OME on Jimny, what's the point?

OT - guess my old leaf sprung Land Rover didn't fair to bad on this

For those who are looking for the OME specifications, you can find both Gen 3 and 4 components in the attached file. Under the specification heading for springs you will find both free height and spring rate and for shocks they list compressed and extended dimensions. I have some outdated information for Trailmaster (Maas Group Gmbh) but they are (at least pre-pandemic) very accommodating and will provide the same information upon request.

In providing this information, I do want to reiterate what I mentioned in my original post. As I mentioned, and as expanded by Roger, the springs and shocks are NOT the limiting factor for articulation on the Jimny. The limiting factor for suspension articulation on the Jimny is radius arm travel. I am not saying that suspension kits like Trailmaster or OME won't provide some benefit but, as Busta mentioned, it will be minimal. The only way around that would be a redesign of the suspension. Personally, while I will continue to test things in an attempt to squeeze a little more suspension travel, I am not unhappy with the Jimny articulation.

A comment was made earlier that by adding a 50mm spacer you would have a 50mm lift and that the brake" lines" - I assume hoses - would not be affected.

Please explain.

Roger

zukebob wrote: For those who are looking for the OME specifications, you can find both Gen 3 and 4 components in the attached file. Under the specification heading for springs you will find both free height and spring rate and for shocks they list compressed and extended dimensions. I have some outdated information for Trailmaster (Maas Group Gmbh) but they are (at least pre-pandemic) very accommodating and will provide the same information upon request.

In providing this information, I do want to reiterate what I mentioned in my original post. As I mentioned, and as expanded by Roger, the springs and shocks are NOT the limiting factor for articulation on the Jimny. The limiting factor for suspension articulation on the Jimny is radius arm travel. I am not saying that suspension kits like Trailmaster or OME won't provide some benefit but, as Busta mentioned, it will be minimal. The only way around that would be a redesign of the suspension. Personally, while I will continue to test things in an attempt to squeeze a little more suspension travel, I am not unhappy with the Jimny articulation.

Thank you for the attached file, most useful.

Re: suspension travel. I agree ultimately it is normally things such as radius arms or the joints that limit travel. However I would challenge that assumption on a stock 4th Gen. Clearly the limiting factor on the stock suspension is the shock expanded length. As longer shocks cause the rear brake line to become an issue, which is the next limiting factor. And on the front the prop will hit the crossmember, which is the next limiting factor there.

Meaning there is definitely more travel to be had on either axle. I would imagine an extra 2" of droop is a fairly significant percentage increase in downwards travel. And should/will make a huge difference off road.

Roger Fairclough wrote: A comment was made earlier that by adding a 50mm spacer you would have a 50mm lift and that the brake" lines" - I assume hoses - would not be affected.

Please explain.

Roger

Assume a 100% standard vehicle, with stand shocks/springs. When sitting on level ground the shock will be partially compressed. Meaning the wheel can move up or down still. I'd guess you'd normally want about equal travel up and down from this standard sitting height.

Imagine if you picked the Jimny up by the roof, so that all the wheels dangled in the air. This would be extending the shocks to their maximum permissible amount, i.e. the maximum amount of suspension droop. With a 100% standard vehicle this droop will not exceed the brake flexi line (hose) length. Nor will it cause the front prop to hit the cross member. The suspension simply does not drop far enough.

So it is entirely possible to fit some spring spacers (sometimes called packers), between the spring and either the upper or lower spring seat.

Spacers can be metal or plastic. And either bolt on to the original spring seat or just sit on the coil. Here is one on a Jeep (the black plastic bit above the spring):
www.rockridge4wd.com/images/M137260740
https://www.rockridge4wd.com/images/M137260740

The spacer will 'lift' the vehicle by the height of the spacer. So a 2" spacer will give you a 2" lift. A longer spring or higher/stiffer spring rate could also achieve the same result.

This will extend the shock by the same amount also, e.g. 2" but with standard length shocks, this lift comes at the cost of reducing your available down travel when sitting level. To put some figures to it.

