The "progressive" spring enthusiasts should enjoy their firmer springs and tighter ride.... as most if not all sports driving enthusiasts do, among which I include myself.
I've not visited this forum in quite some time so I was pleased to see John Olsen's response tonight (last nite... now this morning) and read it with interest.
1st, let me apologize to those with the 230SL model... my statement that the 230SL was more prone to loose it in hard cornering is based on articles I read many years ago (30?) from publications my father had collected beginning in '64, '65 thru the 280SL introduction in '68. I left Germany in '64 to return for University, and my father sent these articles to me in correspondance. ... most were German auto publications as I recall... some may have been from US publications later. I unfortunately cannot cite the precise dates, publications, or authors... the sources were German Automotive magazine articles on the order of Car & Driver. I can say that an MB engineer at the time would not have been inclined to agree with the articles, so it shouldn't surprise John Olson that his MB engineer source would tell him there was no truth to them even if there were. There's also the possibility that the genisis of these articles were propaganda to discredit MB by their competitors for which (at the time) one could cite English and Italien mfg'ers.... and the arch enemy in Germany... BMW.... to a much lesser degree at that time were the Porsche's competing with MB. I doubt the latter possibility was the only genesis however, as the propoganda campaign would have not endured without being debunked by other publications... and as we all know, MB in Germany has a strong and loyal market... both politically and economically, so it would be very surprising that a mis-information campaign by competitors could run without an equally large and more effective campaign financed by MB to dis- the mis-information.
Also, as Alfred correctly noted my mid year '67 250SL was mfg'ed with the 230SL suspension system.... while my father's '67 was mfg'ed near the end of the 250SL series. I've driven both cars.... as has my younger brother (who drove my father's 250SL extensively and to the extreme during the course of his mid-late teens while in Italy... where my family lived for 15 years). My brother, my father, and I have clearly and unequivacably notice that my 250SL leaves little margin for avoiding the rear end spinning out compared to my father's 250SL (this comparison was done in the period before my car was semi-permenantl garaged before restoring to it's now condition) . My brother-in-law (an avid BMW 6 series owner) also noted that my 250SL is less forgiving on extreme cornering than my father's (my brother-in-law purchased my father's 250SL from and owned it for 5 years). I have no doubt that the articles published about the 230SL being notoriously prone to spin-out without warning on hard cornering are true. When you push each to the edge, the earlier model will begin to spin out and with increasing moment (faster) with less time/ability to correct.
Albert also cited the thinner front torsion bar as the single major published difference in the 230SL & the later series W113's suspension system. He also notes correctly that the thinner torsion bar is less stiff (the one on the later 250's and subsequent versions) ... but it's not just a little less stiff... it's a lot less stiff. 22mm diam vs 20 mm diam appears to the non-professional to be only a 10% reduction in 'stiffness'... but in fact the stiffness is a function of the cube of the thickness... or in the case of a cylindrical object, the 4th power of the radius. So the 10% reduction in the torsion bar's radius means it was much less stiff --- in the range of 70% as stiff as the larger diameter one. This means that the front end is allowed to tilt more with the thinner torsion bar on cornering (front end can tilt more than back-end.... i.e. the frame's torsional resistance)... which gives the driver a greater degree of 'feel' as the car progressively reaches it's limits.... i.e. greater warning before the back-end breaks loose.
By it's very nature, the stiffer the car's suspension system the closer the car can get to it's limits of control (i.e. as in spin-out limit) with very little other indication that this limit is being approached.... even if it's limit is increased over that of the less stiff suspension system.
Of course this is an advantage in racing and competitive applications, but it none-the-less makes the car's handling ability more risky for drivers without racing or extreme driving experience. This was and is of major concern to auto manufactures.... since their sales of these types of cars are dominantly to wanna-be's and/or the wives of wanna-be's that can afford them.... and they can ill afford to get a reputation for 'bad' handling among their dominant market. With the exception of the 300SL MB has almost invariably and purposefully catered to the luxury market in post war production .... softer, spongier rides. I agree whole-heartedly with John's opinion that "all three models as sold to the public had atrociously mushy rides."
It was not, nor is it my intent to detract from the 230SL in favor of later versions. Enthusiasts of the W113 will note that the original 230SL styling and driving capabilities were not enthusiastically endorsed at the time.... softening the ride, giving it more horse-power, were marketing methods to give it wider market appeal in Germany and in the US market.... a 'grand touring' sports car was a marked brake from the 300SL (a real sports car with limited sales) and a major improvement over the mass appeal of the 190SL. To this day MB doesn't market a 'sports' car in the regime of the latest round --- M3 (now M4's), S2000's, Porsches, etc.... The closest they come, and it's a far cry, is the SL55's now.... not marketed to the same market segment as the other 2 seater sports cars.
