09 C63 suspension upgrade questions
 

I am looking to upgrade my stock suspension and was wanting thoughts on KW Clubsports vs H & R RSS or RSS+ coilovers?
Its a daily driver..occasional strip..rare track. Getting Renntech rear widebody..20" x 11 HRE 245/315 toyo...Weistec stage III.

I would recommend the KW V3. The Club Sports come with higher spring rates than the V3, and it is really unnecessary for the street. The V3 are rebound and compression adjustable, so you can dial them into your liking. I have just put them on my C63, and I am enjoying trying to get them tuned perfectly for my driving. I don't believe the coil overs offered by H&R for the C63 have adjustable damping, but they are quite a bit cheaper. If you not concerned with dialing int he perfect ride, than they might not be a bad option.

If you widen the rear track, you will want to widen the front as well otherwise you are adding more under steer to a car that already has more than enough under steer. Yes you will have increased rear traction, but you have upset the balance of the car's suspension set up. Since you are adding coil overs, you could try to reduce the under steer by playing with the rebound settings and weight balance settings, but your best bet would be to widen both the front and rear tracks.

TX..thx for the response n info. Def makes sense. Do u think id need to get the Renntech widebody for front to have room for the 245s and spacers? Im checking with wheelsboutique and Renntech on seeing if adding the front widebody will still work with my wheel fitment. Ill prob go with the V3 then, was just seeing if there were any other solid options. I kno that setup is proven in the C63.

I don't know any of the detials of the Renntech kit, but widening the front is always a good idea if you are going to widen the rear. It is also a good idea to go with a wider front tire/wheel. The bottom line is you want to increase the front end grip as you increase the rear end grip. If you don't, you increase the amount of under steer the car has. If you are going with 315 in the rear, I would go much wider than 245.

Sounds good. Im checking on specs now from all and will see what arises.

Agreed on the V3 > Clubsports for a street car - You have a PM!