Brunton Stalker XL spindle

[StalkerXL]

I have a Stalker XL Mspec that was built in 2014. The bolts that hold the rear lower control arms and the threads are shot. Is there anyone who knows what kind of spindles are on this car? They do not appear to be Miata, S-10 or Wilwood. Thanks!

[MV8]

They have used custom made uprights milled from aluminum plate. What you have may be repairable in such a way that could prevent a repeat of the issue. Post pics if you want feedback on if they are custom or something else as well as how you might repair the damage.

[Croc]

@Anaximander Bob - Do you know from your Stalker experience?

[StalkerXL]

I'll send some pics later today, but that makes sense that they're custom.  I rethreaded them and used new bolts (5/8-18) and they were able to hold 180 ft lb torque (spec for 5/8 zinc plated grade 8 bolt), but because about 1/2 of the threads were shot, I didn't trust them.  I used Time Sert thread inserts, 0.875 inch long, and they also hold 180 ft lb torque.  I also placed Time Serts to replace the set screw threads that were stripped, and used new knurled-end set screws to hold the bolt.  The max thread length is about 1 1/8 to 1 1/4, but a modified 1 1/4 Time Sert insert did not hold since they engage at the end of the insert (I believe).  How would you guys feel about using what I did on track?  Would it be worth getting new spindles from Scott?  

[Anaximander]

Scott's XL's have experienced several spindle failures over the years. The uprights are custom made to interface with the Stalker suspensions. I would definitely contact Scott Minehart of Stalkers Cars and get his expert opinion on whether or not your fix provides a sufficient safety margin. IIRC, Scott's original supplier of uprights discontinued business and Scott had to source another vendor to make his uprights. He had CNC specs but I am not sure if they went away with the dissolution of the upright vendor's business? Additionally, Scott's brother Jason Minehart has continued to experiment with Stalker suspensions and there may be additional variants that have come out of the real-world race testing that Jason puts his Stalkers through. I think the spindles may have been sourced from Ford parts but that is a long-ago memory and may not be accurate in the least. In Scott's literature, he talks about "custom aluminum spindles" so I am not sure what he was trying to convey with that descriptor?

 

Scott would be your best source for determining the safety parameters of the XL's modifications that you made. He has a lot of real world race experience with his components from some of his racing and he stays well in touch with some of his customers that use his cars primarily for autocrossing although the XL's were primarily designed for track work given their longer/wider dimensions than some of his other models.

Edited Saturday at 08:29 PM by Anaximander

[StalkerXL]

[StalkerXL]

I've been trying to get in touch with Scott since the hurricanes, but no luck yet. I texted Glen today, so maybe I'll hear back soon. I'll go with the repaired uprights for now, but I would feel more comfortable replacing them. I didn't know why two of my wheels were all scuffed up on the inside until the bolt joining the right rear control arm to the spindle dropped out and scuffed up that wheel. Now I know.  I torqued them all and found one front bolt that was loose, explaining the steering play I've been feeling. 

[MV8]

The lower control arm spherical, carrying the sprung load in single shear is critical. Those are custom made uprights and not from any oem, which would have steel inserts for threads if using aluminum alloy uprights.

 

It is highly unlikely that any mass produced oem upright is a direct fit replacement.

Only you know the quality of the thread repair and setup or how often you will recheck the jamb nuts and torque specs.

[StalkerXL]

Good advice. I appreciate your help with this. I'll continue trying to get in touch with Scott and in the meantime, I'll be checking the torque frequently. 

[Anaximander]

Stalker XL,

With the various Stalkers that I owned (6), with all of the heim joints that Scott uses for adjustability on the M-Spec cars, I would frequently gently test the torque of all of the connecting arms front and back to see if anything was coming loose. The cars have a way of vibrationally, over time, loosening certain nuts, especially on the front end of the car and so I would take a couple of wrenches and without overtorqueing anything make sure that all nuts were secure. When tracking the car, I think it would be prudent to do this before every race weekend and it only takes a few minutes for added piece of mind.

Edited Sunday at 03:07 PM by Anaximander

[CarlB]

Where the rod end connects the spring to the spindle could use a large diameter thick washer to prevent the corner of the car contacting the ground if the rod end joint brakes.

