Torsion bar modifications vs sway bar upfits

[dyn085]

When it comes to suspension I actually haven't yet (still stock), but suspension tuning is suspension tuning. The reason that I bring up pressures/shims isn't because of the low-cost; I would simply rather start with a better contact patch first. Obviously this assumes that whatever path you're taking involves the OEM height, but having a small amount of negative camber added to the rears is going to help that outside tire from wanting to rotate the rear. I would also zero out the toe, but that's just my general preference.

After that, a lot of people want to go to sway/torsion bars to make changes, but you would have to either decrease the rear or increase the front in order to give it better balance in the direction that we're discussing. Because of that and the overall characteristics of everyday life on the OEM parts, I would probably junk the springs/dampers instead and get a good set of coilovers with a higher spring rate but dampening adjustability. The main reason behind that is because you would (assuming you just replaced the springs with a custom set) technically need to increase the spring rates up front (or decrease the rear), and coupled with the short wheel base and OEM shocks it would be even more unpleasant than it currently is.

Part of my break-in involves some high-speed emergency braking from near triple digits to nearly a complete stop and I was really disappointed the first time I did it in the FiST. It was relatively exciting and moderately fun in a controlled environment, but in a true emergency situation it's definitely not what I want. My FoST, otoh, drags itself down in a completely normal manner-almost to the point of being boring.

 

[BostonDriver]

What I realized is that in turns on choppy roads, the car does like to skip/jump/shimmy over the bumps. I didn't like that feeling either. This is due to the over-compression of the stock dampers. With my setup it's been eliminated. However, I would like a bit higher spring rate in the front. I'm thinking of going with Eibach springs, with the least amount of drop possible. I thought of maybe going with the Eibach B-spec, true coilovers with monotube dampers. But the spring rates are way high.

That choppiness was something i didn't like as well and you know what fixed it? The TB performance 2 point front brace! I didn't really expect much from it when I got it and the rear torsion beam, but I was very surprised that the front lost that choppy, skippy feeling it had when really pushing it. My impression of both together is that it really "refines" the handling. When i installed them I had the stock suspension and was like many have mentioned, a little on edge at the immediate rotation the FiST has in stock form. It's nice to have a front drive car that handles like that, but when you're really cranking into a turn I don't like the feeling that the rear end might pass me. I came to learn that it won't, but it still isn't a good feeling. With the 2 point front brace and rear torsion bar installed that was tamed to a very managable feeling which loaded up the car and settled it into the hard! It felt like the rear just sucked into the ground!!!

This past weekend I installed the Mountune springs and now it's perfect. Lower, better ride, and gives flatter turning while retaining a daily drivable ride. It's not soft by any means, but takes the harshness out of the little bumps and road imperfections. I would highly recommend this setup to anyone who uses the car as a daily driver who might take it to the track everyonce in a while (or not). Most people jump on coilovers becasue they're adjustable, but face it how many people are actually corner balancing the car and adjusting dampening settings? Maybe 5% of the people who buy them... I've put them on cars in the past that I tracked a lot, but I don't see the point for street driving...

 

[RAAMaudio]

SHIMS, dyn085 has it right, I have worked on that idea, could of got some made as none available I had seen were what I considered good enough for a car like ours and with plans to track it often on wide sticky tires.

Since no shims were available and not much interest in having 10 sets made so I cut the axle flanges loose, left one corner barely attached as did not need to move it there which made this easier to do, and changed the camber and toe to what I knew would make the care more stable on high speed corners and sudden throttle lift on slower speed ones. This was the hardest part of all I have done to this car but the most valuable I am sure.

-1.9 camber (-1.5 likely a good number, I went a bit further but run -2.5 up front and might go to -3.0 in testing, I did not want a big difference F/R_
0.0 toe

Only once at the track so far, outer loop at MMP which is very fast, the car was amazingly stable and easy to drive all out which was around 200 laps in two days, 5 seconds a lap faster than the Spec Miata national championship cars record which is pretty dang fast. Next outing I will have a great deal more power so even faster yet

Fixing the problem at the source is always better than a band aid fix.

