00firebird

iTrader: (3)

Hello all,
Changed all 4 calipers/rotors/pads today, and while struggling on the final front corner, I realized these bolts were not like the other three sides I had worked on.
The shorter one has a big flange head and only came about half an inch into the caliper. The longer one which seems to have the completely wrong thread pitch took 20 mins with the breaker bar the whole way out, plus it wasn't even snug against the bracket. Needless to say at some point I'm guessing someone used the wrong bolts.

Basically I want to just throw both away and get correct size ones for the new calipers so I don't strip them. If anyone has the specs of the original caliper bolts please send them my way.
Edit: searched and found M12 x 35 x 1.75



Edit:
I believe this might be the one? if someone can verify
https://www.gmpartsgiant.com/parts/g...-18060356.html


My parts store does have a M12 x 35 x 1.75, but it is a 10.9 grade and I believe the stock someone said is 12.9 grade? Anyone know if the 10.9 ones would be ok though?
Good thing I saved pics of all the store's metric inventory.
https://imgur.com/epAKG6J

wssix99

iTrader: (5)

The factory bolts are grade 10.9 and are black oxide coated. The specs are here: https://ls1tech.com/forums/suspensio...read-size.html

The fronts are different from the rears.

The best place to get them is from a GM dealer. They are still stocked and if they don't have them on the shelf, they should be able to get them for you quickly.

00firebird

iTrader: (3)

Ahh if they are 10.9 then would this be ok to use instead? Oxide coating looks like the only difference
I can buy these today, otherwise I have to wait til' tomorrow for the dealer to get it and pay double.
https://imgur.com/epAKG6J

wssix99

iTrader: (5)

Those would be fine if you want to put your car together and move it around the driveway. I would not use them on the car for normal driving.


These caliper bolts transfer 100% of the braking force of the car to the wheels. They are a critical failure point in that system, so I weigh a sizeable importance to them over many other types of fasteners on the car.

Would I use hardware store bolts (who knows where they are made or what type of quality control is behind them) in this application? No. Even to drive down the street? No. They definitely don't have the black oxide coating on them, so they would rust like crazy if left on the car for a long period of time.

I hate paying dealer prices for anything, but do grit my teeth for things like this. (I actually purchase a set of these bolts from a discount online dealer and keep a set on-hand for when I might need them. It's a lot less expensive than going to the local dealer for just a few.) These bolts are a specialized piece of hardware and one has to pay for the service to provide them. Fortunately, the dealers don't gouge us as bad for this type of hardware than some other types of specialized parts.

00firebird

iTrader: (3)

Those are all great points, and I always go with oem for the added security. I think the hardware store bolts will be fine for more than just moving the car in the driveway though. They are still 10.9 grade, same standards etc.
Plus, consider that for 5+ years I had two completely wrong bolts in there and it was never an issue. Using the right ones should do even better. I will probably get the GM ones next time I need to order something else. Thanks for the help.

For giggles:

Corvett z07

iTrader: (2)

I had to get those bolts when I went from my LT to LS1 brakes, never got the bolts with the calipers so I had to buy them separately. I bought regular hardware bolts, grade 10.9. They also had grade 12.9 available but I'd *assume* that grade 10.9 is grade 10.9 based on the standards that are given. But who really knows how well the quality control is anywhere (local hardware or even OEM, however I haven't heard of either OEM or hardware bolts breaking when they were used in this certain type of application, as long as the correct grade was used. OEM is obviously used more often as that bolt doesn't really need to be replaced unless lost.) Anyhow, I personally think it'd be fine running hardware bolts in place of OEM, although the ones that I got had a black oxidized coating on the bolt, or whatever you call it, so maybe that gave me a little more piece of mind that it would hold better against the elements. Nonetheless, to each his own, if you feel comfortable running non-OEM bolts then go for it. If you don't feel comfortable, then don't. Just make sure they're tightened to spec, I have heard of those bolts backing out and then the caliper would swing up or down and scrape against the inside of the rim. Not pretty, or safe

wssix99

iTrader: (5)

If one were to use 12.9 bolts, one would need to calculate a new proper torque...

wssix99

iTrader: (5)

Those zinc bolts will rust really badly if you keep them on the car for any period of time and you might be lucky if you still have good brackets to work with when you get the proper hardware. There is no piece of hardware anywhere on the underside or under the hood of the car that is zinc coated for that reason.


You still don't have a matching bolt. The front bolts don't have a flange head, but the rears do. The fronts look like the bolt to the left in your picture (but they have the proper thread) and the rears look like the middle bolt, but they are the proper thread and length.