Car feels strange/less responsive after coilovers
 

Hi just trying get a bit of understanding whats going before taking it back to the shop to get thid checked out.

Recently got new wheels for my BRZ tS

Rays gramlights 57Transcend and new tyres MPilotSport 4s

Here are my specs

Old Tires: (Pilot Sport 4) 215/40 RS
Old Rim: (STI)18x7.5 +48
Bolt Pattern: 5x100mm

New Tire: (Pilot Sport 4) 255/35 18 94Y
New Rim: 18x9.5 +39
Bolt Pattern: 5x100mm


I got hardrace rear lower control arms and custom coilovers with camber plates.


The car feels very loose now it's hard to describe but it feels like a boat on water when you swerve left and right the responsiveness isn't there anymore like before its somewhat delayed. So you would turn left and the car would respond later than expected and the turn is very smoothed out like you are driving a boat in water.

Any idea what this could be because?

Big wheels and tyres will dull the feel and slow response.

What are your alignment specs?

What coilovers and what spwcs?

Did you get it aligned when you got those parts installed? What does "custom" coilovers even mean? Take it back and have them inspect everything. Though I doubt it's the problem, check the PSI on the tires as well.

If you haven't aligned it, do so.
Also you went from lighter wheels and tires to wider heavy ass wheels and tires, so there's that to slow you down.

That feeling is why I switched from an 18x9 setup back down to 17x7.5. big wheel/tire make this car feel dull

Offset is not that much off, scrub radius/steering heaviness should be similar. 255/35/18. Diameter variance is not that different, so acceleration shouldn't be much worse. Wheel weight similar to stock. Tire width within normal range of wheel width. Wheel/tire switch shouldn't change alignment. Who knows the reason :iono: but i bought this car for handling, and experiences like these makes me happy to not have turned to dark side of stance/flushness :)

That aside, if you mentioned "I got hardrace rear lower control arms and custom coilovers with camber plates." - i slightly guess that you installed these alongside wheel/tire change (for clearance/not rubbing/flushness thingies?). If you mod something in suspension, or even simply unbolt/retighten it's parts - definitely redo alignment. Unlike basic wheel switch, suspension changes will make alignment out of whack, and it can change car handling to wrong one. In this case, i guess that there might be some front toe-in gained or alike. I'd also check if those "custom coilovers" are not dialed too soft.

Why people use absurdly wide tires on a 200 hp car?

Because that nets placebo impression that it's supercar, one cannot afford?

Maybe people who come from owning heavy cars do it out of habit? I got mine because I thought I'd need the grip for being turbo, but I didn't need that much tire. I doubt everyone who has a large wheel/tire setup is 200hp, just the majority.

Start by reading How to screw up your cars handling and ride - step by step! by Racecomp Engineering

I have 18x9.5 wheels with sticky tires and my car doesn’t feel like that. That’s odd. What are the coilover specs? Spring stiffness, bump/rebound?

Before/after alignment numbers?
Before you get an alignment, figure out exactly what you want. Generic alignment just gets you within a very wide range...

+1 on alignment and heavy/wider wheels and tires.

Also check damper settings and experiment there.

Those tires will kill the sensitivity. More than 225 and you really start to feel it