Sanity check: LCA locknut extreme torque required!

[Brian76]

Assembling the rear end of the roadster. All control arm fasteners require a flanged lock nut. However the only nut leftover for the lower control arm to aluminum spindle is a NON flanged lock nut. This lock nut appears to have three "lobes" instead of the oval shape of other lock nuts. I tried installing this lock nut and can barely thread it on with hand tools. Even my pneumatic impact barely moves the nut. The nut threads on easliy the first two turns but as is nears the end of the nut wehre the lobes are it is extremely difficult to turn. I've never experienced a lock nut this hard to install.

I checked the parts list and I can't find the nuts for this joint. The IRS parts list has all bolts and nuts accounted for EXCEPT for two nuts. Can you guys let me know if I've got the wrong nut or if I just need to man up and blast this nut on with a 300 ftlb impact?

9970399704

[edwardb]

I've assembled two of the newer IRS setups, and both came with flanged nuts for that location. Both lower connections (LCA and tow arm) came with flanged nuts. The only one that didn't was the UCA mount. Maybe Factory Five has changed something. My newest was delivered a little over a year ago. That appears to be a distorted thread locknut. Normal for them to be pretty tight the first time through the distortion at the outside of the nut. But what you're describing sounds excessive. I'd maybe back it out and try some anti-seize on it. If that doesn't make a difference, I'd stop and check. Little chance you're going to break off a bolt of that size and strength. But still doesn't sound right. Especially if you're really talking 300 ft/lbs.

[Brian76]

I've assembled two of the newer IRS setups, and both came with flanged nuts for that location. Both lower connections (LCA and tow arm) came with flanged nuts. The only one that didn't was the UCA mount. Maybe Factory Five has changed something. My newest was delivered a little over a year ago. That appears to be a distorted thread locknut. Normal for them to be pretty tight the first time through the distortion at the outside of the nut. But what you're describing sounds excessive. I'd maybe back it out and try some anti-seize on it. If that doesn't make a difference, I'd stop and check. Little chance you're going to break off a bolt of that size and strength. But still doesn't sound right. Especially if you're really talking 300 ft/lbs.

Thanks for the quick reply Paul. I have antiseize on the threads already. Unfortunately the manual does not show the nut side of the joint so its very difficult to determine what's required. The pitch appears ok since it spins freely a couple turns. Its also puzzling that I can't find these nuts in the parts list. I only see the flanged nut listed. Maybe they are in another section.

My impact supposedly goes up to 350ft lbs. Not sure what torque I'm applying with it, but I can barely move it when using a normal ratchet. Definately excessive.

[rich grsc]

STOP!! If it's that hard to turn, you have different threads. One is metric the other standard.

[CraigS]

STOP!! If it's that hard to turn, you have different threads. One is metric the other standard.
That is what I was thinking. 16mm and 5/8 are only maybe .004 to.005 inches different. In fact I hate metal deformed locknuts so I switched all my IRS bolts to 5/8 and Nylocks. Except the two threading into the rear diff cover of course. I would remove the bolt and take it to the hardware store. Try non locking nuts to see which thread you have on that bolt and then grab the appropriate lock nut.

[Brian76]

That is what I was thinking. 16mm and 5/8 are only maybe .004 to.005 inches different. In fact I hate metal deformed locknuts so I switched all my IRS bolts to 5/8 and Nylocks. Except the two threading into the rear diff cover of course. I would remove the bolt and take it to the hardware store. Try non locking nuts to see which thread you have on that bolt and then grab the appropriate lock nut.

Thanks guys. I had not thought of that. We have not used any large metric fasteners in the build yet so it wasn't on my radar. Now I'm curious if these locknuts are supposed to be used elsewhere on the car or if FFR accidentally placed them in the kit.

[edwardb]

Thanks guys. I had not thought of that. We have not used any large metric fasteners in the build yet so it wasn't on my radar. Now I'm curious if these locknuts are supposed to be used elsewhere on the car or if FFR accidentally placed them in the kit.

Most of the hardware for the IRS is metric, according to the FF instructions and also the box inventory lists I've received. The LCA components are grouped together in the listing (similar to the others) and are all M16 x 2.0MM. Both the inner and outer LCA attachments use the same M16 x 2.0MM deformed thread flanged locknuts, part number 14515. Check your list to confirm FF intended to supply those to you as well. If so, and you don't have them, I'd be calling FF. Those are very specific, and I would not expect a hardware or big box store to carry them. My very well stocked Ace doesn't have anything like that. As I said in my first post, for two IRS builds I've done every nut supplied, upper and lower, inside and outside, for the IRS was a flanged nut except the outer UCA bolt where a washer is used.

[Brian76]

Most of the hardware for the IRS is metric, according to the FF instructions and also the box inventory lists I've received. The LCA components are grouped together in the listing (similar to the others) and are all M16 x 2.0MM. Both the inner and outer LCA attachments use the same M16 x 2.0MM deformed thread flanged locknuts, part number 14515. Check your list to confirm FF intended to supply those to you as well. If so, and you don't have them, I'd be calling FF. Those are very specific, and I would not expect a hardware or big box store to carry them. My very well stocked Ace doesn't have anything like that. As I said in my first post, for two IRS builds I've done every nut supplied, upper and lower, inside and outside, for the IRS was a flanged nut except the outer UCA bolt where a washer is used.


I don't have the parts list with me but I do remember M16 listed. It didn't register that this was metric! Per the manual, we've been using 13/16 and 15/16" tools for tightening so I was thinking they were standard bolts. Silly mistake

Anyway, the parts list from what I remember shows (6) M16 bolts for the control arms and (4) M16x2mm flanged hex lock nuts. We have these two non flanged lock nuts and assumed they went on the LCA outer. Non flanged lock nuts are not listed on the parts list for the IRS components box.

I'll be contacting FFR monday to discuss.

[CraigS]

I definitely like the flanged nuts, but I am also happy w/ nylock nut and hardened washer.