Caster Angle
One of the things on my list to do while I have the body off is to correct the caster angle which has been changed by the 2" lift the vehicle has had.
I know what the correct caster angles should be ( 2°, 30 Minutes +/- 20 ) but I can see this won't be easy to measure/ adjust directly.
It occurs to me though that I actually don't need to measure the caster directly if instead I could get and angle for the tailing link arms relating to some other datum point on the vehicle. The question is where? (see attachments).
One problem with this approach is that obviously the vehicle the measurements have been taken from must be original spec and not tired i.e. suspension must be at correct height), otherwise I will end up with incorrect caster the other way!
I know that MB do have some special lower brackets available as special option, but can't find anything about them in the EPC. Obviously they not neccessarily be right, but might be a starting point for modification rather than having to fab them directly.
Any other thoughts?
Hello fcp,
As per my understanding, you can measure the Steering geometry on all aspects of it, but can not make adjustments on KPI angle, Castor angle and Chamber angle.
As long as you do not interfere with coil heights, the steering geometry will not be affected, largely. Any alteration to height done to the body, that is chassis or rolling stock upwards and there is no adverse affects to front and rear weights, this should not affect steering geometry.
The measurements of castor angle can be done by measuring the height in between the centre of the chassis arch, front and rear, to the centre line of the suspension bolt directly beneath that, arch. These figures are then compared with a pre-printed chart called the 'nomogram'.
If you give those measurments in millimeters, I can then tell you what the castors angle should be.
Regards,
I think I've seen castor correction bushes somewhere, definitely for LR, but I'm sure they're available for the G as well.
http://www.pointedthree.com/disc/forums/forumdisplay.php?f=57 forum has photos of someone building and fitting their own drop mounts for the link arms. Copied from a military MB with a lift. Think there are even drawings. Search fails for me though...
Also on there folk have used offset bushes.. either turned down ones from Aussie (Landcruiser?) or some made them using 2 pack polyurethane to (Bill Moss?). Go details if you dig.
To return castor to OEM .. first find out how much the distance has grown from stock at the axle; compare to stock or from Rakesh's data of chasiss/bolt dimension. Then measure stock distance from chassis rails at link mount.. now move the mount downwards so it is = "stock mount distance from chassis" + "extra distance at axle". That keeps it all parallel i.e. in the same place as standard.
I see L/R folk using fabricated but bent link arms to do the same thing..
Hope you have some decent diameter tyres and regeared gearbox/diff.. as that is the first place to go before lifting bodies/suspension.. again.. go look up Loki's comments on that forum ;)
Is there no way of getting the G on a geometry machine, you could slacken the arms off, push the full front supension forward and measure how much further forward the mounting point should be in comparision to where they are just now then reweld the bracket on at that point!
Sorry that is assuming you want to cut the bracket off the chassis! how far away do you think it is now?
If its not far is there enough length in the bolt on the end of arm 10 in the picture to maybe pack out the front side of the bracket
They are www.stockundstein.com/rubriken-a-z/fahrwerk-teile-diverse/mercedes9/g-modell7/caster-kit-fuer-mercedes-g-460461463 but I understand that the are not a prefered solution (and are obviously limited in their ability to accomodate bigger lifts
Thanks.. I have been reading some of the posts and as you say some people have fabricated their own (which I might end up doing as well). Whe you say 'parallel' though - rear is, but I don't think fronts are (at leaast not looking at Mercedes diagrams), if they are then that would make life easier.
Vehicle is already lifted and on 33x15s.... Gearbox and engine to be changed for a tuned OM606 that is sitting on my bench
Yes, brackets are going to come off.. My estimate is that they will need to drop down 50mm below the chassis from where they are now.
Sorry, when I said parrallel .. I meant at the same angle as they are on a stock vehicle. Hard now you have a non stock vehicle. Couple of ways of estimating it;
1. Distance measure off a standard vehicle. Preferrable to a good data i.e. measure in mm from ground or chassis to the pivot points of the links... then repeat making allowance for the lift.. i.e. if the front is 25mm high on yours then the back needs to be 25mm higher.
2. Measuring actual angle is not a great idea as you cannot get better than 1-2 degrees accuracy normally.. but you could do it with spirit level difference over 900mm level i.e. get it level at a know point on a stock vehicle and measure mm at end that is not touching arm. Issues is that need to compensate for ground not being level and need to be careful which points are used.. oh plus most spirit levels are not even consistent (i.e. if you turn them 180 degrees then you get a "different" level)
3. Use Rakesh's data to find out what it should be between chassis and front pivot, compare to yours and hence come up with a difference.. the back/chassis mount needs to drop that same amount.
4. measure caster itself by determine the distance from a vertical level of the top and bottom swivel centres; difference is one side of triangle, then measure distance between points= vertical side of triangle .. get the calculator out and look up Trig (i.e. cos/sin/tan). It is a bit messed up as you need a level ground/car and that camber will make a small error too.. If you had fancy angle measuring you could clamp onto bearing caps and measure parralel to line front/back of car but again do not trust this.
I have done DIY tracking/camber/caster angle setup before but caster is a hard one normally to measure.
hi fcp,
for what it is worth, my g has the 2" bodylift and 2" springs. I have not had a castor kit fitted. Try it first to see if you think it is different. We load our G up quite a bit (so we probably lose a good 1" of the springs) and it doesn't feel adverse or tricky to handle......we run on 32.8" tyres too.
Some history here: I used to own a 110, which I also lifted and fitted with the castor kit. Then I bought another 110, did the same lift, but without the castor kit. Honestly: I couldn't tell the difference........I feel it could all be a bit of a con by the after-parts manufacturers.
In terms of the handling, the car will obviously lean more in corners due to the higher centre of gravity. With regard to the castor angle, it will be altered and it will make the steering more responsive. You just have to drive accordingly.
What you will find with the lift of the kit and springs is that your ball-joints and suspension bushes will wear quicker. I have just replaced the balls joints and had new new poly-bushes fitted.....what an amazing difference!
Before cutting up your chassis, I'd try driving it first. I'm sure you'll find its OK as it is. Just check your ball joints are OK and, if needed, change the bushes to something a little firmer than the standard rubber.
Good luck,
Phileas
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HI Rakesh,
I'm on higher ORC springs (in addition to body) which is why the caster is wrong
The measurement I can do, but I'm just wonder then how to measure the caster as I weld back on the new brackets.