parabolic spring confusion

[Donnie]

Parabolic Spring issue re posted>>>
After reading the entire thread 3 or 4 times I am still at a loss as to the best for the buck springs... I am looking for a good hiway ride, for my 109 2 door rhd wagen, original euro 6 cyl, with a Fairey OD & and 235 x 85 x 16 radials.
It is used mostly on the hiway to get to the flea market with a light load of collectables... This truck is not used off road...

[SHORLAND]

Anytime you can get rid of unsprung weight its always a good thing. BUT I dont have any. When I do purchase another LR I will install parabolic springs right off!

[Jim-ME]

No offense to our hosts but I feel that RM springs are the best way to go.
Jim

[Terrys]

With the exchange rates being nearly equal, and roughly 18% duty on new auto part imports, having used both RM & RN, it's tough to recommend one over the other.

[TedW]

Two leaf front, three leaf rear with standard Woodhead shocks. Same size rubber as you describe. Cushy ride, handles well. I'm told that my shocks have insufficient travel and will top out at some point, but it hasn't happened yet. I had the Old Man Emus but found the ride to be too stiff.
I have a SWB with a soft top.

[daveb]

ted

your ride was too stiff because those springs are too heavy for a soft top 88."

you'd be better off with a 2 leaf rear or two leaf + helper.

I have used both the RM and TiC on my 109 3 door. The 3 leaf RM's w/OME rear shocks and Bilstein fronts gives an excellent ride. The springs are probably just a little light for my vehicle because of the heavy SS roofrack and my propensity to overload it.

My prediction is that the stock woodhead shocks will die an early death. earlier if they are used on anything approaching rough roads.

you will know they are gone when the rear end starts to come off the ground. BTDT, parabolics NEED good shocks. The stock springs don't because thy basically don't move very much.

IOW, stiff ride is not so much from shocks as it is the spring rate.

shocks improve handling by reducing the oscillation of the spring, thereby the wheels on the ground.

stock LR spring and shock combo is pretty easy on the shocks becasue the shocks don't get worked very hard. on parabolics the gas shocks are important because they can dampen the higher frequency oscillation of the lighter springs. oil-filled shocks like the woodheads will probably heat up and foam out on washboard surface when used with parabolics. the foaming causes a temporary loss of dmaping which eventually wear out the seal.

on a more interesting note, I bought some bilsteins from a well-known vendor for the bakc of my 109. I was noticing the rear end hopping alot and people driving behind me said the wheels were frequnetly off the ground going down a roughish highway surface @ 70mph. The vendor eventually figured out that the shocks were too long for the 109 and replaced them free of charge with the OME's.

When I took the bilsteins off they were a sight to behold. the top of the canister was blown clear off (gone) and they were full of dried mud.

So, in a nutshell, 3 leaf rears for lighter HT vehicles. 2 leaf for ST 88's. 4 leaf for heavy 109's. OME's are good shocks from my experience and
others can report on the Pro Comps etc.

My RM's are holding up well so far, as did my Ti Consoles. No experience with any other brands.

Dave





Two leaf front, three leaf rear with standard Woodhead shocks. Same size rubber as you describe. Cushy ride, handles well. I'm told that my shocks have insufficient travel and will top out at some point, but it hasn't happened yet. I had the Old Man Emus but found the ride to be too stiff.
I have a SWB with a soft top.

[TedW]

I'll keep an eye on things - this might be a fun experiment for a while. I do feel that my ride has improved significantly with the Woodheads, and I don't find the rear end to be jumping around (yet).
I don't know how much a hardtop and sides weigh - I have a set in my basement and can check. Must be less than 100 lb. Can that make the difference between two leaves and three? You also have to factor in the (marginal) weight of the canvas and hoopset. I notice that most suppliers don't offer 2-leaf rears - if RN did, I might have bought them.

In any case, the ride is good right now and I'll keep an eye on how the shocks are holding up. I will report back to the group when my shocks explode (or don't!).

[daveb]

yeah, hopefully they won't explode. most likely just slowly stop working and you won't notice it until it gets really bad.

if you are going on washboard roads be ready for the vehicle to try to leave the road at any time. BTDT...