I have a 5-way DIY modded BMW rear sway bar I will be testing as well but does not seem to be needed.

I will be testing a slightly bigger front sway bar next, stock none ST Fiesta, I need to order one in and bushings for it.

My current setup:
BC race spec coilovers
-2.5 camber with redrilled struts, see note below
Stock caster, did not want to add more at least at this phase of dialing in the car
1/8" toe out front, 0.0 rear
Stock front sway bar, stiffer bushings, Steeda adjustable end links to remove preload
Ride height set to maintain proper geometry which is not very low and works great on the street and track
Quaiffe LSD, not suspension but it does effect how the car reacts a great deal, so far love it
15x9 +35 offset wheels, 2mm front spacer to clear struts
225/45/15 RA1 track tires.

I am in the process of making a change to set camber at the strut to knuckle location as it is better place to do so, working out some custom spacers, already have long race studs, 4x100 bolt pattern change and likely will order some Maxxis 245/40/15 front and 225/45/15 rear tires to help with the 300WHP or so I will be running soon. 245 is a bit wide for a 9" wheel but I have talked to somebody that is very familiar with this tire and he believes it will be better overall than the 225 on the front. There is a 15x10 wheel I can get which is a better tire match but would not fit under the rolled and pulled fender and I prefer to not run flares as like my car to be pretty tame looking on the street.

Again, I agree with dyn085.
1) fix the rear camber
2) air pressure adjustments

Other things to look into that I have not tested yet or might not need to as my car already has better rear alignment so this is general info, nothing specific.

Fine tuning the front camber, add more that stock but perhaps -2.0 or a bit less to help balance the grip front to rear.
Front sway bar might be a place to gain some help, I have ran a huge rear bar and no front on a Scion TC that was a very fast track car but it had IRS
Front toe setting, a bit toed out helps turn in and other issues, try a few settings in and out.
Rear ride height, lower putting more weight on the rear of the car might help, or might hurt.
Move the battery to the rear, remove all weight you can on the nose of the car.
Practice hanging the tail out in a safe place so your motor skills are tuned to react instantly and not over react.

Hope this helps
Rick

 

[RAAMaudio]

If you run a torsion beam stiffener keep a good eye on it as there will be considerable stress on the welded joints, watch for cracks.

 

[westcoaST]

Rick, how much lower would you recommend than the stock setup. I plan on getting the BC coilovers from 2J racing. Daily driver with some track time at Adams motorsports park. I'm running 17" x 8 wheels and plan on using 215 x 40 or 45 x 17" wheels. Thanks for your input. I have the 6 pt and strut bar from Pierce.

 

[RAAMaudio]

I will have to take some measurements when I drop the car off the lift, installing the EFR turbo system right now.
Basically the lowest you want to go for optimum handling is the outer ball joint center pivot point needs to be slightly lower than the center pivot point on the inner control arm end. It is a bit tough to get good measurements but I have used a straight edge between the wheels, leveled up, to get a better picture of it. It helps to mark the centers with a bright line with the wheels off car first.

I have seen many cars setup measuring off the pinch welds, that is OK as long as the same diameter tires with the same air pressure is used and a known value has already been determined but if not it can be far from accurate.

Also the method of just looking at the control arms can be quite far off as it is not the angle of the arm that matters it is the center of the pivot points.

Then I set the rear slightly higher than the front, 1/4" or so but on stock rear camber it might end up being different so experimenting is recommended.

-----------

I did a test of a very built and fast Scion tC, set to optimum height compared to just 1/4" lower, had drawn it out in full scale, it made a huge difference on the roll center and 2 seconds on the next autocross run. ( On another thread I think I may of said on a road course but it was an autocross)

 

[RAAMaudio]

Heading back to the shop, break is over, installing the EFR DHM turbo system