Suspension: Shock Absorbers (dampers)


Topics covered:

Users' Experience and Opinions

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From: Shane Ballensky[SMTP:roverme@sunset.net]
Sent: Wednesday, September 13, 2000 12:27 PM
Subject: Re: [D90] shocks modifications

> too. can somebody give me a good idea about the mod I sould make to fit
> an eye-eye shock? (to the rear of the D90 - ed.)

Alberto
You can buy shock adapter from Rockware and the like. Or you can make your own. Its basically a "U" shaped piece of metal thats flat on each of the three sides. The shock goes through the center of the"U" with holes drilled on each side of the "U" for the bolt. The bottom of the"U" has a bolt welded in place that then connects to the stock lower shock mounting point on your d90.
Shane

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Date: Fri, 23 Apr 1999 09:17:46 EDT
From: RVRBRUCE@aol.com
Subject: Re: [D90] Final suspension question

I used the remote unit for several years. DO NOT use it as they become a leakdown problem and its a real bear to lose all your shocks at once. I just gave away all the Ranch stuff as I think they are not as durable as others.

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From: Shane Ballensky[SMTP:roverme@sunset.net]
Sent: Sunday, March 26, 2000 10:00 PM
Subject: Re: [D90] Doetsch Tech Shocks

Ryan Mercado ryanmerc@pacific.net.ph asks:
>anyone has had any experience with Doetsch Tech Shocks?  how do these shocks perform?

I had these on a j**p.  They were the heavier duty ones with a 7/8" shaft.  They are one of the few shocks that are actually capable of being used upside down(unlike ranchos-athough many use them that way anyways).  They also had built-in bump stops which was nice since I had a new suspension settup and no bumpstops.  They performed well as I didn't have any other shocks to compare them too so take that for what it's worth.  I paid around 39.00 each. I would recomend an ajustable shock personally.

.02
Shane
94D90#1316

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From: Richard Hills[SMTP:]
Sent: Tuesday, May 23, 2000 5:45 PM
Subject: Re: [D90] Suspension Questions

Q,

Yes, the nice thing about coil-overs is that springs are cheap, there are plenty of spring rates to choose from, you can assembly your own variable rate spring by stacking different coils, and you can set preload.

The bad thing about coil-overs is the shocks are expensive, if you brake a shock mount or shock shaft, you are out of business, and most significantly, coil-overs are not designed to work with the springs in tension (i.e., it would take some design work and machining to build a coil over that can retain the springs). Retained coil springs allow longer shock travel to be used which increases articulation without decreasing or effectively decreasing (as in the case of the DR system) the spring rate and hence the roll stiffness of the axle. One disadvantage of dialing in a lot of preload on a coil-over to get lift is the shocks tend to top out rather vigorously, which is a bit unpleasant in the ride and bit hard on the shocks and the shock mounts. Top-out circuits help out some, but shocks are not designed to handle significant top-out.

Rich

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Shock Info

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Date: Fri, 23 Apr 1999 10:23:08 EDT
From: SPYDERS@aol.com
Subject: Re: [D90] Final suspension question

>I would like to do the following:
>- - RR left rear .............. Further, I heard that 9014
>provided to much travel up front causing the D90 to stand up on end. What
>shock should I use up front? I heard the RS9207 is a good choice?
>Remeber, I want them to work with the remote control unit.

I seem to remember reading something about the 9012 on Rancho's website. Check out http://www.gorancho.com and on the main page there's a button "products" then look for "specialty shocks". In there, they mention several part numbers that have either harder or softer valving, and I'm pretty sure 9012 was one of the numbers...Ok, I went in since my browser was up, and copied the text I remembered reading:

"Soft Valved Shock Absorbers
Rancho part numbers RS5006, RS5008, RS5010, RS5012, RS9006, RS9008, RS9010 and RS9012 shocks are specially valved for multiple shock kit applications "

I don't know if it applies to LRs, but the info is on the site for all to see. I don't know what it means.

Also, please check out: http://www.off-road.com/toyota/tech/shocks/ for some more info on Rancho Shocks.

Alan_Ottley@mtn.3com.com adds:
I am running 9014's up from with OME 764's with no problems. The springs are MD rears but work great up front. I also use them in the back with 9012 shocks. The rover sits level with the same springs all around. I have a winch up front too.

From: Bill Ritchie[SMTP:billnsandi@kingwoodcable.com]
Sent: Friday, December 24, 1999 6:19 PM
Subject: [D90] Rancho Shock Guides and a Question

I was researching shocks recently and came across some good info on the lengths of avail. Rancho shocks. 2 pages have pretty good stuff -

http://home.earthlink.net/~thediscoho/menu.html
- look under tech and Rancho Shocks

http://www.off-road.com/toyota/tech/shocks/

Both give stats for the shocks commonly used for the DR and RockWare suspensions.

