Actual Spring difference BRZ vs FRS

[Esoteric]

The rear rate bias in the FR-S is to make the car more 'prone to/ easier to initiate oversteer' on demand. Higher rear spring rates also help a chassis feel urgent on initial turn in. The car feels lively

That said, its popular with some drivers, not so much with others.
I'm with Randy, I don't particularly find that the FR-S rates are setup for maximum confidence for grip, but they do make for a wonderfully dynamic and fun driving experience.
If your coming from say, a well setup BMW, the FRS feels over-sprung in the rear. This is my personal feeling of the FRS rates as well.
This isn't to say that BMWs don't often have a lot of rear rate too, its just different from tuner to tuner, driver to driver.

My finding is that the chassis naturally has a lot of grip, more than many of the reviews you read will lead you to think... and this was to help make the rear a little more of a dance partner, but I'm not so sure that this will always be the trend in aftermarket setups for the FT86.

Anyhow, analyzing of these rate differences between FRS and BRZ should finally help dispel and educate people of the myth that factory spring rate ratios front-to rear-should stay similar, but simply increase in total rate. Balance is important but just because a FRS is so fond to to rotate on lift and the BRZ is more setup to 'take a set' doesn't mean one or the other is right.

[blu_]

Originally Posted by Sam Strano

As for more neutral, well, that can also mean "have more understeer" vs. a car that is more free (which doesn't mean it's a oversteering mess either).

It can mean that, but a car can have both an understeer and oversteer character to it (ie a 911, where you have a decent amount of push at entry, which turns into oversteer after the weight transfer gets sorted out mid corner). I have read several reviews that suggested the frs was like this to drive, while the brz was more naturally neutral (most likely a bit sharper turn in from the stiffer front springs, and not as much desire to rotate after that)

Which style you like more is really personal. Like Esoteric, I personally would bet an frs is more entertaining to drive, while some reviews have stated the brz might be more confidence inspiring on a track.

I haven't driven an frs yet though, nor taken my brz to the track so take that for what it is worth.

[Esoteric]

Sorry for the LARGE pic...
Anyway, we adjusted away from factory alignment and I feel the rear biased rates are working a bit better these days on the FRS with this change.
Doing Auto-X this week. Track days at end of the month...

So far, a guy with an S2k got seriously flamed when he talked about the personality of the FRS... but his wording, unhappiness with the power curve, combined with the fact that he found the FRS to feel "artificially RWD feeling" or to that effect caused him to be chastised...
He was not altogether wrong... He was talking about rear "passive steer" and the FT86 has a very different bump steer geometry than most fast RWD cars, this too makes the rear rates work funny... But thats another story for another thread

Once more companies release front sway bars watch how many people go after them like crack.
It will be the same thing that happened in the Impreza/STI world- dollar for dollar it may be a highly enjoyed upgrade, but its only one way to skin a cat.

[Sam Strano]

Oversteer was not a default action on my FR-S. In fact it was very hard to get it to oversteer unless I hugely provoked it and even then it was tough to keep it in such a state.

Now, the car is kind of twitchy feeling on turn in, mine was. But most of that was cured with better tires. Once I got the KW's on it (and the spring changes I made to them), and aligned, oversteer is no issue, at all. In fact the car could easily handle a lot more power.

As for the 911 comparison. Well, that's not the world's most balanced car. Porsche has worked very hard for years to get that platform where it is, and the Boxster/Cayman are as good and better in a lot of ways with much less development. In fact the reason that 911's tend to use up rear tires when raced is because they are *not* well balanced at all. So I would be careful when holding that car up as a good example. The fact is they are fast because they have been engineered to cover some physics issues. One thing that helps it stay "competitive" is the fact they can put down a lot of power with the engine hung out over the rear.

[Sam Strano]

In all seriousness we are at a place where a lot of folks like to guess and estimate. Happens all the time with new cars. This is a HUGE reason I bought one so early, I wanted in front of the curve on the suspension side.

I've already seen some others putting coil-overs on with spring setups unlike what I run or would recommend, and with much larger rear swaybars. If the idea is to make the car not prone to oversteer, that is the WRONG way to go.

[xwd]

Originally Posted by Sam Strano

In all seriousness we are at a place where a lot of folks like to guess and estimate. Happens all the time with new cars. This is a HUGE reason I bought one so early, I wanted in front of the curve on the suspension side.

I've already seen some others putting coil-overs on with spring setups unlike what I run or would recommend, and with much larger rear swaybars. If the idea is to make the car not prone to oversteer, that is the WRONG way to go.

