I think this right here sums up most of the discussion here. Any serious race team will vary their spring rates (and suspension setup) on a per track basis. All of their competitors do.

Just because a company sells one thing to the public doesnt mean they actually use that on their race cars. I'd venture to guess that the reality of the matter is that over in japan the buying public wants equal rates. Companies will sell what the buyers want, so...they are equal rate.

Just because japanese Joe average wants equal rates doesnt mean he knows what is the best any more than american joe average. Just because it came from japan doesnt make it superior... even if the car was built in japan. In the end its all just physic's, and there are plenty of highly intelligent people running race teams in america that seem to think that equal rates are not the way to go.

That being said... I am also baffled at the stupid high spring rates that many of the JDM coil overs run. Are these things marketed as race setups over there? Does the japanese joe average only buy coilovers to make his car a super tizzit race machine? Any american designed setup would consider 900ft/lb's insaine unless the car is a full out race car, or autox car.

The guy running 16/14 or whatever... I cant fathom how that isnt just a rock hard ride. I'd be curious to know how well your chassis is in 40,000 miles. I'd be willing to bet that spring rate is actually causing the "spring rate" of the chassis to come into play. (ie: your chassis is flexing slightly over bumps instead of the suspension doing its job)

 

I ran tein RA's (900lb front and 900lb rear) on my FD at several track events and local time attacks. I experienced severe oversteer on all settings and was never able to get the rear to stick. I was running 275/40/17 on the front and rear Toyo Ra-1. I did really get a lot of heat in the tires and it was pretty quick. But, I never could get to that perfect balance. I'm thinking about getting tein flex's.(10,8)

 

Shocks have a lot to do with how the car feels during day to day driving. I have Gab Super Rs with 500/400 ftlb springs. A friend of mine is running 900/700 ftlb springs with JRZ shocks. His car without a doubt feels softer and more street freindly than my setup. I would not have believed this if I didn't drive both cars myself.

 

I started autocrossing in '04 with a stock suspension setup. I am by no means an expert at driving fast, but I wanted to share an experience I had while upgrading some parts.

The first parts to go in were the Koni shocks. This single mod has to have been the most significant one I've made in this area. The weight transitions in the corners became much more predictable and smooth. I suppose it also helped that the shocks weren't 12 years old either.

Then I decided to replace the springs with a RS-R set 350/260... Not much difference, there.

Next, I added a GC coilover kit with 700/500 springs. I must admit this wasn't the smartest upgrade to make on 235 A032R's. I felt like I was ice staking on a pivot near the front of the car.

At this point, I disconnected the rear ARB to keep the wheels on the ground more. It kept the oversteer in check, but I was still at a loss for lateral grip.

Last but not least, I bought some wider tires (4x275) and started driving with those. Unfortunately, the car pushed like a tractor. Only until I reattached the rear ARB and fixed an issue with the coilovers did the car start behaving properly again.

I had some faster drivers try my car out.
- One (who drives a RWD) said my car was very neutral.
- Another (who drives a FWD) spun the car around a few times.

I figure running a equal spring rate on all fours would create a tendency to snap oversteer not long after the weight transfer lifts off the rear (as many here have already stated). I can't imagine being able to put any power down unless you didn't expect to. That is, just flying through a corner with a more aggressive angle to slip around the apex rather than taking a straighter line.

I might be totally off, but I am here to learn.

 

It's unfortunate the people believe that just because they have a well known name brand shock (e.g., Koni, Tein, etc.) that they can merely put whatever springs they want on the car. And, when it doesn't work they believe the springs must be too high because that is what everyone on the forum says. One of the keys to setting up a car (as I am still learning) is to get the shock SPECIFICALLY built for the springs you are running. For example Koni Yellows --right off the shelf-- can not handle anything more than 500 lb spring rates. They must be rebuilt. I pick on Koni because I was in that situation and I then had to move on to something that made more sense for me.

 

I believe that even a revalved off the shelf Koni would have a difficult time with anything near or above 500 ftlbs. The Koni by design cannot control small suspension movements caused by bumps and dips in a road (or bumpy track). In my experience this is why the konis when paired with stiff springs create large amounts of oversteer, not because they aren't valved properly but because they can't keep the rear tires on the road when faced with less than ideal street conditions. This is where true racing shocks (penske, JRZ) can make all the difference in the world since they can tame very aggressive springs even on bumpy roads.

 

there seems to be a widely accepted theary a stiffer rear spring = snap oversteer however many factors equal driving sensations... one of these and also one of the most common that i have seen is the use of two soft of a spring matched with to much rebound valving one example I have experienced is the matching of the tokico's with h&R springs the tokico's really in my opinion have to much rebound for h&r's which when driven hard on a bumpy surface pack down the chassis onto the bump rubbers. another common problem is that when asking a car to transition quickly, if the initial lateral load is not sufficiently supported by either the spring or ARB the bump rubber comes into play very agresively with a spring rate which is dramaticaly more than the tire can handle over loading it which leads to a uncontrollable snap oversteer situation.

