Proactive CK Rail Mods

[garserio]

For those of you with the Proactive CK skid, you may have warped and cracked your rails like I did.

This skid is weak everywhere, especially when you start to add more stress to it when shock revalving or other major suspension mods.

I cracked my rails just forward of the rear bump stops and made a failed attempt at welding and strengthening the area. Typically when aluminum cracks it is a sign of bigger problems such as cyclic fatigue failure where the alloy has yielded. Since a set of new rails run almost $400, I still decided to give it a try without success. You can see from my picture that the rail is bent like a banana and even my strengethening bars cracked along the same original crack area. The steel piece in the picture is a straight edge and on both sides of the rear bump stop, there is ~3/8" of deflection! Let me just say that this caused quite the Hyfax wear issue! So I picked up a set of undamaged used rails and came up with a strengthening scheme.

I custom fabricated 3 gussets for each side. The top gusset is a 3/4" thk "U" profile while the bottom gussets are simply 1/4" thk x 0.85" high aluminum strips mounted on both side of the rail. I used 3/4" grip length S/S rivets to sandwich it all together. Welding aluminum can result in residual warpage if not done properly, so I decided to stitch it all together with rivets. The final detail is that I used Apex LTX/Attak rear bump stops which have straight sides to mount over my gussets. Another detail not shown is that many of the rivets for the bottom gussets are mounted through the stock rail slots. In order to ensure proper mounting through these slots, I pressed in an aluminum spacer in each slot. These are 1/2" diameter x 1/4" thk spacers with a 3/16" thru-hole for the rivet.

While I was working on the rail, I also decided to address the inadequate hyfax mounting holes that easily strip out and whose thread breakout of the rail wall thickness. I simply made a custom barrel nut as shown and mounted it into a 1/2" hole that drilled thru the rail web. The picture is self-explanatory.

Finally, I added a Fix Powersports wheel kit to the rear of the rail to help with future hyfax wear. I liked the idea of this kit because it used a cross-shaft which which also stiffen the rails and maintain rail width in this unsupported area. However, as you will see, these poor little wheels had no chance of survival in this harsh area. I only got 100 miles before they self-destructed and that was in favorable clean and loose snow trail conditions. Oh well... At least the cross-shaft will help

FYI and good luck to all...

 

[ReX]

It looks like they should be quite solid.

I don't think welding ever really works with slide rails. It screws up the temper and they end up even more prone to fatigue failures.

Did they bend like that before you welded them? If so, are you bottoming out hard alot?

BTW, you should check out my shock valving 101 post. I'm not sure what Hygear uses for shock valving, but the custom mutli-stage stacks I'm running now work incredibly well.

I also just installed a pair of new rails on my 07 RTX last week. In my case the cracks are appearing right where the optional, inner rear idlers mount (single bolt, cantilevered mount). I'm not seeing any signs of stress at the location yours broke.

I did consider reinforcing them, or not installing the optional idlers, but instead I installed 135mm idlers in the front 4 locations and installed 130mm idlers in the optional inner locations. Hopefully that will reduce the stress enough that my new pair won't crack...

The other thought I has was to get Ulmer Racing to manufacture some extra strong rails for me. They already machine custom rails that are supposed to be stronger than stock and I was thinking of asking them to change their CNC program a little to add a significant amount of thickness and some height.

I also measured the rails a few days ago on an 08 REV-XP MXZ X and found they are quite a bit thicker and taller. The I section is also quite a bit wider than what Yamaha runs. The REV-XP rails seem to be holding up on my buddies sleds so I figured those dimensions would probably make a good starting point (and then thicken then proportionally for the increased weight on the Yamaha - maybe an extra 20%). The REV-XP rails are already something like 30-40% stronger than the RTX rails based on the measurements.

 

[garserio]

I believe that my rails cracked and bent at the same time, but the welding only made things worse as they sprung in the same direction from the heat. Bottoming definitely is the culprit and the cracks showed up before I made any significant valving changes to prevent bottoming.

I added the optional idlers, too, but mounted on the outside of the Yamaha optional location by using my own custom collars. I believe that inner idlers take too much abuse from debris (ice, sand, etc) that gets caught up in the track between the rails. I've had no problems with rail cracking by mounting them this way. Another consideration for me was that I am running the Ohlin clicker on the rear and its reservoir is mounted on the side which would strike the inner idler at full compression. I really had no choice but to move the optional idlers outboard anyhow...

I'm quite satisfied with my Hygear valving which is on its 2nd iteration. From your description of your setup it appears that you are satisfied with yours as well. Regardless of how you get there, it is obvious that this skid was improperly valved by Yamaha and that any improvement attempt is a must.