Assume you have 7" of suspension travel from shock collapsed to fully extended. Collapsed is likely limited/controlled by a bump stop. When 100% standard sitting on level ground. The shock is extended half way. Giving you 3.5" of up travel. And 3.5" of down travel.

With a 2" spacer fitted, the shock will be more extended when sitting level. Giving you only 1.5" down travel in this example. And 5.5" of up travel. The problem here is, you are likely to lift wheels off the ground a lot in cross axle situations. Even though your total travel has remained the same, you will find it harder to use all of the up travel. And the limited available down travel will make it less capable off road.

The plus side is, you will have gain in ride height, so have more clearance under the chassis and may be able to fit bigger tyres for more clearance. Because the shock length has not changed, as full extension of the shocks (picking the vehicle up and dangling the wheels in the air). There will be no risk of exceeding the brake lines or hitting the cross member).

So back to my point being. A lift on its own has no direct bearing on if you need extended brake lines or if the crossmember will be an issue.

In fact, if you where willing to loose all of your down travel, you could probably put a 3-4"+ lift onto a JB74 and still not have issues with the brake lines or crossmember. The vehicle would likely be dreadful, but that would be a different conversation


On the flip side. You could have no lift at all and have suspension that would require longer brake lines as well as needing to lower or notch the front crossmember to prevent the prop hitting it. Either by using longer softer springs or keep the standard springs and have a dislocating setup. Combined with much longer shocks.

It is pointless adding packers if no attempt is made to gain from it. By your own admission, if you go to far, the vehicles ride would be awful. Yes, add your packers but add suitable shocks that will work with them and, if necessary, longer brake hoses. The more packers you put in, the more you restrict suspension movement because you haven't fitted longer shocks and the less articulation you will finish with.

Roger

300bhpton wrote: I just wished they offered essentially the same kit with some longer shocks, extended brake lines and the crossmember dropper brackets. Best of both worlds then. I'm not after more lift, just retain the compression this kit currently offers, but offer more droop. An extra inch travel can make a big difference off road sometimes.

This is pretty much what I've got - the OME shocks with stock springs and Goodridge extended brake lines. Gives more droop without any lift, just with the potential risk of stock springs dislocating at max droop.

Roger Fairclough wrote: It is pointless adding packers if no attempt is made to gain from it. By your own admission, if you go to far, the vehicles ride would be awful. Yes, add your packers but add suitable shocks that will work with them and, if necessary, longer brake hoses. The more packers you put in, the more you restrict suspension movement because you haven't fitted longer shocks and the less articulation you will finish with.

Roger

Packers can be viable on some vehicles for some uses. I was however simply trying to point-out. That it isn't the amount of lift that requires longer brake lines or addressing the crossmember. But it seems to be repeated on here a few times that the OME kit doesn't need these due to only being 40mm lift vs the 50mm lift kits requiring them. When the truth is, it has nothing to do with the lift, but everything to do with the shock lengths.


BTW - I put a "budget boost" lift kit on a Jeep Cherokee years back. Spacers at the front for the coils and longer shackles for the rear. It worked fine as the suspension had plenty of travel in it and the Cherokees rode low from the factory.

Yes there is definitely more travel to be had than the standard springs and shocks allow. However every lift kit I've ever seen comes with stiffer springs than standard. Whilst you gain down travel from the longer springs and shocks, unless you increase the weight of the vehicle significantly you lose at least the same amount of up travel, so the end result is the same amount of articulation or, going by some pictures, even less than standard.
I think a lot of people judge a vehicles articulation simply by looking at the arch gap above the lowest wheel. Whilst a wheel dropping down 2 feet below the arch looks impressive, it's the difference between front and rear that counts, hence my examples with the lines.
I currently have front springs on the rear of my Jimny. They are roughly the same rate as the standard rear springs, but are about 50mm longer overall giving about 20mm of lift. My Jimny would benefit from longer rear shocks to utilise the extra spring length but I haven't got around to working that out yet.

When I fitted a 2" lift, I did fit extended brake lines, only because it seemed a cheap fix and you don't have to worry about whether they'll be stretched. The ones I fitted are bright yellow so that makes the vehicle at least 17.8% better off road!!