Ride height with new MM control arms

[mustangwolf]

When I changed my 7.5 to 8.8 I installed Maximum Motorsports lower control arms in the rear of my 83 GT. Stock rear springs, MM sport lowers, stock replacement uppers, stock sway bar. When I set the car down it looks like the rear ride height is very high. Very High! Looks several inches too high compared to my 91 GT. No engine in right now, but that missing weight is on front so I don't think that is problem. Only weight missing from rear is spoiler and no gas. I also double checked and made sure I had the spring pigtails turned the correct way to match the installation diagram.
Is this common? Is it possible the bushings being new are just stiff and have not settled? or do I possibly have something else going on.
Can't find anything in the MM literature to indicate they should raise the ride height.

[bob85gt]

upper and lower control arms should be NOT tightened till the weight of the car is on the suspension. then tighten.

[Patrick Olsen]

Yup, what Bob said.

[mustangwolf]

upper and lower control arms should be NOT tightened till the weight of the car is on the suspension. then tighten.

Originally they were tightened with weight on suspension.
To make sure there wasn't an issue there, I went back yesterday and set the car on elephant stands, loosened the upper and lower control arms and re-torqued them in the required sequence. Didn't change anything.

[KevinVarnes]

You say stock rear springs. Does that mean the springs you took out of the car or new replacement "stock" springs?

[mustangwolf]

You say stock rear springs. Does that mean the springs you took out of the car or new replacement "stock" springs?

The originals from 1983. Car has TRX suspension.

[Jack Hidley]

The ONLY control arms which must have their pivot bolts tightened at ride height, are stock style control arms which have rubber bushings in them where the rubber is vulcanized to the crush sleeve and to the outer shell. This is because the rubber bushing in this case is a torsional spring. By tightening the bolts with the car at ride height, this spring isn't affecting the ride height of the car.

Were the same spring isolators installed with the new parts?

Were the SAME EXACT rear springs put back into the car which came out of the car?

The bushings in the old RLCAs are 38 years old and have prelowered the car. That is a certainty. The bottom of the rear spring is connected to the chassis through these bushings. As the bushings degrade, the RLCA moves downwards in the car, because the bushing deforms. This causes the ride height of the car to drop. With RLCAs which have new bushings in them, the ride height comes back up to stock height.

Unless the cg of the engine is directly above the front axle centerline, it must affect the ride height in the rear. If the cg of the engine is in front of he front axle, the rear ride height will go down, when the engine is removed. If the cg of the engine is behind the front axle, the rear ride height will go up when the engine is removed. The engines cg is significantly behind the front axle. If the transmission is out of the car, that will also make the rear ride height higher.

The MM RLCAs will put the car back at exactly the same ride height as new set of stock RLCAs will put the car at.

[mustangwolf]

The ONLY control arms which must have their pivot bolts tightened at ride height, are stock style control arms which have rubber bushings in them where the rubber is vulcanized to the crush sleeve and to the outer shell. This is because the rubber bushing in this case is a torsional spring. By tightening the bolts with the car at ride height, this spring isn't affecting the ride height of the car.

Were the same spring isolators installed with the new parts?

Were the SAME EXACT rear springs put back into the car which came out of the car?

The bushings in the old RLCAs are 38 years old and have prelowered the car. That is a certainty. The bottom of the rear spring is connected to the chassis through these bushings. As the bushings degrade, the RLCA moves downwards in the car, because the bushing deforms. This causes the ride height of the car to drop. With RLCAs which have new bushings in them, the ride height comes back up to stock height.

Unless the cg of the engine is directly above the front axle centerline, it must affect the ride height in the rear. If the cg of the engine is in front of he front axle, the rear ride height will go down, when the engine is removed. If the cg of the engine is behind the front axle, the rear ride height will go up when the engine is removed. The engines cg is significantly behind the front axle. If the transmission is out of the car, that will also make the rear ride height higher.

The MM RLCAs will put the car back at exactly the same ride height as new set of stock RLCAs will put the car at.

Exact same springs. I did put new upper spring isolators.
Transmission is in car and a mock-up block, but not a complete engine.

[stangPlus2Birds]

Exact same springs. I did put new upper spring isolators.
Transmission is in car and a mock-up block, but not a complete engine.

