Its time for the "rebound" test

[Zak33]

Lo blokages.... and ladies when you pop by.

Anyone know what a shock absorber really does? and why its so damn important?

Cos we all have them on our chariots of fire....and the amount of older cars with knckered ones scares me to death....I drove a Part Exchange yesterday with seriously buggered shocks at the front....I memtioned it to the owner and he had no idea what I was on about....

so here goes....

Springs....they do the BOUNCY work....they hold the car above the road, and yet allow the suspension to jog up and down over the imperfections in the street. If the car was on blocks of wood, in THEORY it would drive OK , and maybe even corner ok...ON SMOOTH roads.....but as no roads, and not even tracks are smooth, we have to allow the weight of the wheel, and tyre and brake components to go up and down WITHIN the confine of the wheel arch...and its the SPRINGS job to determine how FIRM the bounce up is gonna be...nice and soft and the ride comfot is ACE, cos the wheel gooes up and down while the body shell goes straigh along.

BUT.......it leans badly with soft springs.....so you get harder, and sometimes shorter (ie lower) springs to control the body roll (excluding anti roll bars)..and you get harder ride.

BUT.......look at ZEBEDEE.....look at the springy little geek.....

look at ANY SPRING......its just so.....damn.......errr....SPRINGY.

So if you had JUST SPRINGS...I kid you not....you would drive over the pot hole, the suspension would drop into it, and then back up into the arch, and then the body shell would slowy follow.,...and follow...and follow...

and you would BOUNCE ALL THE WAY to the next hole where it would get worse....

and when you CORNERED>....the suspension would compress on one side and as you came out of the corner it would push you back upright...and then the weight of the car would push it the OTHER way....and it would BOUNCE left to right....

it would virtually ROLL.......twisty left to right and back

HORRID.....

so you need SHOCK ABSORBERS>......and its hard to define and not all have fluid in, but I shall attempt.

Imagine a tube, just like a BICYCLE PUMP...in fact IMAGINE a bicycle pump

Now....take it apart and where the plnger fits perfectly into the tube to push air.....well take the circular plate that fits so snugly and DRILL HOLES IN IT..equal and quite small.....so the pump will no longer pump air...it will LEAK OUT as you push.

OK? cool

Now.......push the plunger in and to the bottom.....now FILL THE TUBE with OIL......go on...fill it........

Now...seal the end with an O ring that hold ALL THE OIL IN, but allows the pump to be pushed in an out...

we have a bike pump with holes drilled in the plungers plate, filled with oil, and the pump can still be pushed in and out.....

now TRY to push it in and out...go on....

its DAMN HARD>...cos the oil is having to go through the little holes....it WILL move.....but its so damn hard.......and its hard in both directions....

now use that as a shock absorber.....so under intense pressure it DOES move, but is SLOWS the springs movement and by the time the spring wants to come back the other way, it controls THAT too....

so you dont get WOBBLE...or BOUNCE.

So..out you go to your car...and PUSH DOWN HARD on each corner ...just ONCE...push it down in one big PUSH.....

hopw many times does it BOUNCE? Cos it ideally SHOULD just go down, with your effort, and raise back up and stop. Some softer ones go a bit above the original and then resettle to "home" in one fluid soft looking comfort mode...

and dont be fooled by HARD SPRINGS.....just cos you cant push it yourself doesnt mean the shocks are fine.....cos with HARD SPRINGS you need HARDER SHOCKS...top control the forces

Does that all make sense?

Now try making the holes in that pump BIGGER>..allow more oil to whoosh through....or try thicker oil.....or try multiple disks/plates on the ned of the plungers.....try using oil that softens a bit when its warm (Vectra GSi TiG) cos some cars are HORIBLE for 3 miles....TO HARD....then they mellow....become more "compliant"

Hope it helps people

[Russ]

very nice explenation zak, if any body like me tried the experiment, do it AWAY from ur pc.....

i need a new Keyboard

[Tumble]

The Landy was awful with the standard shockers on - just plain old oil ones - after an hour two of the rough stuff, they'd just get hot & the damn thing was pogo-ing everywhere.... got some nice Nitrogen charged shockers on it now - sweet ride

[5lab]

i got dampers on mine that work fine, but due to having more travel than tumbles landy it still handles like a boat

[TomWilko]

Thats very useful...i honestly had never heard of anything but springs...but now i know a bit more

[Lowe]

Good post Zak.