9012 rears and 9014 fronts (DR) and 9207 fronts (Rockware).

The front shocks as we all know have "S1" pin type ends, so the choice is somewhat limited.

Bill Ritchie
'97 AA Yellow Defender 90 ST #2078 (with a few mods)

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From: farvin[SMTP:farvin@gwis2.circ.gwu.edu]
Sent: Tuesday, June 06, 2000 10:56 AM
Subject: RE: [D90] Shocks

>I used this site as a reference for awhile, then found a site in Japanese that
>had (to my knowledge) every 9000 made. All 61 of em with specs which is about
>3* the Toyota page.

I just put it up on my site. Go to:
http://gwu.edu/~farvin/Misc.html

and scroll to the bottom. Either right mouse click to "save as target" or double click to open. Feel free to save this to other sites, D90 references etc. Again, props to Matt at Rockware for getting the information ball rolling.

Tom

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From: Leonard Tanti Bellotti
Sent: Friday, May 19, 2000 7:30 AM
Subject: Rancho Specs

You might already have this somewhere on D-90.com but just in case
http://www.gorancho.com/images/Specs.PDF
downloads a full spec sheet in PDF format of all their shocks.
  Keep up the good work

Leo

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From: Gbrovers@aol.com[SMTP:Gbrovers@aol.com]
Sent: Thursday, February 24, 2000 11:04 AM
Subject: Re: Bilstein Shocks

Kelly
You are corrrect in your observations about Bilstein shocks and I have to say that BP is totally wrong about them. Comparing the bushing size, diameter of the shock and the weight of them shows a lack of understanding of the technical aspects of shock absorber design.
(NOTE: Bill is referring to information presented at:
http://www.britishpacific.com/icaweb/britpac.nsf/b141befe8fb1c2ea882564360001be0c/4ff98194c7f235ec8825687f0063af15?OpenDocument

Skipping the technical stuff for a second, here is some other info about Bilstein shocks.
1) Bilstein invented the gas pressure shock in 1953 in conjunction with DeCarbon and perfected what is called the "high pressure gas monotube" design. These are different from regular "gas shocks". Most companys don't manufacture monotube designs because it is harder and more expensive to do. The other companys that make monotubes are companys such as Penske, Cararra, Fox and DeCarbon. With the exception of DeCarbon all of these companies make specialty race shocks. That should give you a hint about the superiority of a monotube design.
2) Bilstein shocks totally dominate most classes of racing such as NASCAR, SCORE/HYDA, CART, IRL and Formula 1. This is even more amazing considering that Bilstein originally didn't pay contingency fee's and may still not! I've been out of the racing end for a while and just don't know anymore.
3) Bilsteins have been installed as original equipment on some of the worlds most expensive sports cars and touring sedans and many vehicles known for the outstanding performance. Examples Mercedes Benz (since 1957), BMW, Porsche, Ferrari, Chevrolet Corvette (since 1984 including the computer controlled Active Ride suspension), all GM uprated optional Z71 off road suspensions on both mid and full size 4 wheel drives. There are numerous other examples but I hopefully I have made the point.

Concerning the technical aspects of Bilstein shocks, there are two major limiting factors to a shock absorbers performance -
1) the ability to maintain its damping efficiency, which is usually lost due to the oil in the shock "cavitating". Cavitating is a fancy way of describing boiling. A shock absorber converts motion to heat. Under extreme conditions there is so much heat generated that the oil literally starts to boil and in the process the oil turns to foam. Regardless of the type of valving the shock has, foam just doesn't cut it! i.e. you lose all damping ability. The major function of the gas pressure in a Bilstein is to raise the boiling point of the oil. if you understand the function of a pressure cooker this should be obvious. As mentioned earlier a Bilstein is a "high pressure" gas monotube. The pressure of most Bilstein shocks (not steering dampers) ranges from 360 to 420 lbs per sq inch. This contrasts to most other gas shocks which usually have somewhere in the range of 45 to 60 lbs of pressure, including OME shocks. Another thing to consider is that a monotube shock will transfer heat much more efficiently than a twin tube hydraulic shock (a tube within a tube), which is what most other shocks are, including OME's. A related point, most people have heard of shocks with external resevoirs, the major function of an ER is to increase the volume of oil in the system to keep the temperture of the oil down hopefully below the cavitating point. A quick point about shock tube outside diameter, the OD of the shock is not nearly as important as the OD of the piston inside of the shock. A monotube design shock has the largest possible piston because there is no wasted space i.e. a tube within a tube.
2) The second major factor in shock performance is valving design. Bilsteins use what is known as deflective disc valving as opposed to check valve arrangments. Valving is extremely important because limitations in valving cause what is known as "hydraulic lock". Hydraulic lock happens when a shocks valving reaches its limit - the shock absorber temporarily becomes a solid unit (imagine running over a curb at 60 MPH). The problem with check valve valving is that they are basicly a hole with a ball and spring to control fluid transfer. If you remember from high school or college physics - unlike gases or solids, liquids do not compress! So if you try to ram more liquid through a hole than it is physically possible to do - the result is hydraulic lock i.e. no movment/harsh ride!! This is what happens to a normal shock. There are several ways to try and deal with this - multi-stage valving (when one check valve locks another one kicks in) or using a low pressure gas reservoir, so the gas compresses to compensate for shortcomings of the valving. As noted earlier, Bilsteins use deflective disc vavling. The difference is that most of the piston is actually mostly open and not solid, and sealed with flexible discs. The more pressure that is exerted on them the more they will flex, thereby allowing more fluid to flow thru the valve. This is why Bilsteins are described as having infinitely adjustable valving. This is hard to describe verbally so I would encourage anyone wanting a more complete explanation and pictures to visit Bilsteins website
www.bilstein.com.
Hope this info helps clear up most questions, any more let me know.