 

Heh, I'm resurrecting this thread because, well, I can!

Let's talk about the kinds of things that would affect what type of springs you might run on a car when you want to drive it differently than was intended by the designers--in this case, Mazda:

1) weight distribution
2) wheel width
3) wheel stagger
4) tire compound
5) differential setup
6) wheelbase and track
7) aerodynamics
8) horsepower
9) braking
10) and so on...

Any single one of these would change the way you would set up the car. Anyone who argues that spring rates are set due to CPM or some other classical analysis has never tried to set up a car for racing.

It's not always about balance. Springs can have affect on turn-in, mid-corner, and exit. They can affect aero efficiency. They can effect braking stability. They can affect traction under power. It's not just balance.

Here's a simple example: a modern champcar weighs about 1700lb with the driver and has a weight distribution of about 40/60. It has about 750HP and a lot of aerodynamics. The motion ratio (depending on rocker arm) is similar at the front and the rear, varying maybe by about 10-15%. The dampers, while different, are not completely dissimilar on either end of the car.

Anyone want to guess what spring rates they run on a road course?

-ch

P.S.: as soon as you change anything significant on your FD, you need to be willing to experiment to find the right setup. That means a lot of work and a lot of testing--or use a setup that has been proven with a car that's very similar to your own.

P.P.S.: I forgot to add:

11) track surface (abrasiveness)
12) ambient temperature
13) track condition
14) ...

A good setup for the Nurburgring won't be fast at Laguna Seca, and vice versa.

 

I've got some ideas but I'm not sure what you're trying to tell us:

So you know what spring rates (more appropriately wheel rates are what should be discussed) Champcar runs on a "roadcourse" and then you go on to tell us the setup at different roudcourses will be completely different anyway. What point are you trying to make?

 

Only that spring rates that work well on an street-driven FD at near-factory weight with a stock diff, lightly modified motor, DOT tires, and no aero are probably not a good proxy for race prepared FDs where all that stuff I just listed is changed, potentially dramatically.

The argument over whether the Japanese suspension manufacturers are 'crazy like a fox' or just 'enamored with drift' seems difficult for us to answer without knowing what kind of FD those kits were designed for. Because our notions of balance and wheel frequencies hardly apply to real-world racing conditions.

Things change quite a bit under those circumstances.

-ch

 

^ Agreed. Different horses for different courses.

A purpose built racecar has little in common with a street car.

 

Right. A big fat wing on the back, and a different diff would probably change your rear spring requirements dramatically.

 

LOL ahahahahah what??? why is this thread still alive ok i'll spout out some more meaningless crap

A DP @ utah ran well with 2000 in front and 1800 in the rear Xsoft FARB med RARB, 0 front droop and about .100 air gap to a black penske bump rubber. w/penske 8760s

that same car @ mid-o ran well with 700 in front and 900 in the rear with med FARB xstiff RARB, 0 front droop and o airgap to a yellow penske bump rubber w/ ohlins tt-44s

so what am i really saying?

 

sereneseven- Every course requires a different set-up, and then its different for each driver! Do I win?

I was just starting the process of picking some springs for my race car to start out with. While it is an FC and not an FD I may end up with pretty close to the same spring rates front and rear. The motion ratios of the front struts are different from the rear trailing arms and my car has about 60 rear weight bias. All these things add up to wheels rates that look like they will work together on the track I will run on first. I just need to get the center of gravity height so I can figure out what bars I need.

What does this all mean? Pretty much the same thing that sereneseven's post got you, a bunch of info that doesn't mean anything to any other car! Somewhere in this thread I saw the best advice. Do some math and figure out what YOUR CAR needs. The more background work you do in the build of your car the more you will learn why something is happening and what to do about it.

 

^ yea!!!! sorry no door prize

the bottom line is that many components affect the way a car handles on its limit, change just one and the whole thing falls apart. with that said yes you can calculate yourself somewhat close to the ballpark but in the end there are many factors that you simply cannot calculate thats why race teams test all the time. since the majority of people here don't profesionally race theyre cars chances are you will just buy an off the shelf kit and live with the results but if you do have some extra $ burning a hole in your pocket just try some different rates untill you find one that matches your needs.

 

Please take a look of this file and give me your opinion about it.

I made a Excel file with all the spring rates of kits that I have found , including some information given in this page.

 

I tink that the Tein Flex , with 670lbs spring rate in front and 560lbs in rear are the perfect ecuation for the street and track , but I have no try this yet