Suspension 101: Stiffer is Better? Text by TANABE U.S.A.

[INFO]

Suspension 101: Stiffer is Better?
Text by Michael McFall, Tanabe Racing Development, USA
Photographs by DRIFTING.com

Car club meetings and car shows are home to a strange, if not disturbing phenomenon. Perhaps it’s a guy thing, or subconsciously the end result of an environment that constantly tells us to buy enlargement pills online for cheap. If you’ve been to one of these ‘meets’, you’ve more than likely been witness to these bizarre occurrences. A group of people standing around a car will be looking down, excitedly pushing down on something, and then one person will look up; wild eyed, and comment “hey, that’s pretty stiff!” It’s not really something you would want to hear out of context; like say, in the men’s bathroom. Now that our minds are in the right place, it’s time to tear apart this preconception many of us have about having a stiff ride.



“So how stiff is it?” This question is akin to going to a used car lot and kicking the tire to see if it’s a good car. The question isn’t completely without merit, but it’s in the context that we find its true purpose.

Why do people want stiff suspensions? What is it, and what does it do?

While I can’t wholly answer why many people desire a rock-hard suspension package for a daily car, I do have a feeling it is Napoleonic in nature. People typically upgrade their suspension so their car can handle better. In The Basics - Handling section that is coming soon we will learn that loosely, handling is simply a matter of traction. (aka putting rubber to road.) Traction lets us do all sorts of fun things, on many different kinds of road surfaces. Naturally, different suspensions perform better under different conditions—lets take a general look at some different kinds of roads:

City Streets – Constantly changing from smooth even surfaces, to bumpy an horribly uneven.

Highways – Typically smooth and even, with an occasional bump here and there.

Mountain Roads – Elevation changes, debris, and other road anomalies (this includes animals!)

Raceways – Immaculately smooth and grippy tarmac, the perfect road condition!

Let’s see how a high spring rate uber stiff suspension handles on these types of roads. (dampeners should always be mated with the spring rate, and never exceed it!)

Putting ‘Stiff’ to the test:

City Streets – Constantly changing from smooth even surfaces, to bumpy an horribly uneven.



On the smooth surfaces the car will handle nice, and your tyte ryde will look pretty hot slammed with that new aero kit and blingin rims. Once you take that right turn onto a bumpy street, the ride quality can become unbearably rough as the car jostles and bounces all over the place. This can cause hernias, headaches, and possibly even a break-up with your significant other as your passengers will HATE YOU.

On a serious note, if you have to brake hard or take a turn on a bumpy road, the springs which are meant to absorb the bump, will not perform their function and you will lose traction. This is very dangerous and can cause you to get into a serious accident.

Highways – Typically smooth and even, with an occasional bump here and there.

Luckily, most highways are very smooth. Occasionally you do get the occasional bump, but for the most part you will have a very smooth stable ride. You will be able to take that nice long sweeper at a nice speed and not have to sweat it.

Conversely, if you hit that bump taking that long sweeper at a high speed, you could essentially lose [traction] and under/oversteer into the center divider, provided there is one.

Mountain Roads – Elevation changes, debris, and other road anomalies (this includes animals!)

Stiff suspensions and mountain roads do not mix. Take the bad situations of City and Highway and multiply it by ONE MILLION. Mountain Roads are generally not well maintained, so that 2000 dollar racing suspension is really going to work against you here. The car will be bouncing from the bumps, as the springs will not absorb them. Weight is going to be transferring all over the place, so you’re going to need as much grip as you can get.

Braking under rough road conditions will more than likely cause an understeer condition. Barreling through a turn on a rough road will cause understeer, or oversteer. If you have to brake hard to avoid an animal and the road is rough…you can kiss your Takumi aspirations goodbye as you plow into that Initial Deer.

Raceways – Immaculately smooth and grippy tarmac, the perfect road condition!

Ahh, the raceway. If all roads could be so immaculately maintained, I would drive a racecar everyday. My daily driver is a ’92 Geo Storm, unfortunately. Anyhow, the stiff suspension really shines on the track, because ‘duh!’ that is what it was built for! A stiff suspension, with the combination of a [GOOD DRIVER] and great tires will result in amazing lap times and fun times, indeed.

There is a limit to how stiff you can go, but on the raceway, most of us will never reach that point or would be able to afford it.




