Stripped both bolts on the rear caliber of E53
 

Hi guys,

I was replacing the rear left brake pads and accidentally stripped both caliber bolts.

Didn't find out both threads were stripped until I try to thread back the bolts after installing the pads.

The bolts went into the caliber bracket without issues. But it won't tighten up. As I continue to turn the bolt, it will seem to hit resistance, but then I make one more turn and the bolt loosens up.

I managed to turn it where the bolt is having a little resistance to the turn.

The anti rattle clip went on fine.

I am leaving it in the garage until my replacement caliber bracket and bolts come in so I can replace the threadbare brackets. I will also use new bolts just to be safe.

My question is, how dangerous is this caliber right now?

Do you guys think it's a big safety harzard?

It's actually not all that hazardous. The force on the bolts is a after m a shear force and a single rear brake supplies about 15% of the breaking force.

That said, DSC is quite dependent on expectation of each corner doing its job on command so their is risk.

Would I drive a car in such condition around town using the brakes more gingerly than usual? Yes I would.

Would I drive on the freeway? No I would not.

Are you sure you stripped the bracket not the bolts?

You can shim a worn bolt with thin metal even such as copper wire down the threaded hole to get full strength.

Did you use a torque wrench ? I recently changed brakes on a 328xi and was surprised by the relatively low torque on some of the fasteners.

Brake is safety issue, I would not play with it.
Park the car until you get replacement parts.

- If the bolt threads are stripped, then the solution is easy: new bolts from dealer (use realoem.com to find PN):

- The the caliper threads are stripped, then get a new bracket at local junk yard or ebay.

https://www.realoem.com/bmw/enUS/sho...diagId=34_1051

It's hard to tell whether the bolt or the bracket is worn. The threads on the bolt still look decent, but I can't get a good look into the bracket since it's still fixed onto the brake assembly. I will attempt the copper wire fix to see if the bracket can grab on tight onto the bolt.

Looking at the picture of the caliper with the bracket, it seems the caliper is simply moving up and down along the shaft of the guiding bolt, hard to imagine any actual force being applied to the bolt itself if I lubricate it well.

By the way, what's a good lube for this guiding bolt? I've seen quite a few install video and almost everyone suggest some type of lubricant on that bolt to make the caliper work smoothly.

Gonna buy an used bracket and some new bolts from fcpeuro.

Thanks to andrew and CN90 for your very helpful suggestions!

Nothing - the guide bolt is suposed to be clean and dry - that's it. Same with the rubber boot it slides in. No lube...

https://www.bimmerfest.com/cdn-cgi/i...1&d=1253105210

Is the caliper comes lose while driving, your risk is that it jams in the wheel barrel. That'll either destroy the wheel, or possibly even lock up the tire.

It's not great. If I had to get the car rolling, I'd cap the brake line and remove the caliper entirely.

^What he said. I never lube the guide/slider bolts on BMWs. Just clean them well. But I know people who do lube them with no ill effects, so it might be okay either way. :dunno:

I had this exact thing happen when I did a set of brakes on an FX35 about 4 years ago. Don't know if I did not torque it or? Rear caliper bracket rotated after bolt backed out and jammed the rear wheel locking it up. I now use a bit of locktite on caliper bracket bolts...

I have used a light oil on guide pins but more as a cleaning agent. Wipe with oil then rub it off with a rag. Just enough to help assembly not enough to gather dirt and dust.

The last set I did a week ago the pins were in good shape no surface wear or corrosion I just wiped them down before installing.

Back on topic; how sure are you the pins stripped and you didn't just round off the fastener head? I believe those are 7mm. If you tried to use 6mm it will likely tighten and slip and feel much like a stripped bolt.

Very logical. I've known people to use a vice grip to close off a defective corner to get a car to a shop.

:thumbup: Good thought. Easy enough to check. Pull the guide bolts out of the calipers, rotate calipers out of the way, and try to thread them into the bracket.