MY05 WRX Inverted Suspension
17 September 2004, 02:20 PM
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The standard springs allow lots of wallow and float at high speed on B roads and gets even worse on coutry lanes in Dorset. Get the Prodrive springs which gets rid of this problem, along with that up on stilts look that the standard car suffers from ie 22 mm at the front 20mm rear drop. The standard spring leave a massive gap from the top of the front tyres to the bottom part of the front wheel arch so much so that you could put a tent up in the space.LOL
17 September 2004, 03:58 PM
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Originally Posted by zerolight
Is this going to be dramatically different to the suspension on my MY04 or a subtle improvement?
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18 September 2004, 10:25 AM
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As no-one seems to have a definitive answer then here goes with a theoretical one.
With normal struts the shock absorber is within the strut body, the piston sticks up out of the shock absorber, goes up thro the spring into the top mount.
With inverted struts the shock absorber bit is upside down. What was the bottom of the shock absorber body is attached to the top mount. What was the top of the piston is anchored to the insdoe of the bottom of the strut. So as the strut is compressed the outside of the shock body moves in and out of the strut casing.
Advantages 1 - the whole assembly is more resistant to bending because the bit that moves in and out of the strut casing is 2 inches in diameter (shock body) rather than 1/4 inch (piston rod), so the whole assembly is more resistant to bending. Useful on a rally stage, theoretically useful on the road, in practice who knows?
Advantages 2 - The heavy bit of the shock (the body, valves, oil, gas reservoir) is attached to the chassis, the light bit (piston, rod) is "attached" to the wheel. So reduced unsprung weight. Theoretical handling advantage as wheel frequency is lower, ie the lighter components can respond quicker to small bumps meaning the tyre is in contact with the road surface for more of the time. This could well be significant for a racing car with ultra lightweight uprights, tyres, wheels and brake components but, although theoretically better, is it significant on a road car? Who knows?
Disadvantage - as above the heavy bit is higher so cofg is higher. Even more theoretical this as the relative weight is tiny is comparison with the rest of the car.
So all in all theoretically better. In practice probably marginal on a road car if at all.
More likely that whether Subaru get the shocks made by company A or go to company B, who shave 3p per unit off the bulk purchasing price of 10,000,000 units, is far more important than whether they are upside down or not. But this is out of your control so you don't worry about it.....
With normal struts the shock absorber is within the strut body, the piston sticks up out of the shock absorber, goes up thro the spring into the top mount.
With inverted struts the shock absorber bit is upside down. What was the bottom of the shock absorber body is attached to the top mount. What was the top of the piston is anchored to the insdoe of the bottom of the strut. So as the strut is compressed the outside of the shock body moves in and out of the strut casing.
Advantages 1 - the whole assembly is more resistant to bending because the bit that moves in and out of the strut casing is 2 inches in diameter (shock body) rather than 1/4 inch (piston rod), so the whole assembly is more resistant to bending. Useful on a rally stage, theoretically useful on the road, in practice who knows?
Advantages 2 - The heavy bit of the shock (the body, valves, oil, gas reservoir) is attached to the chassis, the light bit (piston, rod) is "attached" to the wheel. So reduced unsprung weight. Theoretical handling advantage as wheel frequency is lower, ie the lighter components can respond quicker to small bumps meaning the tyre is in contact with the road surface for more of the time. This could well be significant for a racing car with ultra lightweight uprights, tyres, wheels and brake components but, although theoretically better, is it significant on a road car? Who knows?
Disadvantage - as above the heavy bit is higher so cofg is higher. Even more theoretical this as the relative weight is tiny is comparison with the rest of the car.
So all in all theoretically better. In practice probably marginal on a road car if at all.
More likely that whether Subaru get the shocks made by company A or go to company B, who shave 3p per unit off the bulk purchasing price of 10,000,000 units, is far more important than whether they are upside down or not. But this is out of your control so you don't worry about it.....
18 September 2004, 11:37 AM
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the main benefit of upsidedown suspension is that it lowers the unsprung mass on the car. If you have a lower unsprung mass then you can fit harder springs (for cornering) without losing "small bump sensitivity". Small bump sensitivity keeps suspension engineers awake at night because in a fast road car you want it to be stable in cornering but not fly off the road on a road ridge, drain cover, or one of those lines on the M40 - you get the picture.
In a track car car it doesn't matter really because there aren't that many ridges and things on a track - thats why if you've ever driven a track prepared car on the road it is a spine shattering experience.
Unsprung mass also includes the wheels (alloy wheels are lighter than steel), brakes, hub assembly and a percentage of the mass of the struts and wishbones. BMW took over 140kg out of the rear of the 740 a few versions ago and it drastically improved the feel of the car.
If the poster above is correct, even though the upside down shocks are heavier, they will still reduce the unsprung mass and this will give engineers many more options for stability of the car.
hope this helps. I design suspension for mountain bikes and will be doing similar stuff for cars in the future. On a race mtb it is really sensitive to unsprung mass so we use 4 pot disk brakes that weigh <200grams!!!!!
rd
In a track car car it doesn't matter really because there aren't that many ridges and things on a track - thats why if you've ever driven a track prepared car on the road it is a spine shattering experience.
Unsprung mass also includes the wheels (alloy wheels are lighter than steel), brakes, hub assembly and a percentage of the mass of the struts and wishbones. BMW took over 140kg out of the rear of the 740 a few versions ago and it drastically improved the feel of the car.
If the poster above is correct, even though the upside down shocks are heavier, they will still reduce the unsprung mass and this will give engineers many more options for stability of the car.
hope this helps. I design suspension for mountain bikes and will be doing similar stuff for cars in the future. On a race mtb it is really sensitive to unsprung mass so we use 4 pot disk brakes that weigh <200grams!!!!!
rd
getting them fitted at the same time as it gets its 1000 mile service.
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