Poly or rubber?
What brand/make?
What did the old ones look like?
Also, did the old ones even exists? Often, in the rear, they are gone, or completely compressed.

Also, define "the rear end of the car is now 30 feet too high".
Get a tape measure, and measure to the mid of the fender lip.
Also, what exact tires (also the year made) and rims do you have?

There's no magic anti-gravity device in MM RLCAs.
Unless you have adjustable MM RLCAs, any change in height is due to the other parts you put in.
Especially ploy isolators compared to the paper thin almost non-existent isolators that you removed.
I'm assuming, of course, that your old RLCAs weren't rusted to h*ll, and bowing downward about to break in half.


For reference, my '86 Mustang sits ~~1/2" lower in the front and rear in the following pictures:
http://www.veryuseful.com/mustang/te...Mach1_springs/


Also, note, that my barely lowered Mustang is lowered from an already OEM, from the factory, LOWERED GT platform.

I need to drive on real-life New England cr*p streets, which are often just pot-holes connected with small sections of asphalt. I know people that have/had B-springs, and other lowered Mustangs in the area. Imho, as a daily driver (my usage in the Summer), those lowered cars in New England, are as useful as a string bikini in 40mph winds when it's -10F outside.
Fwiw, New England is also very hilly, and rarely flat. Many reasons for that - tectonic plates bashing togaether, and being ripped apart, and glaciers tearing up the land every ~~~200,000 years(iirc).


Good Luck!

[mustangwolf]

Poly or rubber?
What brand/make?
What did the old ones look like?
Also, did the old ones even exists? Often, in the rear, they are gone, or completely compressed.

Also, define "the rear end of the car is now 30 feet too high".
Get a tape measure, and measure to the mid of the fender lip.
Also, what exact tires (also the year made) and rims do you have?

There's no magic anti-gravity device in MM RLCAs.
Unless you have adjustable MM RLCAs, any change in height is due to the other parts you put in.
Especially ploy isolators compared to the paper thin almost non-existent isolators that you removed.
I'm assuming, of course, that your old RLCAs weren't rusted to h*ll, and bowing downward about to break in half.


For reference, my '86 Mustang sits ~~1/2" lower in the front and rear in the following pictures:
http://www.veryuseful.com/mustang/te...Mach1_springs/


Also, note, that my barely lowered Mustang is lowered from an already OEM, from the factory, LOWERED GT platform.

I need to drive on real-life New England cr*p streets, which are often just pot-holes connected with small sections of asphalt. I know people that have/had B-springs, and other lowered Mustangs in the area. Imho, as a daily driver (my usage in the Summer), those lowered cars in New England, are as useful as a string bikini in 40mph winds when it's -10F outside.
Fwiw, New England is also very hilly, and rarely flat. Many reasons for that - tectonic plates bashing togaether, and being ripped apart, and glaciers tearing up the land every ~~~200,000 years(iirc).


Good Luck!

New upper isolator is SVE polyurethane.
Existing stock upper isolators were intact and still in good shape. I just measured one, it is still about a 1/4 inch thick.
It also had intact lower isolators. The lower pigtail sits right on the MM arm so there is not a lower installed now.
No damage issues to existing arms, they look to be in great shape, I'm just upgrading with the 8.8 installation.

Car has 275/40/zr17. There is 5 inches from top of tire (center) up to fender lip. Nitto NT555 G2 on 5 lug 17x9 Foxresto Pony wheel, few months old.
Also, the tire is closer in front than in rear (not centered in fender well) as it sits. If compressed more the arc of swing arm would obviously correct that.

For comparison I measured my 91 GT from top of tire to fender well. It is 1 3/4 with 225/55/r16.

Maybe it is just the weight, I just can't see it moving it that much. Hope I'm wrong and it just sits right down with complete engine.

[qtrracer]

FWIW, I used poly and stock rubber isos to get ride height the way I wanted. For example, on my 86 PS, I had a stock rubber upper cut into a "C" shape due to the spring seat being deformed. The open part of the "C" straddled the deformation. On the DS, I used both a poly and the stock rubber uppers to level the rear static height. Then adjusted my MM lowers to where I wanted it to sit. You also need to have the rear springs clocked correctly. l also found during the process that the poly isos raised the car as much as .5" over the stock compressed rubber isos.