Torsion bars and lowering theory/method help
 

I have a stock 76 S still at the original ride hight PO never lowered it to E-Spec like most people have at this point. I need to replace the rear Spring plate bushings so I figr' its time to lower it to E_spec (25.5" Maybe?). anyhow, What is the theory to calculate how many teeth I need to move the T Bars when lowering it. I am sure there is a method that works very well, Any input from lowering pros?
As I understand it it should be level across the rockers front to rear but I am still not sure of measurement specs.

Front is a piece of pie I see..

Thanks
Chris

Rear Torsion Bar Adjustments.....
 

Chris,

You need a good protractor (angle finder) to do this adjustment and minimize the trial and error procedure. As you are aware, the car's door sill should be near to horizontal. Measure this angle and the spring plate angle. It would also help if you know the sprung and unsprung angles of the swing plates as your reference.

The rear torsion bar has 40 inside/44 outside splines and each spline corresponds to 9 deg./8.18 deg. So if you move the inside spline setting one notch, the effect is a 9 deg. change (keeping the outside setting as is). However, if you move the outside spline setting one notch (opposite direction) the effect is less than one (1) degree. This how you get the smaller increments less than 8 deg.

Having an adjustable swing plate makes the work a lot easier. Hope this will help.

TD

I have found do and die method....one up and on dwn. Reweigh and re measure. The protractor will tell you the angle but the corner weight will be what tells you to do next...no mater what the angle is.
I would go get adj. spring plates and make life a bunch ezr

Do a search for springplate angle calculator. It will work like a charm.

SHould have mentioned I have a friend with the protractor.

Adj Springplates? How much and from who. Used?

Chris

all I know is the protractor will give you the angle..you will have to do a corner weight and then re adjust, mabe I am missing some thing here but I do not See how a protractor will help

I use this $10-20 hardware store unit.





http://forums.pelicanparts.com/uploa...1157162333.jpg

OK call me DUmb, What is corner weight-ing? Those in the "know" give me the definition... It sounds cool but what the hang does it REALLY mean?
Afterburn?
bueller?
anybody?

There is a specification for corner weighting the car. Here is some interesting reading: Corner Balance Discussion
Pat

Wow..lets see in simple terms, AND this is more important then most give credit too.....corner weight : separate weight of all four wheels with car level , you actually can "jack" the car so one wheel carries a lot more weight intentionally or by mistake...for the street you want a 60/40 ratio rear hvy of course.
so as you set the ride ht you are also setting you corner weight. (diagonals too) sounds all complicated but after some research you will see its just a little math. For simple terms lets say you car weighs 2000 lbs. You want the front to Carry 40% and rear 60 % ea rear wheel would Carry 1/2 of the 60.....so that would be 1200 on the rear (600lbs per wheel) and 800 for the front (400 per wheel) this help ? ( hope I did my math right too many beers)

The way I do it is with bath room scales, 4 lined up under each rear tire with a 2x6 across them to carry the whole load and add them all togather , and 3 under each front tire - same way 2x6 across them and add again.
( most bath room scales only go to 250 lbs so you need a bunch ..but they are a lot cheaper then paying someone to do it for you.
Now some may argue in favor on nuclear or digital....what ever...I ant going there,- + or - a couple of oz is never going to mater....even 10 lbs if you want to say they could be that far off....but they will not be

OK I have use of a friends scales he uses for his short track stock car so that problem is taken care of. I guess I never put 2+2 together to fig'r out what they were doing. I asked and low and behold that is is what they are doing. so Coool.
But I still have one more question. Does anyone have optimum (street not Pimp!) ride hight for a narrow body car? I am running 15X6s with 205/60s front and 15X7s with 215/60s rear Factory Konis and T-Bars.

One more thing. How much Fuel should I have in the car? Does it matter, or is the idea that weight distribution will always be the same in all 4 corners no matter what is in the tank ?

TIA
Chris

Try 24" rear & 24 1/2 " front for a nice (but low) street height. When checking your changes, be sure to roll the car back & forth a few times to be sure it settles into your height as it will sit a little high after being set back down on the ground. Also, if you are replacing bushings, allow a little fudge toward the high side as it will probably settle a bit the first time you drive it.

Matt

I raised mine which is still bellow the Euro ride hight. The previous owner lowered it too much and the car handled like a lumber truck(bad bumpsteer). It really helps to use the scales. And after you've lowered and corner balanced it it might be a good idea to take your car too a Porsche shop w/ the knowledge and eguip. to 4 wheel align your car.

Its definatelly worth the time and money to do the job right. You'll feel the difference.

