Swift BRZ springs: too low for stock struts
 

Installed Swift BRZ Sport lowering springs along with Raceseng camber plates a couple of months ago. I chose these springs based primarily on the rates being about what I wanted to go with the stock Sachs dampers, 34% stiffer front and 43% stiffer rear versus stock. Didn't want to go more than +50% stiffer and didn't want to increase front stiffness bias. And 1.1" lower front, 1" lower rear seemed like it would be a good place to be for street/track.

Initial install was with unmodified stock bump stops. Ride was intolerable due to the car sitting *hard* on the stops. After cutting all four bump stops in half, the the fronts still seemed to be fully locked-up over any bump, however small. I cut the front bump stops down another ~8-10mm, to about 1/3 their original height. Moderate improvement, but still, any bump bottomed the fronts *hard*. Ouch... At this point ride heights were 1.5" lower in front and 1.25" lower rear vs. stock, quite a bit lower than 1.1" front 1" rear advertised, particularly up front.

Last resort: To gain some desperately needed front bump travel, I had a couple of 1/4" aluminum spacers machined up to go between the front camber plate spring perches and springs. Honestly this worked better than expected, the car now goes over modest bumps normally. But still, any bumps bigger than maybe 3/4" to an inch => BAM!!! But at least these are the kind of bumps that are encountered maybe once every few miles as opposed to every 150 feet or so!

The good news is the car is fine at the track, I'm holding my own in time trials competition, so they're not all bad! And I have to say the car looks GREAT at this ride height! But I wish I'd gotten RCE yellows instead (0.8" lower than stock and come with their own bump stops)...

What tires and aero are you running? Sounds more like the springs are too soft for your needs and not necessarily an issue with the swift spring itself.

Tires: 225/45-17 SottoZero III, 245/40-17 RE71R, 235/40-17 NT01. Aero = none (unless you count the dinky stock '17 BRZ Limited "wing"...)

But it is nothing to do with tires, aero, or spring rates being too soft. It's 100% the springs lowering the front of the car too much relative to available front bump travel.

As I think about it, I wonder if the Raceseng camber plates might have something to do with it?

I cut the top 1/3rd off my bumpstops when I put mine in on the stock shocks. I had the FRS rates, but shouldn't be extremely different from an overall experience over bumps.


I didn't notice it hitting that hard over any bumps I normally hit, but the odd really big one I could really feel.


I'm now on V3's at roughly the same ride height, and it's definitely more composed over bumps though.

Yeah, agree, shouldn't be fundamentally different. Did you have stock strut isolators?

It could be partially due to the Raceseng camber plates. If they position the top of the strut higher relative to the spring perch that would take away bump travel. Also they are solidly mounted, no isolation whatsoever. And the bump stop is compressed into a solid chunk of aluminum, whereas it might compress into rubber on the stock setup (I'll check this when I get home).

Stock upper mounts. The bump stop would compress between the stock upper spring seat and the shock body, so metal on both sides.

Hmmm, the middle of the Raceseng spring perch is raised significantly, ~25mm I believe, relative to where the spring seats. If in the stock setup the bump stop gets squished into a surface even with the top of the spring, then the Raceseng setup bottoms ~25mm sooner! Well, that's significant...

^I did the same on the same Swift Sport BRZ rates with MY13 dampers and had similar experience with them. Front did not bottom out easily as you've described.

It's probably about 5mm higher than the top of the spring max, definitely a significant difference to what you've got with your upper mounts.

Are you actually hitting the stops or maybe just not used to the harsher ride?

RCE yellows and Sachs are quite a bit less comfortable on bad pavement than stock springs, and on big dips at highway speeds you will get airborne in your seat if you're going too fast.

It is definitely bottoming out. I've streeted more track-oriented cars on much stiffer springs, it's definitely NOT just the stiffer spring rate. Read description of symptoms and results from raising front 1/4" in previous posts ^^^

Why not just get some Bilstein B8?

Reading the original post, I see you got the Sport springs based around the rates, but would the stiffer Spec Rs perhaps have been a better choice as they would not engage the bumpstops as often? Or is the problem just really limited travel no matter the spring?

Problem is really limited travel no matter the spring rate.