suspension changes....ADVICE needed

[gopack]

Well here goes.
While I am waiting for the body shop to be ready to take my car, I thought I would start on the suspension upgrades. I have 911 struts and hubs and calipers and rotors for the front end, so I thought i woudl start there. I guess I should replace the ball joints, and the A arm bushings as a matter of course. I am also thinking about upgrading the torsion bar, and want to know which size is appropriate for spirited weekend mountain driving? (who knows I might look into auto X in the future). I am also looking at fitting sway bars in the front. Again the question is which diameter is best (objective question i know , but i want opinions)?
Also I read all sorts of problems with noisy bushings when the poly ones are used, but it seems the popular opinion on the needle bearing is that they are racing only. Is this becaouse of lack of compliance? Also , what abbout where the strut mounts to the top of the inner fender? new strut bearings? i see the monoball shock mount, but again this seems to be a pure racing part.

One last question> My car is a 72, but has the u brackets attached to the A arms.... i thought this was only on the later cars?

Just so everyone knows, this is a '72 that the PO has installed a 2.0 liter with dellortos. no suspension changes that i can tell.

Here are some pics of it currently:http://f2.pg.photos.yahoo.com/ph/marktw31/album?.dir=/e3dd&.src=ph&store=&prodid=&.done=http%3a//f2.pg.photos.yahoo.com/ph/marktw31/my_photos

any advice is appreciated, before I order all the pieces from PP. (why don't I ever have a 10% off Email cupon when I need to order!?)

I also want to plan appropriatly for the future upgrades in back when I do the front, so the car stays balanced and fun.

SORRY for asking so many questions in one post!

thanks
MARK

[Dave at Pelican Parts]

The key to suspension setup is to achieve a balance. You don't want the front end too much stiffer than the rear, or you'll get terminal understeer and the car won't turn. You don't want the car much stiffer at the rear end than the front, or the car will oversteer like crazy and you'll always be chasing the tail end.

A stock front sway bar, stock torsion bars, and stock or 100 lb/in rear springs makes for a pretty well balanced, good handling car that is very civil (for a 914) on the streets.

Using stock torsion bars, 140 lb/in rear springs, and a 19mm front sway bar (adjustable is nice!) makes for a car that rides somewhat hard, but is still streetable and handles more predictably at the limit.

You can go stiffer, but the ride will get harder and harder. You can upgrade the front torsion bars to give the car the front roll stiffness instead of a large front sway bar. (In which case, remember that the spring rate of a torsion bar goes up with the fourth power of the diameter!)

I have heard that the roller-bearing setup is OK for the street, but a lack of DOT testing forces the manufacturer to label it "racing only". I would think, but don't know for a fact, that there would be more noise/vibration/harshness transmitted into the car with them. Ditto the monoball upper strut mounts.

...Frankly, I'm not sure what to recommend with the bushings...

--DD

[914GT]

Yeah, you always get the discount AFTER you make an order, then good for maybe two weeks. How convenient...

[Dave at Pelican Parts]

Well, that's the point... To get you to order again. It can help with things you found you forgot, though.

--DD

[Robert Gwinn]

I am also upgrading my front suspension. I need help choosing which poly bushings to use for the A-arms; street or race compound? Is the difference noticable? Are they both equally squeaky? I've also read about using a dremel tool to put a groove in them to retain some of the special grease. Is the groove on the inside, outside, or both?

Current set-up is stock springs & torsion bars, old bilsteins in rear (front unknown), factory front 19mm sway bar, and no rear bar. I have some 21mm torsion bars available. What changes would be needed to balance using them? My goal is a strong auto-x car that's tolerable on the street. Opinions are appreciated.

Thanks, --Rob

[ss6]

If you aren't ready for the roller bearing approach, take a look at the poly/bronze bushings from Elephant Racing (& Tarett Engrg, & ???). I used them to replace stock rubber bushings recently, one DE on the clock, and they are great. Built in grease fittings, no perceivable "stiction", and at least a little bit of polyurethane to keep your teeth from rattling. No noticeable change in road noise, though my suspension is quite stiff to begin with. Wish they had something for the 914 trailing arm, had to go with delrin bushings back there.

[mike_the_man]

I have no personal experience, but I've heard from many people in the know that roller bearings are the way to go, if you can afford them. They say that the car rides better, with no more vibration then rubber bearing, but makes the cars handling mich tighter, because of less deflection.

Mike Mueller over on 914club.com makes roller bearings that are supposd to be of very high quality. If I could afford them, I'd would definately buy them. Check out 914club and ask a few question over there.

[Dave at Pelican Parts]

Originally posted by Robert Gwinn
... I've also read about using a dremel tool to put a groove in them to retain some of the special grease. Is the groove on the inside, outside, or both?

Wherever there will be movement.

Current set-up is stock springs & torsion bars, old bilsteins in rear (front unknown), factory front 19mm sway bar, and no rear bar. I have some 21mm torsion bars available. What changes would be needed to balance using them? My goal is a strong auto-x car that's tolerable on the street.

Stock front sway bar is 15mm, the 19mm ones are aftermarket and usually adjustable.

21mm torsion bars are almost twice as stiff as the stock 17.9mm bars. So with the rest of the suspension being stock, you would want something on the order of 180-200 lb/in springs to keep things relatively balanced. You would still have to tweak things, of course, to get the final balance set. My own feeling is that this is hard, but not intolerable for the street. I would definitely consider a 19mm adjustable anti-roll bar in front with that setup.


...Oh, and you can check Mike's stuff out at http://www.muellerdesignwerks.com .

