Te31 Suspention?

[te31(707)]

i got a 78 rolla I'm trying to stiffing up the suspension i was wondering if someone could help me find what kind of parts i need

[altezzaclub]

Stiffer springs and shocks to match.

 

Ask a shock shop and get all the info you can about it to start with. You will need to have an idea of what rate springs you want before you do anything, and once you've decided that then chase a shock set that will handle those springs. You've also got to decide if you want gas shocks or not, and adjustables or not. It depends on what you're planning on doing with the car. It also depends on your pocket- I found two grands worth of adjustable Koni shocks worked very well, they can be changed for ride height and stiffness.

 

...or you could do the usual clown tricks and get a set of Falcon springs & cut them with a grinder.... Read a few build topics and see what people have done.

 

Go through this guy's webpage- great stuff.

 

http://farnorthracing.com/autocross_secrets5.html

 

As the chassis rolls from zero roll at the entry phase of the corner, to maximum roll at midphase (or near it), and then back out to zero roll at corner exit, a number of things happen:

 

1. The shocks compress, then uncompress;
2. The springs compress, then uncompress;
3. The sway bars (if any) twist then untwist;
4. The bushings at the pivot points of the suspension control arms deform; and
5. The wheel and tire move through an arc defined by the layout of the suspension control arms.

The primary goal of the suspension, from a racing point of view, is to do all these things in such a manner as to maximize the amount of time that the tire spends in its "happy place" where it is making maximum grip. A secondary goal is to perhaps induce behaviour conducive to balancing the car or affecting responsiveness - things like toe and roll steer come into play here. But for the time being, we'll limit discussion to the primary goal.

 

The first (and most important) consideration is that no suspension can "create" grip. The maximum amount of grip is produced when all four tires are equally loaded and in their "happy place" from a temperature, pressure, camber, and slip angle point of view. That's the best you can do. Suspension tuning can "unlock" potential grip, and a poorly tuned suspension can indeed lock away a lot of grip, but a happy tire is a happy tire.

 

Secondly, the factors that dictate what constitutes a "well-tuned" suspension are mostly related to the tire. A tire that is insensitive to camber angles is not going to require strict control over dynamic camber. A tire whose load curve falls off very slowly will be tolerant of changes in weight transfer, and so on. The factors remaining tend to be environmental, particularly how bumpy the race surface is and the nature of the course layout.

 

Thirdly, the basic design of the suspension we use (assuming a production-based car as I do) is largely determined by the original manufacturer - and they may have had goals in mind other than maximum lateral grip. For an OEM, packaging (fitting the suspension in a small space) ride quality (both passenger comfort and NVH (noise, vibration, harshness)), and cost tend to be higher up the food chain than pure performance.

 

But whatever type of suspension the car is equipped with, that is likely the type of suspension you are going to race with. The rule book, the highly integrated nature of unibody construction, and economics makes it very difficult to switch from (say) a MacPhearson strut to a Double-A Arm.

 

Accordingly, the first step in improving a suspension for race use is to figure out what the current one is doing. This is so important, relatively easy, and reasonably cheap and yet almost nobody does it because it looks scary and hard. Instead, everybody wants to rush in to buying shiny parts and starting the Great Cut and Try Cycle.

 

Measuring and modelling the OEM suspension saves enormous amounts of time, energy, and money, and can give you an initial setup that is most of the way there right out of the box. Time spent measuring is seldom wasted.

 

 

Modelling the Car

The steps involved in modelling the car are as follows:

 

1. Measure the key components of the suspension and transfer the data into a modelling program like WinGeo. I particularly like WinGeo because its data collection procedure is very simple and straightforward (it's NASCAR-proof). Example of how it is done here. This process will give you camber curves (both bump and roll), caster, bump steer, motion ratios, and roll centres. It will also allow you to play with the car, rolling and pitching it and whatnot, and see firsthand what all the components are doing. If you spring for the top-dollar version, you can even play back the data from your wheel position sensors through it and watch your suspension react to real-world data (which is awesome for validating the numerical model);
2. Weigh the car and get corner weights. Weigh the unsprung masses too;
3. Measure the Center of Gravity height. This one is annoying because it involves lifting one end of the car up in the air while the other end is on the scales. If you have a Formula Ford, it is pretty easy. For production-based cars, it takes a little more ingenuity. Having access to a lift or forklift helps, but there's more than one way to skin that cat. (Future expansion, describe the process);
4. Dyno the shocks and springs. Shocks are complicated enough to deserve their own chapter; and
5. Measure the sway bars.

With all this information, you can now plug values into the Dynamics Calculator and start to get an idea of what is going on.

 

Because the grip level of race tires is so much higher than street tires, usually the next step is to pick springs.

 

 

Spring Selection

A spring change to a stiffer spring limits the amount of motion that the suspension undergoes in reaction to a particular acceleration (so does a change in CG height and track/wheelbase, but those are much harder to change than springs and for most practical purposes less effective too)

 

But there are upper limits on how stiff we can go with the springs, so we need a measure of "stiffness" to set the boundaries.

 

That number is the natural frequency of the suspension - it is worked out for you in the Dynamics Calculator. Rule of thumb is rear NF slightly higher than front (by a tenth of a Hz or two - it keeps the sprung mass from pitching too much because the front wheels encounter bumps first so the rear needs to react a little faster) Street car: 0.8 Hz. Occasional autocrosser: 1-1.5 Hz. Full-bore autocrosser: 2.2-2.5 Hz.

 

Yes, it really is that simple. Measure your corner weights, unsprung masses, and motion ratios, and then pick springs that put the front NF at 2.2 Hz and the rear at 2.5 Hz.

 

Edited June 8, 2011 by altezzaclub

[Crowie55]

i got a 78 rolla I'm trying to stiffing up the suspension i was wondering if someone could help me find what kind of parts i need

Altezzaclub is on the money for front shocks and springs, for the rear leaves just purchase another leaf pack, take the second and third leaf out of the spare set and put them below the leaves of the same length in your original set, Go down to your local nut and bolt shop and grab some new high tensile gear to hold them all together. Hit your local suspension shop up for some rear shock solutions depending on how stiff you want it to be.

Cheers, Crowie