I've tried some searching for what rate coil springs to run in my FC race car– all results have been street oriented.

My car is fully (and I mean fully) gutted and I will be running 225/50/16 falken azenis tires (my class requires a 200 treadwear or above). Currently I have tokico blue's and what appear to be stock springs.

The car is being setup for big tracks much more so than auto x events.

What rates/brands are you guys running on your racecars?

Thanks,

Evan

 

http://www.evasivemotorsports.com/me...=SWIFT-SPRINGS

http://www.pegasusautoracing.com/pro...sp?Product=186

Either of those, depending on your budget..(swift being more expensive, and thought slightly higher quality of generally). Normally track Rx7s use spring rates north of 8kg/mm(10kg/12kg is pretty common), the Japanese tuners will run up to 16kg-18kg/mm springs(18kg/mm=1007.1 Lb/In which is scary. lol) Spring rate is dependent on a lot of things, such as the track, how much down force the car creates @ speed, size of anti-roll bars used...ect. ect. Make sure you get a spring thats the right height for your car, but wont become loose in the perch in the event your tires go into droop(airborne). (Helper springs are a lazy persons fix to that problem) The best thing to do is have multiple sets of springs of different rates you can switch between.

Kyle

 

Thank you for the links! 1000 lb/in is incredible lol!

My main focus is to minimize body roll and excessive ride height as much as possible without overwhelming the relatively small (225) street compound tires I will be running. I've had experience with too stiff of springs making street tires feel like they're greased on track.

 

1000 is really high for an FC....

most FC people run around 325-350-400-450F and 225-250-275R springs.

i don't know about aero, we've never done any kind of testing, but the tire, vehicle weight, suspension, design, ride height, and driver will dictate spring rates, kind of in that order too.

more traction = more G forces = more body roll = you need stiffer springs.

http://farnorthracing.com/autocross_secrets5.html

http://www.optimumg.com/OptimumGWebS...Tech_Tip_1.pdf

as you can see they just use an equation....

 

Thank you for the excellent racing sites. I have been doing some extensive reading on them and it is sounding like I should stick to the low side of the spring rate spectrum until I start running a wider stickier compound tire.

At the speeds I will be running aero will most likely be negligible.

The car is apart and getting a cage right now but It should be all back together in a month or two.
It's an 88 SE with turbo II trans and Diff, and street ported S4 NA

So far we have removed weight like crazy but I won't have a final weight until the cage is in. Kind of curious to see what it tips the scales at all said and done.

 

8 and 6kg/mm are what i use now
10 and 8 were too stiff to the local torn up track.

 

i was thinking most FC people just buy whatever springs (8/6 is popular, and it works) and just leave em.

on the honda though, it didn't have the body of knowledge that the FC did (does?) so we've actually gone thru a bunch of spring iterations.

springs are cheap! spend the money on good SHOCKS, and experiment a little.

the cool thing is that even something soft like 350/250 is in the ballpark enough that you can play with the rest of the car, and then do the springs later.

 

What swaybars are folks pairing with these soft springs? I have 400F/275R based on a recommendation from MazdaComp long, long ago. Paired with whatever swaybars were in the MazdaComp ITS package way back then, too. Suspension Techniques, I think, out of the 1997 print catalog. :-)

 

I've got 7 kg/mm front (~400 lb/in) and 5 kg/mm rear (~275 lb/in) paired with a Racing Beat front and stock rear sways. With a full interior on 225 wide R's the handling's just on the understeering side of neutral, and I mean just. A stripped car might need less rear bar due to less weight back there.

 

yeah that front bar is fine. when you get to that point, you'll want to try that rear bar, the stock rear bar, and no rear bar.

the mazda comp package works well, i'd run it and let the data tell me i need to make changes.

 

I was talking to a friends and competitor the other day about usage of rear sway bars.
I'm usually pretty good at picking up on the theory and physics of suspension geometry but i was very confused on this subject.
the point of his attempt at explaining it is that removing the rear sway bar you gain rear traction at the cost of front traction. that the front wheel outside wheel will take more weight then the rear outside.
I'll be playing with this a lot more this year but it something to thing about.

 

This is the sweet spot for anything south of 2600lbs race weight.

We used 8k/6k and the car was too bouncy. It greatly depends on weight for the FC (being a strut car). With MacStrut cars its a game of compromises. For instance 9k/7k works great on my turboII (3100lbs with me and a full load of fuel). Even better than the 7k/5k I run on the racecar which is right around 2600lbs with driver and fuel. But, running stock bars we cant go any lower than those rates on the race car.

 

shocks are important too. my friend recently put together a car with 450/250? springs and KONI's and it not only handles great but it RIDES as good or better than my stock gxl!

no idea on weight for that one, GTUS, no AC, but full emissions, and interior, 2700 even maybe?


we played with the rear bar on the spec E30, which is like a 5 year olds cartoon drawing of an FC, and the gist is sort of that the rear bar ties the two sides together, so they act less independent. we found no rear bar was better on a big fast* track like thunderhill, but @infieon which is tight, hooking the bar up was better. so you really need to try both

oh yeah so this points out that you can have a different, and even asymmetrical setup for different tracks. infineon is mostly rights, and t-hill is mostly lefts....

*fast is relative in a spec E30

 

Swaybars are weird, right? They actually affect the opposite end of the car... you mess with the rear bar if you want more or less front grip, and vice versa. Now I realize we all soften the rear bar if we're loose, but in reality that's taking away front grip to balance the car, right?

That said, if you have binding or the bar is so stiff you can't even get reasonable travel you're going to have other issues.

Is anybody running the MazdaComp suggested dual-rate rear set up with the 150# tender and 275# main spring? I went with a 10" 275# instead of an 8" with the tender... I've seen some folks using dual-rate spring set ups in order to run smaller swaybars (keeping things independent) while retaining some good, soft initial travel...

 

It's said that after tires, shocks are the most important factor in making a car handle well and go fast. With good shocks, stiff springs can be liveable, but you'll still certainly feel their stiffness over bumps and such. If you live in an area with good roads, you'll notice less, if you live in an area with lots of potholes and frost heaves, you'll notice more.



One other thing to keep in mind is wheel offset. A lower offset will make thewheel rate drop (the effective spring rate as seen by the wheel), since the wheel now has more leverage on the suspension. If you run different offsets front and back, this could have an effect on the balance of the handling.

 

88Turbo II approx 2650lbs, Swifts Springs, 9k front, 7k rear, Koni Yellows, Yaw Control Strut Assembly (Roll Center Correction), Sus Tech front anti roll bar, no rear, 1/4 front rake.

Slight oversteer (Buttonwillow). Yaw Control setup allows for a very low (for 2nd gen racecar standards) right height. "Stuck" w/the yellows up front until I can incorporate a 3-way into the design.

This thing rides better than my daily driver and is a terror on the track.

 

For the smaller tires you run I'd suggest keeping the spring rate quite soft. the 400 275 rates suggested above sounds quite good. A good shock to partner with the soft springs and a decent sway bar will make for a predictable handling car.

-Trent

 

This!

I run a decent quality shock and softer "than normal" spring and my car does very well!

 

Im getting a lot of recomendations to remove the rear sway bar and replace the front bar with a stiffer one. Is this the norm on FC's? I understand that a looser rear is going to make the car a lot less tail happy, but is it necesary?

 

Front 450
Rear 275
Speedway front bar
Rear toe eliminated
AD double adjustable

 

nope! we ran stock bars for years. i do suggest you take the 5 minutes and disconnect the rear bar, and see what you think. depending on the track it may be better with or without