FWD Spring Rates Front VS Rear.

[Martini Focus]

Short Version.
After taking my coilovers out for a clean I noticed that I was getting coil bind on the front springs. My rear springs had sagged to the point that I was getting some fender rub.
My front springs were 2.5"x 7" x 275lb and my rears were 60mm drop in a standard Focus size approx 225lbs. I decided to replace the front springs after consulting with a few people who race and or Rally their Focus with a 2.5" x 8" x 375lb spring. I wanted a taller spring to move my perch back down the thread and gain some more fender gap, not much just enough to keep it off my rim. For the rears I bought a used GC rear Focus kit with a 2.5"x 8" x 350lb springs. The reason I got the GC setup was because nobody makes a spring for the rear of the Focus that higher than about 250lbs that doesn't drop it to the ground... well other than H&R and in that case I was going to have to buy the full kit which was twice as expensive as the GC setup.

My question is did I make a mistake with my spring rates being too close? I've been told that a stiffer rear spring will help make the car rotate in the same way a bigger rear bar will.

What's got me confused is that with some of the kits available for the Focus the front springs are between 80 and 100lbs higher than the rear and in other such as the H&R the rear is 50lbs higher than the front.

Worst case I guess is that another set of springs to fix this is only $100, but I'll wait until I install them on Friday and run them on Saturday and Sunday to reserve final judgment.

Anyone got any suggestions, have I created my own personal undrivable handling nightmare??:confused:

[AndyC]

Should be better than stock --It will rotate better with the stiffer spring out back. Alot of honda/acura's run a much stiffer spring in the rear e.g. my integra had 500lbs front and 670lbs rear and some go as much as560F and780R. Pretty rough on the street but great at the track. If you want more rotation add a stiffer rear sway bar

[ScotcH]

I had H&R on mine 300 front 200 rear (about). I upgraded to GCs 500 all around, and the car definitly rotates more. I don't think the idea is that the spings need to be higher in the rear ... just that the ratio of front rear favours the rear compared to stock. Does that make any sense? For example, my H&Rs were 3:2, now I have 1:1 (or 3:3) so the ratio favours the rear more. I'm sure that if I went with even higher rates in the rear (like 800), I'd get even more oversteer, but as you said, better try it first, them make your decision.

Also, remember that the rear is only like 40% of the weight, so even though the rates are the same, the rear is actually stiffer since the spings are carrying less weight.

Ok ... time for the experts to speak :)

[ctenche]

Kits usually do come with stiffer front springs, not because that is the optimal setup but because it is the "safer" setup whereby the car will understeer. Stiffer rear springs will definitely help your FWD car get mroe rotation, which is as Martha Stewart would say, "a good thing."

I'm surprised that you're having such a hard time finding the spring rates that you want. You can get Eibach ERS linear rate springs, in a wide variety of diameters and lenghts from Wheel and Tire Zone or Northern Performance to name a few. You should not have any problems getting the right springs. FYI, the GC springs are rebadged Eibachs.

[Martini Focus]

Originally posted by ctenche
I'm surprised that you're having such a hard time finding the spring rates that you want. You can get Eibach ERS linear rate springs, in a wide variety of diameters and lenghts from Wheel and Tire Zone or Northern Performance to name a few. You should not have any problems getting the right springs. FYI, the GC springs are rebadged Eibachs.

Finding the springs was only a problem because on the Focus the rear shock mount and spring mount are separate so I can't run a true coilover. Other than the H&R I couldn't find a spring that would fit the OEM application.

The reason I'm getting them from the US is because I have a warehouse in buffalo where I have everything shipped then I just drive over and pay the GST on the way back. I was originally dealing with RacersEdge in Nashville as they were a Leda distributor and I wanted to make sure that I was getting something that would work with the setup I already have. I'll have to look localy next time.

I was aware that the GC's are rebadged Eibachs, but the spring that was in the used kit I bought was not suited for my application they were 10" 200lb springs. The springs I'm getting are hypercoils.

Thanks for the help everyone, I guess I haven't inadvertently created a poor handling monster, but I'm excited to see how it handles now.