--DD

[gopack]

I have to ay that i am kind of scared of the adjustable anti rollbar! isnt it ahrd to get set up right? what are the consquenses of different setting on each side , etc. also how deos the sadjustment alter teh ahndling... i knwo that this is a complicatedx issue, that is why i am a little scared. also how about read anti roll bars?

[silver2.0]

Just my 2 cents, but thought I would chime in from previous experience on a 240sx nissan. I wanted to make a killer Auto X, so I upgraded the suspension, and put needle bearings in it also. Big mistake for the street. Go with poly. It is plenty stiff for the street, and it won't jar your brains out. If you want a full race car I would say, don't use anything but needle bearings, because they are far superior on smooth roads, but the first time you hit a pot hole, it will knock your fillings out of your teeth.

[DDS]

FWIW:
I run urethane bushings with grease zerks dremel-ed on the inside. I don't find it harsh or noisy. I used the entire 911 suspension setub so I could run the slightly thicker 911 torsion bars, and have the option of 911 bars as an upgrade. I don't see why you'd want much heavier ones on the street. I do have an adjustable front swaybar, a rear bar, 140 lb rear springs and limited slip and the car is quite comfortable on the street (till you hit a pothole) yet still pulls wild g's in the corners with very little roll. (I have 245's on each corner also) The traction is amazing!
I haven't really flogged a 914 with narrower tires, but would bet that all that fancy stuff like roller bearings and camber plates wouldn't be worthwhile for the street. If its anything like my car, a more supportive seat and a 4 or 5 point harness would be a better investment. Don't go nuts on it till later!

Dave

[Dave at Pelican Parts]

Originally posted by gopack
I have to ay that i am kind of scared of the adjustable anti rollbar! isnt it ahrd to get set up right? what are the consquenses of different setting on each side , etc. also how deos the sadjustment alter teh ahndling... i knwo that this is a complicatedx issue, that is why i am a little scared. also how about read anti roll bars?

Adjusting the sway bar will make it stiffer or softer. A stiffer front bar will make the tail of the car stick better; a softer front bar will make the front of the car stick better. (Yes, it sounds backwards, doesn't it?) That's pretty much the only effect. Having different settings on each side will effectively give you the average stiffness between the two settings.


The rear bars are usually not recommended, particularly for cars without limited-slip differentials. They can cause the inside rear wheel to lift, which means you lose all acceleration and you can spin. They can also "bottom out" on the rear trunk floor if the car is lowered, which leads to instant oversteer.

Rear roll stiffness can come from stiffer rear springs. It's not the same as a rear sway bar, but it can work pretty well.

--DD

[Alfred1]

Originally posted by ss6
Wish they had something for the 914 trailing arm, had to go with delrin bushings back there.

I would like something similar to the stock bushings for the trailing arms so for the engineers out there that want to know what products they can make for the 914 this might be an idea ...

[Robert Gwinn]

I plan on installing polyurethane bushings on the A-arms. How much difference is there between "street compound" and "race compound"? I realize it's impossible to answer this type of question, but i'm still interested in anyone's experiences or comments.

--Rob

[DDS]

Originally posted by Dave at Pelican Parts

The rear bars are usually not recommended, particularly for cars without limited-slip differentials.
--DD

I've heard that too. Mine has a LSD, and I cannot break the rear free on clean pavement. I can make it twitch if I try really hard. Never tried it with the bar disconnected.

[sean_V8_914]

Porsche never raced a 914 with a rear swaay bar. nobody at the track has a sway bar on teh rear of teh 914. Steve Dente's (ESPN, Speed channel, Daytona) 914 does not have a swaay bar in teh rear. my v8 car tail wagged like maad till I dis-connected it. I have a rear sway bar for sale.

[sean_V8_914]

with the balls on teh shock bolts...

[Dave at Pelican Parts]

Originally posted by sean_V8_914
nobody at the track has a sway bar on teh rear of teh 914.

Not actually true. While many or most do not, I know a number of 914 race cars that do have rear sway bars. Some are the same style as the factory, some are a different type that does not bottom out as easily. Just about all of the ones who have the rear bar do have a limited-slip diff. Usually the rear bar, if present, is significantly smaller than the front bar.

Which is backwards from the stock sway bar setup, which is 15mm front and 16mm rear... However, the stock setup works well for a stock car. I preferred the way my then-bone-stock car handled with the rear bar to the way it did with the rear bar disconnected. (Of course, now that I've upgraded the suspension the rear bar is gone.)

--DD

[AJS]

Originally posted by silver2.0
Just my 2 cents, but thought I would chime in from previous experience on a 240sx nissan. I wanted to make a killer Auto X, so I upgraded the suspension, and put needle bearings in it also. Big mistake for the street. Go with poly. It is plenty stiff for the street, and it won't jar your brains out. If you want a full race car I would say, don't use anything but needle bearings, because they are far superior on smooth roads, but the first time you hit a pot hole, it will knock your fillings out of your teeth.

My experience is the same, though with Delrin bushings. Completely unreasonable for the street (a Corvette was one glaring example........made for a absolutely miserable street car). When I asked about replacing bushings on my 914, many said go with the needle bearings, they're sweet. Well, I don't know what "sweet" means, but if it's anything like Delrin, no thanks! Race cars or cars trying to mimic a race vehicle belong on the track, IMO. Been through lots of stiff cars, and found a well tuned suspension with reasonable spring/shocks/bars was much nicer to drive.

Andy

[sean_V8_914]

...and what percentage of 914s have LSD? so im wrong because the 2 cars in X class have rear sway bars? am I wrong about Porsche factory cars to? did any of those run a a rear bar on teh track?