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Hi guys.
Tein S-Tech Springs & KYB Excel G Combo on an NB8A. Predictions?
Any feedback on these two products separately or together would be welcome. And of course some predictions as to the difference I can expect from my stock 10 year old OEM suspension.

Looking forward to any and all opinions!

Is the Excel G the same thing as the AGX? If so it will be a fairly good combo, though you will probably want some shorter bumpstops to go with it (or cut the factory ones a bit - Racing Beat have good instructions).
I wasn't a huge fan of the AGX for the short time I had a set in my old car though, can't really put a finger on it though.

(insert gratuitous plug for the FM springs I have for sale....)

I've got King Springs and the KYB Excel Gs on my NA6 and they are much much better than stock. A much stiffer ride but not unlivable. Good for street and track in my opinion. I got improved turn in and less roll after installing them.

Also, the Excel Gs are not the same as the AGX as the Excel Gs are non-adjustable.

In that case they're not really designed for springs much stiffer than stock... I'd choose better dampers

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.

Thanks guys. Back to the drawing board!