how to know when to replace shocks, springs?

[Vendetta]

Sambo, if your bump stops/"spring helpers" are contacting your axle at all times during forward motion, something is seriously wrong with your setup.

Test it out. Put some powder on the axle underneath the stop, drive around the block, (assuming you don't live in an overly bumpy potholed neighborhood) and see if there's been contact.

EDIT: Also, I just picked up full set of Rancho 9000XLs from Summit (finally!). They're having a special where Rancho will rebate you the cost of one unit when you purchase a set of four.

[blacksambo]

I don't think so. There is only, per factory specs, a quarter to half an inch open space there (between the spring helper and the axel rest plate), which easily colapses to zero with the forward inertia of a two-ton vehicle. Our springs are strong, but not two tons at 30mph and only a quarter of an inch margin strong.

[catskilljay]

You're right, Maddawg - they've got nothing to do with noise. The spring helpers may provide a small, coincidental measure of sound damping due to the fact that they have mass and are bolted to the frame and thus attenuate some vibes but they in no way insulate the axle from the frame. The exact same axle/frame contact points exist whether the spring helpers are there or not. Sound damping is not their reason for existence. The spring helpers take advantage of the hysteresis of rubber in order to provide rollover protection.

Yes, the sway bar helps limit body roll but, being a torsion bar (i.e., steel spring), it offers the same resistance whether it's being twisted slowly or rapidly and it also returns almost all of the energy it stores. This applies to the coil springs too. Without spring helpers present, the shocks would provide the only damping to control rapid oscillations such as would be seen in a high speed avoidance maneuver - and the engineers apparently decided stiff shocks and springs weren't enough to prevent rollovers and the attorneys and bean counters decided spring helpers were cheaper than settlements, thus we have spring helpers instead of bump stops.

Due to the elastic hysteresis inherent in rubber, the faster the spring helper is compressed, the more resistance it offers, and it doesn't store and return all of that energy but rather converts it to heat. This gives us some rollover protection from botched avoidance maneuvers but the ignorant little chunks of rubber can't tell the difference between a frost heave and a swerve to avoid a deer so we have to put up with a harsh ride if we want avail ourselves of the full measure of safety designed into the VX.

Or one can roll the dice, chop the chunks and roll over square edged bumps in relative comfort - and hope one doesn’t roll over in any other way!

Anyway - the original question was which pieces need to be fixed when the boinging starts. The answer is.... THE SHOCKS!!!! But if it's just a harsh ride you're talking about then that's normal. If you're getting a lot of brake dive and pogoing then the dampers are no longer damping. If you've still got the OEMs, you might want to try just adding nitrogen. If that doesn't work, they can be rebuilt. If you've got worn out aftermarket shocks then it's time to replace.

so what is this "add nitrogen" you speak of?? my ride has become quite the bouncy mess in past few months, and i chalked it up as needing shocks.

[blacksambo]

You can refil the OEM shocks with nitrogen to help restore performance. Bike repair shops seem to do this service.

[Vendetta]

You can refil the OEM shocks with nitrogen to help restore performance. Bike repair shops seem to do this service.

...and I just dropped 4 bills on new Ranchos. Ahh, it's all good I guess. I'm pretty sure the bike shop wouldn't rebuild my 14 year-old, never-serviced OEM shocks anyay. Plus, I've been dying to see what all the fuss is about with the 9000XLs! Hopefully Summit gets 'em to me by the weekend.

I've got that pre-season madness going on now to get her in game shape for the winter.

[catskilljay]

hmm ok thanks sambo Ill look into it

[VX KAT]

There's a guy named Bruce that's rebuilt our OEM shocks.
http://www.brucessuspension.com/
At least 2 owners have had him do it (Little Beast, VR4-QUEST)

Here's some old threads on it, including recharging them with nitrogen.

http://vehicross.info/forums/showthr...ighlight=bruce

http://vehicross.info/forums/showpos...1&postcount=12

http://vehicross.info/forums/showthr...s+shocks+bruce

http://vehicross.info/forums/showthr...ighlight=bruce

http://vehicross.info/forums/showpos...9&postcount=14

[Vendetta]

Thanks Kat! (How ya been, lady?)

I'll be reaching out to Bruce once my OEM's come off.

Anyone have any data on the life expectancy of the Rancho 9000XLs?

-V

[SlowPro48]

I'm not trying to be argumentative here but....the spring helpers do touch the axel at all times when the VX is in forward motion, so therefore they are constantly insulating the axel from the frame, thus causing a noise deadening effect...

Sambo, I'm getting too old and tired to argue anymore. Nowadays I like to agree with people. I'm curious though - exactly how do you think the spring helper insulates the axle housing from the frame by being in contact with it? Do you know how a mechanic's stethoscope works?

Will you agree with me that the axle housing is attached to the frame via a center link, a lateral link and two trailing links, which provide a pathway for vibration (sound) to be transmitted to the frame?

Will you agree with me that the shocks and coil springs also provide a pathway for vibration?

Will you agree with me that these pathways exist whether the spring helpers are touching the axle housing or not?

Will you agree with me that when the frame-mounted spring helpers are NOT in contact with the axle housing it is physically impossible for them to transmit the vibration from said axle housing to the frame?

And finally, will you agree with me that when the spring helpers ARE touching the axle housing, they do not insulate but rather provide an ADDITIONAL pathway for noise from the axle housing to reach the frame?

Fortunately, they don't provide much of a pathway because rubber does not transmit vibration very well. That's why the links and shocks are rubber bushed and there are rubber donuts between the springs and the frame.

