I finally got them tested at Eibach.

Chuhatsu lift springs:
Front: 129 lbs/in
Rear: 206 lbs/in

For comparison purposes:

Car: Front OE Spring Rate:
Subaru BRZ 27 N/mm (153 lbs/in)
Scion FR-S 23 N/mm (131 lbs/in)

Rear OE Spring Rate:
Subaru BRZ 34 N/mm (195 lbs/in)
Scion FR-S 37 N/mm (211 lbs/in)

A bit of a hijack, but sort of related to Mav's post above: Are there different spring part numbers for our cars based on option packages/vehicle weight, or are all BRZ springs (non including special package models like PP, tS, etc) or FR-S springs the same rate? I've been wanting a set of BRZ front springs for my FR-S, but want to be sure my ride height is going to stay where it is right now. Since our cars have very few items that are optional, I assume they are all the same within a given model, but just want tbe sure.

Hmm, it looks, like fronts may become a bit overdamped then? As side gain, maybe car will be less understeery then stock even without camber changes.
P.S.
Maybe worth adding those rates to OP.

Thank you so much for posting the spring rate information.

Near OEM spring rate and an extra 15mm of wheel travel, I am ready to get a set.

How do I order a set for AT for delivery in the US?

Thanks for that. Interesting...basically close to OEM FRS spring rates.

- Andrew

Well, if you have extra travel available, you don't need a stiff rate to control movement in as restricted an area.

The fronts are barely softer than stock FR-S, so it may just be sample variation. Impossible to determine that conclusion based on one single spring test. In N/mm it's 22.68 front on Chuhatsu vs 23 on stock FR-S.

Are there any installation instructions in English? Any North American suppliers?

https://frsport.com/chuhatsu-plus-cp...z-zn6-zc6-2013

No need for installation instructions in English unless you're doing spring installation for the first time ever.

this is exactly what I need. Now to decide whether to use OEM dampers or get Konis...

If not the shortages of Bilstein, i'd also think of B6. Otherwise .. OEMs, if they are in good shape. Used MY2017 when they appear among classifieds. Koni yellows? Hmm, also probably may work.

I've had a set for sale for dirt cheap for months... A little damage, but they still work. I don't think anyone really wants them. "Coilovers and slammy McSlamerson, camber, Bruh."

Hi Mav, are the OE springs used for comparison on the BRZ, from the older MY or 2017MY?

Data pulled from other parts of the forum.