I currently have the Tanabe Sustec Coils, I was wondering about the part # on the rear springs, I am interested to see if i can order stiffer springs for the rear.

What are your thoughts anyways?
currently the F/R is 10/9 mm/kg spring rates
after putting sways from hotchkis everything is great but i feel like it would be perfect if the rear was a little stiffer.

so I was thinking about going up to a 10 mm/Kg spring rate in the rear.

 

Uhh I guess it depends what's the MM on the coils either 65mm or 60mm...

Tanabe USA Inc. - PRO210 Max Custom Springs

I remember someone telling me that the sustec coils for g37 can't use pro210s... something about factory style springs. You might want to give them a call.

 

The rear springs used on the G37/370Z fitment are not from the Pro210 line, so you won't find them that way. Call Tanabe and have them check the diameter's and free length of the rear springs used in the Pro Seven 350Z fitment can be used on the G37 and if they can be purchased.

^HOWEVER, IMO I would not go to 560lbs in the rear. A large measure of what your senses are telling you are likely simply related to your rear spring's being progressive. I converted Pss9 coilovers from a progressive rear to linear, but with the same peak spring rate. Made a noticeable differance, well worth the effort which was not a standard swap (had to machine a adaptor)

You should be able to do a 500lbs linear conversion in the rear by simply measuring your rear Tanabe springs outside diameter and free length. Then find a Eibach ESS spring that will work. You will need a miter saw to cut one end of the spring so it can sit in the oem lower control arm.

 

Ill have to double check then, i though they came with the Pro210, in that case yeah, I will have to either measure or get info from Tanabe on the current springs, and find something matching. it does make sense for the progressive springs to act that way I guess, I just think the rear on the tanabe is designed in a way that you dont hit the stiffer part of the spring unless you are being extreme, I didnt have that issue with my Eibachs pro kit.

 

I called Tanabe a while back and was told that the PRO210 springs weren't made in sizes specifically to fit the Sutstec S0C. This was some time last year so that may have changed. However, if you can get the info on the spring diameter and length, you may be able ot experiment with different ones that fit and see how they feel to you.