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240 Performance Alignment Specs?

I agree. IF the spring is at the halfway point between bushing and ball joint (and a 144 is close, haven't measured an 1800), it has a motion ratio of 0.5, so the pressure at the wheel is half that of the spring, and the distance the ball joint moves is twice that of the spring. 500lb/2 inch, which gives a wheel rate of 250 lb/inch.
For non-easy numbers, we square the motion ratio. (0.5 x 0.5 = 0.25 mr^2)
 
That’s a very, very soft front spring. We are running either a 1” or 1 1/8” IPD front bar, 925lb front springs with 200lb rears and no rear bar on our 2300lb 142. Granted, we’re using Hankook RS4 tires that are sticky sticky in mostly endurance racing scenarios with -3 degrees of front camber, but 450lb springs on a double wishbone setup is more of a performance street spring rate. If it’s balanced well on the less grippy tires and reduced camber, it’s all good, that just stood out to me. I do think the factory rate is somewhere between 300-350lbs or so?

klr142 As I have mentioned to you a couple of times before the setup is a compromise because of the rules and in addition to being raced it is also driven on the road about 5K miles a year, and the reason for the softer spring rates. Yes, the original front spring rate is only about 300lbs.

We race with the VSCCA and according to the rules all post 1959 cars have to remain as "could be bought off of the showroom floor." The Club is one of the last holdouts in the vintage racing scene that continues to do it the old-fashioned way, and a number of the cars are still driven to the event. Only original tire sizes are allowed and only treaded racing tires are legal.

The rules state that all post 1959 cars have to remain as "could be bought off of the showroom floor" which means "showroom stock." Despite this the setup in the car is working well and after you learn how to race with this way it works out OK.

Despite having a trailer it has been driven to and from competition meets since starting racing in 2018. In pre-Covid times it has covered about 1k miles a year on the the track or in hillclimbs.
 
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Ah yes. Good info to share and I believe it does just fine! My street/play 240 is very softly sprung as well but does fine enough on the track in short bursts. That car is still stock upper strut mounts and lower control arms so it only has about a degree of camber up front. It could definitely benefit from more, but it does ok for what or is. :cool:
 
10-year bump. Curious if Towery has any updated input or if the wisdom from the old days is still where it's at.
It's still where it's at. Whatcha workin' with? Car, parts, goals, wheels, tires, springs, bars, alignments, etc. I've just tried enough different combinations that I have a good feel for what worked and what didn't.

He?ll tell you to crush your race car.
He speak'eth thy truth. Live look at the vessel in the shipyard out back, being broken down. Big stuff comes out soon.

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