Most of the suppliers USED to offer 2 leafs. Don't know if they still do. Maybe Ti Console was the only one making the 2 leaf + helper.

Anyway, I wish you only success! :)

rgrds
Dave


I'll keep an eye on things - this might be a fun experiment for a while. I do feel that my ride has improved significantly with the Woodheads, and I don't find the rear end to be jumping around (yet).
I don't know how much a hardtop and sides weigh - I have a set in my basement and can check. Must be less than 100 lb. Can that make the difference between two leaves and three? You also have to factor in the (marginal) weight of the canvas and hoopset. I notice that most suppliers don't offer 2-leaf rears - if RN did, I might have bought them.

In any case, the ride is good right now and I'll keep an eye on how the shocks are holding up. I will report back to the group when my shocks explode (or don't!).

[greenmeanie]

I've had the Rm 2 leaf front and 3 leaf rears on my 88 with the Rancho shocks for the last six years. I've run her topless with the screen down and with the roof on. She rode and handled well in both configurations. Empty, with no roof she did lose a bit of flex in the more extreme stuff but I usually have her loaded down pretty well when I off road as I like to go prepared!

When I was getting ready to buy I talked to Ray at RM and discussed my uses and his general rule was that if you wanted to build something super flexy for of road then the 2 leaf rears were the way to go but if you planned on carrying any sort of load then the 3 leafs were necessary.

Personally, I never liked the helper spring thing as they always looked like they would hook up on stuff. In the inevitable parabolic thread wars that go on I've seen a few pictures of helpers that got damaged but it all comes down to personal useage of the vehicle.

The long shocks are a must in my book. With the extra height of the parabolics the oem ones run out to the ends of their travel where the damping is less effective. Having said that if you've got em on, they ride how you want and the allow you to enjoy your truck in the manner you desire then all power to you. When they wear out I'd replace them with the longer ones but that's about it.

Cheers
Gregor

[TedW]

Most of my driving is on tarmac (Maine roads can be pretty bad, especially in the Spring). In winter I keep 150 lb. of sand in the back for snow traction, so that might help hold things down. The truck is a gas in the deep stuff.

Question: If I want to stay with these shocks but need more travel, could I go with rear shocks in front and a 109 shock in the back?? Advice is welcomed....

[greenmeanie]

Hmmm. When choosing shocks there are four main factors I can think of:
- Strength.
The shock you use should be strong enough for the application. In the case of an 88 any light truck shock would most likely do.

- Mounting.
It sounds obvious but you need to make sure the eyes and bushings match your application. This is what kills us trying to find aftermarket set ups for the 101. I can’t say I’ve looked at a 109 in detail enough to say it will be OK. Someone else will no doubt chime in with the eye to eye length of a stock 109.

- Length.
With the truck at rest on a flat surface you want to measure the length between the mounting pins for the shock. Knowing this you want to choose a damper whose length causes the piston to sit around the mid point of the tube. This is where the most effective damping is. If the piston sits out towards the end of the tube the damping becomes less efficient and the travel of the suspension becomes severely limited in one direction.

The limiting dimension on your suspension travel should also not be the piston hitting the end stops in the damper. This puts a lot more stress on the part than you want for longevity. It is also an easy way to break the shock. In you current configuration I would shorten the limiting straps to prevent this.

- Damping.
This is a function of many things and within limits is very subjective. Go to a downhill mtn bike race and talk to riders about their suspension set up if you want a laugh. You can end up playing with spring rate(linear or rising rate), high speed compression damping, low speed compression damping and rebound damping not to mention a couple of things unique to bikes. Too much damping and the truck will ride stiff and wheels will bounce losing traction. Too little damping and the truck will wallow around like an old Caddy and feel unstable.



Buying the shocks suggested by RM takes a lot of work out of the choice for you and most are happy that way. You could ask Ray if the Ranchos are different from the yellow ones. He may even tell you the Rancho part number so that you can xref it and see if there is a part that will fit with the characteristics you desire. If you like the damping but want longer shocks a lot of places can measure your existing shock values and provide a matching set up. I am almost certain the stock Rover shocks cannot be mixed and matched to achieve what you want and would no doubt be more expensive than going aftermarket.

Just my tuppence worth.