The spring helpers may damp some vibration/harmonics in the frame and maybe even in the axle housing simply due to the fact that they have mass and are bolted to the frame/touch the axle housing - like play-doh on a tuning fork or a string silencer on a hunting bow - but they in no way acoustically isolate the frame from the axle housing by making contact with it. I wish they did because I would appreciate a little less whining from my differential.

Hey maybe I should bolt six or eight more spring helpers onto the backof the VX to quiet things down a bit!

Just think about it...

[SlowPro48]

Oh and to the OP: If your shocks aren't leaking fluid, just take them off the vehicle, pop the metal cap off the reservoir and clean everything up - especially inside the schrader valve. Take the shocks to a motorcycle shop or tire shop that has nitrogen and tell them you want 250psi. Then go to Lowes/Home Depot/Grainger/any plumbing supply place and get rubber caps and jubilee clips to replace the metal caps you destroyed. Put the shocks back on the VX and see if it helped.

If not, you can get them rebuilt as long as the shaft isn't bent or dinged up. But a lot of times, just pumping them back up will do the trick. It's the same principal that allows the water in your radiator to go well over 212 degrees without boiling - only at about 20 times the pressure. If the shocks aren't pressurized enough, the fluid will cavitate when forced through the shim stacks and you end up with a bunch of air bubbles in the fluid. It's like boiling water in a pot except it's caused by pulling a localized vacuum on the fluid instead of having the vapor pressure of the fluid exceed atmospheric pressure due to heating. But the end result is the same - bubbly, frothy fluid that offers no resistance when forced through the piston/shims and therefore shocks that don't damp.

Give the nitrogen a try - it's a cheap gamble...

P.S. you can use a drill and slide hammer to remove the caps or they're thin enough to just hammer an awl in and pry the cap off - but do your drilling/punching off center! The shrader valve is in the center!

[chadzu]

I just installed a set of moog 784 springs in my vx. You just have to cut off the pig tail and they are perfect for the isuzu. Depending on how much you cut off you get between about 3" lift to low rider I supose.
I am running 315 75 16 tires, so I went with 3". The ride is so much better than stock. It is like a new vehicle. I imagine that if you cut them so you had 1.5" it would still ride nice and you wouldn't have much lift. I got mine from Advance auto for $79 delivered.

[blacksambo]

[QUOTE=SlowPro48;265437]Sambo, I'm getting too old and tired to argue anymore. Nowadays I like to agree with people. I'm curious though - exactly how do you think the spring helper insulates the axle housing from the frame by being in contact with it? Do you know how a mechanic's stethoscope works?

Will you agree with me that the axle housing is attached to the frame via a center link, a lateral link and two trailing links, which provide a pathway for vibration (sound) to be transmitted to the frame?

Will you agree with me that the shocks and coil springs also provide a pathway for vibration?

Will you agree with me that these pathways exist whether the spring helpers are touching the axle housing or not?



I think you said it with the tuning fork analogy. The spring helper blends all these contact points into a balanced resonance and thus makes the clatter from this symphony of metal arms less prevalent .

I can attest from personal experience that it works this way. And my wife who has no particular mechanical expertise mentioned it first...."what did you do to quiet this thing down." Installed the missing spring helpers....simple.

[VX KAT]

Oh and to the OP: If your shocks aren't leaking fluid, just take them off the vehicle, pop the metal cap off the reservoir and clean everything up - especially inside the schrader valve. Take the shocks to a motorcycle shop or tire shop that has nitrogen and tell them you want 250psi. Then go to Lowes/Home Depot/Grainger/any plumbing supply place and get rubber caps and jubilee clips to replace the metal caps you destroyed. Put the shocks back on the VX and see if it helped.

If not, you can get them rebuilt as long as the shaft isn't bent or dinged up. But a lot of times, just pumping them back up will do the trick. It's the same principal that allows the water in your radiator to go well over 212 degrees without boiling - only at about 20 times the pressure. If the shocks aren't pressurized enough, the fluid will cavitate when forced through the shim stacks and you end up with a bunch of air bubbles in the fluid. It's like boiling water in a pot except it's caused by pulling a localized vacuum on the fluid instead of having the vapor pressure of the fluid exceed atmospheric pressure due to heating. But the end result is the same - bubbly, frothy fluid that offers no resistance when forced through the piston/shims and therefore shocks that don't damp.

Give the nitrogen a try - it's a cheap gamble...

P.S. you can use a drill and slide hammer to remove the caps or they're thin enough to just hammer an awl in and pry the cap off - but do your drilling/punching off center! The shrader valve is in the center!

These were my OEMs when I replaced them with Ranchos 9000XLS
I'm curious, is the rusty looking crudy end cap/piece in the first 2 pics indicative of them leaking something?

oh...and Hi V!...I'm hangin'....

[catskilljay]

Thanks for pics and help Kat

[vt_maverick]

Really recommend anyone looking to reduce bounciness, jarring ride, etc. take a look at this thread:

Recommendations for Leveling Out Suspension

Pricier than Moog or even OEM springs but they're adjustable based on your load and they shouldn't wear out as quickly. It smoothed the ride in my VX while maintaining sharp handling, and when we couldn't find replacement springs for my wife's Axiom we had these installed instead. Probably handles better than the day we bought it.

Good stuff regardless of the answer to the "spring helper" / bump stop debate.

(Btw Isuzu calls those "rubber stoppers" on the Axiom, so there's a 3rd name for them. )