Bad Threads in IRS Upper Control Arm

[KayzDad]

I have a problem with the threads in one of the upper control arms for my IRS. The threads are messed up in some way and prevent the adjuster bung from being threaded more than 0.7” into the bad control arm. This issue is true for both of the adjuster bungs in my kit, and both bungs thread easily into the other (good) upper control arm (all the way, by hand).

There was some rust on the threads in the bad upper control arm which I wire-brushed away, but to my untrained eye nothing else jumps out at me.

In the case of the bad upper control arm a wrench must be used after the first few turns of the bung and even with the wrench the bung stops turning after 0.7”. With the bung in the bad control arm screwed in the maximum 0.7” it allows, and screwing the rod end in all the way I can achieve the 293mm rough alignment length in the assembly manual, but there is no way to make it shorter if necessary.

Any thoughts or suggestions on what should I do? So far I haven’t contacted FFR in the hope the wise folks on the forum will have a simple solution, but contacting them is Plan B.

Thanks in advance.

Geoff

[FLPBFoot]

I too had some trouble with mine. It was powder coat on the threads and I used a wire brush on a dremmel tool to clean them. Took a good bit of effort and had to get a long shaft wire brush to get in there to the full depth of the threads. Used some PB Blaster to help lubricate them going together. Once all good I cleaned all the PB Blaster off.

[RoadRacer]

Can't you just buy a tap and run it down the threads?

[KayzDad]

Can't you just buy a tap and run it down the threads?

Thanks for your comment. The diameter of the opening is around 1.18" (presumably I can get the precise size from FFR) and I suspected the cost of a tap that size would be close to the cost of a new control arm. But this may not be the case.

The cost of a pair of rear upper control arms from FFR is $180; I don't know if they'd sell a single arm. I've been trying to find prices for a 1 3/16" tap online
and at this point am confused more than anything. But it does appear I'd be able to get a tap for $50-$100 so this might be the way to go.

[RoadRacer]

Oh wow context is everything! With no photo I was imagining a 3/4 thread at most. Still, as you say.. and you can probably buy a cheap one since it’s almost a one time use you’ll need.

[F500guy]

Could try buying a hardened bolt, use anti seize and work in out 1/2 turn at a time, slowly and get the threads to open up and clean out. Could be an easy try before you buy a tap or new a-arm.

[flyboyjy]

I had trouble with one side, the other was fine. My solution was to get the right size tap and die.TAP AND DIE.jpgTAPPING ARM.jpg

[Hoooper]

Seems to be a common problem with these. Mine had a little weld splatter on the threads as well, luckily I was able to clean it up with careful use of a pick. If it cant be cleaned up with tools you already have you should have FFR send you one that doesnt come with factory installed splatter on the threads, you shouldnt have to buy a new tool to fix their bad welding.

[KayzDad]

I had trouble with one side, the other was fine. My solution was to get the right size tap and die.TAP AND DIE.jpgTAPPING ARM.jpg

Thanks for responding, and for the photos. Safe to assume the 1 1/4 x12 size in your photo is the correct size for this?

What brand tap did you use? I'm seeing a wide range of prices online and don't know which brands are reputable and which are junk.

[flyboyjy]

Yes the thread in mine at least was 1 1/4-12 and I can't imagine they have changed in 8 months. I got the set from this place: https://drillsandcutters.com/

[KayzDad]

Yes the thread in mine at least was 1 1/4-12 and I can't imagine they have changed in 8 months. I got the set from this place: https://drillsandcutters.com/

Thanks very much!

[KayzDad]

I ordered the 1 1/4 x 12 tap from https://drillsandcutters.com/ for $36 (including shipping and tax) and used it to clean up the threads. Now I can screw in the adjuster bung all the way in by hand, just like the other upper control arm, so problem solved.

After some emails back-and-forth to clarify the issue FFR offered to send me a new control arm. But the tap arrived a couple hours before the offer of the new control arm and I had already fixed the problem. Good on FFR for the offering the new part.

Thanks to all who offered advice, and especially to flyboyjy for the tap size and link to a source!

[narly1]

Me personally I would have just purchased the appropriate sized bolt and made it into a thread chaser by doing this:

https://www.youtube.com/watch?v=pfPm...l=RJTheBikeGuy

Earl