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Registered:
August 2002
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Double wishbone suspension vs. macpherson strut
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Thu, 31 March 2005 09:33
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I can only assume its an improvement, but having never owned a car with this setup im only guessing.
Just wondering what the pros and cons of the double wishbone suspension is over the conventional macpherson strut?
What will be the rammifications of installing coilovers in a double wishbone setup?
Is there any adjustablity with the double wishbone setup?
thanks guys!
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Location:
Adelaide
Registered:
May 2002
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Re: Double wishbone suspension vs. macpherson strut
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Thu, 31 March 2005 10:25
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Black,
Rex suggests the type of suspension is of little consequence, providing it keeps the wheel dead flat at all times: eg, cruising, breaking, cornering etc.
Having said that, He believs that the double wishbone offers a slight advantage because when designing a system from scratch (eg a Clubman or Whatever) The arms can be oriented to add or remove camber from a wheel as a car rolls onto/off of its suspension.
Saying that, Old Mac Pherson and his farm struts are the more easily tuned of factory systems.
Installing coil-overs in a double wishbone is too of little consequence as the arms remain in their spot.
However when the ride height of any car is altered, so too is the roll centre's of the wheel.
Big, tricky area indeed, suspension is.
Rex
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Location:
South Australia
Registered:
July 2002
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Re: Double wishbone suspension vs. macpherson strut
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Thu, 31 March 2005 12:11
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Are we talking front or rear suspension?
Either way, I thought that MacPherson strut was easier to manufacture (less parts). But double wishbone suspension has greater rigidity?
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Registered:
August 2002
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Re: Double wishbone suspension vs. macpherson strut
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Thu, 31 March 2005 12:12
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In respect to MZ21 soarer.
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Double wishbone suspension vs. macpherson strut
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Thu, 31 March 2005 22:11
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with respect to the MZ21 soarer, we are refering to a vehicle of strong pimping prescence. Thus the use of double wishbone suspension is a more valid, superior performing and more attractive design to the Mcpherson slut.
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Location:
Adelaide
Registered:
May 2002
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Re: Double wishbone suspension vs. macpherson strut
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Thu, 31 March 2005 22:25
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I thought that if you need pimping presence then you gotta strut and bone?
Seriously though, as far as I know (having been involved in the design of a double whishbone suspension on a racecar). The reason for using macpherson struts is that they package extremely well in a passenger car, are cheap to manufacture and offer quite good geometry.
Using double wishbone setup allows much greater freedom to play with the geometry of the suspension (such as camber curve design and roll centre placement among other things). It usually turns out to yield a smaller unsprung mass (because macpherson struts inherently have the shock etc as unsprung and double whish bone can use pull/pushrods).
I'm sure there are other reasons why they are better too..
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Location:
Adelaide
Registered:
September 2003
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Re: Double wishbone suspension vs. macpherson strut
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Thu, 31 March 2005 22:26
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Glenn,
The coilovers have the same end effect as per the McPherson strut (ride height tuning and greater spring selection and hence tuning), but it doesn't allow the ability to adjust camber (by providing greater scope for movement) on a double wishbone setup.
In general terms, double wishbone is better, but more complex to make and install.
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Toymods Vice President
Location:
Sydney
Registered:
May 2002
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Re: Double wishbone suspension vs. macpherson strut
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Fri, 01 April 2005 01:10
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The double wish bones allow you to keep better/more consistent tyre angles.
Basically when you use a strut front end the hub is connected to the end of a trianlge with two fixed length sides, the control arm and the distance between the control arm inner pivot and the strut top, and one side who's lenghh changes, the strut. Due to the hub being directly connected to the strut the angle of the hub will change in relation to the strut body itself.
In a dual wishbone setup the hub can be one end of a square meaning that when one end of the squre moves vertically the angle of the horizontal links change angle however the hub can stay in exactly the same angle. In reality this isn't how the dual wishbones are setup as they tend to be setup with a shorter top link so that as the wheel moves up the top is pulled in increasing negative camber.
Basically it's all about controllability and consistency of the angle of the wheel.
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Location:
Adelaide
Registered:
May 2002
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Re: Double wishbone suspension vs. macpherson strut
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Fri, 01 April 2005 01:48
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I saw a car setup last year like that (parallel wishbones)... all I can say is:  ,not to mention 
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Double wishbone suspension vs. macpherson strut
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Fri, 01 April 2005 03:56
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Performance has more to do with the detail geometry of each set up. For instance, a lot of double wishbone setups are designed with shorter top arms, this basically allows the outside tyre to remain vertical in cornering. Problem is that in road cars, most people think they know better than the engineers and lower teh car 3inches and automatically put the tyre in a bad part of the camber curve, seriously reducing tyre grip, especially under brakes. The macpherson strut is less susceptable to this, so a modified MS would perform better than a DW setup.
A lot has to do with packaging. Try using double wishbones on the front of a FWD car. There is barely any room in there. The same thing goes for putting V8's in double wishbone setups, The exhaust comes out where the upper wishbone sits. In most cases this can be worked around though.
For a passenger type car, the MS is a cheap and easy thing, but try packaging that on the front of an F1 car.
The old valiant that I have has a neat setup, having double wishbones with a torsion bar spring acting as the lower hinge point. Nice and compact, save for the damper.
Performance wise, the DW can be made to work better but in a mass produced car like the soarer, changing ride height significantly will rarely help the handling. A better option us to use a "dropped Spindle" which is basically a new upright with the stub axle a little higher than the standard location. That way the car is lower but the suspension geometry remains as per the manufacturers design.
Man I can dribble, I think I will stop typing now.
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Location:
Adelaide, SA
Registered:
May 2002
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Re: Double wishbone suspension vs. macpherson strut
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Sat, 02 April 2005 07:22
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I wonder how much work would be needed to convert from macpherson to double wishbone... I've seen a few double wishbone setups and they seem simple enough.
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Double wishbone suspension vs. macpherson strut
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Sun, 03 April 2005 00:12
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Probably no harder than putting a v8 into a GT4..... My guess is that the chassis rails would not be strong enough on their own to support both uper and lower wishbones. My thinking being that normally they are both mounted on the chassis rails with a small vertical frame inbetween. This will put a big torsional load into the chassis rail and in a macpherson strut type front end, the chassis is only designed for bending, not torsion.
Having said that, depending on how your engine sits, you could probably triangulate it and stiffen it up enough quite easily. The engineer may want to see some reinforcing of the inner guard where you make the cut out for the upper wishbone.
Take a look at some old kingswoods, valiants and falcons for an idea of how it all goes together, you will notice that the subframe is a fair bit bigger in cross-section than an equivalent sized car with a macpherson strut front end.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Double wishbone suspension vs. macpherson strut
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Sun, 03 April 2005 00:44
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all i can say is it depends on how much the car rolls...
the point of having a camber curve is not to keep the camber when the car rolls, but to keep the tyre as flat as possible relative to road, regardless of what the body of the car is doing.
if the car doesn't roll much, you don't need much camber.
if it rolls a lot, you need heaps of camber to keep tyre flat during cornering.
how you achieve that is up to you, but think of MS as a relatively fixed camber setup (only changes as the lower arm changes it's "width"), and DW as a variable camber setup.
Cya, Stewart
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