theguyondacouch

What is the difference between a shock, and a strut?

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deportes

A strut is a cartridge that goes inside an outer shell that has a spring and a way of hoilding the shock absorber inside a mc pherson stru. a shock is a shock absorber that doesn't go inside a strut assembly. they do practically the same job but more expensive to replace is the strut.

Moonduck

The strut, as an overall assembly, has more of a role in your suspension than the shock does. The shock simply dampens down movement in one axis (vertical, obviously), the strut actively serves as an integral part of your suspension, with various other suspension compenents bolted to it.

thadon

and if I am correct ... strut assemblies are only used on FWD cars and they do not use upper or lower control arms

Mill

They have got to have a control arm (lower) of some kind as a pivot piont. They can be used in both front and rear wheel drive.

Sion

thadon, a macpherson strut is the primary front suspension part on most (but not all) fwd cars, minivans, even some awd light trucks.

because fwd vehicles have both the engine and tranny as well as drive shafts all up front, there is a serious space issue. the macpherson strut solves this problem by taking up much less space than a pair of upper and lower control arms on either side would. the strut assembly consists of a housing that bolts to the steering knuckle on the bottom. atop the housing sits a small coil spring (about half as big as a rwd's spring would be). inside the house is a shocklike dampener unit. the dampener extends up through the coil and is bolted to the strut tower (a chassis part) by means of a strut bearing plate. the whole unit takes up about 1/3 the space of a conventional ctrl arm and coil spring assembly.

here is a picture of a (semi) typical front strut setup:



what isnt show in this pic are the cv drive shafts.


now, as I said, this applies to MOST fwd cars. however, there are some (like my 85 Buick Riviera) which use other suspension setups. My Riv has conventional upper/lower ctrl arms and coil spring in between them. There are also other types of struts that are used, like for example on Town Cars that have air-ride systems, that do not use a coil spring like the macphersons do. In the case of the Town cars, there is an air bladder that provides the "lift" that a suspension unit is designed to do (ie lift the chassis off the ground). also, the town cars have both front and rear struts.


now, just out of my own curiosity, why do you ask about the differences between struts and shocks? you going to be working on something that has struts?

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Sion

hehehe Mill, you did the exact same google image search that I did. I saw those pics but didnt use them because they are not your typical fwd setups.

also, while Mill has a point that there has to be a lower pivot point somewhere, most fwd cars still manage to avoid using a control arm. usually, the steering knuckle provides this. the s.k. bolts to the front subframe by means of a ball joint and this ball joint is the pivot point. the steering knuckle is a very comlex part that serves not only as the point of connection for the strut, but also the piont of connection for the whole assembly to the front subframe, as well as the point of connection for the tie rod ends which attach to the steering gear (rack and pinion in 99% of the cases) which translates the circular motion of the steering wheels to a linear motion to turn the wheels. the steering knuckle also holds the brake calipers and rotors as well as wheel bearings. finally, the cv drive shafts pass through it too.

quite an impressive device, that steering knuckle.

__________________
He's the best, of course, of all the worst.
Some wrong been done, he done it first. -fz

I jus' want ta thank you...falettinme...be mice elf...agin...

Moonduck

"quite an impressive device, that steering knuckle."

That is the first time I've ever seen such a thing on an internet 'motors' board. I salute you as a fellow car-geek. Most so-called motorheads only care about engines, boost, what-have-you. I find the whole thing endlessly fascinating. I'm am as likely to be excited by a chance to get into and play around with a Model T as I would a Koenigsegg. I find all portions of an auto to be neat in some way or another.

theguyondacouch

I thought In ws the only on like that Moonduck. I'm interested in all parts, not just the drivetrain. But thats probably because I've always been into offroad, where supension is the first thing modded.

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