Oh WOW... I so wish that I'd gone to Luft 10.

I think stock front/27mm rear is a great starting point. You can always hand the parts down to one of the other cars or they are easy to sell. I've used both ER and Sway-Away bars and have been happy with both. I did use the ER Hollow on the Rot Rod for weight savings. It's marginal but if you're chasing pounds, it's probably worth it, rear especially.

Speaking of pounds, I know you probably got the tires already (and I do lust after the A008P's...) but the Yoko's are not light - 21 pounds front and 24 pounds rear. Well, not that they're particularly heavy but there's an option that's lighter.

I'm fully on board with your tire/wheel size choice. I'm a wheel-weight-weenie (I remember your thread about the Fuchs!) and got the same featherweight Fuchs for The Carbon Copy project, but in black/silver. My chosen tire will be the Potenza Sport, which is 18 pounds for the front and only 20 for the rear. I have a pretty lofty weight goal, so that 14 pound savings is a big, big deal.

Frank and Jonny, thanks for the feedback on the V3's. I'm tempted to just go that route to get the 19mm raised spindles as part of the total price, but at $4200 shipped from Germany to me, I would want to drive someone's car with the V3's installed first. I really do like the Koni Sports on my car as-is, so I'd have to remove those. Before I did that, I would want to see if the V3's are "better enough" to justify the price for my street-driven car.

Bill V: Re tires and spring rates, yes, tire stiffness, especially sidewall stiffness makes a big difference in how a tire feels on the road, noise, harshness, etc. I just don't think that they change the suspension spring rate significantly. In a hard turn with maximum weight transfer to the outside tires, how much do they compress? Maybe 1/2 inch? And distinguish that from the visual appearance of compression which is actually the tire or suspension rolling over on the sidewall.

I'll noodle on it some more.

This is a fantastic thread! Great discussion while maintaining a decent tone! Very much appreciated all the way around. I don’t understand half of the data but believe I can still follow somewhat :D

If it was me I’d run stock TBs up front and 26 or 27 rear. I have 19/26 on mine together w the KW shocks and adjustable sways from ER. Very happy with it all around, on both street and track. Ran 22/29 on my old 3,2 and that was way too stiff in my opinion

Driven
 

I had driven PHM of Jonny's before it went to its new owner. I definitely was impressed with the KW's during regular and spirited driving.
They are a spectacular improvement over what I have on the Herring which are a great set of raised spindle Bilstein's that I bought from Jonny.

Take the plunge... you wont regret it!

The change in tire spring rate is likely relatively small but the total change in handling can be large this is largely due to the change in slip angles


even a change in wheel width w/ the same tire makes a noticeable difference in handling, again this is largely due to the change in slip angles

a square set up will not handle the same as a staggered setup

a 300hp car can induce throttle steer more easily than a 200 hp car

a 2000# car will not feel the same as a 3000# car

having all mono-ball bushes feels different from stock rubber which in turn feels different from sport rubber bushes

track widths can make a huge difference

w/b makes a difference

weigh distribution makes a difference

I appreciate that rubber isolates and sphericals do not, from a NVH* perspective, but all other things being equal what's the difference in overall spring rate between rubber lower A-arm / spring plate bushings verus sphericals?

It's apples and pumpkins, but when I went from rubber A-arm bushings to sphericals in my track prepped Lotus Elise, the NVH went up, but not by much. Admittedly, that car had plenty of NVH beforehand.

input/response time goes down and is more precise

just an example
my 993 started w/ street rubber
went to sport rubber RS bushes
went to all mono-ball

each step was incrementally quicker to respond and more precise in response

it's similar to tires
my '72 started w/ 4x 6 & 185/70
went to 7 & 8 w/ 185/70 and 215/50
then to 215/60 & 235/55
each step was incrementally quicker to respond

or polar moment reduction
on the '72 going from steel S bumpers to f/g didn't change much because the weight change wasn't much
but going from stock to f/g on my '76 w/ a 33# change front and 28# change rear allowed the car to turn much more easily, There was a 438 lb-ft change in the torque needed to cahnge direction, also helped on whoop-des on the road

Dang, Bill. I love the impact bumper esthetic and have been firmly entrenched in the "impact bumpers for life" camp. But those values make a strong argument for fiberglass (even just the rear).

Ugh. One change at a time. Let's see how the KWs do once the snow melts and then we'll talk polar moment reduction.

How about Carbon/Kevlar? SmileWavy

Love kevlar! The 80's SCCA S2 racers I prep have all been rebodied in kevlar. It's much lighter than fiberglass and is less expensive than carbon. Kevlar seems more forgiving than carbon, which is good because our drivers like to mix it up with Porsche Cup cars weighing twice as much - our cars always lose that fight :eek:

I have bumper ideas... will PM