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#3319259 - 03/21/14 06:35 PM Better gas mileage with stiffer suspension.
Nayov Offline


Registered: 08/01/09
Posts: 814
Loc: ME
Well, why not? Shock absorbers (struts) soak up energy and turn it into heat which is wasted energy. When a car bobs up and down while going down the road, it cost energy to lift the car. Anyone who's ridden a dual suspension bicycle knows that it saps energy from the rider.

So taking this to the absurd level, would a car with no suspension render better fuel mileage? I know it would be undriveable, so it's for illustrative purposes only.

I got to thinking about this after I replaced all 4 struts on my car. It now rides dramatically harder and I'm wondering if I will see better fuel mileage.

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#3319262 - 03/21/14 06:40 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
zzyzzx Offline


Registered: 05/18/12
Posts: 2940
Loc: Baltimore, Maryland, USA
This seems unlikely to me.

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#3319263 - 03/21/14 06:43 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
It seems to me that a softer suspension would be the way to go (less energy lost compressing the suspension) for fuel economy over bumps but realistically it isn't going to add up to much. It really isn't all that much energy wasted.

For the suspension to provide a real-world benefit to fuel economy you want a setup that reduces or eliminates the need to brake before cornering. That will save you a lot more wasted energy than gliding over bumps.

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#3319266 - 03/21/14 06:47 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
PandaBear Offline


Registered: 08/05/02
Posts: 13028
Loc: Silicon Valley
Compare to aerodynamics and rolling resistance, suspension loss is nothing.

A stiffer suspension means your car will bump higher and then bonce a bit stiffer than softer suspension, just how long will those "bonce around" turns into heat, but they all turns into heat eventually.

The only way I see it is a harder suspension reduce comfort, and force the driver to slow down to be more comfortable. It is like saying speed bump reduce speed and make your drive more fuel efficient.
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#3319273 - 03/21/14 06:57 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
This discussion has me wondering if those BMW control arm bushings that always break might be designed to do that. The front wheels, when hitting a bump while the bushings are broken, get shoved rearward and accelerate upwards more slowly so as to change less forward motion to upwards motion, then they snap up over the ridge of the bump. UFO

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#3319278 - 03/21/14 07:05 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
Trajan Offline


Registered: 07/16/05
Posts: 3730
Loc: SE PA
Originally Posted By: Nayov
Well, why not? Shock absorbers (struts) soak up energy and turn it into heat which is wasted energy. When a car bobs up and down while going down the road, it cost energy to lift the car. Anyone who's ridden a dual suspension bicycle knows that it saps energy from the rider.

So taking this to the absurd level, would a car with no suspension render better fuel mileage? I know it would be undriveable, so it's for illustrative purposes only.

I got to thinking about this after I replaced all 4 struts on my car. It now rides dramatically harder and I'm wondering if I will see better fuel mileage.


A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy.

Nothing more. Nothing less.
_________________________

Lack of harm is not proof of benefit.

There are in fact two things, science and opinion; the former begets knowledge, the later ignorance. Hippocrates





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#3319286 - 03/21/14 07:14 PM Re: Better gas mileage with stiffer suspension. [Re: Trajan]
Nayov Offline


Registered: 08/01/09
Posts: 814
Loc: ME
Originally Posted By: Trajan

A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy.

Nothing more. Nothing less.


Yes, but I would add that dissipated energy (heat) is wasted and it costs fuel, but I do concede that the amount is in all probability immeasurable.

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#3319289 - 03/21/14 07:16 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
Burt Offline


Registered: 01/08/09
Posts: 1222
Loc: texas
I have a hard time seeing how vertical motion/energy is converted into horizontal motion/energy by a stiffer suspension.

Kind of like hitting a hammer up or down on your car and expecting it to move forward.
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#3319299 - 03/21/14 07:28 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
Trav Offline


Registered: 11/20/06
Posts: 13049
Loc: MA, Mittelfranken.de
Originally Posted By: Nayov
I got to thinking about this after I replaced all 4 struts on my car. It now rides dramatically harder and I'm wondering if I will see better fuel mileage.

Go a step further and remove the shocks totally. Use the bouncing motion of the springs to run a generator to charge the batteries in a hybrid system. LOL

No. Stiffer struts wont improve fuel economy unless its a Nissan Maxima then it might get 20% more.
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#3319314 - 03/21/14 07:42 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
spasm3 Offline


Registered: 05/30/10
Posts: 5886
Loc: out there
If you have to slow down more to corner and turn due to the body roll with no or really soft shocks, you will consume more energy getting back up to speed. Verses coasting at a faster rate around corners/s turns and using less fuel to accelerate from a higher exit speed due to better suspension.
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#3319345 - 03/21/14 08:07 PM Re: Better gas mileage with stiffer suspension. [Re: Trav]
Nayov Offline


Registered: 08/01/09
Posts: 814
Loc: ME
Originally Posted By: Trav
Originally Posted By: Nayov
I got to thinking about this after I replaced all 4 struts on my car. It now rides dramatically harder and I'm wondering if I will see better fuel mileage.

