[Mr.Steel]

Hi everyone,

First time poster but not my first bmw. I’m working on a 06 330i sedan, and need some fine tuning advice on spring rates. The rear subframe strength seems like the limiting factor with these cars, so how stiff can you go before risking damage? Most people seem to say max 1,000lbs or 12k, but I’ve seen others using 14-18k rear rates. To maintain a reasonable 2.0 motion ratio a 12k rear limits you to 6k or 7k max front.

I’ve had a E46 with 7k front /12k rear, and thought the rear too soft but loved the handling. Currently my e90 came with crap eBay coilovers at 10k front / 9k rear and disconnected front sway bar (wtf). I like stiff low cars, but BC Racing is only offering 6k or 8k spring increments. so I’m think of getting 14k rear rate with 8k front. That should allow me to fine tune front to 7k swift springs if needed, or possibly 14k to 15k rear without ordering new dampeners.

So my concern is seeing people say 14k+ will rip the rear subframe off the car. Is that remotely true? I’ll be driving on track, and running UHP summer tires on wider wheels. And I want to be low without rubbing.

I need help from the pros, thanks

[Joe_in_WLA]

Have you contacted Turner? They have some off-the-shelf options and experience building BMW racecars

https://www.turnermotorsport.com/BMW...forcement-kits

https://www.turnermotorsport.com/t-racing-newsitem-548

[Mr.Steel]

Originally Posted by Joe_in_WLA

Have you contacted Turner? They have some off-the-shelf options and experience building BMW racecars

https://www.turnermotorsport.com/BMW...forcement-kits

https://www.turnermotorsport.com/t-racing-newsitem-548

Spoke to them today, they didn't think it should be a problem.

It seems BC use to sell their kits with 8k front 14k rear. I’m finding enough people using those rates that it’s probably not a concern.

[Joe_in_WLA]

Cool. Yeah, they would know. 👍

[Mr.Steel]

Originally Posted by Joe_in_WLA

Cool. Yeah, they would know. 👍

Realized I was using an inaccurate conversion. The 8k 14k combo is basically the M3 KW Clubsport specs .. I have a lot more confidence ordering that now

[Joe_in_WLA]

Got it 👍