How To Corner Balance a 914, Need some help... Options

[Joseph Mills]

I will be renting a corner balancing "facility" (shop, scales, and a guy that oversees the scales) for my 914. They have no experience with 914s and you perform you own adjustments.

My car has an early 911 front end (19mm torsion bars?) 22mm Weltmiester swaybar with 250# rear springs on adjustable collars (no rear bar). Camber, caster, & toe has been set.

Since the facility is rented by the hour, I want to be well prepared and understand the step by step process.

Where do I start?

[Jeroen]

QUOTE (joseph222 @ Feb 13 2005, 02:18 AM)

Camber, caster, & toe has been set.

Too bad, 'cause that's back-ass-wards. Corner balance first, align after
The changes in ride height will affect your alignment...

First set the approx ride height you want (you could do this before you go to the shop to save time/money)
Raising a corner height will take weight off that corner (and add weight to the corner diagonally across of it)
Sit in the car while measuring weights (or put something of your weight in the driverseat). Most measure a 1/2 tank of gas
Between adjustments/measurements, bounce the car to settle the suspension

I'm not 100% sure on the front/rear weight distribution to aim for. I think it's 48% front and 52% rear
Left/right should be 50/50
Get as close as you can...

[IronHillRestorations]

If you change the ride height you will need to have the car re-aligned.

Disconnect the sway bars for ride height and corner balancing.

Ballast the car with your weight in the driver's seat, and at least 1/2 tank of fuel.

Set the ride height first. You can check the factory or a aftermarket service manual for the stock settings, but that is on the high side. You probably want the front ride height at about 105mm or more. This is about 15mm lower than the factory setting. You measure the center of the wheel and the center of the torsion spring, and the difference is the ride height. The higher the number the lower the car. If it's a street car and ride quality is important, don't go too low. You want at at least 1/4" minimum rake (front lower than rear), you can measure at the rocker panels. You can go more, but 1/4" is minimum.

You really can't get perfect equal distribution on the four corners of a 914, so you wan to get it as close as possible without loosing rake and ride height. Shoot for getting equal side to side weights by adjusting the front torsion springs, and rear perches.

250lb springs are really hard for a street car, and you may have a hard time getting a good feel with good balance. Why is the car sprung so hard in the rear?

If you have sway bars with adjustable drop links you can fine tune, the balance by tweaking the drop links, but that's a little tricky cause the bar tries to balance the car side to side (that's why you got it right?).

You will have to get a good four wheel alignment after you are done, by someone who knows Porsches. Porsches are a little different in that once you jack them up the suspension reacts differently than if you drive it around the block to jounce and bounce the suspension. Most alignment shops will think you are screwy if you tell them this, unless they are familiar with sports car suspensions.

Good luck!

[Joe Bob]

Yup....balance first, align after......weight in the front seat, 3/4 tank of gas....

[Joseph Mills]

Thanks guys. (IMG:http://www.914world.com/bbs2/html/emoticons/beer.gif)


The alignment is over a year old (by Porsche shop). It has a pretty aggressive alignment and suspension setup for AX - car doesn't see a lot of street use. I will plan on having alignment confirmed and adjusted later.

The ride height and rake is set (A-arms are parallel to ground), front doughnuts are about 4.25" to ground - rear doughnuts are 3/8" higher. These are the figures on the spec sheet they provided and I confirmed them with my own measurements.

The 250# springs (in combination with the 22mm F bar), provide very good rotation thru slow speed AX turns ( -50mph).

What's the target weight difference L to R to strive for that's reasonable? 10, 20, 30 lbs?

I run 4 gallons of gas at AX, so was planning on that amount for the settings.

Still not clear on making height adjustments. Should I jack up the car a bit to lift some weight off the particular wheel being adjusted? Somewhat concerned about stressing or stripping the adjusting bolt on the front A-arm or thread on the rear collar - or is this nothing to worry about?

Should I bounce the car between adjustments, or not? Drive around the block?

Think I can do all this in two hours? (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

[Sammy]

Do not get all caught up in trying to make the left weights the same as the right. It doan work that way and will drive you nuts unmless you start physically moving parts around to chage weight distribution. Sure you want to get it as close as possible, but it will never be completely even and it is dependant on ther other end of the car how close you will get.
What you should try and do is to make the difference in the front (percentage) equal to the percentage of difference in the back in the same direction.


In other words:
suppose the left front is 20 pounds heavier than the right front and that works out to be 5% (just makin up number here) and that's as close as you can get it without upsetting the balance in the rear and creating cross-corner rocker.

ideally, you would shoot for having the left rear 5% heavier than the right rear to be balanced to the front.

[KenH]

check this link

http://www.nsxprime.com/FAQ/Performance/co...rnerbalance.htm

I found all I had to do was make a small adjustment to the front ride height adjuster to bring mine in balance.

Be sure the tire pressures are equal.

Remember you only adjust the corner-to-corner balance.