Welcome to the import tuner community. Slap some $1000 coilovers and a rear swaybar on the car and the suspension is "tuned." Tuned to slide into an off-ramp barrier.

Some of us greatly appreciate having some very knowledgeable people like yourself doing early development on the car.

[Jackson]

Originally Posted by Sam Strano

I've already seen some others putting coil-overs on with spring setups unlike what I run or would recommend, and with much larger rear swaybars. If the idea is to make the car not prone to oversteer, that is the WRONG way to go.

I've seen this too and I think a lot of people are quick to "reuse" the WRX rear bar on the FR-S/BRZ since it's the same fitment. It's interesting to see what companies are doing their homework and which companies are not.

[atledreier]

So, I may be reading too much into this, but the GT86 is even stiffer up front and softer in the rear than the BRZ, so by the numbers it should be an understeering pig. Now, I haven't read too many reviews of the '86 yet but none have mentioned understeer. I'm going crazy over the choise of spring rates, and my car is still 7 months away!

[BAE]

Originally Posted by Motopythons

I found this bit of information regarding the spring rate differences between the twins. The majority of the FRS owners will stick with what they have I assume. But for those BRZ owners who wish to induce a bit more oversteer (while maintaining close to the factory feel)

If you are after lap times I wouldn't set up the BRZ for more oversteer. In this test they run lower lap times with the BRZ because it is more neutral at its limits.

http://www.ft86club.com/forums/showthread.php?t=6776

[ABQautoxer]

That's likely more about the shock package difference than the spring rates IMO.

[icemang17]

great thread......interesting on the stock spring rates & the plausibe differences between the BRZ-FRS.....but for just about anyone who does Autox or trackdays it really doesn't mean much, since the stock parts are going straignt to the bin anyway....

What I find intersesting is how heavy the rear springs are in a front engined car with 55% weight bias to the front..... In my front engine-rear drive race car thats 52% on the nose I run front springs nearly twice as heavy (800lb front 450 rear)....mostly to reduce roll in the front vs running a stupid large sway bar that picks up the inside tire and reduces overall traction..

My intial impressions on track with my bone stock FRS was interesting....while its extremely "lively" on turn in with great feel, the tires SUCK and the suspension does need improvement.....its a great street-track tradeoff but for serious track work it needs to be much stiffer with more roll control, more rebound control and lower ride height....

[Racecomp Engineering]

Originally Posted by icemang17

great thread......interesting on the stock spring rates & the plausibe differences between the BRZ-FRS.....but for just about anyone who does Autox or trackdays it really doesn't mean much, since the stock parts are going straignt to the bin anyway....

What I find intersesting is how heavy the rear springs are in a front engined car with 55% weight bias to the front..... In my front engine-rear drive race car thats 52% on the nose I run front springs nearly twice as heavy (800lb front 450 rear)....mostly to reduce roll in the front vs running a stupid large sway bar that picks up the inside tire and reduces overall traction..

My intial impressions on track with my bone stock FRS was interesting....while its extremely "lively" on turn in with great feel, the tires SUCK and the suspension does need improvement.....its a great street-track tradeoff but for serious track work it needs to be much stiffer with more roll control, more rebound control and lower ride height....

You can't directly compare the spring rates from two different types of cars. The rear suspension of the BRZ and FRS has a lower motion ratio than the front, so even though there's more weight on the front you would need a higher spring rate to get a similar "wheel rate."

See this thread for an explanation:
http://www.ft86club.com/forums/showt...688#post280688

- Andrew

[blu_]

Originally Posted by Sam Strano

As for the 911 comparison. Well, that's not the world's most balanced car. Porsche has worked very hard for years to get that platform where it is, and the Boxster/Cayman are as good and better in a lot of ways with much less development. In fact the reason that 911's tend to use up rear tires when raced is because they are *not* well balanced at all. So I would be careful when holding that car up as a good example. The fact is they are fast because they have been engineered to cover some physics issues. One thing that helps it stay "competitive" is the fact they can put down a lot of power with the engine hung out over the rear.

I was just making the comparison to point out that understeer and oversteer are not mutually exclusive. The 911 is the first thing that came to mind when thinking about cars with initial push, followed by oversteer. It still seems to me that Toyota purposely tuned the spring rates to create a more drift friendly/fun unbalanced car. The larger point though is that its not possible to compare the brz vs frs as understeer vs oversteer.

[blu_]

Also, as far as contemplating putting a WRX rear sway bar on, which I definitely have contemplated... the idea was to make the car more prone to oversteering. If you have one laying around why not see what happens

At least with me, I knew it wasn't going to be faster around a track, or more stable.