Can someone school me about ride height and corner balancing?

[kyngfish]

I just finished doing an entire suspension refresh. All the rubber came out. New dampers. Sway away Torsion bars. I dialed them in reasonably well. When the car came down al four corners were within an inch of my goal ride height. Now it’s time for the alignment and corner balance. And I have a question. Why is using scales a necessity for a corner balance. Wouldn’t a car where all four corners were sitting at the correct height and aligned be corner balanced?

Just trying to understand why I need to spend 400+ vs. 200 ish.

[ian c2]

All at the same height isn’t balanced , it’s just all corners at the same hieght . Lol
The oil tank on the right will obviously put more weight on the paasenger rear wheel , a battery On the left Will Obviously put weight on the front drivers side wheel .
Corner balancing will adjust ride hieght on each wheel to balance out these differences.
If you’re track only , it will be balanced with driver in place , and a decision will be made on what fuel level to balance at .
Bear in mind rake will also effect handling , and front/rear balance .
So discuss with your shop what your goals are and they’ll set hieght and rake , then balance to suit .

[Jonny042]

Think of a 4 legged table sitting on a mattress. If all 4 legs are the same length, it will sit perfectly level.

Cut exactly 1" off two diagonally opposed corners, and it will still sit level, but the weight bearing down on each leg will be dramatically different.

And then the table will suffer from oversteer in one direction and understeer in another, plus feel really wierd over bumps.

[Mahler9th]

In my experience, for the majority of stock street cars and street car driving applications, corner balancing with scales is not necessary.

If you set the car up with ride heights in spec, the factory design parameters are just fine.

Even at lower-than-factory ride height specs, corner balancing is likely not going to change the way most drivers perceive handling for most types of street driving... even spirited/fun driving on windy roads.

I have been doing my own set up for 25+ years with a variety of Porsches and other cars, and I have helped many friends. I have leveling platforms, scales, and the ability to measure with high accuracy and precision. But my application is performance driving and racing.

Years ago I had a stock 993 cab. I lowered the suspension by installing aftermarket springs and factory US M030 shocks. I did not do that alignment myself-- I had it done by a dealer tech who is a fellow racer and has served on and/or run the PCA tech committee for a long time. The result was a great handling street car-- better than at factory ride height.

We did not need to corner balance the car-- for street driving it just would not make any difference.

[kyngfish]

Originally Posted by Jonny042

Think of a 4 legged table sitting on a mattress. If all 4 legs are the same length, it will sit perfectly level.

Cut exactly 1" off two diagonally opposed corners, and it will still sit level, but the weight bearing down on each leg will be dramatically different.

And then the table will suffer from oversteer in one direction and understeer in another, plus feel really wierd over bumps.

I appreciate everyone taking the time to respond so please don't take this as me being critical. I am very much trying to understand.

In your analogy the table would have springs exerting force to keep the legs on the floor, and those springs would be roughly equal strength at the corner pairs (parallel corners where one set of corners is the "Front" and one is the "Back". If opposite corners (one front corner and one back corner) were shortened by an inch then the greater force of one of the spring sets would push the lower force area downward and the height across the parallel corners would not be level.

In order for the car to be level, there necessarily HAS to be the same amount of weight pushing down at each parallel corner. That's why corner balancing is done with weights in the passenger seat.

[Bill Verburg]

In a car where the front springs and rear springs are different the masses are mostly symmetric side to side but the driver isn't andd the masses fore/aft are wildly different

Sheet medal isn't the best metric to judge weigh distribution, it can be bent, warped, hung differently etc.

Like a boxer a car wants weight evenly distributed on all it's supports, I agree that for street use this isn't critical but if one is into it it is worth setting the car up right, the dynamic behavior depends on on the corner weights not the corner heights

You want to set the car up so that the diagonal sums are at least close to each other

for instance if the corners are
504 542
780 820
that at first glance looks bad, but the diagonal sums are
LF+RR=1324 and RF+LR = 1322 which is great

An issue is hat when the corner weights are right the corner heights are likely to be off a bit, some cars more so than on others, many choose to split the difference for stret use so that the car looks better, not all cars are this way

[Mahler9th]

"In order for the car to be level, there necessarily HAS to be the same amount of weight pushing down at each parallel corner. That's why corner balancing is done with weights in the passenger seat. "

No, that is not correct. We put a nominal driver's weight in the car because we want to set up the car in as close to an "as driven" configuration as possible. This is almost never done on a stock street car for street driving applications. A 200 pound driver in many modern street cars does not change the ride height enough to make any difference in CB or alignment settings that would in turn affect handling.

