CV-6 

It appears that the drilling for the brake bolt is off kilter. If you are not familiar with how Mafacs mount, the arms should be pretty much parallel with the stay. I have tried other brakes and different mountings with the same result. The question...Is this an issue or much ado about nothing?

juvela

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i would think so but happily defer to those more knowledgeable

have had several frames exhibiting this trait pass through me workshop o'er the years

the one instance where it can be a snag is if the caliper one wishes to employ is at the limit of its reach and the angle has the effect of increasing the brake reach beyond what the caliper can offer...

input from il perpetratore di gugieficazione would seem to be appropriate here...

gugie


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Wildwood 

Certainly not an issue for stopping if the brake bridge is secure and the pads strike the brake track well.

gugie 

There are two types of brake bridges.
1. Cheap piece of tubing with a hole in it.

This is why they call me the Bike Butcher of Portland. In this case I'm hacking the bridge out prior to removing the seat stays for a repair.

Then there's the nice ones that are cast with flats on each side.


Recessed bolt version from framebuildersupply.com - just one of many examples

The first kind typically has some slop in it, you can rotate the brakes a bit due to the hole being oversized. They use conical washers on each side for the bolt and nut to have flat purchase on . The second type has a flat that the brake bolts up against, no slop.

Lynn, yours appears to be the first type. You might try loosening the nut, swivelling the brake and tightening it down. Braking forces will make the brake want to rotate back in the direction you want. Indeed, most centerpull brakes tend to touch the seat stays for this very reason.

If the hole isn't tangential to the rim, and the brake bolt limits how far you can rotate it, I wouldn't worry about it. Looks to me that it's an aesthetic issue. If it really bugs you, take a rat tail file and carefully remove some material so that the entire brake is perpendicular to the rim.

gugie 

So now I'm a perp?

Don't let my parole officer know...

El Chaba

Shouldn’t be a problem since the brake pads are easily adjustable in that plane anyway….If it helps, think of it as a little extra toe in….Photos are needed of the entire bike, btw….

CV-6 

Thanks to all for responding. I considered doing the file but was concerned that the bridge might be compromised as a result. It bugs me enough that I shared it, so it will get resolved. I am also thinking that not fixing will lead to brake noise. Enough potential for that without the funky arm angle.

Bianchigirll 

You need to get a 3D printer and Unicorn bone to make a wedge washer to get the brake at the proper angle

Dylansbob 

I need to see the seatstay caps to give an answer.... and the headtube, fork, better yet. A full bike photoshoot?

gugie 

Not sure how this would instigate brake noise.

Why not just try riding it and see what happens?? Rear braking power isn't super critical anyway.

bulgie 

If it were mine I'd file it, because it's an easy job and we're not taking off enough to hurt the function in any way. Otherwise it would bug me. Once fixed, you can forget about it forever. The tiny surfaces that are now unpainted could rust, but with a smear of grease and covered with the radius washers any rust will be minimal, years down the road, and never seen.

I would use a chainsaw sharpening file. They are untapered and fairly fine of tooth. I would use a 1/4" file even though the hole is nominal 6 mm, slightly less than 1/4", so you may have to open the hole slightly with a smaller file first to get the 1/4" file in. The holes are often a little oversized already though so the 1/4" file may go right in.

Just a few strokes should do it, so keep checking with the brake. Going too far would be a tragedy. Well, that can be fixed too, but generally by brazing in a "top hat" reinforcement, which requires a repaint, at least locally.

Another request for a photo shoot! Please?

Mark B

CV-6 

Mafacs use any excuse to make noise. But my thinking is that the plate not firmly on the stay will allow more flex.


Photos. Not yet. When it is done. I have already shared the frame.

gugie 

True that!

If the backing plate touches the seat stays, you eliminate one place that it will flex, which is why I suggested filing out the brake bridge hole so the brake can rotate and touch the seat stays.

I've got a set of those golden MAFAC 2000's on my Pimp Eroica Grand Sport - which has a very oversized hole in the brake bridge, so it was easy to rotate it and get the backing plate touching the seat stays. They howl like a banshee going down super steep hills, like the backside of Cypress at Eroica California, or Sullivan Hill at Cino, but otherwise only give a light squeal when in use.


Don't mind the saddle angle, I've fixed that - rode into work a few years ago with the saddle adjustment a bit loose.

Feldman

I wouldn't worry about it and would just adjust the brake pads to run properly with the rim. I see no functional problem here. In my experience you only see consistent perfect finish and dimensions on frames by the elite of mostly American custom builders.

scarlson 

+1 on this recommendation, I love those chainsaw files for elongating holes for exactly the reasons you specify.

repechage

Buy a rivnut that fits the bore, push it in.
now you have a choice.

my route would be file with a small Chainsaw file ( constant diameter ) the hole so that it is the direction you want.
then decide how to fit the backside.
you may have to counterbore the spacer immediate to the brake caliper to get things to nest.
I have done this, after you are done, no visible witness.

CV-6 

The above is the route I am taking. A little on Carré. His shop often used a piece of sheet metal rolled into a tube for the brake bridge on just about anything. I have at least two Lejeune 531 frames (and this frame) where this was done. At least the shop also stuck a piece of tubing in the bolt hole for strength. I have already progressed to being close.

CV-6 

It just does not look right. And I would bet that a good many of you would look at it and say the same thing.

CV-6 

I may do some fine tuning.

gaucho777 

The angle does give a little extra tire clearance below the caliper. I did a workaround on my recently built Colnago. The 30mm tubulars just barely skimmed the bottom of the caliper. I filed a thick washer so it was thin on top. Once installed, it created a slight angle similar to what was shown originally. I’m not saying it was done intentionally on your frame, but if clearance is an issue, that angled bolt hole has its advantages.

elcraft

Maybe he meant “proprietore”….

gugie 

Well, I did resemble the remark.

gugie 

I measure that off by 0.02 degree from parallel. I'd be happy to take it off your hands, heck I'll even pay shipping for that clearly damaged frame.

repechage

one of the silent issues with Colnago is the fork crown on an early 70's bike is quite short front to back. Mount the caliper direct and the only way to use the Campagnolo brake center bolt flats is to remove the wheel. I tried a steel bushing and got brake pulsation. Flex in the system. So it goes.