Corner balancing

Arctic 3.2 · 12:26 PM

I've just bought new torsion bars for my '86 Carrera, 22mm front and 29mm rear to get it stiffened up a bit. But living way up north in Norway, there are no workshop here able to corner balance the car. A good 4-wheel alignement can be done though, and I think setting the ride height right will be manageable - using the pre-installation height and angles. The car is mostly used for aggressive street driving, and occasionally track driving (1-2 times/year). How critical is the corner balancing? Should I just go ahead installing the torsion bars?

tonythetarga · 12:37 PM

corner balance is kinda critical when you install new t-bars and set the ride height. Particularly when you will do some high speed driving. If you search around here there is a way you can get a reasonable corner balance with 4 bathroom scales. I don't know the procedure but I have seen it here in the past.

edit: found one: Home ride height and corner balance success story

Arctic 3.2 · 05-15-2008, 12:45 PM

Thanks for the reply! Yes, I've also read about the bathroom scale method. But I'm very uncertain how accurate I'll be able to get it balanced this way. On the other side: It'll probably be better than no corner balancing at all? I can also put some effort and several tries to get it better and better, test driving it in between.

911pcars · 05-15-2008, 01:20 PM

Look in the corner balancing or ride height archives under "tripod". This is described in the factory service manual. If the side-to-side ride heights are about the same front and rear, the corner balance should be fairly close.

The key issue is to not allow one end of the car to impact the ride height/weight supported of the other end of the car. You do this by eliminating the influence (lift one end of the car off the ground from the middle). This creates a tripod support. Now it's easy to adjust the two legs (corners). Otherwise the 4 wheels act like a 4-legged bar stool with a shorter or longer leg, but you now have to find it

Sherwood

imcarthur · imcarthur's Garage

Here are 2 threads that are worth a read as Sherwood points out.

* CORNER balanced - numbers from this...and the weight

Corner Balancing, Weight Jacking, Tripod Method

Ian

Peter Bull · Peter Bull's Garage

In my experience, after having checked the corner balance with a set of Intercomp scales; if you use t-bars and you make sure that you get the ride height set right, you will not need to adjust the corner balance.

There are two very important parts of this, the car cannot be twisted or bent because then the measurements will be off, and you have to be careful when setting the ride height so that it is within Porsche's allowed difference from side to side.

Even with somewhat bigger t-bars than stock the suspension is soft enough to make it reasonably easy to measure a difference in height if the corner balance is off.

/Peter

jester911 · jester911's Garage

I upgraded my suspension last winter with 22/30s and Elephant racing bushings. I did all the work myself and got the ride height pretty close. I drove the car a bit on the street afterward and it felt awful until I had it cornerbalanced. The car totally handled like a dream afterward and I have driven on the track twice since then.

IMHO a cornerbalance is a must especially if you are going to the track.

OH and setting the ride height I had the car even heights side to side but after the corner balance they were no longer even. YMMV

Noel · 05-16-2008, 09:42 AM

Quote:

Originally Posted by 911pcars

Look in the corner balancing or ride height archives under "tripod". This is described in the factory service manual. If the side-to-side ride heights are about the same front and rear, the corner balance should be fairly close.

The key issue is to not allow one end of the car to impact the ride height/weight supported of the other end of the car. You do this by eliminating the influence (lift one end of the car off the ground from the middle). This creates a tripod support. Now it's easy to adjust the two legs (corners). Otherwise the 4 wheels act like a 4-legged bar stool with a shorter or longer leg, but you now have to find it

Sherwood

I used the tri-pod method about 4 years ago when I upgraded my suspension. After, I had the car aligned and it drove great. Out of curiousity, I recently had it checked and found that the cross weights were within 20 lbs of each other. I was impressed. The key is to lift the car from exactly the center and be on level ground. Good luck.

Arctic 3.2 · 05-16-2008, 12:11 PM

After reading about alignment and corner balancing for hours now, I think I'll go for the "tripod" method. Seems like that could be adequate for my use - especially if I can get a good feel with the car afterwards.

Thank you all!

911st · 05-16-2008, 05:32 PM

I suspect:

First, good corner ballance and allianment helps in braking. If the suspention is preloaded, then under a high G stop, one or two wheels may lock up faster.

In a corner, good weight ballance, icluding provision for the drivers weight, should make the car's dynamics in the corners closer to the same side to side. Compaired to being say being tail happy turning left, and not so much turning right.

Alignment effects how the car tracks at speed and how quick it wants to turn (toe in/out, front & rear). Also, effects how well the tire contacts the road surface (camber) in a corner and under braking (trading one off for the other).

I suspect the alignment and corner ballance needs to be done togeather as they effect each other and it is a rare shop that is able to do so on a 911, and few that are good at it.

For example, adding neg camber lowers the car, especially in the back. So if you took it for a corner ballance, and then take it for an alignment, your ballance will be off. And vise-versa.

Having adjustable rear spring plates and adjustable sway bar drop links is very helpfull.

I wonder aboutthe front sway bar's influance on a 3.2 Carrera. The way it is installed, it is difficult to get this out of the equation to the point that using a tripod method may not even come close. I have not checked yet but I hope we can loosen it up on the main body of the sway bar. Then we migh get close.

I have used what I will call the tripod method on a couple of cars by jacking the car up under the motor for the front, and under the center of the front, for the rear. When doing, the sway bars must be disconected.

I tested the effect of my siting in the car on my stock suspention 85 Carrera.

The driver side droped 10/16's and the passager dropped 5/16's.

The sway bars can transfer a lot of load from one side to the other. I suspect if the sways were not hooked up, the differance would have been more significant.

I would try for a 1/2" differance for a 200-230 lb driver on a stock Carrer w/o sway hooked up. 1/4" with 22/29 or 22/28's which are about 100% stiffer, not counting the sway bars.

This is so the car is balanced with the driver in it.

My car is up on jack stands as I wright this so I have been thinkin a bunch about it.

Just my $.02...

Todd Simpson · 05-16-2008, 07:21 PM

Make your own corner balance scales?

In the above thread you will see the "deco weight checker" listed and where to buy it.

$150 is the cost and it is one of the cheaper/easier ways to corner balance.

Zacko · 05-17-2008, 12:38 AM

Quote:

Originally Posted by Arctic 3.2

After reading about alignment and corner balancing for hours now, I think I'll go for the "tripod" method. Seems like that could be adequate for my use - especially if I can get a good feel with the car afterwards.

Thank you all!

I also used the "tripod" method and had the weight checked when the car was in for alignment. The cross weights were within 25 lbs of each other and guy at shop was impressed.

Good luck "neighbor"

/Hans
911 3.0 SC -79