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[Dave69]

When you look on the yank sites, everyone mentions swapping to long arm suspension or making their own. There are alot of excel programs that will calculate the lengths and details to make your own. A few companies will sell you bolt on or weld on conversions for the front end (xj) but is it they way to go forward.

A few of the suppliers claim better road handling as an addition to the articulation. I can see the benefits of converting the rear leaf springs to coils and arms but is there a practical benefit of swapping the front.

JJ is doing an excellant job with his jeep but that is realy overkill for the UK but we know that it will be shipped back to the USA where it they have the terrain to be used properly.

So what are the benefits of doing a conversion in the UK ?

[Bubba]

i dont realy think an xj is that good a platform for extreme supension...................stands back and lights touch paper

[isle of man]

Tough one this......I have have had three Wranglers first a short arm then short arm with lift and flex joints then long arm by Gasser and finally a Clayton long arm I would say it's progress to your next level.

It's a trade off you need to decide.

[Dave69]

your probably right with the xj not being a good base model but it's what i have got at the moment so it's what i have to compare with.

I understand flex is the main point but what are the real benefits for vehicles fitted with them and are they real improvement for a vehicle in the UK.
IOM refers to it being the next level ? please enlighten, what does the next level gain ? I do like the look and the engineering but is it realy neccessary ?





OK this may sound as a stupid thread but i'm trying to get my head around the need for them over std suspension and conventionaly modified suspension.

[isle of man]

Dave - jump, bum, beg, steal or borrow a drive in a long arm and then decide if it's for you.

[JamesH]

It's all about angles, the long arms sit only slight angled down from body to axle at ride height. This means on-road the  that less bumps are 'banged' into the body and offroad, the axle travels up and down 'straighter' (less arc) and also allows more travel.

It's a no-return setup normally so you make yur choice and pay your money and go the route you think suits you best.

[Warthog]

The concept behind a long arm setup is simple. With fairly short control arms from the factory, there is only so much flex available. By simple physics, longer control arms allow for more articulation. A basic illustration is to hold your arm straight out and move your forearm upward using your elbow as the pivot point.

Next, use your shoulder as the pivot point and move your whole arm. Notice how much more range of movement there is and how the angle change of your fist is a lot less. Now imagine an axle attached to the end of your arm and you can visualize the benefits of a long arm system.

[Dave69]

thanks for the reply's done a bit of web browsing and just confirmed what people have said.

this is aimed at the XJ and i was mainly asking for peoples views and experiences from here, so probably answered my own initial question

the std suspension (Short Arms) move in a small arc which is good when sent out from the factory. when lifted the travel downwards gets reduced in proprtion to the amount of lift. If you have 5"s of downward tavel when stock, then you lift the jeep 3"s the amount of downward travel is now reduced to 2"s. This inturn puts more input into the body through the lower control arm rather than being absorbed by the suspension.

the Long Arm conversion moves the pivot point further back along the jeep and giving a larger arc for the suspension to work with. This then allows the suspension to be lifted higher with less effect to the amount of downward travel available. The upward travel of the LA is now limited by the long arm itself comming into contact with the body, so adequate bumpstops need to be sourced. With this the inputs into the jeep are now transfered more through the shocks rather than the lower Control Arms

the general concensus is that SA's are good for 3-4 inch max, higher than that LA's are suggested. Drop brackets can be bought to lower the LCA's to reduce the LCA angle and aid with ride, but these are large bolt on brackets and do look cumbersome.

Short Control Arms's due to the small arc will pull the front wheel back to the wheel arch where as the LA will allow a full drop in the centre of the wheel arch.

short arm on full drop, this is limited by the control arm angle, notice how the wheel arcs to the rear part of the wheel arch


Long Arm of equivalent drop, this is limited by the steering connection


a brief summary


Short arms are acceptable for your suspension needs upto 5"s but at this height the road inputs and bump inputs are or can be more noticable. The downward drop of the suspension is reduced the higher the lift fitted.

