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June Sprints 2019

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#61
Steve Scheifler

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I think he was referring to the shoulder of the bolt against the powder coat on the caliper?


Ah, reading again I think you are correct, thanks. All the more reason then, not unlike lug nuts on painted wheels. (another phenomena I’ve never experienced. Perhaps I’m just really good at torque. :) )
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#62
Dave D.

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Yes, that is what I meant and yes, I have had wheel lugs back off with powder coating on the lug nut seat area. Although they were magnesium on a GT car, so maybe the added higher levels of brake heat combined with the "softer" mag and soft powdercoat combined to give that result.......

    At the shop(working on street car that actually pay the bills...) I have found in recent years that care has to be taken when putting brakes and wheels back together. with the very aggressive de-icing solutions put down on the roads in winter  The alloy wheels corrode more at the mounting surfaces and if not taken back to a bare shiny  surface, the wheels can come loose even if torqued properly the first time. Also care is taken to make sure the mounting surfaces of the brake calipers, brackets and spindle/uprights are also clean of all corrosion.

     So, while it's nice to have all that shiny,clean  powdercoated suspension, I make sure it's removed from all machined mounting surfaces .



#63
tylerbrown

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Yesterday I took a stock Caliper Bracket Pin out of a caliper bracket that I took off of a street car that has never been remaned. When you loosen the pin in the slightest, the amount of "play" in the threads between the bracket and pin is quite eyebrow raising. When you go to tighten, even when you finger tighten the pin, there is still a (at least what I would consider) large amount of play as if there is too much tolerance in the threads. 

 

Whenever I get calipers from a reman, I pull the pins out, clean both threads, then red loctite, and install. After every session at Road America I pull off the calipers and try to see if I can wiggle the pins. I have had pins come loose following this procedure. 

 

Waiting for Mr. Dewhurst to chime in here.


Tyler Brown

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2019 June Sprints - 1st Place

2019 Blackhawk Farms Majors - 1st Place

2018 CAT Majors @Road America 1st Place

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#64
Bench Racer

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Yesterday I took a stock Caliper Bracket Pin out of a caliper bracket that I took off of a street car that has never been remaned. When you loosen the pin in the slightest, the amount of "play" in the threads between the bracket and pin is quite eyebrow raising. When you go to tighten, even when you finger tighten the pin, there is still a (at least what I would consider) large amount of play as if there is too much tolerance in the threads. 

 

Whenever I get calipers from a reman, I pull the pins out, clean both threads, then red loctite, and install. After every session at Road America I pull off the calipers and try to see if I can wiggle the pins. I have had pins come loose following this procedure. 

 

Waiting for Bench Racer to chime in here.

Adding to what One (inside comment) referenced:

 

Referencing Tyler's pictures:

It's the upper rear caliper bracket bolt which fails/fractures, correct.

Ask yourself or check the thread internal and external threads dimensions (even when using red Loctite). Are these thread quality for a race track rumble strips or for a grocery getter?

Check the distance from the bolt seating surface where the bolt breaks.

Check how far the bracket first full thread is from the bolt seating surface.

Check the bracket mounting surface for the failed bolt. 

Check how much of the failed bolt seating surface seated on the bracket and observe the bolt undercut.

As yourself, why does the lower bracket bolt with the same size threads not fail/fracture? The thread is 9mm x 1.25 pitch.

The bracket and bolt metal makeup and toughness and hardness also play a roll in the bolt fail/fractures.

Theses are clues to think about to as why the bolt fails/fractures.

 

Happy 4th to all.   :bomb:  


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