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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,167
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Torsion bars. . . outstaying their welcome?
Torsion bars. . . outstaying their welcome?
I continue to read of torsion bars as a bad design. Would someone please explain to me the problem with the torsion bar design? While I am aware of the benefits of other designs; I’m thinking the torsion bar design has some design benefits that set it apart. 1) The heavy spring elements are low, unlike coilovers. 2) They are exceedingly space efficient; golfers should appreciate the 911 up to ‘89 3) Easy maintenance & adjustment. So what makes these so bad? '81 Platinum Metalic SC COUPE |
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07-27-2001, 10:17 AM
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Registered
Join Date: Jul 2001
Location: Connecticut
Posts: 1,942
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Keep in mind that formula1 cars use torsion bars. They're more compact and controllable. Of course, their torsion bars are a little different than ours.
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07-27-2001, 10:23 AM
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GAFB
Join Date: Dec 1999
Location: Raleigh, NC, USA
Posts: 7,842
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Quote:
2-Yup. 3-Dunno about easy to maintain OR adjustable- if you want to adjust spring rate on a tbar 911, you pretty much have to replace the bars. Not pleasant. If you want to adjust height, you've got to diddle around with the splines. Bruce Anderson makes it sound easy in his book, but it's a nightmare to the uninitiated. -d ------------------ Dave 1972 911T (E motor) RSR replica project http://members.nbci.com/dtwinters/garage/ |
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07-27-2001, 10:24 AM
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Heavier than coils? You may find some examples of lighter coils but the typical coils will weigh at least as much. Remember a coil spring is a torsion bar, it just happens to be wrapped into a coil shape. Unwind it and it is longer than a 911 tbar.
Adjustable height? No "spring" has adjustable height, it is the surrounding mechanisms that are adjustable. The front height on 911 is easier to adjust than any car I know of. The rears are easy with adjustable spring plates. Changing height on coils typically requires complete replacement or cutting of the coil, or adjustable perches. Adjustable spring rate? I don't of any coil that can do that either. Only air adjustable. The beauty of the tbar is the low height of the weight and compactness. |
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07-27-2001, 10:38 AM
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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,167
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QUOTE:
. . .3-Dunno about easy to maintain OR adjustable- if you want to adjust spring rate on a tbar 911, you pretty much have to replace the bars. . . .. Yeah, spring rate is a part of the bar spring, but if you want to adjust spring rate on coil overs you still pretty much have to replace the springs. So, again, where is the advantage? '81 Platinum Metalic SC COUPE |
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07-27-2001, 10:39 AM
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GAFB
Join Date: Dec 1999
Location: Raleigh, NC, USA
Posts: 7,842
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Quote:
I guess Island was talking stock-type coilovers, which are a toss-up wit stock tbars. I agree, I like the low cg and space-saving characteristics of the torsion bars. We were just talking about the F1 torsion bars the other night! Apparently they are quite short? Must be very high spring rate to deal with cornering and downforces. Makes sense in short bar, but I can't imagine the torsional stresses! What kind of materials and production techniques are they using? Do they fail and if so how? ------------------ Dave 1972 911T (E motor) RSR replica project http://members.nbci.com/dtwinters/garage/ |
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07-27-2001, 10:44 AM
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Registered
Join Date: Mar 2000
Location: Irvine, CA
Posts: 1,200
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I think the only downside to torsion bars is that you are somewhat limited as to the size you can use, which limits how stiffly sprung the car can be.
Not a big deal for a street car, because you can fit torsion bars plenty large for street use. Different story on a race car, though. For a full blown 911 race car, coil springs are really the only way to get the necessary stiffness. |
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07-27-2001, 12:45 PM
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Clark I have to disagree with you about the weight of coil springs weighing more then torsion bars. A 33mm torsion bar is a very heavy piece of metal. Also when you compare the weight of the torsion bar to the coil spring setup you have to remember to include the shocks. I have coil springs on the rear of my 911 and I can tell you for a fact that they are lighter then the torsion bar and shock setup and the height is adjustable simple by turning the collar. Also While at the track if I needed to change springs I could probably do it in about 5 min.
Michael Marshall [This message has been edited by MMARSH (edited 07-27-2001).] |
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07-27-2001, 03:33 PM
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Senior Member
Join Date: Nov 2000
Location: Stuttgart FRG
Posts: 2,307
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Hallo
Most advanced American Sportscoupe featered the longest torsion bars in car history. Like most things in life each has two sides. Grüsse |
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07-27-2001, 08:45 PM
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Senior Member
Join Date: Jan 2001
Posts: 539
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I think technically the bars are better. Aside from the attributes already listed, don’t bars have better consistency throughout the whole range of motion vs. coils? I think I read that somewhere. The bars they use on the F1’s are really cool looking. They showed one on the last GP and it looked like it was only @ 7-10 inches long.
------------------ Mark The Beast mark@hargett.com |
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07-27-2001, 09:24 PM
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Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
Posts: 25,308
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With torsion bars, the spring rate is always smooth. To achieve a "progressive" spring rate, coils are needed.
------------------ '83 SC |
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07-28-2001, 07:05 AM
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Registered
Join Date: Jan 2000
Posts: 6,950
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With all these advantages, you would wonder why all car don't have them? Joking aside, I think the bars were integral to the initial design of the car and Porsche stuck with them up until they had no choice to change (964). As far as better, during these years, they put coilovers in the racing 911 cars also. The suspension on the pre 89 cars is rudimentary by any standards. That the car handles the way it does says alot about simple design and function.
------------------ 8 9 9 1 1, The last of the line. |
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07-28-2001, 07:18 AM
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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,167
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89911;
The suspension on the pre 89 cars is rudimentary by any standards. Do you mean the standards set by the manufactures still producing leaf springs on solid axles? and Superman, With torsion bars, the spring rate is always smooth. To achieve a "progressive" spring rate, coils are needed. It kinda has a Clintonian spin. Using descriptors "smooth" (read- slow) and "progressive" (read- New age) Do you mean to say with torsion bars, the spring rate is linear. To achieve a "nonlinear" spring rate, coils are needed? I'm beginning to get the idea that because it was done "in the past" it can't be as good as the ubiquitous design of today’s commuter car. Thanks '81 Platinum Metalic SC COUPE [This message has been edited by island911 (edited 07-28-2001).] |
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07-28-2001, 08:49 AM
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Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
Posts: 25,308
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Yeah. Springs can be non-linear or progressive. I surely would be among the last to belittle yesterday's technologies. Torsion bars do a great job and are huge space-savers.
But even an old fart like me has to admit that today's cars, including and especially their suspensions, are excellent performers. ------------------ '83 SC |
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07-28-2001, 02:17 PM
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Registered
Join Date: Jan 2000
Posts: 6,950
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"Do you mean the standards set by the manufactures still producing leaf springs on solid axles? "
NO, I mean the design done on other sports cars! Duh. You don't think a single control arm the was designed for the 356 and allows the suspension to travel in one rotational axis is superior to a double wishbone that was being used in the late eighties on any number of sports cars! Try designing that suspension on torsion bars. ------------------ 8 9 9 1 1, The last of the line. [This message has been edited by 89911 (edited 07-29-2001).] |
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07-29-2001, 05:38 AM
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72 Porsche 911T 3.2 
V70R