[StalkerXL]

I had a great conversation with Glen Minehart yesterday.  He seemed to think the Time Sert would work fine, but to check the torque on all the control arm/spindle bolts before every event.  This has been a problem with other Stalkers, just as you all noted.  His son, Sean, has had the same problem on the front spindles, so he had a slot machined in the spindle so he could put a jam lock nut (short lock nut) in to hold the bolt in place.  It seems to be working well for him.  One of the former owners of my car put a set screw in, but Glen cautioned against that since it would mar the bolt threads, which would mar the threads in the spindle when removed.  It sounds like the best solution is to put a torque wrench on them before every track event, and periodically at home.  Thanks again for everyone's help with this!  I wish I had joined this site a year ago!

[MV8]

If the threads do not hold, I would ream out the threads to the bolt shank od, invert a bolt so it drops in from the center, then add a 90 degree .125" thick lock plate to bolt to the inboard face of the upright and holds the hex head on top so the bolt cannot turn. The bolt would only be threaded from about .375" above where it protrudes from the bottom of the rod end and long enough to protrude by at least three threads from a nyloc or other prevailing torque nut or a jamb/thin nut on a standard nut. The practical way is to buy the bolts based on the unthreaded shank length, then cut off the excess thread and radius the cut end. Grade 8 but grade 5 should be fine. Use fine thread. From the rod end down should be a spacer for clearance, then a safety washer (previously mentioned by CarlB) that is just a large, thick washer to keep a worn rod end from completely letting go if the ball pops out of the rod end housing. 

[StalkerXL]

I would love to see a picture or diagram of what MV8 and CarlB are describing.  I'm having trouble visualizing it.  I attached a pic of the bolt that holds the lower control arm to the spindle.  There is a spacer above and below the heim joint.  Would the large washer go between the bolt head and the spacer?  This would prevent the bolt from coming out of the control arm?

[MV8]

Yes, it would be a washer with a large od than the opening in the rod end housing and fit between the spacer and bolt head. I see in the picture a set screw. I'm guessing it may hold a steel threaded insert in the upright for the bolt (ergo, easily replaceable). Maybe it is a mod by the PO? DO both sides have this set screw? Somebody used a lock washer under the jamb nut which is also odd. Maybe sits in a groove in the insert so the insert can't come out and also prevents it from spinning?

 

If it is an insert, a new one could have been made to replace it instead of a thread repair, but I guess it is good enough for now, with a safety washer.

[StalkerXL]

The set screw was apparently placed by a PO who must have had the same problem.  They used a grade 8 1/4" bolt with a jam nut and lock washer.  When I placed the thread insert for the pictured bolt, I also placed an insert for the set screw, replaced the set screw with the one pictured (with a knurled tip) along with a new jam nut and lock washer.  The set screw goes through the insert to prevent rotation of the large bolt.  Glen recommended against the set screw as it will mess up the bolt threads, so I'll likely remove it the next time I take things apart.  

[Anaximander]

Stalker XL, Consider scratching the use of a torque wrench because there are no standards for how much torque should be applied to the various bolt/nuts. Just check for snugness before each race weekend and you should be fine. Many of the suspension connections require two wrenches to tighten opposing nuts on threaded components and are not even accessible to a torque wrench. Glen had suggested to me what I am suggesting to you and I would only occasionally find one or two nuts that had slightly loosened up. Using a torque wrench without knowing what would be optimal torque settings feels like the potential for disaster in the making?

 

Additionally, what you are referring to in your picture are called cone washers and Minehart has design reasons for using them in some places and not in others. I can't remember what the logic is for their use but Glen would be able to explain the various uses of flat vs. cone washers and where they should be used. Glen helped me build my AXR a few years ago and it was pretty stout.

Edited Tuesday at 09:25 PM by Anaximander

[StalkerXL]

That makes sense for the torque on the suspension bolts.  I used the torque spec for Grade 8 bolts, but I have no idea what the threads on the uprights and the steel thread inserts can handle.  I'll keep them "snug".  

 

The cone washers are smaller on one side to articulate correctly with the heim joint, and larger OD on the other side where the bolt head comes against it.  The space created by the thickness of the cone washer allows for movement of the heim joint as the suspension moves.