Thread: Leaf spring question

There is one major reason TO fit travel restricting check straps and that becomes fairly obvious if you follow the force generated by the initial impact all the way through its short journey, and think through what happens when one wheel is lifted off the ground, and often, violently.
Let us follow the force exerted through the axle, then the spring to the damper.......and then where? When the damper reaches its limit, all this force is still transmitted further on through the measly little mounting that holds the damper to the chassis, and then finally to the thin metal that makes up a Land Rover chassis rail itself. End of journey.
In earlier vehicles this fitting was mounted by a single bolt that protruded through the chassis rail. This is the piece (chassis rail) that ends up wearing all the force whether your new fangled shockies have internal travel stops fitted or not, and in some severe cases and over time, this component will fail and tear. Is this a part that you want to damage?
Travel check straps are a relatively cheap consumable that have been put in place to protect much more expensive parts such as, the damper itself, the brake line system, the prop shaft universals and sliding splines, the integrity of the single point mounting system of the damper itself and finally and most importantly, the skeleton of the vehicle itself. This is done quite simply by spreading the shock over a wider section and therefore minimising the shock in any one part of the frame. The strap itself, because of its make-up, offers a certain degree of elasticity that further absorbs/dampens shock.
I can not see one reason at all that would make it beneficial to remove this vital protection item, to apparently gain a couple of cms of wheel travel, something that can usually be ably compensated by a bit of applied driving technique.
Regards
Glen

All good reasons to fit check straps. But I concur with isuzutoo-eh that it would be to protect the brake lines primarily. That hadn't occurred to me.
I disagree that a quality shock will fail because of repeated full extension because the inherent damping when extending will control the rate at which the shock extends. Compared to the forces the shock and suspension under goes under heavy/full compression, full extension is small beer.
For cheap shocks I'd always use a check strap as they are generally cheap for good reason, but with a quality shock I'd be happy to take the risk for that extra 10mm. Each to their own.
Under no circumstances would I be happy to run without bumpstops.

Originally Posted by JDNSW

As far as i know they are to protect the shock absorbers. Many people have run without them without problems, but they are probably only needed in extreme conditions - heavy load, well lubricated springs, very rough conditions and shocks overheated and not damping properly so that they reach the end of their movement with the axle/chassis distance still rapidly increasing.

They fill the same role as the bump stops, but in the opposite direction. Properly installed, they should limit articulation no more than the shock absorbers themselves do.

John

Check straps can stretch much more than a fully extended shock absorber, so they would need to be shorter, thereby increasing effective spring rates and/or limiting travel.

I would suggest that myself and others in the LROCB who do (or did) fairly serious offroading in series landies with no check straps would have found the need for them if there was any.

For the last ~17 years (and longer for some other LROCB members), I have regularly been doing things like:

Heavily loaded (1.1T of Jarrah)


Long distances (Brisbane-Perth) with heavy loads in hot weather and soft well lubricated springs, including plenty of offroading.


Plenty of serious offroading that flexed the springs to the limit:



All with (very) soft springs, no check straps, and either OEM military or OME shocks - which were often past their best!


In all that time, I have only broken one FRONT shock (which were never fitted with check straps) and no rear shocks.

We are all forgetting that coil-sprung landies use the shocks to limit travel from the factory, yet don't need check straps.

All the arguments on here are idle speculation with no basis in reality. the check straps were an idea dreamt up by over cautious engineers in the late 40's and based on 1940's metalurgy/shock absorber strength.

Originally Posted by zulu Delta 534

There is one major reason TO fit travel restricting check straps and that becomes fairly obvious if you follow the force generated by the initial impact all the way through its short journey, and think through what happens when one wheel is lifted off the ground, and often, violently.
Let us follow the force exerted through the axle, then the spring to the damper.......and then where? When the damper reaches its limit, all this force is still transmitted further on through the measly little mounting that holds the damper to the chassis, and then finally to the thin metal that makes up a Land Rover chassis rail itself. End of journey.
In earlier vehicles this fitting was mounted by a single bolt that protruded through the chassis rail. This is the piece (chassis rail) that ends up wearing all the force whether your new fangled shockies have internal travel stops fitted or not, and in some severe cases and over time, this component will fail and tear. Is this a part that you want to damage?
Travel check straps are a relatively cheap consumable that have been put in place to protect much more expensive parts such as, the damper itself, the brake line system, the prop shaft universals and sliding splines, the integrity of the single point mounting system of the damper itself and finally and most importantly, the skeleton of the vehicle itself. This is done quite simply by spreading the shock over a wider section and therefore minimising the shock in any one part of the frame. The strap itself, because of its make-up, offers a certain degree of elasticity that further absorbs/dampens shock.
I can not see one reason at all that would make it beneficial to remove this vital protection item, to apparently gain a couple of cms of wheel travel, something that can usually be ably compensated by a bit of applied driving technique.
Regards
Glen

Nice theories Glan but no basis in fact. Those that remove check straps are not breaking rear shocks, just like coilers don't go around breaking shocks.

The one time I broke a shock (FRONT). I managed to do another 2 days offroading then drive ~300 km home with no problems. On a series landie you could remove all 4 shocks and drive around without any problems, as even soft springs like mine provide sufficient damping and resistance to over-extension.

