Another one (suspension heights and car ballance)

[dangerous_daveo]

As per topic...

Suspension hights and car ballance.

One day some old bloke who had been in racing since he was knee high to a grasshopper, raced everything from formular ford to sports cars (the stupid big wing things with V8s in the passenger seat), he told me he used to have this tool balance a car by changing the hights of the suspension.

Now my question is this true, if so how is it done, like can any old suspension shop do it, or is it a lot of stuffing about and not worth it. (btw I have coilovers so its no prob to change the settings)

Also by balance I mean an even or purpose set distrabution of weight around the car.

PPS, also what difference does hight in general make to the cars overall handeling and dynamics.

Thanks!

[blind_elk]

It's not necessarily the height that makes the difference. It's the weight - how it's distributed, and how it transfers.

There will be some places around that can corner weight your car. I had this done the other week, and found that my right rear and left front were carrying more weight than the other 2 corners. I put it down to a pre-load on the rear sway bar, so I got hold of some adjustable link pins. Now all I have to do is get the car re-weighed.

Basically, the car is set up on 4 bathroom scales (bit more sophisticated, but you get the idea). The surface needs to be perfectly level for the measurements to be accurate. The little computer can tell you what each corner weighs, and the weight distribution (%FR, %LR, %diag). A good technician should be able to tell you how best to redistribute the weight, either by adjusting the pre-load on the coil platforms, or by moving things around (like battery to boot, etc).

Get yourself a good book on suspension, like Fred Puhn's "How to make your car handle" for an official engineering explanation.

[Sydneykid]

Think about a table with 4 legs. If one leg is shorter than the rest, then the table rocks unstably. It easily moves, until the short leg hits the ground, then it stops suddenly. But then it easily rocks/bounces back (diagonally) until the opposite leg hits the ground, then it stops suddenly again. This rocking motion is very unsettling for a car, it jumps around suddenly with only slight inputs (brakes, steering, acceleration etc). This makes it very hard for the driver to feel what is going on.

The short leg (in the table example) is actually the suspension corner on the car with the least amount of weight.

[(B1) MR_fanny]

so how much does one of these weight balance corections cost?? sounds interesting.

[dangerous_daveo]

Also or more so, does anyone know of anywhere in Brisbane that can do this? As Im guessing its a bit of a fine art.

And if anyones got the answer to the other question, being does hight in general make a difference, other than the obvious raising the center of gravity.

[blind_elk]

I know Meridien Motorsport in Melbourne will hire out a set of scales - around $150 per day. Or they will do the setup for you for around $300 I believe.

You could try contacting them for a Brisbane-based equivalent, or simply hunt around the Yellow Pages until you find one.

As well as the CG, the ride height will also affect the roll centres (the point in space around which the suspension rotates), which in turn affects the "roll axis" (the line down the middle of the car, joining the 2 roll centres, about which the car "rolls").

It's a very complex interaction between all the components and the geometry. I can't recommend Fred Puhn's book enough for a thorough explanation of what's going on.

[blind_elk]

If you're intersted, Fred Puhn's book is on special at Pitstop Bookshop - www.pitstop.net.au, item# 1734 - for $34.95 (+p&h)

[jnr32r]

I was recommended this, but i wouldnt have a clue who in Syd does it... Anyone??

if the scales could be hired and done at my own time it would be awesome...

[dangerous_daveo]

I was recommended this, but i wouldnt have a clue who in Syd does it... Anyone??

if the scales could be hired and done at my own time it would be awesome...

After thinking about doing it myself I think its worth while to pay someone for this job. As you lift/lower one corner, the other one does the opposite, so its a LOT of stuffing about if you dont know what your doing (ie, if you lower one corner 5mm the other corner will need to go down 1mm etc) I think you would just keep going round the car till its a 4b or sitting on the ground

[Roy]

There are actually 4 pads/scales that the car sits on at the same instant.

[dangerous_daveo]

There are actually 4 pads/scales that the car sits on at the same instant.

Yes I realise that, but you change one setting, the other 3 also would change. Therefore going round in circles for a few hours.

[blind_elk]

There is only a finite amount of weight to distribute. Therefore adjusting one corner will change one or more of the others by a calculable amount. Go and get Fred's book, it has an example calculation in there. And it will give you the lowdown on what and why. You've driven the car as it is until now; a few weeks more while you get a handle on the process won't matter a great deal.

But, it's really quite simple. And if you are in doubt about which corner to adjust, then simply grab hold of the wheel arch and lift the corner, or load up a corner and see what happens. When we did ours the other week, it wouldn't have taken more than perhaps half an hour to get a reasonably even weight distribution.

You're unlikely to get a perfect 50/50 F/R weight distribution, but you should get something close to 50/50 L/R distribution, preferably with driver in the car.

It may reach a point, however, where no amount of adjusting suspension will solve it; you get to a point where the answer is to move weight (like battery to boot, etc).

[Roy]

Out of interest, what is the weight distribution of aa GTST, big iron 6 cyl and all? And is 50/50 really the ideal weight ditribution for a RWD car...i have read a few different schools of thouhgt...im more interested in knowing what works on GTSTs:)

[dangerous_daveo]

I think Roy thats an even trickier one, as you would have grip being another factor, front and rear suspension settings, dampener rates, spring rates etc, and driving style/preference.

[Sydneykid]

Hi guys, think about the table analogy. What you are trying to do (with corner weighting) is to stop the table rocking diagonally. You can either lengthen the short leg or shorten the other diagonal legs. Either way it will stop the table from rocking. If you have a big pot of soup on one end of the table, moving it around won't stop the table from rocking.

Getting the diagonals to total the same weight is what we are trying to do with corner weighting. So whether the car has 50/50 front to rear (or left to right) weight distribution is not something you can change with corner weighting. You simply want to get the diagonals to total the same weight.

Our race GTST is 62% front and 38% rear and weighs a little over 1200 kgs. It has had all the usual stuff removed, spare wheel, jack, tool kit, boot carpet, rear seats, air con etc. Note that most of that stuff is from the rear of the car. Then I added a bigger engine, gearbox, oil cooler, FMIC, remote filter, extra 3 litres of oil in the sump, larger radiator, bigger front brake rotors, twin plate clutch etc. Most of that weight is in the front, so that's why it ends up at 62/38, it was around 59/41 standard.

You have to physically move stuff to change the weight distribution (front to rear or left to right). This is why circuit race cars have lots of stuff moved from the front to the rear. Battery, dry sump tank, oil cooler pumps, filters, surge tanks (for fuel), brake fluid reservoires, etc etc. The big one is the engine itself, it's heavy, so moving it as much rearward in the engine bay as possible can be quite worthwhile.

When you consider the driver is seated in the right hand side, you also need to make sure that there is as much weight moved to the left hand side in an attempt to compensate. So if I put the battery in the boot, I make sure it is on the left hand side. I see so many Skylines where the fuel system (pumps, filters, tanks) is on the right hand side of the boot. It may be easier to put it there, but it would be better for weight distributioin if it was on the left hand side.

Hope that helps some more:cheers:

[blind_elk]

The GTS4 is around 57/43, with the RB25DET sitting up front. Don't imagine it is THAT much heavier than the 20.

[Sydneykid]

The race GTR weighs 1,510 kgs, with similar stuff removed as the GTST. It's weight distribution is is almost exactly 70/30 as it has the ATTESSA, front diff and drive shafts all in the front half of the car. So we can't get its weight distribution to be better than the GTST:cheers: