Should someone sit in the driver's seat while measuring?

And here's a photo of my baby.

Thanks guys!

Umanng.
 

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#2 ·
Ride height is typically done with a full tank of fuel, tires at specified PSI, and 150 lbs in the drivers seat. Unless otherwise specified, the measurement is from the lip of the wheel arch to the ground, using the center line of the tire as a line up point. If you're comparing from "saggy stock" to "firm lowered", as long as you've done everything the same for both measurements, that will establish your baseline and modified results. I've found that unless the driver weighs over 250 lbs, or the car is very small and/or light, the driver's weight doesn't affect the height that much(I've actually done what I call "big guy" alignments on smaller cars, where I've put the drivers weight in sandbags on the seat, and then performed the wheel alignment). Bouncing the car 2 or 3 times should "settle' the suspension. I lowered my '65 coupe about 2 inches using lowering springs and Shelby drop in the front, and rear lowering blocks and shackles in the rear. I had to play with it some to get the stance I wanted, as I wanted the car to sit level, not slightly "nose up" as was typical of the cars in that day. Nice ride BTW, good luck with lowering the suspension.
 
#4 ·
Thanks for tips guys. The longest owner of the car was definitely a heavy guy (from his photos, I never met him). So I like the wording you used - comparing from "saggy stock" to "firm lowered".

I was surprised you said my car looks high. Here's another photo, without the harsh shadow on the tires. Let me know what you think.

Also, now that I know how to read tire numbers and calculate the diameter I'm astounded to learn that my 205/75/R14 are larger than most others.
 

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#5 ·
With the rear farther from the camera the perspective distortion makes its more difficult to tell. The straight-on view from the side removes that problem. The numbers at the site I referenced should tell you; the numbers for the rear are less than for the front.

The original tyre size diameter was the same as a modern 195/75-14. There were several different size standards between then and now, including the A/B/C sizes, and conversion charts between all of them in the 80s sometimes suggested 185-75's but those are actually smaller than stock. Many Mustangs, including our '66 coupe, once used the too-small C78's which was similar in size to the 185-75's.
 
#6 ·
Yeah, next opportunity, I'll fill my tires, fill my tank, find level ground and measure everything up now that I know how and will report back with what my stance measures.

As it stands, my tires are 0.75" less in height/diameter than stock. And I though they were small! Next tire change I might only need wider tires in that case.
 
#7 ·
FWIW I'm running a 195/70/14 tire on all 4 corners (very close to the stock diameter, and just a little wider). I have manual steering and a 6 cylinder engine, so I was going more for stance than anything. I also wanted to keep the width of the front tires down, as I built the car for my wife to drive it, so narrow tires make parking lot maneuvers easy. Here's a side view of my car right after I lowered it. I know it's kinda hard to see the actual fender lip/top of tire relationship with the car being black, but you can tell it sits lower than stock.
 

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#9 ·
Thanks for the compliments. If you like how your car looks and drives with the tire size you're currently running, just lower the car enough to minimize the gap between the top of the tire and the wheel arch. Like I said with my car, It's all about the stance. With the slightly firmer lowering springs and the Shelby UCA Drop, the car rides and drives a lot better than with the worn out stock stuff. I picked the size tire I'm running based on the stock diameter, as the tires that were on my car when I bought it were shot from the car sitting 20+ years. If I had bought a driver with fresh tires instead of a project, I'd have probably been inclined to match the drop to the tires on it, even if they were a little taller than stock.
 
#10 ·
With the height dropped to "minimize the gap between the top of the tire and the wheel arch" like you suggested, I would risk contact between the body and the wheel.

My front end is noticeably bouncy at the moment - original springs but recently changed stock OEM shocks.

My question is, to stiffen up the front bounce, would I rather change to stiffer performance springs, or better performance shocks, or would both be necessary?

Thanks!
 
#11 ·
I did both springs and shocks in my car because the springs were tired, and the shocks were shot. Because my car is a 6 cylinder, I got the lightest weight lowering springs that NPD offered, which were still rated stiffer than my stock springs, and I put KYB gas shocks at all 4 corners. Before I lowered it, just replacing the worn out shocks with new ones helped tremendously, but the car always felt a little "nervous" at freeway speeds. Since I lowered it, the car is way more confident at speed, and it corners very well for a 55 year old car.
 
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