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4 minute(s) of a 612 minute read
5-3-2012
Spring is here - time to take pictures again.
No not Spring, spring! 
Here in my garden:
The green spring is Swift front spring, light blue is Bilstein OEM, dark blue is Hypercoil rear spring.
Why springs? From previous post:
>>>>>>>>>>>>>>>>>>>>>
http://www.6speedonline.com/forums/997-turbo-gt2/136096-pics-review-my-bilstein-pss10-lowered-red-turbo-17.html
Say you have installed Bilstein and were happy at first but now want to go to the next step, firmer, stiffer, more like a GT3. What to do? Besides the first and important step of adding R compound tires, this leads to discussion of further modification of the Bilstein, stiffer springs. Note that nothing comes free and this "upgrade" WILL sacrifice comfort for handling. Anyway, IMHO, here are the steps for a "Turbo to GT3 conversion":
1. R compound tires: Michelin Cup, Pirelli Corsa, Toyo Roxes R888, etc. No way around this. If you want GT3 handling, tires with stiff sidewall is a prerequisite.
2. More negative camber, starting numbers: -1 front, -1.6 back. More as needed.
3. Stiffer and adjustable anti-roll bar. For adjustment of understeer/oversteer, body roll, and ride comfort.
4. Bilstein with stiffer springs: A basic Bilstein with R compound are outstanding and already transforms your Turbo to something that is very fast. However, if you want to take the GT3 in tight corners & curves, and if you want to duplicate the subjective feel, IMHO stiffer springs are needed. This is where the beauty of using coilover comes in: it's designed with that in mind, the ability to change springs to your need and taste.
Keep in mind there is a limit as to how much you could increase the spring rates. In general, you could increase the spring rate about 100-120 lbs/in or so; beyond this, the shock absorber has to be sent in to be re-valved. What this means is that since the Bilstein starts at 336 front/560 rear, you could go up to about 460 front and 680 rear without any modification needed. For reference, a 911 professional race car would run in the 800-1200 spring rate range (anyone corrects as needed).
There are two places you could get springs that fit Bilstein: Hypercoil and Swift Springs. The springs you want to look for is 70mm ID, 6 inches long front, 8 inches rear. The process is very easy and cheap - labor should be around 300-400 per axle.
Swift Springs: http://www.swiftsprings.net/products...r-springs.html
Hyperco: http://www.hypercoils.com/PDF/70mm.pdf
Currently my car is set at 448 front/600 rear - versus Bilstein's 336/560. The front spring is Swift Spring part # Z70-152-080, the rear is Hypercoil part number 8P0600. The stiffer springs make steering response more immediate (no free play) and precise (soft steering IMHO is one of the biggest problem of the stock Turbo compared to its GT2/GT3 sibling). The car is definitely on the firm side but has extremely fast reflexes and minimal body roll at sub 100 mph speed. This is the best all around car that I've ever driven: for me, perfect mixture of handling vs. comfort, precise steering, precise suspension response. I love every second that I am driving my Turbo baby! 