Final Thoughts

So the ultra stiff suspension wasn’t all that it was made out to be. It’s like that scene in “A Christmas Story” where the young hero uses his decoder ring only to find out that it was all just a scheme to drink more chocolate milk. Race suspensions do have their place on race cars, but for street cars, it is best and safer to have something a bit softer. The softer suspension will actually outperform the race suspension outside of the track, and there are plenty of options available for the discriminating driver to choose from.

Remember, a suspension is only as good as the driver. 99% of the time, we are not driving on a track, so finding a good balance for your needs and budget is the key. The best suspension upgrade is upgrading the driver. It’s “how you use it”.


Related Links:

Street Suspension
Sustec GF210
Sustec DF210
Sustec NF210

Street/Track Suspension
Sustec Pro S-0C
Sustec Pro S-S

Circuit Suspension
Sustec Pro RR
Sustec Pro DD

http://tanabe-usa.com

[mranlet]

Good thread!

Suspension can be low and roll-resistant without being uncomfortable on the road, though...

Firstly, it's important to understand the differences between dampers (shocks) and springs and what they do. Yeah, it's obvious that a damper is a tube-looking thingy and a sping is that coil but, more importantly:
The spring is the suspension element that supports the weight of the car and determine how much load it will take to compress that corner a certian amount. Spring rates are usually shown as "k" which is a constant representing how much force is needed to compress the spring a given distance. Generally, k is in lb/in but can also be shown in kg/mm depending on who manufactured them. Duly, a spring rate of 150 lbs/in will mean that it will take 150 additional kg's of weight to compress the spring one inch.
The Damper is the suspension component that will prevent the wheel from moving up and down so as to remain in contact with the road surface. A wheel that can be moved up and down too easily will be pushed off of the road surface by bumps, while a wheel that does move up and down easily enough will not absorb those bumps effectively.

Usually over-stiff dampening/damping is what will cause the tire to loose contact with the road surface when traveling over bumps, rather than too-stiff of spring rates, but both do play a part. Stiffening the spring rates alone may help with roll resistance but won't help "plant" the tire better, whereas stiffening only dampening may cause the car to bounce over rough pavement. The right setup of dampers and springs will help the tire remain in contact with the road and may prevent excessive body-roll, which is always the enemy to effective handling.

Why is body roll so bad? When a car is going around a turn (a left turn in this example, because I like left turns), the inertia is still going straight ahead. Straight ahead becomes the outter side of the car, meaning that essentially weight is transfering to the outside of the car. More weight on the outside tires will cause the load to increase (refer to the traction circle to see differences between load and capacity to do work) on the outside tires. Too high of a load on the outside tires will cause the work required exceed the capacity to do work, meaning that in short, the tires will loose grip. Reducing the amount of weight transfered to the outside will more efficiently distribute the weight of the vehicle and therefore enable the inside tires to do more work as well as relieve some work from the outside tires.

Roll resistance can be improved by adding stiff "anti-roll" or "sway" bars or by lowering the center of gravity.

Anti-roll bars essentially connect to the frame of the car and to the right and left lower control arms, tying everything on that end of the vehicle to everything else. A stiff anti-roll bar will definately improve roll resistance, but may also upset a vehicle's handling balance if not done consistently throughout the vehicle - A stiffer front bar will cause initial understeer, while a stiffer rear bar will cause initial oversteer (explaining why some FF drift cars run without a front bar). Too-stiff an anti-roll bar will essentially lock the right and left sides of the car which prohibits the tires to hold the road independently, which will accually worsen handling ability. Stiff anti-roll bars are a relatively comfortable street-friendly handling upgrade, but don't expect to get off with better handling and not have to make any compromises...

Lowering the center of gravity would be as easy as simply lowering the car on it's suspension in an ideal world, but this is not the case. Generally when you lower a car there is peripheral impact to the suspension geometry, often changing the roll center and camber settings. If you want to lower the center of gravity, slight lowering of the vehicle on the suspension (lowering the sprung weight) can be beneficial, but beyond a certian point it will be better to either leave the car alone or to lower the components of the car (engine, transmission, differential, fuel tank, driver, etc)

The Tires may quite possibly play the most important role in the handling of a vehicle. If you've ever ridden in a car that has super-shinny rubber band low-profile tires on it, you will probably have noticed that you can feel the tiniest little bumps through the suspension, whereas big-sidewall tires on SUV's and trucks soak up those bumps completely.