Gary

Here we go again.
You cannot just wack it down.
If you go too low, the rubber stops (Snubbers) in the shocks will bottom out.
You will also get bump-steer.
You will also need an new alignment.
First thing is to check the condition of all the bushings and shocks.
Then comes the lowering (I suggest 25" front/24.5" rear)
Make sure you understand the 40/44-spline principle before you start.
Go to the Tech section on PP and read, read.
If you don't have the bump-steer kit, get it and install under the rack.
Still have the old tie rods? Get the 930-tie rods.
Do more searches on this, lot's of info here at PP.

SO Gunter, excuse my uneducated P knowlege, what is the advantage of the 930 tie rods? and how will I know if I am too low? I only expect I will goto E-spec or maybe to the height you suggested no lower,
what is the advantage/idea of Z Bump steer?

Chris

Search Wil Ferch on this site and you should get a great article on the whole procedure.

http://www.rennlight.com/cgi-bin/spring.cgi

This is the link to Wils method.

Thanks Hoss!! That is super. Everyone should see this.

Assuming he has his calculations right, I'll follow that as a guide.

Cheers
Chris

It worked to a "T" on my "T"!!! Sorry that's lame.

Afterburn:
Are the 2*6's one length for the back and one length for the front or do you use 4 pieces of 2*6, one for each tire indepedently? I would like to try your method! Also I assume you get all (all 14!) scales setup first and then drive your car onto all the scale "sets" at once?

4 pc- you just use them to bridge the scales togather..you could use some other material...but 2x6 is handy....to get real fussy you would have to subtract the weight of what ever you use for the bridge (LOL)

Back to the weight distribution thing....

Weight distribution should be calculated with how much fuel?
60/40 rear to front with how much fuel?

I assume it is with an empty tank that way it will be the actual car weight not weight with a fluctuating component!
am I just splitting hairs?
does Anyone know how much fuel weighs per gallon? is the "pints a pound" rule applicable with fuel or is the specific gravity of 89 octane much different than H2O???
20Gallons of fuel = ?lbs
1pt=1lb
1gal=8pints
1gal=8lbs
20gal=160lbs
yeah maybe I am splitting hairs!
I have a pint right now and it surely doesnt weigh a pound anymore!!
I might have another pound or 2 before I finish this thread if I dont stop.
But seriously, if you have any answers to my questions please let me know.
Cheers
Chris

Weigh it as you would use it, unless you use it with an empty tank. Fuel is abot 6.5lb/gallon. Get the car alaigned AND corner balanced together, save yourself some headaches.
Pat

Basic...repeat .....basic corner weighting procedures call for absolutely level scales. Use vinyl floor tiles to shim. Set the air pressure correctly in the tires. How much do you weigh?? Get sacks of sand or weights or something and put in the seat and drivers footwell until you have added your weight.
Fill the tank to half way. Thats approx 71.5 lbs, depending on your fuel capacity.

DISCONNECT the sway bars! And honestly, if the sway bars don't have adjustable end links, it's getting into the "why bother" stage.

Point being that the front end of a 911 is one of the best steering/feeling front ends ever, and the actual weights you'll see on each wheel will be very light. At such light weights, mistakes are magnified.

I would seriously consider getting a set of WEVO SPSs for the rear. Needle bearings replace the rubber bushings, which you'll be replacing anyway, and include all new parts, including adjustable spring plates. It makes adjustment a breeze....if your time has any value, it's money well spent in the end.

Once the set up is done, tweak the alignment, and reconnect the adjusted sway bar links.

most use a 1/2 tank of fuel....

There seems to be (at least ! ) two diffrent questions "in-play" here....how to lower and what kind of corner balance target to try for.

Let me state something about corner balance...and try to summarize an epiphany I had... talking to Randy Blaylock and others on a corner balance thread ( see thread).

Because the masses on the car are not concentrically located left-to-right... nor front-to-back......each corner would "ideally" carry a different weight. "Perfect" corner balance would have you get to these 4 different numbers...one unique number for each corner.

However, the apparently best compromise is to target equal front corner weights...not the "ideal" individually-different front corner weights. This would promote equal brake response on heavy braking ( won't have one wheel...the lightly loaded one... lock first). Although this is a compromise setting...and is considered "weight-jacked"...it slightly alters the perfect left-right threshold turining characteristics, but it's a good compromise anyway.

Some people do the corner balance assuming one person on board and some with none or two people. Do it with the most common situation you'll find yourself in. Half a tank of fuel is probably best as it changes the least from your "settings" as you go from full tank to empty.

- Wil

brilliant!
Thanks!-C

Bump steer kit, bump steer kit, bump steer kit.
You'll need it if you're anywhere close to euro spec ht with 15" wheels and if you pass on it now you'll be buying a second round of balance and alignment after you intall it.
Do it now, enjoy it forever. Plus it's cheap!