Go a step further and remove the shocks totally. Use the bouncing motion of the springs to run a generator to charge the batteries in a hybrid system. LOL



It's been done! Well, a car powered road generator.

"The Road Surface Generator device is a revolutionary new device that incorporates current technology by utilizing the motion and weight of vehicles to produce clean, economical and ecologically sound electrical current. The Road Surface generator relies on kinetic energy produced by moving vehicles then transferred via a simple device located on surfaces that connect to a turbine generator to produce energy."

http://www.google.com/patents/US20080106103

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#3319353 - 03/21/14 08:20 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
JHZR2 Offline



Registered: 12/14/02
Posts: 37273
Loc: New Jersey
You're assuming that you're converting potential energy of fuel to potential energy of ride height.

Perhaps a bouncy car has a worse aerodynamic profile, but I doubt it is much.

I can see savings from taking curves faster, as forward momentum can be wasted and is valuable.

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#3319369 - 03/21/14 08:38 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
Trajan Offline


Registered: 07/16/05
Posts: 3730
Loc: SE PA
Originally Posted By: Nayov
Originally Posted By: Trajan

A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy.

Nothing more. Nothing less.


Yes, but I would add that dissipated energy (heat) is wasted and it costs fuel, but I do concede that the amount is in all probability immeasurable.


How is it wasted? Shock absorbers do not power or draw power from the engine.
_________________________

Lack of harm is not proof of benefit.

There are in fact two things, science and opinion; the former begets knowledge, the later ignorance. Hippocrates





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#3319382 - 03/21/14 09:01 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
Merkava_4 Offline


Registered: 01/30/07
Posts: 13180
Loc: Clovis, CA
The more you keep the car in a straight line, the better the fuel mileage will be.

A car getting tossed around from stiff suspension is going to affect its straight line.

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#3319401 - 03/21/14 09:28 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
Donald Offline


Registered: 03/21/04
Posts: 16040
Loc: Upstate NY
It the suspension makes a difference at all, the wind and how much coffee the driver has had probably make double the difference as suspension.

Its pretty hard to accurately measure MPG unless you use a flow meter like Consumer Reports does.
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#3319449 - 03/21/14 10:30 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
eljefino Offline


Registered: 06/15/03
Posts: 28634
Loc: ME
The tire theory of setting to not-too-high a PSI is the tire pushes back against the road after it goes over a pebble. Stiffening the tire interferes with that. It stands to reason that stiff shocks might too.

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#3319597 - 03/22/14 09:01 AM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
whip Offline


Registered: 03/03/05
Posts: 2201
Loc: ohio
Originally Posted By: Nayov
Originally Posted By: Trajan

A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy.

Nothing more. Nothing less.


Yes, but I would add that dissipated energy (heat) is wasted and it costs fuel, but I do concede that the amount is in all probability immeasurable.

Until you can convert the energy from the bump into a way to propel the vehicle, it has zero effect on the fuel economy. Buying a lighter car would help more than anything.
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#3320122 - 03/22/14 07:13 PM Re: Better gas mileage with stiffer suspension. [Re: eljefino]
Nayov Offline


Registered: 08/01/09
Posts: 814
Loc: ME
Originally Posted By: eljefino
The tire theory of setting to not-too-high a PSI is the tire pushes back against the road after it goes over a pebble. Stiffening the tire interferes with that. It stands to reason that stiff shocks might too.


Fascinating. I always thought the harder the tire the better for MPG, but, this makes sense. He's to hoping my gas mileage won't be plummeting with my sporty stiff struts. whistle

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#3320138 - 03/22/14 07:26 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
Eddie Offline


Registered: 12/07/03
Posts: 7833
Loc: Florida, Cape Coral
If you make force vs distance diagram you'd see that what you gain is easly lost in the noise. Ed
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#3320221 - 03/22/14 08:42 PM Re: Better gas mileage with stiffer suspension. [Re: Nayov]
jeepman3071 Offline


Registered: 04/15/10
Posts: 2152
Loc: Storrs, Connecticut
The money you save in gas with stiffer shocks will probably not be enough to cover your doctor bills from back problems down the road.
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2000 Jeep Cherokee Sport 4.0L (161k) - PYB 5w30, Napa Gold 1516, Magnefine trans filter

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#3329346 - 03/31/14 04:22 PM Re: Better gas mileage with stiffer suspension. [Re: Merkava_4]
Trajan Offline


Registered: 07/16/05
Posts: 3730
Loc: SE PA
Originally Posted By: Merkava_4
The more you keep the car in a straight line, the better the fuel mileage will be.

A car getting tossed around from stiff suspension is going to affect its straight line.


Shocks and springs are not powered by the engine, nor is any energy from them used to move forward.
_________________________

Lack of harm is not proof of benefit.

There are in fact two things, science and opinion; the former begets knowledge, the later ignorance. Hippocrates





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