I just finished your thread Whiskey and it seems like in the end the you were able to work with the Torque Arm and post some solid times. I know you mentioned it was more of a tuning piece but what were your final thoughts on it?
Everyone I've read that has purchased the Torque arm seems to enjoy it, some very much so. I think the Watts Link is a for sure piece for me but I'm on the fence on the Torque Arm vs Heim Joint UCA such as the MM piece.
Some of the items I'm eyeing is the Whiteline Watts/LCA's/ Relocation Brackets with a MM UCA (I think this would be a quieter setup for a street car and on paper should not have a lot of bind)or The Cortex Watts/TA with the Whitline LCA's/Relocation Brackets.
Then I have Shock/Spring or CO combo to worry about.
All of my suspension will be purchased at once and be installed at the same time so I'll be going from stock to (Hopefully) finished in one push.
Well, Torque Arm cars drive differently than 3 link cars and that has to do with how a torque arm plants power. We can look at %AS as a guide but it doesn't tell the whole story because I know for a fact that it doesn't tell the whole story. My Torque Arm setup with my ride height that I autocrossed in had basically the same %AS as a stock Mustang GT yet I never experienced the intense power on push associated with a torque arm car. Even this last event with it and the car setup looser it would still push if you got on the throttle too soon but it could be "banished", so to speak, by giving the throttle a jab and rotating the car that way. That was my personal observation which was in contrast to to the one made by the resident alien and CSP winner at Nationals who said the car didn't put power down nearly as well as he would have liked and he was hoping for better power down. I think his accelerator and braking inputs were quicker but smoother than mine were and he was dancing on that edge more consistently.
One suggest I DO have is that if you plan on getting a TA setup and plan on getting into autocross or track days, invest in a torque biasing diff. I'm pretty sure the fresh (literally fresh) T-Lok with carbon fiber clutch packs added to the push I had during the autocross marathon. I'm sure with the that diff the car would have rotated under power so much better.
One thing that the Torque Arm did do for me was get my stock levels of forward bite back which helped put power down, it just made the car push as a result (since rear end grip = move towards understeer). It required a different driving style. With the 3 link setup you could almost "momentum" drive my Mustang since it required a ton of finesse to get the car to dance on the edge of grip. There isn't an easy way to momentum drive a TA car and I suspect the best way in which to drive one fast is to get the car slowed down for the corner, get it into the corner sharper than necessary and just mash the throttle and let the power on push pull the car to the correct point on the course. That would be the point and shoot school of thought. It wasn't until I got my second set of tires that this became tolerable to me because I was no longer DDing my race tires and didn't have to worry about frying this set in a year. You could not do this with the 3 link setup because it did not have the same driving characteristics as a torque arm.
In the end, I guess I do like it since point and shoot is a tad easier to drive as than momentum driving is because the actions are more separate so it is easier to drive that way. Maybe that is what people meant by torque arm cars are generally pretty easy to drive. Anyway, there are some distinct things I noticed about the behavior of my car before and after the torque arm:
1.) Power on push - meaning, gas = straighter lines = power delivery. Since the class I was in this past year put me against cars that were lighter and less powerful, I had to use this one advantage to cut the distance. It did on the Strano power course at Nationals I was 2 seconds closer to the time of the leader than I was on the Speidel transition heavy course. It just so happened to be that the cones on the Strano course would even out the time split between the front runners and myself on both courses.
When tuned correctly you can almost set the car up a little more like a FWD car, meaning the car can be looser at entry and be "corrected" with throttle.
2.) Can't be driven momentum style as easily - Because of 1.), it became strictly a P&S car. Carrying speed is still important but because the car gets pushier the gentler the throttle inputs it becomes hard to keep the car balanced in sweepers so generally speaking, err on the side of too much throttle and too much brake. The 3 link setup seemed to do this reasonably well as it doesn't generate the push created by the axle windup being turned into tire planting like a TA does so the car can be setup to be closer to neutral in handling and driven at the edge with minor corrections dancing it between over and understeer.
3.) Axle mounted coilover springs with perches become a bit noisier. Because a torque arm locks the angle of the differential relative to the torque arm, the spring perches do not remain near vertical throughout the travel of the suspension. This creates noise with the coilover setups with divorced springs and shocks because the springs rub against the ride height adjuster.
Anyway, I think between a rod ended UCA and the Torque Arm, I'd take the Torque Arm. You still get bind free articulation in roll (and almost bind free roll steer) without the huge NVH issues associated with rod ends at the UCA mounting point. In the class I was in, it was basically a requirement to have the TA in order to actually use the power I had over the competition which only amplified the reasoning behind picking it over the cheaper UCA solution. Admittedly the driver left a lot to be desired and I was still chasing setup issues (out of lazyness mind you) at Nationals and finished correspondingly poorly but I do know the car has pace to be damn close to the trophies. Probably within a tire width increase of being a top car but sadly that wont happen.
I would also err on the side of more spring rate. I'm not sure if Griggs will be able or willing to help you with choosing spring rates for your car but I know with my car, if I keep it around for more than a few years (and don't ditch it for a 2015+) I will be looking to keep the split between front/rear springs so that the rear springs are about half the rate of the front springs and then tune with roll center height and swaybars. The goal was to get the watts linkage out of the top bolt hole which forced some NVH compromises (watts link arms hitting exhaust over axle pipes on big bumps mainly) that I'd like to remedy.
Probably lower the rear arms as an easy fix no? Or is that illegal?
Definitely not legal for STX or ESP in autocross. The car had 32%ish AS at my lowered ride height with my coilovers which is in the more perfect range for corner carving. The higher %AS at stock ride height might matter more to folks in drag racing though. It was more or less an observation on how radically the %AS changes with ride height and a torque arm. A 2.25" drop in the rear corresponds to a 48% drop in antisquat with a torque arm whereas the 3 link setup doesn't suffer nearly as much drop. The bonus though is that I can have more %AS at a given roll steer value since changing the LCA inclination impacts roll steer. Lowering the axle point such as done for drag racing produces roll oversteer which can make a car feel very twitchy and hard to drive while cornering. I can get the same %AS with less roll oversteer.
Not that you'd want that much %AS in a corner carving car.