I dare not push too hard on my wings - they'd bend. Bloody Clio's made out of tin foil I swear. The bonnet's got dents in it from people not closing the bonnet gentley!

The shocks on it are pretty much brand new. Stuch a set of posh Sach Advantage on it and it transformed the ride. It's still very firm (low profile rubber doesn't help) yet it's still not too bad should the road get a bit rough. I still have to avoid the big potholes though, smack something big and you'll lose fillings.

[schrickvr6]

i once made the mistake of fitting lowered stiffer springs on worn standard dampers...not a good idea,i would't use anything other than bilstein dampers and eibach springs now tho,pretty comfy but very progressive and stiffen up as you need it.its a classic combo imo

[Zak33]

i once made the mistake of fitting lowered stiffer springs on worn standard dampers...not a good idea,i would't use anything other than bilstein dampers and eibach springs now tho,pretty comfy but very progressive and stiffen up as you need it.its a classic combo imo

I have just purchased the same make of both for my rally car

Not sure in the long run about Eibach. cos never had them before, but Bilstein.....just class.

The BEST cars in the classic world, such as Lotus, took the combo that best suits a light car...

Light springs and HEAVY SHOCKS....and given a choice where only one combo was available......thats my choice.

Heavy springs and light shocks are a recipe for nightmare mode.
Both heavy make a good compo car...but hard.
Both light make a comfy but wallowy pudding (see America through the 80's and 90's)

But light springs and stiff shock absorbers......

SO>.....for the "tweaking boys"
.......

forget SPRINGS for your car...get shocks first...and get good ones.

Some are adjustable and the jury is out on that....they have a valve on the top or bottom that adjusts the firmness (not the HARDNESSS>...the spring doesn't change) and you spend all your life fiddling....(thats my opinion anyway......LEAVE IT ALONE ANDLEARN TODRIVE IT )

But they do all come in different rates......

best conversions for value for money and life cycle are often a kit of both springs and dampers/shocks tho...often in combo, cos the fronts are often one unit.....

Macpherson strut

[schrickvr6]

Not sure in the long run about Eibach. cos never had them before

You won't regret getting them, i've used them on every veedub i've had bar one when i used H&R which were good but a little too stiff,suited to track cars really

[malfunction]

Good stuff Zak... One day I may even know how my car works!

All your "how stuff works" posts should be made stickies.

[Pigeon]

my car goes down, comes back up, then goes down again ony less far

but has no shocks or springs :/

[Rave]

New dampers will be the first thing my car gets if I ever get the time or money to upgrade it. I was thinking of Koni adjustables.

Rich :¬)

[Zak33]

Koni make lovely kits....I had a Nova GSI back in 93.....cracking little car....and sold it to a bloke who P'X'd an F reg GTE....and his car had a basic Koni sports pack on it...just dampers...standard springs.

That single change was AWESOME...and he did it to his new GSi straight away cos he forgot how awefullt hey were as standard.

Koni=

[Rave]

Cool, well I'd better start saving. I'm looking at £250ish for 4 dampers, is fitting them expensive? Could I do it myself if it is? I suppose I'd really better try fixing the brakes first though, TBH. They work fine and I rarely if ever brake hard, but the handbrake is a bit crud- it's a known weakness on MR2s apparently, I've already had new calipers fitted at enormous expense, hopefully new discs and pads will get things rosy again. The handbrake warning light keeps coming on randomly too, that's very irritating.

Rich :¬)

[Mart]

A few years back I had some SPAX adjustables on my H plate Astra SRi. Made a really difference to the handling but after a while the front ones developed play which made the steering real woolly. Got some replacements but they went after 6 months too.

I'm guessing something might have been out of balance and been putting a lateral load.

The GTE 16V front anti roll bar was also made a big difference.

[schrickvr6]

its a well known problem with spax dampers,apparently they are better now tho