KiKaZ-tC

iTrader: (1)

I am confused on what kind of spring rate setup would be best for track racing... any info or experiences would be helpful!

First off, I notice the stock spring rate is lower in the front than in the rear, is this because the tC has Mcpherson and double wish-bone suspension? I also noticed that a majority of companys are also making their spring rate setup stiffer in the rear than in the front. I would think that putting stiffer springs in the front would be more beneficial considering that a majority of the weight distribution is on the front of the tC 60/40.

What is your opinion on the best spring rate setup? Stiffer in the REAR or in the FRONT?

KiKaZ-tC

iTrader: (1)

any opinions... BUMP

TheQuietThings

Its the same reason why TRD only puts out a rear sway bar.

If you stiffen the front too much, and go into a corner too hard, there is a GOOD chance you are going to either:
1. Understeer miserably
2. Cut the corner too hard and lose control, and possibly spin out uncontrollably.

the tC's biggest problem is its rear end and keeping it on the ground in hard turns [body roll]. Maybe this is because of weight distribution/glass roof or just because it was not designed for high speed turns. Nevertheless, keeping the rear flat and on the ground will improve the handling and be somewhat safer.

I'm not saying that it is dangerous to tighten the front, but for a driver who is not 120% sure on how the car is going to react in high speed turns. they might be cruisin' for a bruisin'

So IMO

slightly stiffer in the rear then the front

Mid_Life_tC-risis

I'm not a suspension expert, but on a FWD car you want a stiffer rear spring rate so you don't have a front drive wheel breaking loose on hard cornering and spin out, like QuietThings said. On a FWD car you want to keep distributed weight over the front wheels, and over the rear wheels on a RWD.

This article explains it somewhat, it's mostly about sway bars on RWD cars, the FWD info is at the bottom. Since sways effectively increase spring rates during cornering (or on uneven terrain) I think this applies to the discussion:

http://www.stealthtdi.com/SwayBars.html

KiKaZ-tC

iTrader: (1)

I've read several articles on FWD suspension setups and I am definitely no expert which is why I started this topic.
I have some srs eibach springs with ground controls I plan on putting on really soon, now... GC sent me the set of springs with the stiffer springs in the front than in the rear - 440 FRONT/350 REAR. After reading several articles and seeing the suggestions posted by you guys, I plan on switching the springs around so it will be 350 FRONT/ 440 REAR.

More opinions on this topic would be great!

KiKaZ-tC

iTrader: (1)

Generally a FWD stock suspension setup (stiffer springs in the rear than in front) is made to understeer because the average driver may be accelerating into a turn too quick (inexperience) and their car will begin to understeer which naturally this average driver will want to slow down, therefore... they lift-off the throttle, which causes lift throttle oversteer which helps the average driver fix themselves. I may be wrong, but I believe this is the way car manufacturers intentionally setup stock FWD vehicles.

TheQuietThings

a FWD car will normally understeer when the throttle is released, normally getting back on the gas will pull the car back into the turn.

what im saying, is if the front is too stiff, the car will snap/oversteer and you could lose control. You stiffen the rear end so that the rear always has more grip than the front and you won't spin out.

Mid_Life_tC-risis

Doesn't sound like your springs are for a tC, or even a FWD car. For example, Tein's springs & coilovers for the tC all have a significantly higher rear spring rate, and cannot be swapped between front & rear.

Hat_Trick_Hokie

iTrader: (1)

x2, they are different sized springs on the tC.

KiKaZ-tC

iTrader: (1)

GC comes with SRS eibach springs which are interchangeable. Also, I assume your talking about how generally springs are LONGER... not the rate. Both of these eibach springs i have are the same length and the part number is on the ground controls box, I'm not too worried about the length of the springs because these GCs are adjustable. I guess i'll have to see... I tried to put them on today but apparently this gold cap which keeps the shock in the strut housing was in the way of the GC sleeve. Also I purchased these GC used from a SL member, parts# match, spring# match (verified w/ GC).

