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Ride quality coilovers/springs vs torsion bars

I did some searching and it appears that there is some opinion that coilover/spring suspension provides better ride quality for a given amount of stiffness.

Coilover products are getting cheaper, like the Rebel Racing option. And torsion bars are becoming available in larger sizes, like 35mm rears and 24 fronts.

I am looking for more stiffness in my SC and am about to go in on the 35mm rear torsion bars but am very tempted to go the Rebel Racing coilover route, especially if it helps out on the ride quality front. The prices of the two options are comparable enough to be disregarded in the equation, IMO. Coilovers would involve more work, of course, but that does not bother me.

I would like to hear from those who have played with both coilover and torsion 911s and can comment on the difference in ride quality and any other aspects to help me out in this decision.

Thanks for reading
Old 02-01-2010, 11:13 PM
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All things being equal, the reason that ride quality improves with coilovers is due to excessive chassis flex.

Its not an apples-to-apples comparison. A proper coilover package requires serious chassis reinforcements including a proper cage.
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Old 02-02-2010, 12:15 AM
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Max Sluiter
 
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A srpring is a spring.

You will notice a bigger difference with custom-valved dampers to suit your car's weight, spring rates, tires, driving style, etc.

Also, make sure all your bushings are in order- no deformed rubber or squeaky urethane.
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Old 02-02-2010, 12:31 AM
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Tim
 
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35mm ?

I hope it's a track-only car ?

Otherwise: call your chiropractor
Old 02-02-2010, 02:42 AM
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Quote:
Originally Posted by Flieger View Post
A srpring is a spring.
True. A coil spring is just a torsion bar twisted into the shape of a coil. They both work by twisting.

It always seemed to me that one of the main benefits to coil springs was the ability to change spring rates more quickly. Most street cars don't really need that feature.

As far as ride quality goes, it has been my experience that shock valving plays a much more important part - within reason - than spring rate.
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Old 02-02-2010, 03:27 AM
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modern cars often have progressively wound (and even tapered springs) which improve ride quality as they are non-linear

never seen them on a 911 - units for 911s are designed for racing
Old 02-02-2010, 11:43 AM
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Quote:
Originally Posted by RWebb View Post
modern cars often have progressively wound (and even tapered springs) which improve ride quality as they are non-linear

never seen them on a 911 - units for 911s are designed for racing
Similar results you get with a double spring like I use, helper spring adds about 20mm of soft character and more neg travel, not useful for track, but streets aren't that flat everyday :




Huge difference, smoother but more progressive in corners, completely different ride quality
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Old 02-02-2010, 10:48 PM
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Quote:
Originally Posted by proffighter View Post
Similar results you get with a double spring like I use, helper spring adds about 20mm of soft character and more neg travel, not useful for track, but streets aren't that flat everyday :




Huge difference, smoother but more progressive in corners, completely different ride quality
They look great but can you use these on an otherwise stock 911?

What I mean by that is do you have to brace and strengthen the shock mounting points etc...

Those areas of a 911 were never designed to take the weight of the car.
Instead the weight is transferred through the torsion bar mounting points on the body.
I would imagine "loading" a 911 through the shock mounting points would also affect the way the chassis flexes... Am I right???
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Old 02-02-2010, 11:04 PM
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Yes, you're right. I highly recommend to reinforce the weak areas. At least the rear strut tower like seen in this forum before and a strut brace in front. Otherwise you get some stress cracks like me earlier
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Old 02-02-2010, 11:19 PM
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If you want coils so bad , buy a 964
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Old 02-03-2010, 04:47 AM
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Hi Roland,
What are the spring lengths and rates that you use for your main and helper springs? I have 300 lb in the front and 500lb in the back. With these spring rates, my ride is very stiff. The helpers seem like they would be a good addition.
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Old 02-03-2010, 08:27 AM
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Quote:
Originally Posted by luvndasun View Post
Hi Roland,
What are the spring lengths and rates that you use for your main and helper springs? I have 300 lb in the front and 500lb in the back. With these spring rates, my ride is very stiff. The helpers seem like they would be a good addition.
I bought the suspension as a kit from Albert Motorsport in Germany, they have about 30 years of experience with Porsche. I had to give weight ( front:rear ratio) and Power ot the car. Based on this, they adjust dampers and springs with Nordschleife setup (street-usable Track version).

