Which is easier, front or rear suspension?

[GH85Carrera]

I replaced the rubber bushings on my front suspension on my 1985 Carrera earlier this year. I have been busy with other things but I am ready to attack the rear suspension. I plan to replace the shocks, torsion bars & of course the rubber suspension bushings with new Elephant racing bushings.

I have done a lot of reading but I figured I would throw out a couple of quick questions for the group. How much harder is doing the rear suspension than the front suspension? What do you suspect will be my biggest challenge?

OK, one more question, what are the best how to threads ? I have found several but I always seem to miss the best ones.

[tcar]

Why are you replacing the torsion bars? Just wondering.

[GH85Carrera]

When I did the front end the t-bars had some rubbing, so I had to replace them. I went up one size and I want to match that in the rear. At the autocross it is more tail happy now. I can't really evaluate it too much since I still have the old shocks in the rear. I would never try a track day as it is now. Once I get the rear finished I will have a full corner balance & alignment done.

[Superman]

Read some more, particularly about what rear bars will best match your new front bars.

Interestingly, the stiffer end of your car will be the loosest. If you have stiffened the front, then this has made your car PUSH more (understeer). For autocross, you will want more oversteer. The softest part of your suspension is where the tires will grip the best. The stiffest end is where the looseness will occur.

[mtb001]

just finished rear, ready to start on front. I found 2 areas that were troublesome but not difficult.
1. The bolt that holds the swing arm to the torsion bar housing, can't access with engine/tranny in place, have to cut it in half with sawzall and replace.
2. Emergency brake pads, although not difficult, must replace springs in specific order and the pay very close attention to how the butterfly's that operate the pads come out.

The axle nut is tight, i used 3/4 breaker bar with 3' cheater pipe to break free
Pressing the new bearing in the swing arm can be done using long nut/bolt and washer to pull together, mine was fully seated but would not fit back into place, had to grind down the bushing to fit.
Indexing torsion bars is easy enough, iPhone level app, the Bentley manual specifies degrees for various heights or search.

Best of all, search "elephant racing"

[McLovin]

Originally Posted by GH85Carrera

How much harder is doing the rear suspension than the front suspension? What do you suspect will be my biggest challenge?

IMO the rear is 2X harder to do than the front, in theory, and up to 10X harder in practice. Bushings, torsion bars, setting ride height, etc.

The front set up is just a lot easier to work with, at every step of the way, with less things that tend to get "stuck" or frozen.

For example, setting the ride height is a ton easier on the front, you can reindex the torsion bars in a minute or two without even taking the front wheels off the car, and you can adjust the ride height by just reaching under with a wrench, and not even jacking the car up. The rear is not so simple.

[Superman]

Originally Posted by McLovin

IMO the rear is 2X harder to do than the front, in theory, and up to 10X harder in practice. Bushings, torsion bars, setting ride height, etc.

The front set up is just a lot easier to work with, at every step of the way, with less things that tend to get "stuck" or frozen.

For example, setting the ride height is a ton easier on the front, you can reindex the torsion bars in a minute or two without even taking the front wheels off the car, and you can adjust the ride height by just reaching under with a wrench, and not even jacking the car up. The rear is not so simple.

McLovin seems to understand suspensions better than politics.

Yup, the rear is a bit of a PITA. Still, not that many parts. Do-able.

Getting the control arm bolts out with the transmission in place depends on which way the bolts are facing. If you're lucky, they're facing inward and can be removed easily.

Torsion bars sometimes don't want to come out at first, but with patience and finesse they will let go. Use the Wil Ferch Spring Plate Calculator. You will need to rough-set your suspension settings. Ride height first. Then camber. Then toe. Then drive it straight to an alignment shop where you will learn how far off you were.

If you want to replace the bearings (not necessary if your bearings are fine), then any machine shop can easily do that for you. The control arm into which they are pressed will be off the car. And yes, the axle nut is on tight. I mean TIGHT. No less than a half-inch breaker bar will be needed, and you will need to slip a section of pipe over it for leverage. Put the knuckle of the breaker bar into the saddle of a jackstand. E-brake on. Car in gear. It will come loose with a BANG. When replacing that nut, if you fail to tighten it to the correct torque, it will be too loose and that will destroy the bearing. It's technically possible to get it too tight, but your chances of doing that are slim.

[rusnak]

Glen, it's doable in a weekend. You'll need a thin wrench to adjust the ride height (check out McMaster Carr) for sure, and a large allen wrench that you can buy off the shelf from Sears to adjust the toe and camber eccentric bolts. You might want to have a torch and hacksaw handy to remove the old rubber, and a digital inclinometer. It's not hard. I'd leave the axle nuts alone. I can post pics of my rebuild last year if you can't find any good threads.