If this doesn't work, I was also given some longer springs from the former owner of the GCs which he had ordered extra to support the extra weight of his sub and big drop for his 19" rims. I guess he had to get rid of his tC and was getting rid of parts... i got these Ground Controls w/ an extra set of springs for $200 (great deal!).

divisii

I know little, but find it odd that the suspension geometry on Tc is so outta whack.

Maybe the problem's some other source, but I want to research the suspension geometry of other FWD before trying to improve the main weakness in the Tc .. handling.

I can only think, other similar (FWD) vehicles I've had demonstrated better performance with seemingly lessor quality setup (& on smaller tires).

Hat_Trick_Hokie

iTrader: (1)

How so?
Could this also be because of the tC's no-so-light weight, and the fact the glass roof add weight to possible the worst area (top) of the car for handling? Older model Civic/CRX's for instance will benifit from a lighter weight and better center of gravity, not necessairly that their suspension geometry is more advanced.

JSC_Speed

By default (for the reasons the OP stated--the general inability of the normal person to properly control their car) most cars have been engineered to understeer (this causes the car to go straight when trying to corner to fast). FWD cars are more prone to throttle ON understeer because of the limits of adhesion (friction circle). So, when John Smith gets behind the wheel and tries to stay in the gas while taking a turn the car is going to push or understeer. Mr Smith's initial reaction is to LIFT OFF the throttle, and engineers know that is what Mr Smith will do, so they make the car turn BETTER when the throttle is lifted.

So, to correct understeer in a FWD car (assuming all suspension is still stock) you take your foot off the gas.

Of course there is a point at which lifting off the throttle becomes bad, but that point is generally very high and commonly only crossed by those street drivers too stupid for any amount of engineering to fix or those on the track that know when to expect and correct this phenomenon.

This is the same reason aftermarket suspension companies (like Hotchkis) only sell the sway bars in front & rear kits for certain cars (the tC being one of those). If they sold just the rear bar (like I want), there'd be all sorts of non-drivers with tail happy FWD cars.

One reason coilovers and springs for FWD cars have stiffer rear rates is for acceleration and front/rear weight transfer. When you step on the gas the weight shifts backwards, off of the drive wheels. Stiffer rear springs help to keep the front drive wheels in better contact with the ground. These springs don't really do a lot for body roll and left/right transfer...this is where sway bars come into play.

Most autocrossers (and even road racers--to a lesser extent) don't care if the inside rear wheel lifts up, it's not doing anything anyway. My GTi loved to be on three wheels (thanks in part to an super-stiff rear sway bar and PSS9s). I race against Minis that tricycle constantly, and are pretty much set-up to do that. Obviously, in an ideal situation all four wheels stay in contact with the ground, but I can tell you from experience, that there is very rarely a perfect scenario in suspension tuning. It's all about compromise.

KiKaZ-tC

iTrader: (1)

^^^^^ thank you very informative

Menace

x2

JSC_Speed

No problem.

As for correct rates for the tC: There are a tremendous number of variables that play into the "perfect" spring rate. If you are autocrossing then very stiff springs might be in order (the Evo I autox uses 10K (560lb)/12K (680lb) springs plus some big f'n bars--and yes the inside front wheel will lift). For road racing most guys run softer rates (had 6k/7ks on the Evo for that).

For the absolute answer on correct rates try out this calculator<--click

For springs I personally like the Tein H.Techs for street driving and Track days (with OEM dampers). For Coil Overs I would get the SS or SS-Ps if you do a decent number of autox but still daily drive. If you are very serious about either track days or autox, then get custom valved Konis and race springs by Eibach, or get Tein coil overs and have them revalved and pick up some of their race springs.

You should also chat with guys that autox/race the tC to see what rates they are running, but remember, what type and size of tire you run along with wheel size can play a major part in the correct rate.