[ice/solo racer]

When comparing spring rates don't forget to that your really looking for wheel rates over actual spring rates.Comparing the spring rates that work for certain civic versus your focus may prove very misleading.You need to look at the location of the strut mounted on the rear control arm to calculate the wheel rate.
For example the new civic SIR has a different rear setup than the previous generation(the write ups say its the same,its similar but not the same)and a spring rate of 900 lbs only generates a wheel rate of around 500 +,big difference eh?
All I'm saying is the rates chosen for the focus may be that way for a reason,I'm not familiar with the focus at all however.
Give the springs you have a try,than you can decide if adjustments need to be made.Oh yeah don't forget that to get a car to rotate at will at solo 2 speeds will likely be scary if a sudden emergency lane change or other high speed change in direction needs to be made.Perhaps an adjustable rear sway bar might provide to range needed for both slow and higher speed activities.
Just my .02 cents.

[Martini Focus]

Originally posted by ice/solo racer
Oh yeah don't forget that to get a car to rotate at will at solo 2 speeds will likely be scary if a sudden emergency lane change or other high speed change in direction needs to be made.Perhaps an adjustable rear sway bar might provide to range needed for both slow and higher speed activities.

I really appreciate the information, and I totally agree and am concerned that a setup that may well be great on the Solo II course may cause me to write my car off on the street, where I’m perhaps not quite prepared for what the car may do. At the moment I’m really just trying to get the car to a place that is a good starting point that I can build on. Ideally and I feel silly for saying this I would like to go back to the stock setup and learn to drive the car to those limits and move on from there. But now I’m stuck with a Leda coilover system that is light-years more advanced than what I need. The system was also designed at my request for a dropped look for shows and some light track or Solo II use. After a year of showing the car I just want to drive it on the streets on sunny days and get it to as many track and Solo II events as I can. I’ve looked into rear bars and so far nobody is making anything other than a 22mm or 25mm bar for the Focus neither of them adjustable. Good advice or not I was told by two different respectable people that throwing a bigger bar at the rear of the car is that last thing I should do in my situation. I guess I really just need more seat time this summer to improve my driving skills.

BTW are there any FWD driving schools out there??

[andrew1984]

FWD rulez.

[ice/solo racer]

I'd hate to be in your position,you know stuck with those leda's and all!:rolleyes:
You sound like you have resources so why not make your own adjustable rear bar?its quite easy to do,buy the biggest bar you can and weld on a piece at the ends with 4 holes,1 hole shorter than the original end link mount and the other 3 longer than or 2 and 2 whatever you like.
At least then you can make it slightly stiffer or noticably softer for the conditions.
With regards to a FWD driving school,any driving school will help no matter what end of the car is driven.The car doesn't if its FWD,RWD or AWD and any of them can be made to act like the other(within reason)or to respond at will to the right commands.
Just remember that FWD carries about 60%of the cars total weight on the drive wheels,makes it very easy to overload the possible traction up front and understeer like a pig and adding throttle/braking only makes it worse.Smooth driving commands and the right combo of spring rates/bar sizes will make a FWD a real ball to drive.
Oh yeah,when the back end steps out in a FWD the right amout of counter steer and throttle on will PULL you out just about every time.;) .
Does your car have an LSD?if not then adding a bigger rear bar will help in putting power down at corner exits with more weight transfered onto the inside front,stiffer rear springs also reduce a corner exit push by reducing the rear weight transer off the front.
See what I mean by the right combo,simply put its gathering info and trial and error.My own car is working really well this season but I'm still going to try an alignment change to see if I can reduce a slight understeer when the tires are warm(cold tires is fine,so maybe the car will be real tail happy at first).With the hoard of fast BSS guys I can't relax at all,I want my 7 wins to see how I can finish up in the overall points.
I have the copper corolla,come on over and introduce yourself this weekend.

[DuPontRacing]

I know its a little late, but here are some spring rates i found for the focus if its any help to you
SVT
F: 129 lb/in
R: 157 lb/in

ZX3/LX/SE/ZTS
F: 117 lb/in
R: 126 lb/in

Eibach Pro
F: 137 lb/in
R: 171 lb/in

Eibach Sportline
F: 131~262 lb/in
R: 102~171 lb/in

Progress
F: 142 lb/in
R: 160 lb/in

Steeda
F: 136~160 lb/in
R: 190~280 lb/in

Intrax SVT Springs
F: 225~275 lb/in
R: 275~325 lb/in

H&R Coilovers
F: 370~460 lb/in
R: 260 lb/in

H&R Race springs
F: 325 lb/in
R: 375 lb/in

Ground Control
F: 450 lb/in
R: 450 lb/in

Tein S-Tech
F:157 lbs/in
R:179 lbs/in

Tein Coilovers (this was from another thread so I dont know if its correct)

F: 280-504lb/in
R: 392lb/in

Leda Coilover(Custom)
F: 460 lb/in
R: 380 lb/in


hope it helps :)