Alfa Romeo Forums banner

1 - 7 of 7 Posts

·
Premium Member
Joined
·
197 Posts
Discussion Starter #1
Here's another little hardware puzzle, which again I'm probably over-thinking: The front brake calipers on my street-driven 115 have ~2.0mm thick M12 spilt-ring lock washers for the bolts to the spindle. The original washers are well-flattened, so likely don't provide any locking function now. New lock washers from the sources I've found are about 0.5mm thicker. I know that doesn't sound like much, but there are only about four threads of engagement of the bolt in the spindle so percentage-wise this is somewhat significant. Because of the heat generated by the caliper, I doubt that Lock-tite adds any value. So should I a) use the old washers as is b) use new, thicker washers, c) try and re-bend the old washers so they look more like split-rings or d) does anyone have a source for the original-type thin washers?

Thanks for your forbearance.
 

·
But Mad North-Northwest
Joined
·
10,484 Posts
There are split lock washers on there? I don't recall that on my cars, but it's been a while.

Anyway, the tests I've seen show that split lock washers don't actually do anything. Were it me I'd reinstall as is and just use blue loctite and torque to spec. Loctite will work fine: plenty of automakers use it in the caliper bolt application.
 

·
Registered
Joined
·
417 Posts
I hesitate to comment, since I’m not familiar with the parts, but 4 threads of engagement on a 12 mm fastener does not sound right.
Joe
 

·
Super Moderator
Joined
·
10,585 Posts
I hesitate to comment, since I’m not familiar with the parts, but 4 threads of engagement on a 12 mm fastener does not sound right.
I have to agree with Joe. As I recall, those bolts have a fairly fine thread; probably 1.25 or 1.5 mm/thread. Let's say it's the coarser of those two (1.5). Four threads would imply that there is only 4 x 1.5mm = 6mm or about a 1/4" of thread engagement. That can't be the way the factory designed them. Is it possible that shorter bolts have been substituted?

gubi said:
There are split lock washers on there? I don't recall that on my cars, but it's been a while......Were it me I'd reinstall as is and just use blue loctite and torque to spec. Loctite will work fine: plenty of automakers use it in the caliper bolt application.
My memory matches gubi's, though there may have been a flat washer in there. I too use blue LocTite on these bolts.

lpalmer said:
Because of the heat generated by the caliper, I doubt that Lock-tite adds any value
I doubt the calipers get so hot that they would transfer that much heat to the spindle. Perhaps in competition use, but not on a street car.
 

·
Premium Member
Joined
·
197 Posts
Discussion Starter #6
Joe and Jay, you're right about the bolt engagement depth. Turns out there's more like 6 threads of engagement. With the suspension disassembled, I was going by the threaded hole in the spindle boss, saw that the last two threads had some corrosion, and figured the bolt didn't engage that far. Turns out it does, and obviously moisture can work its way in two threads' depth. I will use blue Loctite and continue to meditate on the lock washer choice. Parts manual shows what looks a lock washer there:

1621429
 

·
But Mad North-Northwest
Joined
·
10,484 Posts
Well, that looks reasonable. The GTV manual shows cone washers on there, not split, so that's probably why I don't remember them.

Anyway, split lock washers really don't do anything anyway, so I wouldn't be worried about reusing them. Use the loctite and you'll be fine.
 
1 - 7 of 7 Posts
Top