Cheers
Gregor

[BackInA88]

In you current configuration I would shorten the limiting straps to prevent this.

Aren't the limiting straps there to prevent damage to the shocks from bottoming out.
If he has the stock shocks and now the lower mounting point for them is now closer to the frame because of the thinner spring pack.
Now when the axle is stopped by the limiting strap the piston will be even further from bottoming out than with the stock springs?
Or am I looking at this all wrong?

Steve

[TeriAnn]

Aren't the limiting straps there to prevent damage to the shocks from bottoming out.
Yes but parabolics work by flexing more and easier than stock springs allowing them to better smooth out bumps. You are not supposed to use limit straps with parabolics because they inhibit part of the normal parabolic spring movement. Also LRs tend to sit a little higher when on parabolics.

Shocks are supposed to be matched to the spring rate. The goal is to allow the spring to move and dampon spring rebounds so you don't end up with the body bouncing up and down on the springs. Stock shocks are designed to properly dampen stock spring movement and will not work properly with parabolics. Always check with the spring manufacturer to get their shock recommendations.

Ideally when the vehicle is at rest the shock should be mid way through its travel. BUT Series shock mounts are mounted closely together and a shock can easily reach its limit with parabolics and even with new stock springs. LR fixed this problem in 1983 by moving the shock mounts farther apart so longer shocks can be used. What people usually do with parabolics is mount a longer travel shock that allows increased lower articulation at the cost of upper articulation. Some folks cheat and fabricate new shock mounts that are farther apart than stock.

[daveb]

109 rears use an eye at the top and a stud at the bottom. they won't fit an 88.


Someone else will no doubt chime in with the eye to eye length of a stock 109.

[alaskajosh]

Aren't the limiting straps there to prevent damage to the shocks from bottoming out.


I prefer the explaination that they are to prevent the rear driveshaft from striking the frame (where it passes through that hole).

I can't buy the "prevent shock damage". Why are these the only cars (that I've ever seen) that need straps? The shocks are no different from any other strapless application. It's the driveshaft hole that's unique... not the shocks.

[friar mike]

I prefer the explaination that they are to prevent the rear driveshaft from striking the frame (where it passes through that hole).

I can't buy the "prevent shock damage". Why are these the only cars (that I've ever seen) that need straps? The shocks are no different from any other strapless application. It's the driveshaft hole that's unique... not the shocks.
you havn't worked on many english vehicles have you. by the way when it warms up around here we will have to meet up at the range and shoot some odd guns.

[alaskajosh]

...by the way when it warms up around here we will have to meet up at the range and shoot some odd guns.
I'd sure like that!:thumb-up:

Some of these same shocks have other, strapless, applications. Why are they subject to damage-by-top-out when mounted on a series LR but no worries (straps) when mounted on most any other car?

Maybe it's not for us to wonder why... it's just an "English Thing"?

Kind regards, Josh

[BackInA88]

I prefer the explaination that they are to prevent the rear driveshaft from striking the frame (where it passes through that hole).

I can't buy the "prevent shock damage". Why are these the only cars (that I've ever seen) that need straps? The shocks are no different from any other strapless application. It's the driveshaft hole that's unique... not the shocks.

Driveshaft doesn't pass thru the frame on an 88.:D


TeriAnn,

No question that the parabolics flex more and allow more axle movement.
The statement I questioned was about having to SHORTEN the straps to prevent over extending the STOCK shocks.
The straps are designed to do this and if he is running stock shocks and now that his lower mounting point is even closer to the axle because of the thinner springs I can't see why he would need to shorten them.
He could actually make them longer because of the mounting point change.
If anything the bump stops might need to be longer to prevent the shocks from bottoming out under full suspension compression.
It doesn't matter what springs are on the truck we're talking about the relationship between the strap and the shocks.
Maybe he just wants a smoother ride and doesn't care that much about flex if he did the straps would be gone, longer shocks installed and the driveshaft altered for a longer slip yoke?:thumb-up:

But these are good points he should be aware of.

Steve



.

[daveb]

Josh

All my old Volvo 122s had check straps. They are there simply to prevent the car from damage cause by the axle dropping lower than the design tolerance. Driveshafts can bend or seperate, springs fall out, brake lines tear, and shocks bottom out. It is just one method for doing this.

