Hey Norm,
Norm Peterson said:
Continuing the IC behind the car issue a bit . . . isn't it more likely for this to occur with a combination of shorter UCAs and higher rear ride heights?
Sorta... The spread of the chassis bolts is almost the same as the spread on the axle housing bolts (approx 9.1” for the chassis and 8.8” for the housing). So if the LCA’s are perfectly horizontal with the ground then the UCA’s point up thus the IC is already behind the car.
You are correct in that the IC/AS values can change quicker if the UCA’s are shorter. This can be an advantage in the design b/c this allows less body height adjustments to move the IC where it needs to be. So instead of lowering the car 2” to move the IC 60” with a long UCA the use of a shorter UCA may only require 1” of ride height change.
Not surprising the shorter UCA’s have never been in issue on the Mustangs b/c once the IC is dialed in close to the Neutral Line the car body doesn’t raise up or squat down much so the IC movement has little affect on unloading the tires on the launch.
FYI, the Mustang UCA’s on my kits are 2” shorter than the G-body arms so this tells me that the UCA length doesn’t seem to have much of a negative affect on the Mustang Kits.
Norm Peterson said:
I do see the anti-squat value changing more rapidly with respect to ride height as the UCAs get shorter, which may be a good thing on acceleration. I'm thinking that this may help keep the rear of the car from "overshooting" the ride height it wants to be at under whatever acceleration is happening, which has to be worth something.
Remember the AS value is a number in relation to the Neutral Line. Generally what I shoot for is that as the suspension moves up/down the AS value remains as constant as possible. This is achieved by having the IC move PARALLEL to the neutral line. The IC Length will change but the AS can remain fairly constant and the UCA length does have an affect on this. However, I will add that these values only change as the suspension moves up/down. If the suspension NEVER moves up/down then the IC values never change. In theory if the IC is located directly on the Neutral Line then the rear of the car will never move up/down but there is a lot of other factors that can affect how the suspension acts on the chassis, tho and I won’t get into this can of worms..
Norm Peterson said:
What happens during braking? I'm kind of hoping that reduced anti-lift is at least partly a good thing but I'm having a bit of trouble wrapping my brain around the possibilities.
When you hit the brakes the axle housing rotates FORWARD and pushes on the UCA’s. If the UCA’s are pointing UP then this can/will cause the rear to raise up and the front end to nose dive. So if you start to angle the UCA’s down then there can be more stability during braking.
*I have to add that I am NOT into corner carving and I have no idea what kind of geometry these types of cars need for best performance.=)
Norm Peterson said:
Mostly out of curiosity, was any thought ever given at any point with the Mustang kits to just run a single upper with zero plan view skew with a panhard bar or some other track locating method? I'm intrigued by the possibility of an 8.8" swap, and the new S1979 Mustangs use the 3-link + PHB rear suspension as stock (so the single pumpkin "ear" already exists, and complete axle assemblies are available through FRPP).
The rules won’t allow this type of suspension if the car never came with it. The “lateral angles” must be retained in stock suspension classes.
Kevin