I used a 1/2 tank and the front varies about a 3/8 inch either way when empty of full.

Consider how much clearance you'll need to drive around town if that's your main use for the car. If your rear suspension has is stock T bars and shocks sure it is stiff enough to not allow the rear wheels to rub the inside of the wells. Mine is stock and sitting at 25.25" and might be able to be dropped to 25 but that would be about it. I'm running 205/60 on 15" wheels on my 74.

Someone out there may have a rule of thumb on how high above the rear wheel the fender lip should be. Someone told me you should be able to slide your hand betweel the top of the tire and the edge of the fender.

Do you have any pics of what it looks like now?

I run 25.5/25 as it's mostly headache free on the hy & street w/205/55/16 x 4. The angle measured on the door sill should be 1deg. I run 21/27 t-bars. Some say that's a bit much for street as it's a little more pounding than stock. I love it. Sway bars can be flipped later to tweak.

Above 80mph with high cross winds are a pia though. The front tow hooks or the pelican hd replacement will get used. SC/Carrera ft spoiler and a rear C-2 or duck etc would help big time. The ft spoiler will take hits sooner or later.

Current ride hight
 

Currently my Car is @ 26.5 (F) 27.5 (R) .
http://forums.pelicanparts.com/uploa...1157462569.jpg http://forums.pelicanparts.com/uploa...1157462586.jpg


Chris

almost looks like it is a "Dakkar" eh?

This has 80k miles on it and has never had any suspension work, it is as it was new.
Actually bought new in Canada. I suspect it is N. America ride hight.

Chris

Chris, It does look a bit high and I would drop it for sure.
What is the measurement to the top of the tires, Front&Rear?

Be sure to have the neg camber put in the rear when you finish. That will help on fender rub since the wheel will rotate slightly more as it moves up into the wheel well during hard cornering or bumps. A good shop will have a recommended spec for Camber and Toe-in for the front and rear alignments, but be sure you have a good idea of what you want/need before hand.

++1on the Adjustable Spring plates, but they cost$$.
Consider front strut braces also. They will help front stiffness and help to retain your front end alignments.
Read up on all these related issues before you start. There are lots of good posts and Tech pages in this web site and BB. Get Waynes book and double your expected time to lower the rear.

Take lots of pics. Don't get frustrated.
Good luck and take you time on the rear.

PS the front is easy.

24" (F) 24.5" (R)

205/60 15 & 215/60 15 respectively

Thoughts on Camber Toe etc, appreciated.

as For the work I will do all but the Alignmenr..

C-

Chris - careful posting pics like that! I did the same thing 6 months ago and STILL haven't lived down the shame of all the 'swamp buggy' and Paris-Dakar comments.

BTW, is that amphibious?

Regards,

Joe

At least I knew it going into that post. I am the first one to admit it looks like a 4X4.. I have only had the car for 9 months and I have been whacking away at it. Motor Rebuild (check), Trans rebuild (check), New rims and tires (check), Backdate Exhaust and oil lines (check), Drive it alot (check). Problem with owning a P car in VT is that I can only drive it for 4 or 5 months out of the year and it rains alot so knock off another month. Gives us Yankees alot of time to do "projects"...

Cheers
Chris

Chris, How do you plan to use it? Track, street, highway, and how much tire wear are you willing to tolerate?
Much Toe-in or Neg Camber and you'll wear out a set of tires pretty fast on the street, but it can pay off on the track. I'm not the one to ask if you're a track or AutoX driver.
For my car I used the specs from the Technical article here on Pelican titled: "911 torsion bar replacement" Front -1 deg camber, 6-7deg caster, 0 toe; Rear -1.5 deg camber, -15' Toe (in).

Search this site for "911 torsion bar replacement".
After reading it Read "101 Projects..." on this topic.
Many of your questions will be answered.

Don't know if anyone mentioned this, but on some of those middle years there is a great big thick hvy spacer that need to be removed from the top of the strut assy so as to center your strut piston in the middle again ( after it is lowered....was a federal thing )

Yeah, I did know that. Apparently the spacers put the car at the same level as the behemouth American cars it was going to hit... like that would do any good. From what I understand most P dealers would take them out during the "NEW CAR PreP", But this guy (original owner)had no Clue... He just wanted a Porshaa, like Tony Montana did...
Part of the reason I bought the car is because it has not been molested. The PO (original purchaser of the vehicle) Wasnt into all this. He was just an average guy that probably never took the thing over 80 MPH, he was very conservative. Only reason I re-built the motor was because it had all the origianl heat sinks and air pump crap on it. we all know how hot they \can get and the HP drain too.

Maybe I should keep the spacers? make ash trays or drink holders out of them....

ANd Cookiecutter, I will be driving on the street maybe a D.E. course here and there...

Cheers
C