With leaf springs you need all the advantages you can get offroad. Btw - your assumption that those removing check straps are lacking driving technique are wrong. People like JasonK from LROCB is one of the most skilled drivers I have ever had the pleasure of offroading with, and has been doing difficult offroading in his ex-mil IIA for >30 years with soft springs and no check straps. He has already found the limits, and those with check straps would not be able to come close. He frequently out-drove locked series with check straps still fitted...

edit: Btw - here is Jason's IIA. (No check straps since the '80s!)

Originally Posted by Warb

...

I just don't see a reason not to fit them!

Conversely, the only reason I can see why you would bother to fit them is:
(a) You have a show vehicle which you want to be original
(b) you never leave the tarmac (even then you can save yourself some money by not fitting them).

For anyone who does any serious offroading, they are a significant disadvantage. As above, I know half a dozen series owners who collectively have >100 years experience driving series landies without check straps fitted. None have ever broken rear shocks.

As above, the imaginary purpose to save brake hoses if a shock snaps is just that! (I run standard length (military) hoses all round).

Originally Posted by Ozdunc

I disagree that a quality shock will fail because of repeated full extension because the inherent damping when extending will control the rate at which the shock extends. Compared to the forces the shock and suspension under goes under heavy/full compression, full extension is small beer.

When a sudden load or unload is applied to the axle, in basic terms oil is forced through valves in a piston. The forces involved, and the reaction of the valves (rate of fluid movment etc.) have been carefully calculated by the designer of the system. The reactions are not always linear, a sudden load may allow fluid to move more quickly than a slow push. Equally the resistance to upward movement is less than the resistance to downward movement, so the force of the "bump" is absorbed by suspension movement in a controlled but gentle way, and the car is not then propelled skyward by the spring returning to it's rest position.

None of the above, however, predicts what happens in a shock absorber when it hits full extension. If the shock has been designed to provide the end point to travel, then the mechanism to achieve that will have been built in. Such is the case in coil sprung vehicles, where (as was pointed out by Zulu Delta) the mounting points are also designed to handle those stresses. In the LR Series, none of that is true of the original design.

This does not, of course, mean that the shock will fail, nor that the chassis will fail. But it means that removing the check straps is moving outside the original design criteria and intention of the system. Most systems have sufficient over-engineering that small changes are easily absorbed, but that's a leap of faith unless the calculations are done.

It may be interesting to consider that car manufacturers are notoriously penny-pinching, and very keen to save money where possible. Yet as far as I know in 30 odd years of production they never saw fit to save the cost of the check straps and associated bracketry. It may be that they were originally specified by 1940's engineers, as isuzurover says, but the engineers through to the 80's (?) didn't see fit to change them despite falling profits and all the other problems that the company underwent!

I admit I'm new to Series Land Rovers, but my experience of every other car and bike is that it is always possible to improve the performance, but without careful consideration and often extensive secondary modifications, such improvements almost always come at the expense of reliability or longevity. It's rare for car companies to spend money or limit performance for no reason. But then again, we are talking about LR here, so who knows?

Hey Isuzurover,

Do you know what sort of open/closed lengths your non-standard shocks are? Have you got extended mounts for them?

Sam

Originally Posted by series3

Hey Isuzurover,

Do you know what sort of open/closed lengths your non-standard shocks are? Have you got extended mounts for them?

Sam

Hi Sam,

Mine is a mil chassis so has 1.5" spring hanger and bump shackle extensions, so abut a 0.75" lift over standard. The Mil shocks are slightly longer to account for this - so ~0.75-1" longer, extended and closed lengths.

On the front all I have done is:
Fit softer springs (similar to 88" petrol springs).
Have the OEM shocks rebuilt by WW shocks.
Remove the bump stop spacers (the shocks are just short enough to get full bump stop compression).

Rear:
Softer springs (similar to 109" station wagon springs).
For a long time I ran (reconditioned) OEM monroe military shocks. However I eventually swapped to 110/RRC rear shocks, which are about 2" longer than standard. I still have the military bump stop spacer in the rear so the shocks aren't too long in compressed length.

Note I have not modified shock mounts or spring mounts at all (F or R).

Originally Posted by isuzurover

Nice theories Glan but no basis in fact. Those that remove check straps are not breaking rear shocks, just like coilers don't go around breaking shocks.

Fair call I guess. It appears that over a couple of years I have obviously wasted a fair bit of time and effort re-welding cracked chassis rails and broken shock absorber mounts for no apparent reason.
Regards
Glen

Originally Posted by zulu Delta 534

Fair call I guess. It appears that over a couple of years I have obviously wasted a fair bit of time and effort re-welding cracked chassis rails and broken shock absorber mounts for no apparent reason.
Regards
Glen

Any pics???

I have never seen a broken shock mount on a series. Seized shocks? Rusty mounts?

Cracked chassis rails are likely due to rust or springs that are too stiff. Military 109" springs are ridiculously stiff.

The bottom line is that an ex-mil 109" with OE springs is incapable of fully extending (or even fully compressing) the suspension under design loads. A SIII 109" for example is fitted with 480 lb/in rear springs, so 960 lb for every inch of spring compression, and almost that (plus shoch damping) for extension. Even if you fully compressed the springs and launched the car off a cliff you won't get full shock extension. I have tried (OK, not using a cliff).

Any cracking of chassis rails you have observed would be due to overly stiff springs - and maybe even as a result of having check straps fitted???