yeah i wonder if you (or me!) could tell the difference between 300 and 350....

 

i can get numbers, or the equation if you want, but the spring rate depends on the weight of the car, motion ratio, suspension geometry, and lateral g's that you pull. more g's = more spring.

the whole point to tuning the suspension is to put the tire in its happy spot the most amount of time, and make the driver happy/comfortable. where does body roll put the tire contact patches?

 

I personally think too many people are running way too soft in the rear without the rear sway bar. If you take out the rear sway bar you really need to step up the rear spring weights to prevent body roll and prevent the suspension from binding at the infinate roll point. Once you hit that point there is no controling the car and you get snap oversteer. IMO anything less than 175 in the rear you'd better run the rear bar unless you've ditched the toplinks for a 3 link. The rear sway bar and higher rear spring rates will make the car more tail happy, but it will be a controlable predictive slide. If you're too soft in the rear and have taken off the rear bar (as has been parroted on here millions of times) You're going to easily hit that point of no return in mid to high G turns. I don't think enough people on here are educated in how porly our stock suspension is designed. the 4 unlaterall uneven links for the rear axle actually bind with enough roll and the rear suspension literally locks up and binds and this sends all the energy through the turn to the outside rear tire sending the car into a snap oversteer situation. This can easily be cured with a 3 link setup, but then the watts link is in the way creating another problem to fix. Plus the watts isn't centered and it's located to high. If you're keeping the stock stuff temporarly you have to stop the car from hitting that binding point by elliminating roll, but this requires making the car more tail happy by adding stiffer rear springs or a bigger anti sway bar. Also spring rate setup hugely depends on what tires you're going to be running. if you run too stiff on hard tires then you're going to slide everywhere, to soft on soft tires and you'll be really slow. It's really hard to just throw out a number for someone. You need to know what tires you're going to be running, how you want the car to drive, what other suspension geometry chages you might be making, and where you're going to drive the car before you can make a spring rate suggestion. That's why you talk to someone like Jim or Billy because they're going to ask you those questions before they give you a suggestion. You're literally putting your life in someones hands by taking a spring rate sugestion. If you put the wrong rates in you could end up in a bad situation you can not recover from fast.

 

Thanks for the compliment - it really is a great car to drive.

No sweat - this is a good conversation and allot can be learned on both sides. There certainly are two schools of thought at work here. You have soft springs and big sway bars and I have stiff springs and only a big sway bar at the front. Both setups can work but I think that you will find that stiffer springs will be required on your car if you start running Race compound DOT radials.

Keep in mind that body roll doesn't equal bad handling. Body roll is a function of weight transfer and at some point all cars - race cars too - must have some body roll. In the case of my car - body roll or wieght transfer is necessary to get the car to work. What you are seeing in the picture of my RX7 is the result of speed (about 60mph), lateral G's, Grip (Hoosier Tires) and desperation....the dude behind me wanted his position back! Actually I think the photo shows that RX7 is working correctly - the left side tires are loaded correctly in a right hand turn and the right side tires are still on the ground and working too.

Check out the cars in this gallery:

http://gotcone.com/pgallery/2008_scc...opeka__ks/csp/

These are the fastest CSP cars in country right now. Notice how they lean in the corners and pay close attention to the way the tires are aligned to the pavement in the stills. HPT has a smooth but slick surface so allot of the guys run softer setups.....I tried it too to get my car to transition....didn't work!

 

Some very nice looking cars in there, they've got that very determined look to them...

I actually ran on Hoosiers for the first time last year (3 or 4 events). It was a bit different, and I had to run a lot less camber because I found I was wearing the inside edge way too fast using my street tire camber setting. I think this was mostly due to reduced sidewall flexing on the Hoosiers. But they were at the end of their lifespan when I got them, and will have to be replaced now.

I haven't driven a 7 with the high springrates, but will watch for an opportunity to do so. I'd love to be able to see things from both sides of the fence. But I won't be doing it to my car until she's finished with her daily driver duties (which she may never be). But I think I will reread Puhn's book again before this season starts. I think I learn something new every time I read it.

Thanks for the input into this guy's thread. You keeping up with us Chon?

 

this is why i love the 1st gen section. we can have an intelligent conversation without it turning into a flame war about who is right and who is not.

in short thanks for being awesome guys!

