What Causes Brake Linkage Wear?

[ClayW]

What causes the "ovalling" of the holes in the "L" shaped bracket (seen below in a pirated image from Uncle CD)?

I have some play in my brake pedal linkage that translates to 1-1.5" of play in brake pedal travel. I suspect that I might not be getting a good bleed due to this.

After inspection, we noticed that the holes in the bracket are a little "ovalled." I've got replacement pins and the rod end on the way and we've found a replacement "L" bracket, but I'm curious what might have caused the problem to begin with.

Any ideas? Where else should I look?

[ahlem]

Are there bushings in the thin metal components or just holes in mild steel? Bushings, properly lubed will spread out the force and minimize the oval effect. Working on this same issue on a dune buggy right now and will be adding shoulder bushings tack welded to the pedal arms in our case. We had to bore out the hole to match the OD of the bushing and will use slightly longer pins.

[Napes]

It's caused by use. How old is your car and how many times do you think the brakes have been applied during that span?

Bob Napier

[Colin]

Where did you find the new L bracket?

[jerry]

of the several pedal box rehabs i've done, i've only seen wear on the pivot arm hole, once and it was only slight (however, it's on the 'reserve' list now). most of the wear i've encountered, fortunately, is on the small clevis pins which are easy to replace. i'd suspect that the wear you have is due to lack of lubrication, coupled with fretting (wear and corrosion, combined) and can be exacerbated with a tendency to bear down hard on the brake pedal due to non-optimal brakes.

i always dab a bit of moly grease on those joints for good measure and try to swipe the plastic bushings contained within the pivot arm with some white litium grease to help them to remain free to rotate as necessary.

it helps to make friends with someone with a Tig welder who can buildup worn bushings and such. i've saved several bits and pieces on my 02's that way, especially alternator supports and exhaust hanger brackets.

[ClayW]

Where did you find the new L bracket?

Williamggruff had a spare, but you can find a new LENKFÜHRUNGSHEBEL (yes, that's the name) at http://www.bmwmobiletradition-online.com/bmw/showparts.do?model=2215&mospid=47140&btnr=35_0195&hg=35&fg=05.

[Colin]

Where did you find the new L bracket?

Williamggruff had a spare, but you can find a new LENKFÜHRUNGSHEBEL (yes, that's the name) at http://www.bmwmobiletradition-online.com/bmw/showparts.do?model=2215&mospid=47140&btnr=35_0195&hg=35&fg=05.

Nice! Thank you =)

[Swiftus]

Has anyone thought about installing some nice ball or roller bearings to repair an ovalized hole? I know that I'm certainly not capable of doing it, but think of the smooth braking effort that would result. *heaven*

[TobyB]

err, that would be friction....

remember, these cars were supposed to be done after 5 years...

t

[Napes]

Looking at Max's diagram I'm glad I don't need a new Support Bracket @ $319 a pop.

Bob Napier