I can't imagine needing to make them shorter on a LR.

FWIW I haven't ever had any on my 109.



I'd sure like that!:thumb-up:

Some of these same shocks have other, strapless, applications. Why are they subject to damage-by-top-out when mounted on a series LR but no worries (straps) when mounted on most any other car?

Maybe it's not for us to wonder why... it's just an "English Thing"?

Kind regards, Josh

[TeriAnn]

TeriAnn,

No question that the parabolics flex more and allow more axle movement.
The statement I questioned was about having to SHORTEN the straps to prevent over extending the STOCK shocks.
Huh?

I didn't recommend shortening axle straps. I don't think I ever recommended that to anyone. I DID mention that axle straps are normally not used with parabolic springs because they interfere with the spring's downward articulation.

I have never seen a factory statement as to why LR uses rear check straps but I have a guess. Rear springs are longer than the fronts & the shocks are longer allowing for increased axle travel. Land Rover also uses a prop shaft slip joint that is short. They use the shortest slip joint in the class of slip joints they use (certain type of slip joint that is available in different lengths).

I suspect the primary use of the straps is to keep the slip joint from hitting its stop and over time causing the rear prop shaft to separate. Just a guess. Of course it could be to keep from damaging the upper shock limit and the mounts over time. or all the above. Parabolic spring manufacturers usually recommend a shock with a longer extended limit.

Check straps are frequently added to rock buggys to limit rear axle drop. Usually its a single strap at the pumpkin part of the axle so the ends stay free to articulate.

[greenmeanie]

Huh?

I didn't recommend shortening axle straps. I don't think I ever recommended that to anyone. I DID mention that axle straps are normally not used with parabolic springs because they interfere with the spring's downward articulation.


TeriAnn,
I think it was me who originally suggested shortening the straps. In hind site I would just leave them the OEM length with the OEM shocks. I’m sorry for my error and any confusion it generates.

Rm does recommend the use of straps with their springs. From their web site FAQ:
“Q. Do I need check straps on my rear axle?
A. Yes. Check straps are important with parabolic springs because the springs are more supple than conventional springs and there is a danger of damaging the shock absorbers by extending them too far. For this reason we always supply you with the correct check straps when you buy shock absorbers from us.”

Steve,
There is a lot more to the lower shock pin mounting than spring pack height. These springs are called parabolics because of their curvatures which is very different from the eleptical shape of the conventional springs. It is this, along with the taper leaves that give them their properties. As such, the only real way of determining the eye to eye length is to measure them on the truck.

Finally to make TedW feel better about his set up, again from the RM FAQ:
“Q. Can I use my old shock absorbers with your Parabolic springs?
A. Yes if they are in good condition. It pays to replace the rubber shock bushings and we have a kit for that purpose. Using your old shock absorbers will restrict the downward movement of the axles and for off road use using our EXPLORER PRO COMP or OLD MAN EMU shocks will give better axle articulation as they have a longer stroke.”

I hope this clears some stuff up.

Cheers
Gregor

[yorker]

Rm does recommend the use of straps with their springs. From their web site FAQ:
“Q. Do I need check straps on my rear axle?
A. Yes. Check straps are important with parabolic springs because the springs are more supple than conventional springs and there is a danger of damaging the shock absorbers by extending them too far. For this reason we always supply you with the correct check straps when you buy shock absorbers from us.”



that is odd- they make no mention of using check straps on the parabolics they made for Toyota FJ-40s...:confused:

[2rovers]

I am finding this thread very interesting as I am in the process of think about papabolics for my 88. What I am trying to decide is, I run with the soft top for part of the year and with the hard top for part of the year. So do I go with 2 or 3 leves on the rear?
I do some off road, but nothing really serious. We do take trips with it loaded up pretty good, with both hard top and soft top.
Any Thoughts?

[daveb]

3. No question. get shocks recommended by the spring manufacturer and some good tires


I am finding this thread very interesting as I am in the process of think about papabolics for my 88. What I am trying to decide is, I run with the soft top for part of the year and with the hard top for part of the year. So do I go with 2 or 3 leves on the rear?
I do some off road, but nothing really serious. We do take trips with it loaded up pretty good, with both hard top and soft top.
Any Thoughts?

