I've been dealing with the lower arms of the IFS falling apart on my Enduro Trailrunner for the past while. They're held together by a metal ball stud and a plastic rod end. The original rod ends held together for almost a year, but then they started going. I got a pack of replacement rod ends, but they weren't holding together so great. Either the pack of rod ends was no good or the metal ball studs wore down. However it actually went, I was having problems, and it was ruining my RC outings. I got some hardware from the hardware store to try some things. It turns out the simplest thing I tried first appeared to work the best. You can use a 4mm nut and bolt. The length of the nut isn't so important as long as it's not too short. You're going to want to have a little bit coming down in the end after you cut off the excess. Disassemble the suspension and remove the CV axle. Remove the ball stud and put the bolt downwards into the hole of the steering knuckle. Reinsert the CV axle and get it into assembled position. Then put the bolt into the rod end of the lower arm. Use a bit of thread lock on the bolt where the nut's going to rest, and put the nut on. Putting the nut on requires finesse. You don't want it too tight or too loose. Try a few positions before you leave the thing alone to let the thread lock set. After the thread lock sets, take a dremel and cut off the excess part of the bolt hanging down below the nut. This will keep your tire from rubbing on it while it's squished. Then do this all over again on the other side.
I went to NJ Devils Way this morning to test it out, and it went very well. I had nothing to worry about. It stayed together like it was new. the nut and bit of bolt does hang lower than the original ball stud/rod end combination, but it's a small price to pay for much better durability. And it's so far over to the side that the tires are going to be negating the extra bit of stuff hanging lower anyway.
Potential drawbacks to this include the following: The ball stud and rod end on the upper arm may be more prone to being popped apart now. Sometimes you get a branch between the arms and the CV axle, and the bottom would always torque itself apart. It was always the bottom that torqued apart. Performing the same modification on the upper rod end may be appropriate to mitigate potential future separation. There's a similar setup for the steering linkage near the upper arm, but that's probably at far less risk for popping apart than the upper arm. The rod ends themselves may also break apart under the extra stress. Replacing the rod ends with something sturdier like metal rod ends may be an appropriate fix. Other plastic parts further down the line may be increasingly affected by modifications, so that's a concern. Also, once the nut and bolt modification gets performed, the most practical way to access the CV axle becomes removing the skid plate and the pins that hold in the lower arms. The pins will have to be removed while letting the lower arms swing out to allow for further accessibility. However, the area of the CV axle only becomes a point of concern when major failure occurs like bearing failure or front differential failure. Should the CV axle itself fail, it will potentially snap in such a way that three or even two wheel drive in the rear will still be possible. All in all, I believe the simple nut and bolt modification will prove to be a benefit to the durability of the Enduro IFS system. I will be continuing to put this modification to the test when taking my Trailrunner out.
