Mix & Match stock FR-S and stock BRZ suspension and/or springs

[Weasel Soup]

I've had my FR-S out to three RallyCrosses and one Auto-X and will be using the car in more Rally-X this year, including the National Championship, and probably more Auto-X in 2015. In the first Rally-X, cool & wet conditions, I used a combination of two year old 16" rally tires in the front and new 16" snows in the back. At all the other events I was on the stock Michelin rubber, intentionally, to learn what the car was going to do when it exceeded the traction limit.

I'm now in the process of starting my upgrades. The car will see Rally-X in about two weeks and it will be on a full set of 16" rally tires at that point. The only current changes to the car are a tune and an additional bar to triangulate the front strut towers. I have a set of HVT camber plates on order, along with a rear trans mount insert and a set of the TiC Delrin steering rack bushings. The camber plates are on a bit of a back order so I'm doing a little more digging about springs while I wait.

Don't try to talk me into lowering springs, I'm not interested right now. I did however find this interesting:

SPRINGS Front/Rate Rear/Rate

OEM Toyota 86
Front:0.0"/2.3k Rear:0.0"/3.3k

OEM Toyota GT86 (EU)
Front:0.0"/2.3k Rear:0.0"/3.3k

OEM Scion FR-S M/T
Front:0.0"/2.3k Rear:0.0"/3.8k

OEM Subaru BRZ M/T
Front:0.0"/2.7k Rear:0.0"/3.5k


This got me thinking about putting BRZ front springs onto my car at the same time as when I put on the camber plates. Has anyone done this? Can any of the suspension companies/gurus tell me if this is a good or bad idea? And instead of replying with just a "good" or "bad" could it please be backed up with empirical and/or mathematical data?

Also, has there been any testing done that prove that the shocks/struts/dampers are any different between the FR-S and BRZ?

Thanks for reading. Hopefully I can learn something here.

[wparsons]

From what I remember, anyone that put the shocks on a shock dyno found them to be the same between FRS and BRZ, but I don't have any first hand experience between them.

As for the springs, if you run BRZ fronts with FRS rears you'll shift the grip balance towards the rear so the car will be slightly less neutral, but not as understeer biased as the BRZ since you're not touching the rear rates.

It'll really depend what you're trying to achieve if it'll help or not. Do you find it oversteers too easily for you, or bottoms out too much up front?

[Panman]

Dampers are exactly the same between FR-S/86/BRZ, there was some misinformation in an early review which seems to have perpetuated itself. Shocks/Dampers have changed for the MY15 model year with slightly different valving than prior years in the interest of ride compliance.


Anyone who tells you that the shocks themselves are different between the different models is incorrect. I have the STI Pink springs on my 86 and am very happy with them, but the mix and match approach would be interesting, other option would be to pick up a set of the rest of the world 86 springs.

[Weasel Soup]

Originally Posted by wparsons

From what I remember, anyone that put the shocks on a shock dyno found them to be the same between FRS and BRZ, but I don't have any first hand experience between them.

As for the springs, if you run BRZ fronts with FRS rears you'll shift the grip balance towards the rear so the car will be slightly less neutral, but not as understeer biased as the BRZ since you're not touching the rear rates.

It'll really depend what you're trying to achieve if it'll help or not. Do you find it oversteers too easily for you, or bottoms out too much up front?

I'm not a track junkie, although I did take my '07 WRX out onto the track twice, but my six seasons of Rally-X was all in FWD and AWD cars before the FR-S. I know RWD takes a bit different technique and that I need to use more finite throttle control, but yes, the car does oversteer a bit. I didn't spin the car when using the rally & snow tire combination, though it sure did wag the tail in the mud of the morning course. I did get a full 360 on the first hard 90 degree turn on the dirt/silt w/the stock tires, and have about 6 spins total in the three events on them. Only one of those was on pavement and it was on my third run and happened because I had carried
waay more speed through the kink and into the sweeper than the previous runs.

I've made use of the factory skid pan about three times, one of those used the air ducting as a bit of a shovel and the car was dripping gravel for between 3 - 5 seconds at speed. That said, I'm not that concerned with bottoming out. Although that stance might change after I drop the skid guard for the first car's first oil change next week.

Long story short, I just had the thought of using the BRZ springs last night while trolling the suspension threads and wanted to get feedback from the forum. Thanks guys, keep the responses coming.

[bimmer635csi]

You could do a quick simulation/approximation by stuffing a rubber in the front springs to see how it will change. It is a lot easier than changing the springs only to find out you don't like it.

[wparsons]

Originally Posted by Weasel Soup

but yes, the car does oversteer a bit. I didn't spin the car when using the rally & snow tire combination, though it sure did wag the tail in the mud of the morning course.

Are you getting oversteer at neutral throttle, or off throttle, or just when accelerating? If you're getting steady state oversteer then the springs might help, if it's under power then they won't help at all. Power oversteer means you'll need more throttle control.

[Weasel Soup]

Originally Posted by wparsons

Are you getting oversteer at neutral throttle, or off throttle, or just when accelerating? If you're getting steady state oversteer then the springs might help, if it's under power then they won't help at all. Power oversteer means you'll need more throttle control.

Strangely enough, with the rally front, snow rear setup the car would push off throttle. Especially if I was making the mistake of shifting up while still accelerating out of a corner. The stock tires (obviously) had next to no grip in the dirt.

[wparsons]

Stock spring rates will give steady state push with matched tires, but I wasn't sure how the mixed tires on dirt would react.

If you're getting push when coasting I wouldn't suggest going to stiffer front springs, it will only make that worse.