Thread: Dislocate or Retain?

Originally Posted by lambrover

I didn't know you had that set up. I think we need to take some measurments and compare notes. What limits our down travel spring or shock

I have:

210lb fronts
80series + 2inch konis
haultech slotted bushes

250lb rears
12inch travel merc truck(fronts) konis

due to many reasosn i have still not modded the rear upper shock mount which really needs to be done.

Serg

Been some interesting reading here.

I have a question on geometry now after reading one or two of the replies.

If the trailing arms are lengthened, should the A-Frame then also be lengthened? If so would the best way to go about it be to work out the percentage the Trailing Arms were lengthened and then lengthen the A-Frame but the same percentage?

Hope that is understandable

Originally Posted by Siska

Been some interesting reading here.

I have a question on geometry now after reading one or two of the replies.

If the trailing arms are lengthened, should the A-Frame then also be lengthened? If so would the best way to go about it be to work out the percentage the Trailing Arms were lengthened and then lengthen the A-Frame but the same percentage?

Hope that is understandable

from what i have read, so take it with a grain of salt or 7......

you dont want you A frame lenght shorter than 70% of the TA's but being this lenght helps not increase AS as much during droop....any shorter and youll get funky pinion angle changes during travel

remember that the A frame is locating the axle lateraly, so the angle of A frame (when viewd from above) doesnt want to be less than 40 degrees

its also not just a matter of lengthening but changing the angles (when viewd from the side) to change AS and axle roll axis

I'm not sure what level your understanding is at Siska, but this is a benchmark thread for the basics of suspension geometry with regards to AS etc

[ame=http://www.pirate4x4.com/forum/showthread.php't=168577]Link suspensions for dummies? - Pirate4x4.Com Bulletin Board[/ame]

Originally Posted by uninformed

[snip]

its also not just a matter of lengthening but changing the angles (when viewd from the side) to change AS and axle roll axis

Lengthening arms, whether a solid axle four link or wishbones reduces the rate at which things change from static ride height but doesn't change the static geometry if using stock angles.
As Serg said, you have to change the angles to change the static geometry.
If you lengthen the lower arms so they meet the chassis rails at the same height but further forward you will reduce AS as you have reduced the convergence angle, and I remember Sam did this on his builds, but you have to be careful how it compromises other things as Serg said.

Very roughly, the angle of convergence between the upper and lower links when viewed in section/from the side is what determines how much anti-squat you have. (in relation to the CofG)
The sharper they converge, the more AS, if parallel and horizontal, 0% AS.
You still get a degree of AS with arms sloping up from the chassis end and parallel, with AS increasing the more steeply angled they are.

I've never been a fan of AS (and anti-dive) but they can be useful, particularly with very low spring/wheel rates and lots of power.

Basically the more AS you have, the less compliance in the suspension, it works by binding the suspension against itself to resist a force, as one old race engineer wrote once "it's like trying to pick yourself up by your own bootlaces..."
Reduced compliance = reduced traction. ie. the suspension is less able to do it's thing.

As with everything, it's all a compromise and at the end of the day it all comes down to what your priorities are

Antidive and Antisquat are only one part of the system, and yes we have been discussing them here a bit, BUT they certainly arnt the most important, especially when concerning the SAFE design of a system...IMO axle roll axis, roll center height and vehicle roll axis are more important regarding that....get those right first and its quite easy to adjust the AS/AD. In fact alot of guys build in multi mounting points for say the uppers on the rear 4 link so they can change the AS....also remember to low an AS and when you drop the clutch at x rpm to "lawnch" at a climb etc your rig will squat down and not "hook up" the power/traction as well....but to much AS and it will make the axle crawl under the rig and jack it (vehicle) up....