Bill
Great Basin Rovers
Disclaimer - I am a Bilstein warehouse distributor (somewhat biased) and have been selling Bilsteins for Rovers in NA longer than anyone, I actually started to special order them into NA for Rovers in 1988 thru a previous company (Rocky Mountain Suspension Specialists) and sold them wholesale to all of the other Land Rover parts distributors, including BP. Also concerning OME shocks, do not interpret any of this as saying that OME's are bad shocks, they are excellent shocks ( I also sell them) and they would certainly be my second choice but side by side to a Bilstein there is no performance comparison!
Trivia note: most people pronounce Bilstein as Bilsteen (long E), the best way to remember how to pronouce it is to think of beer! What do you drink beer out of - a steen or a stein????

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Shock Length Selection

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From: matt@rangie.com[SMTP:matt@rangie.com]
Sent: Sunday, February 06, 2000 4:24 AM
Subject: Re: bilstein shocks

> how do i measure the correct shock length? do i fit the shock fully
> compressed? fully extended? static load? if static load - how do i know if
> it's 2 inches over compressed or 2 inches over extended?
> ryan

Remove the shock absorbers from that axle. Fully articulate the axle so that the side you are using to measure is fully compressed, i.e. on the bump stops or the springs are coil bound. Measure the length between the two shock mounts. Take a little bit off for safety, and this is the maximum compressed length of your shock. If you didn't want to modify anything else, then this would decide the shock length. This is set so that you will never over-compress your shocks, which causes them to fail.

However, you may also want to measure with the wheel at maximum droop while not retained by the shock absorbers. Bear in mind that for the maximum droop you are happy with, you have to consider brake lines, springs coming out of the mounts etc...

Once you have picked your maximum articulation point, measure the distance between the shock absorber mounting points again. This will give you your uncompressed length for the shock absorber. Obviously an individual shock absorber can only extend by so much, so you may well find that the two readings can't be matched to a single shock, however, you can then decide whether you want to extend your bump stops to allow a longer compressed length without damage, thereby allowing more downward travel. You may then also want to consider moving shock mounts to allow more travel. Once you have the measurements, then you can try various options on paper, and see which one most suits your driving needs.

Matthew
nr Heathrow, UK
1979 2-dr Range Rover 300Tdi

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From: Richard Hills[SMTP:rhills@nmsu.edu]
Sent: Monday, May 22, 2000 8:26 AM
Subject: Re: [D90] Suspension Question

Ben,

You are correct in noting that the up-down wheel travel (with no articulation) will be only 9.5". However, the wheel travel will be larger in articulation. This is because in addition to the 9.5", you also have additional wheel travel due to the angle of the axle. I calculated that the additional theoretical wheel travel due to articulation (as measured at the tire) is approximately 1.6 times that of the shock travel at the center of the stock wheel. This gives 15.2" of wheel travel. If you measure to the outside of the tire, or have tires and rims, this ratio increases.

Keep in mind that this number is theoretical only. The stock front suspension does not use all of the existing compression travel on the shock travel as it is. By going to the Fox shock with your new bump stops, you can use more of the available compression travel (simply because they are longer when fully compressed). In addition, you gain 2.5" of extension travel.

Unfortunately, the stock front radius arms limits travel due their overconstrained design and you still may not be able to get the full wheel travel. This is why many are going to the 3-link or to the modified radius arm approach.

