Vandit

Okay, so amongst the massive list of things i've been doing to my car lately, I installed the polyurethane steering rack bushings and I followed Marc Shaw's lead and installed the 993 steering rack brace.

In the process, I ordered new M8 bolts in 60mm and 80mm, but royally screwed myself and ordered 1.0 thread pitch instead of 1.25 thread pitch. I never saw thread pitch specified anywhere, and i'm dumb for not comparing the threads w/ the old bolts before attempting to install. Luckily, I caught it after 1 bolt would tighten up itself after a few turns.

So I got the right bolts, M8 x 60 and x 80 in 1.25 thread pitch and went about the install. Well, after applying blue loctite, 3 of the bolts torqued properly to the required 33ft/lbs. The 4th one (the one toward the rear), the one that I had previously tried to install the wrong thread bolt, won't take a torque. It just spins with resistance, fully threaded into position. Not good.

Not sure if the bolt was tight, I decided to see if I could wiggle the steering rack clamp. So I can take a 20mm wrench which is roughly the width of the steering rack clamp and try to apply movement to the side where both bolts torque, and there is no movement. I try the same on the side where the bolt won't torque and there is the slightest bit of movement. It is almost imperceivable, but it's there. Definitely not what I want out of a steering component.

So i've already sourced a replacement subframe crossmember, but installation will be a massive pain. It's not something I want to do unless I totally have to.

I was feeling around the top of the crossmember and I can feel where the bolt come out the top of the crossmember.

This gave me an idea.

What if I drill through the threads on the stripped hole on the crossmember, use a longer M8 bolt (probably 80mm instead of the 60mm that's currently on there), and then put a nut and washer on the top side of the crossmember, to properly torque down the bolt from the bottom side.

What do you guys think?

napaul

what if you repair the threads using a thread insert.drill out member tap to appropriate thread and install new 1.25 thread insert. use them on heads and other high torque components don't see why not on there.

Don Nguyen

I use a thread repair kit as well. Stripped the threads on one of my lower shock mount bolts once. Repaired it and it has held up since. The car is also tracked and street driven with pretty high spring rates.

-Don

Vandit

I think the issue with that is the threaded portion of the subframe is pretty recessed. The bolt is 60mm, but only the last third of its length is threaded. If I had the subframe out of the car, I could do a thread repair from the top end, since that's where the threads are.

jody stowitts

Go with your own solution!!!!!!!

FeralComprehension

What you're describing should work fine; not the classiest fix, but definitely field-expedient. I would do it without hesitation, of course using marine-grade anti-sieze to allow for clean dissassembly next time..

Vandit

Another thing that's keeping me from trying a more elaborate solution is because that would mean teardown of the 3 bolts that are already loctite'd in place. I'm afraid of stripping more threads. It all seems so delicate down there. Keeps me up at night.

Ken D

It should work.

But it's the kind of thing that if I came across it during a PPI, I'd probably run. Would make me wonder what other 'shortcuts' the previous owner employed.

Just MHO, YMMV....

Vandit

lol, if I ever sell the car, I'll give the new owner the replacement subframe crossmember that is currently being shipped to me.

KaiB

I'd feel better if you'd email someone like Steve just to make sure. (or link him to this thread)

Check with someone who has real experience with all kinds of repairs in these cars - and some real race (read stress) experience.

I'd bet you'll feel better also.

Vandit

Just had a good talk w/ Steve. I feel more confident in what needs to be done to make it right but definitely don't feel better about all the work I've created for myself. What a mess.

This movie clip sums it up well.

springer3

As far as the PPI is concerned, you should be OK if you document what you do, and show that it is equal or better than the factory-supplied fastener system. A grade-matched bolt, nut, and washer system is stronger than a tapped hole, simply because the nut will be alloy, while the threads in the frame member are carbon steel. The repair is then part of the service records for the car. There are few parts more mission-critical than the steering, so I would be thorough with both the work and with the documentation.

Be sure you get the correct "property class" for the replacement bolt, nut, and washer. A hardened washer is important on both ends. The washers have a radiused side that must face the bolt head to protect the radius between the shank and hte bolt head. It is OK to move up as many strength grades as you like, but never down. The property class is on the bolt head. I am getting rusty on my metric bolt grades, but I recall Property Class 8.8 is about the same as SAE Grade 5 (heat-treated carbon steel), and all grades higher than that are heat-treated alloy steels.

elbeee964

Yup.

From notes:

metric 4.6 class = (approx.) SAE grade 2 (bigger than 3/4" dia)
metric 5.8 class = (approx.) SAE grade 2 (3/4" dia, and smaller)
metric 8.8 class = (approx.) SAE grade 5
metric 9.8 class = (approx.) SAE grade 7
metric 10.9 class = (approx.) SAE grade 8
metric 12.9 class -> stronger than SAE grade 8

Vandit

Alright, just had the biggest WTF moment...

Went out there, started to back out the offending fastener, noticed that after not even a half turn CCW, I could see the clamp was separating from the crossmember (i.e. the threads were working). So I gave it another shot to torque, maybe less than 1 full turn CW past where I started and the torque wrench clicked at 33ft/lbs. I made the wrench click a second time just to be sure it wasn't a false click.

Tried to use my 20mm wrench on the clamp to induce movement the way I had done previously, and it's super solid, like the opposite clamp.

I think I just got scared off from torquing the fastener fully on my first go round, assuming "oh ***, the bolt keeps spinning, these threads stripped" when I really only needed to go another turn to get it torqued up properly.

I'll follow-up on these once I get the car on the road, but as of now, it seems like it wasn't stripped after all.

KaiB

Good for you!

Experience brings caution, caution helps us NOT screw up and you did the right things all the way through the process.

Cheers...