As a rule of thumb, a bit of chenge in suspension gan be very beneficial, but too much can be bad...

So, how do you maintain a decent ride quality, negotiate city streets and also tear up the track?
If you have the money to buy a set of dampening-adjustable coilovers then this will be your best. For a little more than $1000, SPL or Silk Road coilovers can be had for your car, depending on what you drive. The ability to set dampening soft for driving on public roads will ensure a safe ride on the streets, while cranking the dampening stiffer for the track will ensure optimal control and good times. Obtaining double-shock body-adjustable coilovers for not only changing the ride height but also the shock body's location on the wheel hub bracket will also prevent unnescessary bottoming out, which can lead to all sorts of ugly expensive damage to both you and your car.

If you don't have $1000, KYB or Knoi or Tanabe (?) adjustable shocks/struts can usually be had for a bit less than $100 per corner. Full KYB AGX sets usually run about $350 on Ebay and can be adjusted either 4 or 8 ways from the top or side depending on the model. If you should decide that you also want to adjust ride height or do some cornerweighting (which will be discussed in a later thread), an inexpensive set of street-safe spring rate coils and coilover perches may be had for $100 or so, but make sure that they will fit your shocks or struts!

If you only have some lint in your pocket, you can start removing some heavy stuff from your car (see "Weight Reduction" in my sig), which will help to reduce the lateral load on your tires and enable you to turn both quicker and harder. If truck springs will fit your vehicle, this can be another cheap way to increase your spring rate due to the fact that truck springs have higher rates to absorb heavy loads without lowering the vehicle much.

This isn't any sort of end-all guide, but I thought it may be a helpful addition to the aforementioned guide.

[BENJO]

haha good stuff in there

[GRiDRaceTech]

First post was decent, but the second post rocked the house and fixed some glaring issues with the first.

[INFO]

TANABE will release a few more articles soon.

[GRiDRaceTech]

Can you make sure they get their facts completely correct next time instead of just appealing to the no-knowledge riceboys?

[INFO]

TANABE has already prepared an “Advanced Suspension” article which will be released soon.

Originally posted by GRiDRaceTech
Can you make sure they get their facts completely correct next time instead of just appealing to the no-knowledge riceboys?

[_PG_]

Yeah, instead of being so broad in the description of stiff versus street, what happens when you daily drive your track car becuase you can't afford another ride, plus insurance, parking, storage, etc...

I have JIC FLT-A2 8/7 coils on my S13. Daily drive mountain roads, city streets (drift on both of those too... i wont lie) plus drift days about 2 times a month at a track. What am i supposed to do? But a soft suspension and change it out everytime i drive and want a stiff one?

Let me just say that my car is far from the most comfortable on the road but its not unbearable OR unsafe. 12/10 would be track only. 8/6 or 9/7 etc.. is a good medium, as i think 7/5 is a little too soft for track use and drifting. Of course i am talking about S chassis here. Remember, its all relative to vehicle weight and suspension geometry. A JZX110 with 22/20 kg/mm will probably feel like an S13 with 10/8 kg/mm or so. You cannot compare.

Also, for drifting in the mountains a soft suspension is not desireable. (well drifting in general). But especially with elevation changes, the soft suspension will allow the car to roll a bit more and if its low (your car should be SLAMMED for drifting) your tires will rub fenders, body kit scrape the ground, etc etc....


Speaking of Lowering and Center of Gravity... Koguchi-san told me once to lower the car as far as it will go. A lower CG on a drift car (especially as your skill advances and your speed increases) will outwiegh all the negatives of altering your stock geometry and getting more bump steer, decreased compression arcs, etc etc...

No matter what pen-pushers and "engineers" teorize and lecture, i will always trust a 13 year veteran and master any day of the week.

[s15-spec-R]

haah funny post ...... good too... but how stiff are you???
bahaha

[mechaniac]

none of these things matter if you're a tool and can't sense the difference slight adjustments make in the characateristics of your car. (Remember "sensing" the difference, not imagining)

Engine tuning has a dyno and data logging

Suspension tuning, though has the skid pad, the main tuning tool is the driver.