[rusnak]

I had to get the external HD out anyway:

Measure radius arm inclination before and after removal and replacement:

I think each spline is good for about 3 degrees or 3-4 inches or whatever, but if you re-index the outer against the inner splines, you get 1.5 degrees or so of inclination change. But don't quote me on the exact amount.


Used longer bolts to press the cover on to the new rubber


Done

[efhughes3]

Originally Posted by Superman

Yup, the rear is a bit of a PITA. Still, not that many parts. Do-able.

Getting the control arm bolts out with the transmission in place depends on which way the bolts are facing. If you're lucky, they're facing inward and can be removed easily.

Easily is a relative term. Depending on which way they are facing determines whether they can be removed with the trans in-situ.

When I removed mine with the tranny in, to install ER monoballs, they were the biggest problem I've ever faced in many years of 911 ownership-brake system upgrades, suspension rebuild and upgrades, an engine build and many other projects under my belt, so I think I speak from a bit of experience. Every car is going to be different in this regard, IMO.

I got them off with some heat and a 4' long contraption of a wrench and 210lbs (maybe 225 back then) of body weight, and 4 hours of my life.

[vash]

fronts are easier from the get-go. but once you take apart the rears, again and again,....and again..the rears just get plain easy.

[930chef]

i removed both of my trailing arms today. the nut was outboard which meant i thought i was gonna drop the drivetrain. i removed the nut and tapped the bolt inward just enough to expose the head of the bolt and used my sawzall to cut the head off, then pulled out the bolt by the threads. thank god that worked, i could bear the thought of all the extra work. hope this helps......kevin

[rusnak]

Originally Posted by efhughes3

Easily is a relative term. Depending on which way they are facing determines whether they can be removed with the trans in-situ.

When I removed mine with the tranny in, to install ER monoballs, they were the biggest problem I've ever faced in many years of 911 ownership-brake system upgrades, suspension rebuild and upgrades, an engine build and many other projects under my belt, so I think I speak from a bit of experience. Every car is going to be different in this regard, IMO.

I got them off with some heat and a 4' long contraption of a wrench and 210lbs (maybe 225 back then) of body weight, and 4 hours of my life.

Hey Ed:

See that long fencepost...er breaker bar? Can you tell that I grew up on a farm?

[GH85Carrera]

The main purpose of the project is to get the rubber bushings replaced and the shocks replaced.

I have a 3 foot breaker bar with the appropriate socket for the axel nut so that is covered. I did the rear wheel bearings two years ago. The CV joints were repacked back then. So that part is done. While I am in there I will rebuild the rear calipers since they are 25 years old and never touched.

My biggest concern was getting the trailing arms off, and back on. I guess I will order a set of the trailing arm bolts and get them on hand.

It is good to have the warning about the emergency brakes. I will take pictures and notes as I take it apart.

The funny thing is when I mention rebuilding the suspension to non Pelicans they all think I am nuts. There were times when I was trying to get the front stabilizer bar back in place I would have agreed with them.

[JeremyD]

They each have their own level of suck.

the front can be a pisser of the TB decide they are not coming out or you break off the wedge bolt (or ball joint removal)

The rear can induce you into a swearing tirade if you can't get the tb cover to release or get your spring plate angle correct.

Good times good times...

[rusnak]

Originally Posted by GH85Carrera

When I did the front end the t-bars had some rubbing, so I had to replace them. I went up one size and I want to match that in the rear. At the autocross it is more tail happy now. I can't really evaluate it too much since I still have the old shocks in the rear. I would never try a track day as it is now. Once I get the rear finished I will have a full corner balance & alignment done.

Someone else with race setup experience should comment on this. Won't stiffer rear tbars make it even more tail happy?

[jimbauman]

I just replaced my rear spring plates with SAWs, and already had 30mm torsion bars. It was actually pretty simple. I can see where using stock bars and putting back the original spring plates would be a more involved job, with preload etc., and having to be super accurate with the spring plate angle. I didn't replace the trailing arm bushings - yet...

JB

[efhughes3]

Originally Posted by rusnak

Someone else with race setup experience should comment on this. Won't stiffer rear tbars make it even more tail happy?

They would. Part of this whole equation is also ride height and corner-balance.

[kodioneill]

Why are you taking off the control arms?

[GH85Carrera]

Obviously I have not done a corner balance as yet. After I get the rears done I will have the full alignment & corner balance done.

As the car sits right now the front end is a little too low. It has just a garage alignment. The front shocks are new Bilstien HD and the entire rear is stock from 1985 with OEM Boges. The tires on it will get replaced once the alignment is done.

I took it to our autocross just to see how it does. I have been autocrossing for 30 years and I did not push hard. I was not going to push hard enough to go off course. I can't wait to get the rear end done, I just dread the process of doing it.