The ratio on the rear is even larger. This is because the rear shocks are not vertical. A 1" motion of the shock results in a greater motion of the axle. Multiply this effect times 1.6 and you get a larger ratio. The rear suspension is not overconstrained, and it is much easier to obtain the full wheel travel available by the appropriate choice of spring rates.

In addition, the stock rear has the same problem as the stock front in that the rear shocks are not fully compressed when the rear is fully articulated. The longer shocks (or Greg's drop kit), more efficiently utilize the available travel of the rear shocks.

Rich Hills

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From: Richard Hills[SMTP:rhills@nmsu.edu]
Sent: Tuesday, May 23, 2000 9:54 AM
Subject: Re: [D90] Suspension Question

Shorter travel on the SW:

The higher the cg of a vehicle, the less wheel travel one can afford before the vehicle becomes statically unstable in off-camber climbing situations. I find that a rti of around 1000 (on a well balanced suspension - i.e. more articulation from the front that is possible with stock radius arms) is about as far as I want to go on my SW. This is the primary reason I no longer run the RR long springs with the long ranchos on the front. I found that in many situations, I had to back down because I was about to wheel stand the vehicle. With bit stiffer front springs and somewhat shorter shocks (I am still running longer than stock), I have no trouble climbing the same obstacles. With a soft top, the optimum rti is more if your suspension is well balanced.

Rich later added:
Here are some more specifics for my SW. Because of the increase cg height, I find that a softer front end with longer travel tends to raise up more when climbing a steep high traction rock slab. In addition, the added torque exerted on the rear wheels when climbing tends to lift the front even more. This all has the effect of moving the cg up, shifting more weight to the rear wheels, allowing for the generation of more torque on the rear tires, lifting the front more, etc. With the higher initial cg of the SW, I found that it is easy to lift the front so much that it wants to wheel stand (or worse if I didn't back down and try another line) before the rear wheels broke traction under some high traction conditions. By limiting the allowable upward travel on the front suspension, one can control how high the front lifts in its travel, limit the weight transfer to the back, and climb up (or brake traction) without the tendency to wheelstand.

A somewhat similar effect exist when climbing steep off-camber rock slabs. If the rear is too soft, I find that it is easier to walk one of the rear wheels under the chassis, leaning the vehicle over more, walking that rear wheel further under the chassis, until I have to back down for fear of toppling over. This effect is worse if the front is soft with lots of travel on steep climbs simply because there is more weight on the rear tires which allows more traction to be generated by the offending tire. The higher your cg (relative to the track width), the more tendency to do this with our suspension geometry.

Soft tops have significantly lower cg heights and are less sensitive to these effects.

Rich

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Repair / Rebuild Info

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From: Chris Walker[SMTP:cwalker37@home.com]
Sent: Tuesday, October 10, 2000 11:38 AM
Subject: [D90] Re: Heim joints

RB,
I was talking to some people at a shop called the Off Road Warehouse here in San Diego. They sell Fox shocks, Race Runners etc. I was considering changing the ends of my Stage II Fox shocks to heim joints. I was told by them that heim joints do not last very long. They are used in off road racing, where the joints are changed very often, usually after each race. So I purchased the same ends that are used for heims, but there are bushings that fit in place of the heims, and those will last longer. http://www.offroadwarehouse.com/ You'll have to call thier shop on Balboa Ave. if your interested in that sollution.

good luck,
Chris Walker
95 Disco

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Limiting Straps

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From: Nathan Hindman[SMTP:nahindma@wholepeople.com]
Sent: Wednesday, March 29, 2000 7:18 AM
Subject: [D90] RE: Limiting Straps &"Koly's little problem" Was RE: Suspension Q uestion

>If you are going to go all out with a disconnecting spring type suspension,
>I'd probably recommend check straps. With the Desert Rover and also the
>Rockware, I assume, you can bolt check straps on the shock mounts and
>rubber band them to the shock. While still hard on the mount you get some
>protection for your shocks. I'd be worried if you were jumping your truck
>and clipped something with the axle... Not that the straps would help a
>whole lot then, but it's only about a $50.00 - $60.00 option from Rancho.
And I responeded:
I have limiting straps on my 90 because due to my shocks, the springs were constantly falling out below the cones (3-4" below). I ended up installing the Rancho straps which I believe only ran about $60-75 for the pair. I installed them running from the chassis to the axle. Ever since the install, I've yet to have a problem with the rear springs (just ask anybody who ran with Rover Bruce on Golden Spike last year how big of a problem I was having before the straps) If there's any interest, I can post pictures to either my website or the Q's ever informative d-90.com. But the limiting straps would definitely cure problems like what Koly had last weekend and also solve future "spring fatigue" related problems too.

No affiliation with Rancho, yadda, yadda. I just really like these straps.

Nathan
94 AA Yellow D90 #1811
97 Discovery XD

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