Brake rotor retainer screws backing out on their own

iamtheari · 01-25-2015, 03:54 PM

I pulled the wheels off my 1990 Carrera 4 tonight and noticed that one retainer screw on the left rear brake rotor was loose (which has happened before) and the other was completely gone (which hasn't -- not sure where it went but I suspect the race track in September). The screws backed out without damaging the threads, thankfully. The brake rotor is new and I cleaned the hub carefully before mounting the rotor, so I feel like bearing wobble is the remaining possibility.

The car needs a new clutch so the engine and transmission have to come out anyhow, and there is no easier time to remove the axles and replace the bearings than when the rest of the drivetrain is already coming out.

Has anyone had a similar experience? Am I barking up the wrong tree replacing a wheel bearing due to the backed-out retainer screws? Braking action is smooth and straight, but there is a persistent squeak once per wheel revolution that is probably from this corner.

porterdog · 01-26-2015, 07:37 PM

Is there play in the bearing? Those screws serve no stressed purpose; they're only there to keep the brake disk in position during assembly.

I wouldn't looking to replace my bearings in your shoes; I'd be reaching for the (blue) loctite.

cgfen · 01-26-2015, 09:16 PM

Quote:

Originally Posted by porterdog

I'd be reaching for the (blue) loctite.

agreed

iamtheari · 01-28-2015, 07:24 AM

There's no noticeable play in the bearing. I've been paranoid about it ever since some brake noise issues last spring (ended up replacing the rotors, which made me a little miffed with the shop that resurfaced the previous set). I know some people skip the screws altogether. But it's just odd to me that this one corner has them back out while the others don't. Especially when I think it's the corner that squeaks a tiny bit each time the wheel goes around with the brakes off. But then again I haven't had any stability issues on the track so probably you guys are right and I should replace them on all four corners with blue Loctite for good measure. Thanks for saving me $300 in tools and a trip to the hydraulic press.

Cajundaddy · Cajundaddy's Garage

A little blue loctite or a dab of silicone keeps those guys from backing out until you put a tool on them. Squeaks or rubbing are often from the brake rotor shield that may have picked up a rock or got slightly bent so it drags the rotor a bit. Clean it and use a wedge to straighten if necessary. Bad bearings are unmistakable grinding while rolling, especially with a little lateral G in a corner.

iamtheari · 01-28-2015, 07:39 AM

The squeak I get is definitely rotor-on-pad to my ear. No stones in the shields and they seem straight (though I did almost pull them and throw them away to be sure they weren't the cause). But I'm hearing the same kind of noise in every other car I have been in so probably it's not such a bad thing and my ear is just getting more attuned to brake sounds than before I started working on this car's brakes myself.

cgfen · 01-28-2015, 09:42 AM

Quote:

Originally Posted by iamtheari

But it's just odd to me that this one corner has them back out while the others don't.

maybe the threads should be "left handed"?

back in the 60's MOPAR cars actually had Left Hand threaded fasteners on the passenger side wheels to prevent the nuts from backing off.
NOT their finest moment.

aabarth · 01-29-2015, 08:05 AM

"NOT their finest moment."

That is actually good engineering ! Other makers used right and left handed lug nuts too.
Any car with knock off wheels will have right on right side and left hand threads on the left.
Well, except the C2 Corvette which had the opposite from Chevy and the left side wheels have a tendancy to come off at speed !
__________________

iamtheari · 01-29-2015, 08:11 AM

Dad has a pickup box trailer that was built from one of those reverse-threaded-wheel-stud vehicles. It's absolutely true that, by the time you torque the lug nuts down to 1200 ft-lb trying to remove a flat tire on the backwards side of the trailer, you are pretty much guaranteed they won't come unthreaded on the road. Flying off explosively when the wheel stud fails doesn't count.

I think that there should be a law or at least an SAE publication: Reverse threaded fasteners should be marked in some way, or maybe use some kind of tamper-proof head. Maybe it's not convenient, but it beats the inconvenience of trying to find a replacement reverse threaded fastener or a reverse EZ-out tool when you make a mistake.

aabarth · 08:44 AM

All left hand thread hardware IS marked !

If you ever tried to adjust your front wheel bearings, you would have learned this BEFORE you put 1200 ft-# on it......

iamtheari · 01-29-2015, 08:58 AM

I couldn't find any markings (other than the threads themselves) on my BMW motorcycle right mirror mounting bolt. And I may have exaggerated a bit on the trailer. It's just something you have to remember before you try too hard.

TMc993 · 01-29-2015, 10:20 AM

My '66 MGB GT had wire wheels with left and right thread knock-offs. Each had the word "UNDO" and a curved arrow pointing in the direction necessary to loosen the knock-off. A three-pound lead head mallet was part of the car's "toolkit" and was absolutely necessary to loosen the spinners.

Once I went to a tire shop to have a flat fixed and when I told the guy where the lead mallet was, he just grinned and said, "I'll get it with this rubber mallet."

The rebound of the rubber mallet off the spinner almost took his head off and I didn't have to offer the lead mallet a second time.

Nine9six · Nine9six's Garage

Quote:

Originally Posted by porterdog

Is there play in the bearing? Those screws serve no stressed purpose; they're only there to keep the brake disk in position during assembly.

I wouldn't looking to replace my bearings in your shoes; I'd be reaching for the (blue) loctite.

What I used in reassembly.

Quote:

I think that there should be a law or at least an SAE publication: Reverse threaded fasteners should be marked in some way, or maybe use some kind of tamper-proof head. Maybe it's not convenient, but it beats the inconvenience of trying to find a replacement reverse threaded fastener or a reverse EZ-out tool when you make a mistake.

The phillips head fastener holding the throttle cable holder to the carburetor on a Honda Metropolitan II scooter has a left handed thread. I literally beat the hell out of it, before I used a chisel, and tried it in the other direction.

Quote:

All left hand thread hardware IS marked !

Pretty sure this is not true...See Honda Metro reference.

Sourcing another fastener was a pita...Ended up buying a NFG carb for the fastener.