POLL: Front and Rear Spring Rate Ratio - Page 2

Djazair · Jun 19, 2006, 05:56 PM

remember to inculde the rear sway bar stiffness in this. softer rear spring setups usually have a big rear bar, but this makes the rear suspension less independent, causing inside wheel lift etc. just comparing spring rates without including the sway bar really isn't a good comparison.

chmodlf · Jun 19, 2006, 07:07 PM

Quote:

Originally Posted by Djazair

remember to inculde the rear sway bar stiffness in this. softer rear spring setups usually have a big rear bar, but this makes the rear suspension less independent, causing inside wheel lift etc. just comparing spring rates without including the sway bar really isn't a good comparison.

I hear what you are saying. But I disagree. As a general concept it is a valid question IMHO.

Djazair · Jun 20, 2006, 12:13 AM

Quote:

Originally Posted by chmodlf

I hear what you are saying. But I disagree. As a general concept it is a valid question IMHO.

Hope I didn't imply that I was questioning the validity of your poll, it's just that I've seen too many times where people are looking at specific differences between two cars where there are systematic reasons for such differences. I just hope people in this forum see the forest thru the trees...

redvolution · Jun 20, 2006, 04:10 PM

sway bars: front = stock; rear = 25mm progress bar on the middle setting
camber: -2.5' front, -1.5' rear
toe: zero all around
rear trailing arm bushings and Whiteline anti-bumpsteer kit

I read many threads, books, and other websites relating to spring rates and ultimately decided to go with the Works Stage3 because I like the people there and it's local to me in the SF bay area. I wanted to experiment for myself and actually feel the difference wrought by various changes. Of course learning costs money and this is no different.

After dropping the front rate down I noticed a bit LESS push - since I wasn't near the optimum slip angle at all it was merely a sensation of better balance; the car felt like it was using the front and rear tires together more effectively. Could be my imagination. I'll know more after my July 6th trackday at Thunderhill.

redvolution · Jul 7, 2006, 12:46 PM

After Thunderhill yesterday I can say that I'm happy with the 500/500 setup and I'll be staying with it.

It's reasonable on the street and the front-end bites better especially on downhill (Thill, 5b) and low speed (Thill, 11) corners. Not only that, I could get on the power sooner without the front end washing out (Thill, 2).

A tiny bit of understeer persists but I prefer that for safety. I don't want to drop the front any more because that will result in more roll and more dive.

The afore mentioned handling differences weren't entirely due to springs. I also lowered the rear 2 turns (Ohlins R&T, haven't measured exactly how much it was) and added a tiny bit of toe-in to the rear. I don't claim this is the fastest setup but for me it's great - predictable, safe, decent on the street, etc.

Once again the RacingBrake BBK was fantastic. No fade at all on a 90deg day using ATE fluid. Even when I locked up everything and got squirrelly I kept it under control and on track.

EVOlutionary · Sep 11, 2006, 12:37 PM

Stock has higher spring rates in the rear for a reason. Mitsu engineers aren't dumb.

chmodlf · Sep 11, 2006, 01:49 PM

Quote:

Originally Posted by EVOlutionary

Stock has higher spring rates in the rear for a reason. Mitsu engineers aren't dumb.

Yep. Especially if you want the car to turn!!! That is unless you thrive on understeer.

It seems that folks that use higher rates in the front need to use a strong rear sway bar and high tire pressures in the rears for an evo that rotates.

For those who only drive straight (the drag racers) or do not "race" their evos the higher front rates will give the rear a less twitchy feel.

chronohunter · Sep 13, 2006, 04:12 PM

just got this months SCC and the RobiSpec car entered in the USCC has 450f/550r springs and no mention of an aftermarket rear sway bar...

it all sounds vaguely familiar (that set-up) can't quite put my finger on it

robi · Oct 20, 2006, 01:43 AM

you believe everything you read?....hehehe

EVOlutionary · Oct 20, 2006, 08:22 PM

450/550 - sounds much lighter than what many guys use for autocrossing. Do you find that in general you want softer springs and more compression dampning for slower transitions (road course), and higher spring rates and lower relative compression damning for faster transitions (autocross)?

EVOlutionary

robi · Oct 20, 2006, 09:09 PM

the biggest factor is the total traction avalible....255 ra-1s vs 285/30/18 Hoosier/Kuhmo DOT slicks.....require a whole different set-up......"less expensive" damping stacks also trade precision and travel for "control"....(the last is my opinion) reality is that I can "get away with" 2KG lighter springs with the Double aadjustable KW's and get almost stock wheel travel which leads to a better ride too....

EVOlutionary · Oct 20, 2006, 09:22 PM

Thank you for the info! I can't wait to try my AX setup on the road course next year to see just how good or bad it is compared to a road-race specific setup. As it's set up right now I can get it to power oversteer in almost any corner. With last year's setup it understeered and pushed wide anytime I looked at the gas pedal!

I'm gonna talk with David this winter about getting some REAL downforce for the front end of his time attack car next year. I think I might have the ticket!

EVOlutionary

chmodlf · Oct 21, 2006, 06:58 AM

Quote:

Originally Posted by EVOlutionary

450/550 - sounds much lighter than what many guys use for autocrossing. Do you find that in general you want softer springs and more compression dampning for slower transitions (road course), and higher spring rates and lower relative compression damning for faster transitions (autocross)?

EVOlutionary

As Mark Daddio once told me (if I remember correctly), r compunds in autox require much higher spring rates than a road course setup (900lb???). But then since many daily drive our evos, the ride would be just a bit stiff--even with mysterious magic super duper valving from the suspension tuner of your choice...Unless your world revolves around those autox runs.

EVOlutionary · Oct 21, 2006, 04:03 PM

Interesting . . .

My car "seems" to handle great with the stiff suspension even on lower grip street tires. But then again, there could be a whole other level of grip I can't even imagine just waiting for me somewhere out there! I definitely want to check out some other setups next year when I attend a time attack, road race, or open track day/HPDE. It is cool how even with the same car, there are so many variations out there!

point&shoot · Jul 31, 2007, 06:57 AM

So what spring rates are you using, evolutionary, and how did those spring rates work out for you this year, in AutoX? I'm trying to set up my Evo for AutoX, and am having trouble making the car loose enough. I went from the default Stance coilover springs (500F/450R) to (500F/550R) and that didn't seem to help significantly. I also have a 25mm Perrin rear sway bar set to full stiff, but its not enough. (This is on 255 width Kumho V700's, by the way, so I don't have a huge amount of traction.)

We're also having trouble with inside front wheel spin on corner exit. (I've got an '03 with the open front diff.)

I believe that there's becoming a consensus that you want about 1/3rd stiffer spring rates in the rear, than in the front, do you agree? I know at least one top driver is using 12kg front / 16 kg rear, for example.

Thanks.