While replacing my power steering rack today I broke the head off of the inner passenger side bolt for the subframe brace on my EG2, and I'm a bit worried about running with only the remaining three. The rest of the bolt is seized in place with slightly more than the width of the brace end exposed. All other stabilizer system connections are sound, which makes me feel the remaining bolt on that side of the subframe brace would become the "weakest link" of the system.

I would attempt to drill out the remnants however the ABS system is in the way of my standard drill, a 90-deg might work but would be hella tight. There is a hole on the bottom of the subframe that allows partial access to the welded nut from below; I was considering trying to blindly whack it loose with a chisel and then install a washer and nut onto a new bolt with a flexible magnet through that hole.

Also the transmission is removed from the engine bay at the moment so I sort of have access to the broken bolt from above. I just really don't want to remove the ABS system or replace the subframe if I don't have to. I don't have welding equipment, and judging from the torque I was applying when the bolt broke I don't think welding on a nut would withstand the forces required.

What do you think? Am I freaking out over nothing?

 

A) Drop subframe and drill it out
B) Buy another and replace.

 

Would rolling with just the three bolts be dangerous?

 

Simple answer = yes.

 

Yeah it does freak me out when I think about it, looking into a replacement subframe. Thanks

 

If you can smack the welded nut out as well as get the broken bolt out, you could potentially use a stainless steel rivnut to replace the welded nut. This would provide you the strength you need.

Using a rivnut is far better than trying to dinker with trying to get a washer and loose nut inside.

The one thing to be aware of though, Honda tends to use custom fine pitch metric threading. Larger bolt diameters don't usually come 1.25mm thread pitch so a rivnut will likely mean a different bolt than OEM. You will want to get the highest grade 1.5mm thread pitch bolt to fit the rivnut. I don't remember off the top of my head what the top grade bolt is for metric, but it should be the equivalent or better than the 8.8 SAE grade bolts.

 

Class 10.9 is about 1:1 the same as SAE Grade 8. Class 12.9 is about 20% stronger than that. "8.8" is a metric class, about equivalent to an SAE grade 5. Note that stainless hardware is not necessarily stronger than alloy. Easy to get this stuff mixed up. Your point on the fine thread stuff is very valid though. Might need to change the bolt size to repair.

 

Carbon Steel used in Grade 8 Fasteners:
91 ksi in single shear
130 ksi tensile yield
150 ksi tensile ultimate

17-4 Stainless Bar heat treated to H1025 (this would be the likely condition for a bolt)
95 ksi single shear
145 ksi tensile yield
155 ksi tensile ultimate

https://ck5.com/forums/threads/stain...-thing.196221/


Make sure that whatever rivnut you get matches the grade bolt you use since when using nuts and bolts the strength is tied to the grade of the weaker fastener. Using grade 8 with a grade 5 results in the equivalent of using both grade 5 pieces of hardware.

 

Thanks for this, first I've heard of the rivnut - the major diameter of the OEM bolt is 10mm, so if I'm able to clear the bits out the hole would be roughly that. Would I look for a rivnut that accepts like a 3/8" diameter bolt to account for the width of the rivnut?

 

Do you have access to a welder?

 

To be clear, when you say subframe brace, are you talking about on of the bolts that fixes the subframe to the body?

 

No welder access, unless I can find someone with a mobile rig




Subframe brace is #4 here, attaches to the top of the subframe with four #43's. It's right in front of the steering rack

 

I thought it might be. That’s not a terribly critical part. Most didn’t come with one. You can drive the car just fine without it.

I’m pretty positive that everyone in this thread thinks you were talking about one of the six bolts that attaches the subframe to the body

 

oh... brother...

 

I sure thought so.

Some people with swaps leave it out because it’s in the way.

No big deal if you leave that out. X2

 

Hey, it's better than him just shrugging off breaking a subframe bolt!

 

Thanks guys. Yall provided all the great details and great knowledge as always. Greatly appreciated.

Being the less critical part, you won't have to be as concerned about trying to get grade 10.9 rivnuts etc. The bolts are usually easy to find specific grades while the rivnuts, not quite as easy. If you want to rivnut it and it's an M10 bolt, you will find available and get a M10 x 1.5 rivnut and will have to get an M10 x 1.5 bolt of equivalent length to the bolt that was there, You then use a carbide cutter on a dremel or such tool to widen the hole just big enough for the rivnut to slide in and then you cinch it in place with the install tool.

The steel rivnuts most commonly found are probably SAE grade 5. The reason I suggested stainless rivnuts was they don't rust but I doubt it's any higher grade than SAE 5.

 

I was pretty sure it wouldn't be dangerous to drive it as is, lol. I'm more concerned about the stress on the subframe with there being sort of an "open circuit" now in the stabilizer system, I've read that this brace counteracts the shock tower brace so it would follow that the subframe would take the brunt of the forces without the brace (the suspension and sway bars came beefed up on this model)

I now feel safer driving with the subframe brace attached by only the three bolts, I would rather have a bit of a brace there than nothing at all, and since the subframe is essentially compromised by the broken bolt I may as well experiment with it ; I'm going to see whether the single bolt will be affected at all by hard cornering - that way we'll see how functional the brace actually is - if I hear a loud pop from the bolt shearing mid-corner then it's safe to say the brace is necessary in the presence of upgraded suspension, and I'll proceed to cop some rivnuts and drop the subframe for repair.

Sorry for wasting anyone's time on this, I thought I articulated the issue properly. I know what rivnuts are now and hopefully this thread will help someone in the future

 

you will 100% be perfectly fine missing 1 bolt from the brace all lower model civics and del sols did not even come with the brace from the factory.