[daveb]

Rocky MTn makes springs for fj40s???


that is odd- they make no mention of using check straps on the parabolics they made for Toyota FJ-40s...:confused:

[Alaska Mike]

Shock mounting and shock length is different on an FJ, making it less of an issue.

[TeriAnn]

I am finding this thread very interesting as I am in the process of think about parabolics for my 88. What I am trying to decide is, I run with the soft top for part of the year and with the hard top for part of the year. So do I go with 2 or 3 leaves on the rear?
I do some off road, but nothing really serious. We do take trips with it loaded up pretty good, with both hard top and soft top.
Any Thoughts?
I'm not an expert on parabolics but I suspect 3 leaf rear would be a good choice. You might be over sprung going topless unloaded, but you don't want to be under sprung with hard top and loaded and driving off road. Its hard to limp home with a rear main spring broke. "OK everyone sit on the front left wing and front bumper then hold on tight!"

If you have a favorite brand and want to help out an American retailer:

Woodhead brand springs (India) = Rovers North
British Steel brand springs (UK) = Maybe Atlantic British - ask first
Rocky Mountain brand springs (Canada) = British Pacific
Hytsee brand springs (Spain?) company name used to be T.I. Console = Great Basin Rovers

[chester rides again]

I just ordered my RM springs today, with OME shocks. Dana was great in answering my questions on the phone. They had a Christmas special and he threw in the straps for free!

My wife wasn't impressed that I ordered springs right before Christmas, but it's going to give me a good project over the Holidays.

[friar mike]

Josh

All my old Volvo 122s had check straps. They are there simply to prevent the car from damage cause by the axle dropping lower than the design tolerance. Driveshafts can bend or seperate, springs fall out, brake lines tear, and shocks bottom out. It is just one method for doing this.

I can't imagine needing to make them shorter on a LR.

FWIW I haven't ever had any on my 109.
My 109 has them. thay were broken and when raised on my hoist the driveline hit the cross member without them. I work on old english cars and most of them have them and when hard cornering it limits body roll in the rear it old school now we use sway bars in the rear. ( hard cornering just dosn't seem to be a problem on my 109 ):eek:

[yorker]

Rocky MTn makes springs for fj40s???

Yes and no. It kind of depends on RM's mood. Once in a while he'll put a set up on ebay, my brother got a set that way.

Ray Wood claims there is no market for them in the TLC community, yet the TLC crowd seem to trip over one another to get the TI Console ones when they were available?

[rosims]

Yes but parabolics work by flexing more and easier than stock springs allowing them to better smooth out bumps. You are not supposed to use limit straps with parabolics because they inhibit part of the normal parabolic spring movement. Also LRs tend to sit a little higher when on parabolics.

Shocks are supposed to be matched to the spring rate. The goal is to allow the spring to move and dampon spring rebounds so you don't end up with the body bouncing up and down on the springs. Stock shocks are designed to properly dampen stock spring movement and will not work properly with parabolics. Always check with the spring manufacturer to get their shock recommendations.

Ideally when the vehicle is at rest the shock should be mid way through its travel. BUT Series shock mounts are mounted closely together and a shock can easily reach its limit with parabolics and even with new stock springs. LR fixed this problem in 1983 by moving the shock mounts farther apart so longer shocks can be used. What people usually do with parabolics is mount a longer travel shock that allows increased lower articulation at the cost of upper articulation. Some folks cheat and fabricate new shock mounts that are farther apart than stock.

This has answered my questions. I should have searched. I figured this has come up before. Thanks

[JDLalama]

Ideally when the vehicle is at rest the shock should be mid way through its travel. BUT Series shock mounts are mounted closely together and a shock can easily reach its limit with parabolics and even with new stock springs. LR fixed this problem in 1983 by moving the shock mounts farther apart so longer shocks can be used. What people usually do with parabolics is mount a longer travel shock that allows increased lower articulation at the cost of upper articulation. Some folks cheat and fabricate new shock mounts that are farther apart than stock.

So, does this mean if you by a remanufactured frame for a Series III, 88 inch the mounts will be in the 1983 position since production ran until possibly the end of 1984 when they were replaced by the Ninety?