I think you have a ways to go in terms of understanding this.

For a couple of decades I have recommended the age old Fred Puhn book "How to Make Your Car Handle." I have even given a few copies away as gifts.

It explains all of this very well and has lots of other helpful information.

There are also likely other threads in these and other Forums in which experienced folks with knowledge have taken the time to explain the benefits of CB, processes and methods.

If one were trying to decide between paying someone for a good alignment or for a good alignment and CB, and the difference was say $100... and the application was street driving, I'd suggest eschewing the CB and spending the money on some performance driving event (AX or track). That could help one understand handling and opportunities for improvement.

I still remember my first performance driving event... bone stock 944 with <20k miles at Lime Rock in 1988 with PCA. No AX or karting before that event. I had read about understeer.

I experienced it at Big Bend on my first lap. I did not care about understeer in street driving. But I cared a lot about it in AX and track driving.

[Mahler9th]

And by the way, the car on the cover of the Puhn book is a Porsche 935... with local roots and connections to my current race car. And to Apple computer. And to Paul Newman.

The world is small.

[ClickClickBoom]

Originally Posted by Mahler9th

In my experience, for the majority of stock street cars and street car driving applications, corner balancing with scales is not necessary.

If you set the car up with ride heights in spec, the factory design parameters are just fine.

Even at lower-than-factory ride height specs, corner balancing is likely not going to change the way most drivers perceive handling for most types of street driving... even spirited/fun driving on windy roads.

I have been doing my own set up for 25+ years with a variety of Porsches and other cars, and I have helped many friends. I have leveling platforms, scales, and the ability to measure with high accuracy and precision. But my application is performance driving and racing.

Years ago I had a stock 993 cab. I lowered the suspension by installing aftermarket springs and factory US M030 shocks. I did not do that alignment myself-- I had it done by a dealer tech who is a fellow racer and has served on and/or run the PCA tech committee for a long time. The result was a great handling street car-- better than at factory ride height.

We did not need to corner balance the car-- for street driving it just would not make any difference.

Caution,
Corner balance is critical for proper braking and cornering as well as overhaul handling.
When I got my car from the previous owner all corners were within 1/4” height. The braking was horrible at anything greater than slow driving speeds, go faster and the car would pull all over the road depending on braking intensity. At high effort braking, it was scary, one front wheel would lock prematurely, and the car was squirrelly. I aligned it with strings and corner balanced it with scales and it became a pure delight to drive from parking lots to the limits of adhesion. Now with the new suspension it will threshold brake from 60mph to 0mph hands off.
Some pagers from FSM Group 44:

[patkeefe]

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

[GH85Carrera]

I did a total suspension refresh, and the standard upgrades. New torsion bars, all new rubber, Turbo t-rods, new ball joints and Bilstien HD shocks. The car needed an alignment front and rear after all that. I wanted it at the "Euro" ride height, and I borrowed a friend's corner balance scales. I had a tech at the local dealership that is 40 years as factory trained tech. He let me watch and "help" with any help I could. Just a small change on one corner will make a change to the other three corners weight and ride height. It is just like a giant scale beam balance. Change one thing and the other end is affected.

In the end it did make a big difference in braking and overall handing. If you only drive on the street in a conservative manner, it is unnecessary. If you like spirited driving and curvy roads, and autocross or a track day, it makes a difference.

[dannobee]

Back to basics here, guys. He said that he refreshed the suspension. If that included R&R torsion bars, there's a chance that they weren't clocked correctly. You could adjust the ride height to make the car's stance "look right," but that doesn't tell the whole story.

There's a reason why we "scale" race cars. And as pointed out above, the corner balance could be off and affect braking and handling. And make sure that your floor is level before hand.

Getting left side or rear weight to move requires physically moving weight around the car, but if a spring or torsion bar is off, it will show up in the cross weight (LF and RR heavier or lighter than RF and LR). If you want to do it right, you'll need to temporarily disconnect the front and rear sway bars by unbolting one end link from each sway bar to avoid any binding of the bar, then rolling the car back and forth to settle the suspension. The final operation would be to reinstall the end link bolts, with said bolts easily going back into position (i.e., NO hammering, binding, or spinning in with an impact gun).

If there's a few percentage points of cross weight (AKA "wedge") in the car, it'll handle better in one direction than the other. If you're racing, you can use this to your advantage. If it's a street car, it would likely be better to avoid much cross weight in order to make the handling more predictable.

[Mahler9th]

Again, I have been doing my own set up work, including alignment and CB since the 90's.

More experience than most DIY folks. My application has been racing.

I have never bothered to CB a car with TB's... thankfully I have never had to do this.

