Shock absorber question

[Olazz]

I have searched and googled for ages but cannot find an answer that makes any sense.
Assuming one has made the necessary adjustments to mounts etc, why can one not have the same shock on the front and the rear.
If one has model X on front can one also have model X on the rear? .....and if not why not?

What is the point of lifting a truck, installing longer shocks, then adding limit straps surely that defeats the whole object no

In addition, If one has 10" of travel on a shock, say 24' extended, 14" compressed, should the shock have 50/50 travel on compression and rebound, or would this not work and there should be some other proportion?

Finally, does the length of spring actually matter? on a 6" lift you can install an 8"- 14" travel shock, so what has spring length got to do with the whole issue?

HELP!!!!

 

[Jon Wildsmith]

Usually the rear needs a much longer shock than the front and the front needs a much smaller compressed length so the only way to have matching shocks would be if you limited the rear to using a front shock.

It may be that the shock that best fits the travel you need is a bit longer than your setup can handle so you use a limit strap to stop your 14" shock at 13" but still have 1" more than a 12" shock Also, not all shocks can cope with being the travel end stop annd need something else to stop travel.

Spring length matters for keeping it captive with long shocks unless you have some sort of dislocation kit as is popular on LR's.

Can't help you with the best valving balance.

 

[Dave Docwra]

There will be a limit on the prop shaft, the slider will allow the two sections to disengage or weaken by using an unacceptable length of spline..

 

[Dave Burgess]

I have searched and googled for ages but cannot find an answer that makes any sense.
Assuming one has made the necessary adjustments to mounts etc, why can one not have the same shock on the front and the rear. Often they require different rates due to loading and spring strength, though it becomes less of a problem the further you go up the weight scale
If one has model X on front can one also have model X on the rear? .....and if not why not? May not fit physically, may be different rates, may be different lengths, may be different strokes.... the list is endless and vehicle specific

What is the point of lifting a truck, installing longer shocks, then adding limit straps surely that defeats the whole object no It may appear to limit the droop, but it will depend on the design of damper and where the bump stops are located, what the damper ratings are, what the droop and compression measurement are, reliability, (as Jon says) spring location, (as Dave says) other design limitations outside the spring/damper set up

In addition, If one has 10" of travel on a shock, say 24' extended, 14" compressed, should the shock have 50/50 travel on compression and rebound, or would this not work and there should be some other proportion? Not necessarily, the rest point of the damper may not (probably not) be in the centre of the stroke. The bounce will not be damped at the same rate as the rebound and the spring invariably works (in our applications) in compression, so there is more droop available in the travel. Expensive set-up will be user adjustable in each plain.

Finally, does the length of spring actually matter? on a 6" lift you can install an 8"- 14" travel shock, so what has spring length got to do with the whole issue? This is all about location, free length, spring rate, linear or progressive, loadings, bushing and component freedoms, pre-loads, sag, intended use, and taste.

HELP!!!!

As a basic rule, look at your use and load and level of comfort. Get a set of springs rated to carry your greatest load (which provide enough comfort empty - progressive rates), with a free length and installed length that suit your needs, terrain and use. The dampers should then be chosen at a rate that controls these springs effectively (and comfortably), with a length and idle point that allow the compression stroke to the bump stops, and a rebound stroke to the droop limit (or inner bump stop in the damper).

This may beyond one's capability or wallet depending on one's situation, but most available set-ups have been trialled by someone who has written about it somewhere.

New springs and dampers will always feel better than the OE after the average mileage of our trucks. My Iron man B Type +50mm suit my needs well, but the Pro Comp/Dobinsons springs I had before were a lovely ride but woeful with a load on.

Hope this helps rather than confuses further

 

[Olazz]

Thanks for all of the helpful responses.

I am looking to totally revamp my suspension and am learning the rudiments of suspensions PDQ.
Trying to find useful information is pretty hard, and especially for an 80 series truck. Its exacerbated by the fact that I have a 6" lift that seems to have been cobbled together, albeit professionally done.

So far I have managed find out that there are a number of 6" lift suspension kits. Almost every one supplies/recommends a different shock length.
Some even recommend the same length front and rear (hence my questions)

What is interesting though, is that for a 6" lift shock length recommendations vary from 620mm extended to 708mm extended, all with varying degrees of compression and shock travel.

A veritable minefield.

I hope to post my project, findings and final solution on here for anyone who is interested.

 

[pugwash]

the general way to choose shocks and springs is to calculate the "normal" weight of your truck, work out the height you would like, and then calculate the spring length and compression ratio based on that weight.

You then match your dampers to your choice of springs. For example a stronger spring needs a sgnificantly stronger damper.

As you ave found getting exact specs can be hard, but you may like to consider getting some springs custom made- they aren't that expensive and there are at least 2 companies in the UK that specialise in making automotive, short run, springs.