I would recommend that the rear sway bar should be used in conjunction with whatever front bar it was originally used with.

Adding a rear sway to a car which never had one without using a front sway that originally was matched with the rear sway may result in oversteer on the limit which is something to be avoided in a car driven on the street.

In example, on the 123 cars sedans came with front and rear sways. The wagons have slightly larger front and rear bars. I would not change one without changing the other.

Going to a larger front bar will make the car understeer more at the limit which is generally considered a much more safe condition than oversteer at the limit.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

My Coupe is a '62

The guy at Coxracing did install a sway bar in the back and apparently he was happy with the result. I don't see why the compensating spring would interfere with the action of the sway bar.

BTW, I never really understood how that compensating spring works. It seems to me that it seconds the action of the main side springs. Stiffer main springs may paliate for the lack of it. So why is it there?

Thinking of it, that's true; the rear sway bar would counteract the action of the compensating spring. In a left bend, the rear right wheel goes up, pushing on the compensating spring which in turn pushes the left wheel down, exactly the contrary of what a sway bar would do... So I'm wondering if it would make any sense to have those two devices counteracting each other on the same axle...

So, is the role of the compensating spring to keep some traction with the inner wheel by pushing it down in the corners?

Not to nag, but remember he said this car will occasionally be driven on the track. We can refer to figure III below.

I'd vote progressive. If you dont want to sacrifice ride, it's the way to go. It's similar to what I did on my Charger, putting on an SRT8 suspension Vs a KW or similar setup. The "Progressive" lowered me the perfect amount - any lower and I'd scrape on the crappy roads, parking lot entrances/exits, and other obstacles that line up in NEPA like old people at an Old Country Buffet. The handling is superb, with just the right amounts of oversteer and understeer to warn that I'm "on the edge" vs a super-sport suspension that gives little warning before snapping loose into a tree, or understeering off a cliff.

Ultimately you must do what's best for YOU, but I would not go any firmer personally. My next suspension change (if I do any more) would be stiffer sway bars, in the rare case I try to autocross after I do my heads/cam/intake combo, but my own personal experience says progressive will leave you smiling, not scraping!

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

A few guys over at the sl113.org site installed the Olson springs. The stiffer springs reduced nose dive significantly.

IIRC another poster on the site got springs made up using Olson's specs for significantly less than amount he charges.

My 2c. As said, suspension design is complicated. Primarily because there is a trade-off between comfort and roadholding. MB's original designs reflect such a compromise where probably there was compromise made towards comfort. I think my MB has a more comfortable ride than my MGs, but definitely rolls a lot more in the corners too (and has more oversteer). I think improvements for more sportier ride can be made. Like you do, I would rely on experiences of others and also check what MB did in its rally days. For example, the MG factory race cars all had thicker front sway bars, indicating that this was/is a good upgrade. I am not sure what mods MB W111 race cars had. Having fiddled with my MG suspensions, a thicker front sway bar worked wonders (reduced front roll), as did uprated/adjustable rear shocks (I kept stock springs). Sometimes soft stock springs with added sway bar seem to work better than stiffer springs, but in the end, a lot of this is trial and error and a bit subjective (e.g., some prefer controlled fishtail versus total car skid). Lowering the whole car is another preferred option for race (and road), but is complicated and may cause clearance problems.

Again stating perhaps the obvious, I would check what other 111 owners have done uprating their suspension, get their opionions, and start with the simple/cheap options first. 113 owners would be good too, but the mass of those cars is less than your 111, changing the dynamics, so be carefull. Personally, slightly uprated/progressive springs would also be my first step given that the car is still heavy and likes to roll, as would be uprated front sway bar and heavier adjustable shocks in the rear (they do allow some dialing in). If you get adjustable shocks, make sure you get those that are adjustble when installed. Of course you could also try and put a modern active suspension system in. Would be an interesting engineering problem, to say the least...

Fun project. Look forward to your road test impressions.

Bert

__________________
'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8

it's now old, but still a very interesting thread - i've been in the market for a W111 coupe for some time, and i have been looking at a bunch of intriguing options out there for performance upgrades, for those of you who like to "hot rod" these old cars!

any updates and/or photos?

cheers,

brad in seattle

Here is more info on my Coupe, with some videos: '62 220SE Coupe 5.0 Presentation

The car is a blast to drive. I like it so much that I repeated the adventure on a W113 Pagoda, the story is here: http://www.sl113.org/forums/index.php?topic=15521.0