A few more comments regards some of John's statements.
1) "An open secret here (that all Mercedes owners should know) is never lifting the accelerator once it is applied in a corner. Lifting gives up the benefit of low pivot and negative angle of the rear wheels."
This is true of all rear-wheel drive / front engine cars in general, not just MB.... some more than others, depending on weight distributions. The driving forces during cornering are from the rear wheels 'pushing' the car thru the turn. When the accelerator is lifted in the turn the engine speed reduction puts a brake on the rear driving wheels... i.e. deceleration. This action is tantamont to applying the brakes to the rear wheels without braking on the front wheels... though the braking action by deceleration is less than actually braking. While in the turn the front wheels are trying to turn the car (from an engineering view... the turned front wheels are pushing the front of the car side-ways in varying degrees depending on how far the front wheels are turned... while the rear wheels are trying to push it straight ahead. A body in motion tends to stay in motion in the diretion of it's motion. When you brake the rear while pushing the front to the side, the car (body) has more than just a little tendancy to spin out ... i.e. the rear tends to keep going in the direction the wheels are turning while the front is being pushed side-ways (relative to the rear).... that's a spin-out when the rear looses grip. The more you decelerate in the turn the closer the body gets to it's traction limits with the road. Keeping the rear and/or front wheels from rolling over is an effort to minimize the effect.... hence the desire for minimizing wheel tilt (axle tilt).... wider wheel-base, stiffer suspensions... which also bring the car closer to the edge without giving warning signs.
There's no doubt that a W113 can take higher G's without spinning out than a Cobra.... but this is dominantly due to the W113's wider wheel base... and probably if the facts were known, also to it's more centered weight distribution. I don't have fact sheets on the Cobra but 2 weeks ago I had the opportunity to be up-close and personal with 2 of them (being used in to take pictures for a future promotional marketing campaign at the co. I work for)... both used in current racing among the Cobra enthusiast crowd. From observation only.... and there's not too much that's not fully visible on a Cobra... I'd guess that the weight distribution is closer to 60/40 --- front / rear.... and the wheel base is much, much narrower than the W113's. The degree to which the swing axle suspension on the W113 plays in ability to achieve higher cornering G's than the Cobra may in fact be an artifact of the other conditions in setting up the cars than the swing-axle to which John appears to give the lions share of the credit if not all the credit.
As to the 'progressive' description of the springs John sells...which was the topic of my original interest in this thread... I believe John cites the nature of all springs, coil or otherwise, when he states once again (as is similarly expressed on his web-site):
"When placed in a spring tester the weight needed to squeeze the spring (deflection rate) increases progressively with every inch it is squeezed."
I have previously cited the engineering principles of steels and any other material in any form related to their deflection under force... and the equations governing these relationships and unless or until the material reaches it's in-elastic limits (at which point it begins to permanently deform and won't recover to it's orginal dimensions), or begins to bottom out on itself (i.e. one coil bottoming on another...metal-metal contact), the spring behaves as all springs... regardless of changes in winding pitch between the end points, or diameters, or "custom pitched to new angles".... These variables only change the stiffness ... they don't give it a progressively increasing spring rate.
Should John once again puruse this forum and topic, I repeat my original request to simply provide the force vs displacment curves he cites as being measured by the spring mfg'er in spring tester.... more usually referred to in the engineering community as a 'tensile testing' machine.... which can either push on or pull on the object being measured (i.e. applying compressive or tensile forces on the object). Such tests have to be repeated in 2 successive tests to show that the object has not gone beyond it's elastic limits such that the at rest dimension after the 2nd application of forces is identical to the dimension at the start of the 1st test sequence.
I believe it's more probable that John's application and use of the word 'progressive' is not being applied to mean an increasing spring rate as function of force applied...rather it's being used to mean that the displacement is progressivly greater as the force is progressively greater.
By the way... what is the spring rate of these 'progressive' springs John sells? The spring rate isn't shown on the Web-site nor has it been cited in comparison to standard springs or the off-the-shelf higher stiffness springs optionally sold by MB as "Special Versions: 1) Harder Springs for Bad Road Conditions, PN 113 324 02 04", compared to Standard Springs PN 113 324 04 04.
MB sold several optional springs for front and rear.... for SLs various combinations of extra's... from none to 2 optional extra's.... auto trans, power steering Air conditioning, etc. I surmise these were springs to compensate for added weight of these extra's.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