 

great info!!!

 

I figured as much. We have allot of new guys lately. I am happy the site is still growing and the new guys feel welcomed. Allot of the same questions are coming up. There are many variables that must be taken into account. Although trying to be helpful, they sometime point them in a direction without that understanding.

-billy

 

Thanks guys for all the great advice. I’m really glad you’re all so willing to help out newbies like myself. Not only is this going to be the first car that I will be setting up the suspension for road racing and autocrossing, but its also going to be the first time I’m going try to race competitively, so guys’ advice is greatly appreciated.

To answer your question Billy: street driving only on the weekends 70%, road racing 20%, and autocrossing 10%. Since this is going to be the first time I going to participate these types of competitions, I’m really not sure which I will like doing more so the percentages can change.

Thanks again everyone.

 

That blue 99/199 car race in our region. 3rd place in Nationals....

Back on topic, I agree with everyone with the Jim Susko book. The book was great and helped my car a lot. Still way too slow compare to that blue miata tho. I gave up and moved to FSP... Going to Nationals next year...

 

what would you guys say as far as running 300 front and 250 rear, or maybe 400 front and 340 rear?

 

That all depends on what you want the car to do. Typically, you're going to want the rear springs just a little over half the rate of the front springs. The numbers you posted would probably result in horrific oversteer, but might be desirable if you were doing nothing but drifting (no street use at all).

 

what do you want to do with the car?

i know most people will kill me for saying this, but if you want to understand suspension a little bit better play forza2. play with the spring rates. and you'll notice a huge difference when the rear is a little over half the rate of the front. it's a cheap easy way to see differences in modifications without having to do it in real life.

of course do remember not every car is the same.

wish they had an sa or fb in that game

 

Augh, I'll second that...

 

i was saying those rates for the fact that i used the stock spring rates x 3 or 4 and then chose the closest rates

i plan on roadracing it mainly

 

i run 300/200 with very neutural handeling with easy controlable oversteer. All I have to do is let off mid turn and it starts to slide. But the spring is soft enough to weight transfer back to the rear wheel when I reapply throttle and it hooks up again and pushes me thropugh a corner. I'd suggest 300/200 for a car that sees mostly street and autox use, but that's how I like my car to drive. Do what i did and drive as many friends cars as you can ad see what works for you. i run stock sway bars for now. I plan to run a bigger front and modified rear bar later.

 

A couple years ago I got a "bargain" on coilovers on ebay. Without knowing anything about the correct spring rates, I got 750 lb front and 500 lb rear. They came with Koni yellows that had the extra valve added to allow adjusting BOTH the compression and rebound settings. I have the most level-cornering, lowered FD on the planet, but on anything but the smoothest road it loosens my teeth. On a really rough road it skips from the top of one bump to the top of the next. (not real safe to drive at speed). I have put up with it until now- am going to replace with 250 lb front and 200 lb rear. The Konis stay- they are great.

 

3rd gens are completely different, so you can't compare spring rates for that with those for a fb. I think the 3rd gen guys are recommending something like 500/400 Lbs.

There is a great thread on how to set up a 3rd gen, look in the racing section, its always near the front page. I think the name in the title is Howard Coleman.

 

I actually agree with this. Obviously this may not teach mustanghammer anything but for the total beginner I've found that some of these better sims are really good at getting you to understand how all the settings interact and how slight changes here or there influence the behavior of the car.

It's a nice cheap, low stress way to play with stuff, i realize that none of it transfers over, but back when I was in middle school I learned the textbook theoretic fundamentals of bound, rebound, ride height, downforce, etc on gran turismo. And now that I've actually but those lessons to steel, I have to say that as of yet, on basic general concepts, gran turismo was right.

Now I would never tune on GT and then apply that to my real car expecting good results however. That's just silly.

 

yeah. been able to shave off lots of seconds on most races, by messing with the suspension settings. in some races i'm ranked 400 ish, i.e. road atlanta... guess that doesn't really mean much but its still great, cheap fun.

i gotta admit, laguna seca looks so real in that game. i doubt i could ever drive as fast as i do in that game.

 

Some good reading here, was going to ask the same question.

STILL DON'T KNOW NOW. But looks like trying different things is the answer and I know from Kaarting that it is all about what the driver wants and likes.