So here are my springs (Eibach)

Front: 180-60-50, helper 60-60-30

Rear: 180-60-70, helper 60-60-40

I think that means: Length-Inner diameter-force

BTW, it's a 930 Turbo weighting 1040Kg
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Old 02-05-2010, 01:15 PM
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If you want coils so bad , buy a 964
I believe we have a WINNER!
Old 02-05-2010, 02:55 PM
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Many good points raised here for discussion.

I feel that a few have been missed. Torsion bars have a progressive rate, and not all coils do. Torsion bars also do not wallow up and down, and tend to need less rebound dampening to control spring jounce.

I have coils on mine, but it was in order to allow me to run softer (weaker) springs to improve ride quality, as well as allow long wheel travel. I drive on very bad roads sometimes, and I already lowered the car (raised spindles) by a quarter inch. Having said that, yes I have scraped the chin spoiler on an agressive corner a few times.
Old 02-05-2010, 04:32 PM
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I do not believe that torsion bars are inherently progressive rate. The lever arm needs to change through the range of travel- more than just the cosine of angluar displacement times the ball-joint to torsion bar radius. Coils can use engineered coil binding or conical wires to achieve this progressive rate. (F=kx^2, not F=kx which is a normal, linear rate).
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Old 02-05-2010, 08:15 PM
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Quote:
Originally Posted by RWebb View Post
I believe we have a WINNER!
Pretty poor advice.... if you want a 964, buy a 964. By a honda or a toyota or a vw if you want coils.... right.....

But if you have a torsion bar car that requires (based on use) higher spring rates than are available with torision bars, by all means convert the car to coils.

I have run my own track car, and a few customer cars, on coils for years. All are happy with the performance. I have to question a blanket statement that chassis flex is what contirbutes to a sense of "better ride". Search around and you will find some threads that go in to detail on the differences in the two chassis, both front and rear.

Cheers
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Old 02-05-2010, 08:45 PM
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Quote:
Originally Posted by Steve@Rennsport View Post
All things being equal, the reason that ride quality improves with coilovers is due to excessive chassis flex.

Its not an apples-to-apples comparison. A proper coilover package requires serious chassis reinforcements including a proper cage.
I'll resurrect an old thread and disagree with Steve; double dumb perhaps. Maybe I'm taking the post too literally, but I'd want to clarify as follows:

Absolutely true that coil-overs require chassis reenforcement to work properly, however once reinforced the ride quality with coil-overs will be better than torsion bars all else being equal. This is the result of lower loads on the trailing arm bushings and hence lower friction in the pivots.

A coil-over spring puts spring force on the trailing arm very close to the wheel axle. The result is a load path the goes from the spring almost directly to the hub and wheel. This puts very little bending moment on the spring plate and hence very little load on the bushings at the spring plate.

With torsion bars the opposite is true- the spring plate carries a lot of bending force, as the load is on one end (the wheel) and the spring force is on the other. The bushing reacts to this force, meaning it is very highly loaded with torsion bars. Since friction is proportional to load the torsion bar suspension has higher friction. High friction results in poor ride quality and lower suspension performance.

This might not be a big issue if there were quality bearings at that location, but unfortunately we have bushings, even the best of which are relatively high friction.

The same problem occurs both front and rear, and I feel it is primarily responsible for the improvement in ride-quality found with coil-overs (unless the important bushings have been converted to bearings).


The other point I'd make is that there is another important reason to convert to coil-overs in the rear, and that is to allow the relocation of the rear pickups. Nearly every 911 I know of is lowered significantly, most probably more than they realize. With the stock rear pickup points this causes some significant ugliness in the toe and anti-squat geometry. I wouldn't bother going to coil-overs without also moving the outboard (with the 935 spring-plate) and preferably also inboard pickup points (assuming the rules allow it). The exact amount of movement needed depends on the individual car.

Given these two points I'd suggest that coilovers are worth doing for many people even without spring-rates beyond the limits of torsion bars, but obviously coil-overs do also come with drawbacks and are not for everyone...
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Old 05-03-2011, 03:09 PM
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I love my custom JRZ's and 935 spring plates. The transformation in handling is unreal.



Old 05-03-2011, 04:03 PM
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P AG and every other sports car maker in the world devote enormous resources towards getting stiffer chassis.

- tell you anything?
Old 05-03-2011, 04:10 PM
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Yes, stiff chassis is desired but must be optimized wrt weight. Pete agreed that chassis reinforcement is needed but his point about bushing friction sounds valid, though with Rebel Racing bushings and monoballs I think the difference would take a very sensitive driver to notice, since there are other interfaces which will be loaded more with a coilover spring vs. torsion bar.
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Old 05-03-2011, 04:49 PM
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