Postby Noodle » Sun Oct 04, 2009 8:02 pm
Keeping in mind I haven't been in an MX5 with either S-Tech Springs or KYB Excel G's. It's just a prediction based on information I gathered while looking for suspension for my car.
According to FatCatMotorsports, the stock vs. S-Tech spring rates for the NB are:
Front: 2.9kg/mm VS. 4.2kg/mm (~45% increase)
Rear: 2.1kg/mm VS. 3.1kg/mm (~48% increase)
According to KYB when I was looking for new dampers for my car for their 4-way adjustable NB AGX's:
Setting#: Relative Value
1 - Same as Factory 100
2 - Same as our GR2 products (10~15% firmer than Factory) 115
3 - 50% firmer than #2 172
4 - 30% firmer than #3 223
Note GR2 is what the Excel G's are called in the US.
So with your planned setup you'll have approx 45~48% stiffer spring rates with only 10~15% increase in damping. From that I would predict your car would make more oscillations after a bump before it settles down essentially making your car feel more 'bouncy'. How acceptable/unacceptable it is I can't comment on.
Having said that, I recently helped a friend replace his standard 150000km old dampers in his Corolla Sportivo already fitted with King Lows. We replaced them with Excel G's. The ride afterwards we noticed a reduced amount of 'shake' (caused by small road imperfections and the resulting wheel going up and down at high frequency), better turn in and a more controlled feeling when going through big undulations at high speed.
Hope that helps.