Ken

[914efi]

This is my poor man's corner balancing tool. Just put a piece of paper under the wheel being tested, and when it just lifts off the ground, note the reading on the pressure guage. I have found that to get get consistant readings that you need to take the reading while the jack is being pumped. This eliminates a sort of hysteresis as the jack settles. I took my car to the scales after doing it with this and it was good. I originally designed this for use with narrow fuchs, but it works with other wheels with a bit of fooling around. You could build it for any rim, or use the center hoile as I did. total cost, about $30.00.

[Joseph Mills]

Thanks for the additional opinions and insight.

I'm starting to have a pretty good overview. The article from that link puts it in pretty simple terms. Even makes sense to me. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

914efi: great idea - did you tap the hole for the gage?

No one has addressed whether the weight needs to be lifted for an adjustment. Should I jack up the car a bit to lift some weight off the particular wheel being adjusted? Somewhat concerned about stressing or stripping the adjusting bolt on the front A-arm or thread on the rear collar - or is this nothing to worry about?

[Sammy]

Whoa, hold on just a darned minute!
I really, really like that bottle jack idea, but need more details please!

What kind of fixture is that where it goes into the wheel? Does it hook on the wheel or the hub?

How big of a jack is that and how sensitive is it, in other words how much pressure on the gauge translates to how much weight? seems like the smaller the ram the more sensitive the pressure gauge would be.

That is 'zackly what a CSOB like me needs to check corner balance and I will be building one very soon, i just need to pick yer brain a bit so I don't have to re-invent the wheel.
Tanks in advance. You're my new hero.

[Downunderman]

If you can do it while its on the ground its much easier. The torsion bar screws are no problem, but you may have trouble doing the rears with it on the ground.

The trick with corner weighting is to get the ride heights right first, and then juggle the corner weights around without messing up the ride heights too much.

On my 6 the fronts are (in kg multiply by 2.2 for pounds) L 232 R 234 Rears L 287 R 281. The f/r works out about 45:55.

[Joseph Mills]

QUOTE (Howard R @ Feb 13 2005, 01:31 PM)

If you can do it while its on the ground its much easier.  The torsion bar screws are no problem, but you may have trouble doing the rears with it on the ground. The trick with corner weighting is to get the ride heights right first, and then juggle the corner weights around without messing up the ride heights too much..

Thanks Howard. More good info. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

I'm getting ready to do a valve adjustment, so am going to test the rear spring adjustment with it lifted and with full weight on the ground.


I'm with ya sammy - come'on 014efi... more info please. (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif)

[anthony]

Anyone ever use scales like this to corner balance a car?

[KenH]

You can adjust the front without removing any weight. You may be able to change the back but it requires a lot of effort. Too keep turn the collar and keep the threaded sleeve from turning.


Anthony,

I have had good results with the "ruggles" type scales.

Ken

[John]

QUOTE

Anyone ever use scales like this to corner balance a car?

That is similar to mine. I made mine about 15 years ago. The hardest part was to find 4 identical bathroom scales in a store.

I put all four wheels up on them and adjust away.

I found that if I can get both diagonal weights the same the car really acts neutral.


You need to put the car on a LEVEL surface!!!! (an alignment rack should be a level surface)


You can tweak the weights for as long as you can stand it, but at some point you call it quits.

As others have said, the front torsion bar adjusters can be adjusted on the ground/scales. The rear should be raised slightly to do adjusting to protect the threaded collars/nuts. Just raise the car enough that you can rotate the spring and you should be fine.

Two hours? Well you could get done if you don't want it adjusted down to a gnat's ass.

[Dr Evil]

Looky what I found after being encouraged by ya'll.

A whole set for $239 shipped
http://cgi.ebay.com/ebaymotors/ws/eBayISAP...ssPageName=WDVW

Check out his ME link. Sounds like a nice guy.

[SteveSr]

QUOTE (Sammy @ Feb 13 2005, 11:26 AM)

Whoa, hold on just a darned minute! I really, really like that bottle jack idea, but need more details please!

Sam,

I am interested in this too,so I talked to an engineer here at work about this and it is just like you said. If you were to build one that works well, you would want to use a "smallish" hydraulic cylinder with a gauge that has a wide range so with just a little change on the opposite corner you could see a differance. The number on the gauge doesn't "mean" anything,the idea would be to get the corners as close to the same number as you can.......Very cool indeed!!! (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/aktion035.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)

SteveSr

[Joe Bob]

Bottle Jack....

Hmmm, sure he's not refering to a "Bottle of JacK"? Like Jack Daniels.....


BTW....best to roll the car off the scales and drive it to settle it...then re-weigh it....see if it changed a bit....

[URY914]

When my car was weighed yesterday w/o driver this is what I have:

LF=303
RF=261
LR=403
RR=348

This gives me 42% front and 57% rear. 1% lost? (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)

[Eric_Shea]

Paul,

With a driver, aren't your left numbers going to go even higher? Or... did you have weight in the seat? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)