[mikesil]

i agree with _PG_ here.

if you want a full race car, you'll sacrifice suspension life for better lap times and better car handling.

of course being lowered 4" with a bodykit is ludacris on most city streets. that's just not smart.

my silvia has KGMM springs and GAB 4 ways, which do not have too bad of a ride quality on our streets even on the stiffest damping setting. KGMMs are only 369/291 for the stiffest spring, and they lower the car about 2". they're much more mild than other setups i've ridden on like 450/350 for HPs and 800/600 in my friends eclipse.

[MrMigs]

Just get stiff swaybars and soft springs. I'm running 6kg/mm front and 4 kg/mm rear with whiteline adj. swaybars, and the setup is fine for street, crappy mountain roads, and drift events.

[Whisky]

There seems to be a lot of confusion and misinformation floating around out there about weight transfer.

First lets define weight transfer as the transition of vehicle weight off of the inside tires and on to the outside tires during cornering. We also need to understand why this is a bad thing.

A given tire can only produce a given amount of grip before it slides. The total amount of grip your car has is determined by totaling the grip from all four tires. When a car transfers a lot of weight from one tire to another, two things happen. First, the outside tire gains some grip due to the increased vertical load, but the inside (partially unloaded) tire loses even more, so you have lost some of your total potential grip between the two tires. Second, as the vertical load increases on the outside tire it becomes very easy to exceed the traction potential of this tire and cause it to slide (yes, increased weight means increased grip, but not at a 1:1 ratio). This leads us to the conclusion that your car's total grip is highest when the tires are all loaded evenly. Obviously your car has four tires, so this happens not across two tires, but across four (in a left hand turn your right front will load most and your left rear will unload most).

Weight transfer due to cornering, in its simplest form, its actually very easy to understand. It is proportional to CG height, weight, and lateral acceleration, and it is inversely proportional to track width.

What does this mean? It means that to reduce weight transfer you need to either reduce weight, reduce lateral acceleration, lower the Center of Gravity, or increase track width.

Reducing weight has countless benefits, but for many people any significant change in total vehicle weight is cost prohibitive. Nevertheless, you should remove as much as you are able to cheaply.

Reducing lateral acceleration is out of the question too.

Increasing track width is not always a good thing, but it doesn't really matter because to make any significant impact on track width also requires a huge bank account.

Most people therefore turn to lowering CG height. This is most easily accomplished by lowering the whole car with aftermarket suspension. The lower the car, the less it will transfer weight, right? Right.

So lower is always better, right? WRONG!

When you lower your car excessively you are placing the suspension geometry in a state of permanent deflection. This static deflection changes the angles of the various control arms, struts, etc. that locate your suspension. This alteration of suspension geometry can create a number of negative consequences such as poor camber curves and bump steer. Most importantly, however, it changes your roll centers and your instantaneous centers, which always changes your roll couple, and usually for the worse. Without getting into a lengthy discussion of moments and couples, let me simply say that an increased roll couple means that the car will want to roll more than it did before.

How do we kill body roll? Stiffer springs and thicker "sway" bars. So the stiffer the car, the less body roll, right? Right. So stiffer is better, right? Well, no, only to a point.

But wait a minute! I thought body roll caused weight transfer, and that stiffer springs minimized weight transfer!

Well, this is again a yes-and-no answer. While there is a lateral movement of CG location due to excessive body roll, and this movement of CG does cause some weight transfer in itself, the changes in tire loading as a result are actually rather small.

Just for giggles, lets do a little math to help me drive the point home.

Weight Transfer = (CG height x weight x lateral acceleration)/track width

Lets generalize a 240sx and say your car weighs 2800lbs, has a CG height of 20 inches, a track width of 58 inches, and is able to pull 0.85G lateral acceleration. Also assume the car has a perfect 50/50 front/rear and left/right weight distribution (it does not, but thats a different discussion). Clearly these are rough numbers, but close enough.

Weight transfer = (20 x 2800 x 0.85)/58 = 820lbs

What happens if we lower the CG by 2 inches? Weight transfer becomes 738lbs.

Lets also assume we have been able to shave 200lbs off the car in addition to the 2" drop, weight transfer becomes 686lbs. Thats a pretty significant 16% reduction in weight transfer.

I've subjected poor Migs to this rant before...

[MrMigs]

Haha yeah this writeup seems all too familiar.

Sheeit, I didn't know you post here.

[touge sil80]

thanks for keeping this as a sticky.. learning is fun. and knowledge is power