There is a reason that CB is not a typical process for trailing arm 911 cars that are stock and 99-100% street driven.

An achievement of ride height "within an inch of specs" does not seem appropriately rigorous.

Of course when I measure ride height, I measure to 1/16 of an inch or so. But my car has coilovers so those changes are easy.

My car weighs only about 1900 pounds and the weight is pretty easy to manipulate and dial in.

[RWebb]

Click2Boom1 - substitute overall for overhaul above

overhaul handling is an interesting concept tho

[911pcars]

Front and rear corners have an affect on all corners. To isolate, jack up one end and see what happens.

The factory repair manual describes a ”tripod method” to determine if each end is affected by the other. This requires lifting one end from a center location so only two front or two rear wheels are on the ground, thus the tripod support.

As Dannobee suggests, disconnect the sway bar end to make each corner totally independent. At this point. Measure and/or compare the ride height of the two corners on the ground, then adjust accordingly. The fronts are easy. The torsion bar rears not as much. Repeat for the opposite end.

Installing adjustable sway bar down links ensures there’s no/little/minimal weight jacking to affect ride height.

Sherwood

[chrismorse]

I’ve got adjustable drop links on the rear, but a stock Carrera 20mm front bar and a full suspension refresh, so want to get the weights right.
Does shimming the chassis bar mount eliminate preload, where non-adjustable attachments are used, (like the undermount bar to A arm connection?

On a separate but related matter, With the driver AND the battery AND the 50 gallon washer tank, how close to equal is it possible to get? :-)
chris

[dannobee]

If the car is on the scales, disconnect the U-tabs and see if the cross weight changes. Make sure that the ground/floor is level though. Any deviation from level will throw off your readings.

Yes, a bunch of stuff on the left side doesn't help if you're turning both ways on the track. It's almost as if Porsche wanted us to go circle track racing. ;-)

Want to see the extreme left side weight car? Google West Coast Supermodifieds. By rule the limit was 70% left side weight. In "open shows" the rule was sometimes 90%, not that anyone could get that much, but more to "run what you brung."

[BER]

Originally Posted by Mahler9th

"In order for the car to be level, there necessarily HAS to be the same amount of weight pushing down at each parallel corner. That's why corner balancing is done with weights in the passenger seat. "

No, that is not correct. We put a nominal driver's weight in the car because we want to set up the car in as close to an "as driven" configuration as possible. This is almost never done on a stock street car for street driving applications. A 200 pound driver in many modern street cars does not change the ride height enough to make any difference in CB or alignment settings that would in turn affect handling.

I think you have a ways to go in terms of understanding this.

For a couple of decades I have recommended the age old Fred Puhn book "How to Make Your Car Handle." I have even given a few copies away as gifts.

It explains all of this very well and has lots of other helpful information.

There are also likely other threads in these and other Forums in which experienced folks with knowledge have taken the time to explain the benefits of CB, processes and methods.

If one were trying to decide between paying someone for a good alignment or for a good alignment and CB, and the difference was say $100... and the application was street driving, I'd suggest eschewing the CB and spending the money on some performance driving event (AX or track). That could help one understand handling and opportunities for improvement.

I still remember my first performance driving event... bone stock 944 with <20k miles at Lime Rock in 1988 with PCA. No AX or karting before that event. I had read about understeer.

I experienced it at Big Bend on my first lap. I did not care about understeer in street driving. But I cared a lot about it in AX and track driving.

You inspired me to get out my copy of Fred’s book that I bought in 1986, right after I purchased my first 911. Chapters 2 and 3 are well worth my re-reading again!

[Mahler9th]

Once you understand the theory, you realize that there are many ways to deal with pre-load. The easiest is just to have adjustable drop links. It is even easy to convert a later-style factory rear bar to adjustable and use adjustable drop links. All kinds of ways to be clever.

Yeah that Puhn book is a reference-- I kept my copy in the "reading room" (bathroom) for about a decade.

The car on the cover has huge local significance as the Garretson-Barbour crew ran many of those 935's out of Mountain View at their place on or near Old Middlefield Road. Many of my friends volunteered on that team or worked on that racing team.

And in an interesting coincidence, a fellow Dartmouth alumn owns a 935 in that livery. He is a former Atlantic and IndyCar driver.

[Mahler9th]

Here is an example result from a set-up on my race car from about 8 years ago:



The car weighed about 1950 then... it weighs about 1900 now. It has a full racing coilver suspension-- much easier than dealing with t-bars.

Back then I did not need or run a rear ARB.

I have my own custom spreadsheets and note sheets for set ups.