The Long arms allow for higher lifts and are not worth fitting below the height of 4"'s. Above this they work well giving a better ride over bumps articulation and downward drop.

major down point of a longarm conversion is that it is a one way route due to body modification.

After reading about this as said by Bubba and IOM it's not lift that's required it's the amount of suspension drop. Short arm's can't provide this so Long arm's are the way to go. The downside with the XJ is the unibody and how thin it is. Bolt on kits are favourable but also there are weld on kits which can raise questions to the quality of the weld and the competance of the person welding into place. The other point is that do you fit full 4 arm link of fit a simple 'Y' arm setup.



ref links

http://www.savagesun4x4.com/enter/viewpoints-technical_discus/long_arm_vs_short_arm_for_t.html
http://www.jeepforum.com/forum/f11/long-arm-suspension-492962/

[Warthog]

Even though you have gained a better suspension geometry. Without lockers, wouldnt you agree that. At a point in the suspension cycle, traction is going to be very minimal? There isnt going to be much force pushing down, only the wieght of the axle and tyre will be available.

The truck will definatly be more stable though.

Why i mention this, is i have a fair amount of flex and do o.k. But a stock truck with lockers generally will get further than me. (Its a Lardy, i know. But the physics is the same)

Wouldnt the money spent on a Long Arm be, best spent on a re-gear and lockers?

Are there many people running long arm, without lockers?

[Bubba]

this is the thing that gets me traction verses flex  flex is not worth shit if you still have no traction where a wheels in the air truck will do very well with full on traction

long arm is deffo better but the traction verses flex isue is very interesting

[Dave69]

i was thinking about that after i posted. with short arms the weight of the vehicle is pushing down to give traction, but with long arms that weight transfer appears to be reduced when the suspension is articulated (reasons for that unknown). One of the other unanswered question.

i guess it might be a case of the relationship between the wheels and the amount of articulation they are seeing. max articulation on one side vs none on the other: max articulation has minimal traction where as the minimal articulation has the assumed full weight of the vehicle and that is where the traction is, possibly with short arms this is not as noticeable

[JamesH]

Get Lockers 

[Warthog]

IMO

I think people can get an Hard-on for Flex, as it looks cool and secondley can achieve good results for traction. However at some point i think the flex for traction option cancels itself out. This is where lockers come in for traction, and all that flex then contributes to the stability of the truck with traction a second attribute.

Am i stating the obivious?

[scrw]

Down side with LA is loss of pitch control of the front, up steep hill can mean more weight shift to the rear

[Warthog]

Down side with LA is loss of pitch control of the front, up steep hill can mean more weight shift to the rear

Anti-Squat characteristic?

[JamesH]

That all depends on what type of long-arm setup you go for - many have a single body link and Y to join the axle in two places (like a radius arm - same as a LR?). Mine has 4 separate arms just like the stock design but longer (4 link). You can also go for a 3 link which gives even more flex (doesn't constrain the twisting of the axle).

The XJ is a funny beast with it's leaf sprung rear and potentially very flexy front. For me it gives a balance of stability and flex - coils on the rear would flex more but it could easily get very tippy. I'd definitely agree that traction aids are important. I'd also add that the benefits of long-arm are expensive to get when compared to other mods.

[Dave69]

with a y link long arm this gives more articulation and flex due to only being connected by two points, but with a four arm set up doesn't that behave in the same manner as std but just with longer arms ? so still keeping the same ride characteristics and possibly anti squat ?

[Warthog]

with a y link long arm this gives more articulation and flex due to only being connected by two points, but with a four arm set up doesn't that behave in the same manner as std but just with longer arms ? so still keeping the same ride characteristics and possibly anti squat ?

Due to the location of the long arms the CG and Effective centre geometry points will change. Which im lead to believe on a long arm will lower the anti squat. Causing wieght transferance to the rear on accleration, for example giving it gas to do an hill climb.

A good read is; Chassis Engineering by Herb Adams

or have a read of http://www.4x4.hr/2007/index.php?option=com_content&task=view&id=69&Itemid=9