blame springs or dampers most
 

We are tiring of the jiggly harsh ride. Everything is o.e.

Tire deflation from 35 to 31 makes negligible difference but when worn we will replace with ones with softer walls.

The next step is suspension. Which is mostly to blame of these two --- the springs or dampers?

Dampers are more likely to fail first. How many miles/km do you have on the car? Could try to get a fresh set of OEM dampers or upgrade to coilovers.

Coilovers won't necessarily be an upgrade...it could very likely result in the opposite unless the dampers are high quality and tuned well. That said, if OP is willing to spend the money on a quality set, it could yield some good results.

OEM dampers won't be much better IMO, though the Sachs dampers from the newer models are markedly better.

If ride quality is your primary concern, maybe consider getting smaller sized diameter wheels with taller tires? Like a 16x8 maybe? Having a taller sidewall will provide some extra cushion over the bumps and can make a noticeable difference in ride quality, especially if you choose a cushier tire.

2013? OE shocks? Imho they might be to worn by mileage. Try to get used set of MY2017 shocks from someone parting out after change to coilovers.

My 2017 PP Sachs suspension was rubbish in my "opinionated" opinion......

They lasted 4k km before I swapped them out with some MCA Street Performance coilovers.

The MCA's are much much better everywhere.

Thanks for the comments people. Although everything is still o.e. and are now 5 years old, the mileage is only 30,000miles / 53000km. It has hardly done any distance on rough dirt roads.
Moreover, I recently demo-drove a latest BRZ to compare ride quality as I heard they were better. I took my car on the same route. Beforehand I ensured tire pressures on both cars were all at 35psi. Any difference was minimal so I do not think the dampers are deteriorated.

So my question remains is the harshness/jiggliness due more to springs or dampers?

Dampers

Well in my opinion, mine were rubbish on anything but smooth roads, bumps and speed humps = crash bang.

My new coilovers are much more compliant on low speed bumps and speed humps, and the performance at speed is night and day.

I believe the OEM valving was designed around smooth surfaces, throw some real world local roads in the mix and the OEM's fall over badly.

Opinions will vary.

My advice is to go for a spin in a car with "decent" coilovers and see what you think.

Be aware that alot of aftermarket stuff, if it isn't valved and sprung right, will be poor for daily use.

My coilovers are valved and sprung for real world roads, but are still very good for "spirited" driving and the occasional track day and khana.

There is always a compromise when you want performance and comfort, I believe mine are on point for my requirements.

Happy hunting

IMO...

Dampers - Upgrade to koni yellow or Bilstein B6. This should (if any of the reviews are honest) give you a better and more comfortable ride.

Springs tend to not wear out. (though older springs sagged pretty bad) I am betting with the miles (kilometers?) you have put on your car, that your springs are just fine.

OE springs are as soft as you'll get, aftermarket is stiffer. Maybe if koni offered their fsd that'd be the way to go but idk, everyone who buys a sports car wants to make it sportier, not softer. I agree, OE ride is pretty sub par.

Ride quality is almost all down to damping. Crappy dampers will feel both *harsh* due to excessive high-speed damping, and "jiggly" due to insufficient low-speed damping. Decent dampers cost more...

I would have to agree and say that the 2013 Scion FR-S rides pretty harsh. I recently swapped my suspension to Tein Flex A coilovers and I tuned it to about 15 clicks and it's almost as soft as a normal passenger car. I am running 35 PSI and MPS4. There is body roll if you corner hard though... of course you can click it to something stiffer.

The Flex As also have a Hydraulic Bump Stop (HBS) to help with bumps and stuff like that. It seems to have helped out for comfort in the terrible LA roads we have here.

Did you re-use your OEM tophats?

No. I used the camber plates that Tein supplies on their coilovers. I didn't modify the coilover.

What tires do you have on the car?
(NOT size,but actual brand/model)