| Author | Message | ||
     Mark (Roverwrecks) New Member Username: Roverwrecks Post Number: 19 Registered: 10-2003 |
I've read a few threads about a shimmy after installig these. I have an XD that I am going to Run with HD OldMan EMU springs, most like a RoverTim Front bumper with a Husky 10K winch, oh yeah some sort of moderately aggressive all terrain tyres a little over stock in size. In thinking and the engineering, I don't see why a shimmy would occur. | ||
| Perry Ray Miller (Discojunky) Member Username: Discojunky Post Number: 41 Registered: 03-2003 |
After installing a 3" lift on my Disco I tried to save money and leave off the radius corrections arms and trust me it was REAL steering sensitive. I had stock tires and no equipment and again I could not live with the handling. I put on 33" tires and that helped. I also put a front bumper and 1200lbs winch and this to helped. Sliders helped etc... The more wieght you get up front and the bigger the tires are the more it will cover up the steering sensitvity but to get it even close to stock you will need the radius arms. I know this because I went thru it but maybe someone else can explain the physics. From my understanding it reduces the angle of the 3rd member (caused by the lift) back to stock. But once you add the correction radius arms and correct that angle you will almost certainly need a double yoke front drive shaft because now the angle at the drive shaft is much more severe. I hope that helps but if nothing else maybe it will gererate some some responses. | ||
| Peter Matusov (Pmatusov) Senior Member Username: Pmatusov Post Number: 1199 Registered: 09-2002 |
Perry, in the stock setup, the kingpin axis is tilted slightly back (by castor angle), so when you turn the steering wheel, you actually lift the front of the vehicle. The weight of the vehicle will push it down, forcing the wheels to return back to the stable location, just like a pendulum. When you lift the front end, you cause the radius arms to make a larger angle with the ground, and kingpin angle will make less and less angle with the vertical. At some point, you will lose the self-centering feature of the front suspension, and the vehicle will wander all over the place. I don't remember off the top of my head - what is the stock value of the Disco's castor angle - but, given ~40/60 weight distribution and short wheelbase of a Disco, even minor lift will make the truck squirrelly. Adding the weight to the front helps in more than one way - you change the front/rear weight distribution, and also load the front more so to increase the "returning force." The probability of shimmy to occur also increases with decreased castor angle - rather, the frequency of shimmy will become lower, and stock steering damper would not be able to suppress it. A stiffer damper helps - Bilstein or OME (I have both on different rovers, they both work great). | ||
| Papillon (Papillon) New Member Username: Papillon Post Number: 7 Registered: 12-2003 |
Peter, Great post! Where or how did you get the 40/60 weight distribution figures? Papillon | ||
| marc olivares (Pugs) Senior Member Username: Pugs Post Number: 289 Registered: 12-2002 |
peter, nice explanation stock spec castor is 3 degrees (+/- .5) positive. a 2" lift is usually around 0 degrees castor. a 3" lift is usually around -2 degrees negative castor. double cardon shafts help with vibes if the castor is within 2 degrees of spec. mulitple doubles in my opinion should never be used (way to heavy). and of course there is always an exception to this general guide line. even discos set up with the same springs, corrected radius arms etc... will typically not yield the same results. hope that helps, marc | ||
| Clay W Davis (Cwdavis4) New Member Username: Cwdavis4 Post Number: 33 Registered: 09-2003 |
I am planning on adding a 2" lift to my '03 Disco in the next month or so. Do I need to worry about adding a radius arm offset as well? No major weight additions other than factory brush guard, skid plates, and rock sliders if that makes a difference. Regards... | ||
| Rick Neff (Lostinboston) Senior Member Username: Lostinboston Post Number: 253 Registered: 06-2003 |
RTE has offsets for a D1, not D2, or at least when i called them last. If you want you can send them your radius arms, and they can correct them. Adding a tt up front will fix the highway wander though. I would only fix the castors when i switch to ARB instead or want more room for bigger tires. | ||
| Mark (Roverwrecks) New Member Username: Roverwrecks Post Number: 21 Registered: 10-2003 |
I already have the RTE arms, both front and rear. Once I have the springs I'll give them a try, here is another questions. I bought some southdown equipment a while ago for my defender and when it sold I kept the equipment, looks like can use the rear diff gard, what about the front diff gard, has anyone here used a defender front diff gard on their disco or do I need different mounting brackets? |
