uncle uncle

https://www.velo-pages.com/main.php?g2_itemId=25925

hmmm....

Cynikal 

A threaded center hole would make a really nice dyno light mount.

capnjonny 

If you could do that it would be awsome. My address is 20221 Thelma Ave. Saratoga Ca. 95070

As far as I know all the Mafac breaks had the same basic dimensions except for the arm length. I have some heavy aluminum stock I can carve them out of. Anything you need?

My e mail is 143cabinets@att.net

cudak888 

Maybe if the plate had a mounting tab that rose above the arms and didn't foul the yoke, that' be possible.

However, given the 2.55mm thickness mentioned above (and the fact that there's barely enough clearance between the arms and the plate; none if the forward arm happens to be bent ever so slightly), that's barely enough thread for securely mounting anything on the Cupertino design.

-Kurt

pastorbobnlnh 

I'm certainly enjoying this thread and look forward to seeing Kurt's results. BFers have shared some great ideas. Fantastic group collaboration.

But--- I'm wondering if I installed my Racers incorrectly on my recent Voyageur II build. They don't squeal a peep--- and I did nothing special to set them up.



What did I do wrong?

tiger1964 

I'll check the "brake parts" box of bits later; it's in there, I saw it earlier.

EDIT: Found it! Gee, it's not the most beautifully engineered product -- I'd presume it could be improved. OK, now to visit the #*%&# post office.

repechage

orange pads

Reynolds 531 

BMX cable crimp

bulgie 

Congrats, well done!

I can see some toe-in on the one pad visible in the pic. Since they don't squeal, I'm going to risk a possibly invalid assumption that the other pad is toed in too.

I've had Campy brakes that always squealed, and Mafacs that never did, so the idea that Mafac is somehow uniquely associated with squeal is bogus.

Good pads, clean rims and a little toe-in is usually tolerably quiet. One problem is if the toe-in goes away when you apply the brakes hard, from slop in the pivots and/or flex in the caliper. So brakes that are quiet at first start to howl when you apply them harder. This can be helped by brass bushings, a booster plate, brazed-on pivots, anything that helps keep the toe-in from going bye-bye.

Or, keep the squeal as a horn, can be helpful in traffic. (kidding, I almost always hate squeal and I don't miss it on brakes that don't)

Mark B

cudak888 

I suspect that the soft compound helps maintain more consistent friction than the old pads, thus avoiding the harmonics of the arms (and thus the pads) fluttering.

But I'm not a structural engineer, so this is entirely a guess. But it would be interesting to throw some original Mafac pads on there without affecting the toe-in.

-Kurt

Mr. 66

Can one butcher up an old set for bracket, and mount that as a faceplate on the good set? I think people were doing that for the diacomp cp

I always thought they were some of the best brakes of the time as is, if you can improve that's great.

79pmooney

Canti bosses are located wherever the framebuilder decided to put them. There might be a sacred distance but there are a lot of atheist builders. That bridge also needs to clear the tire if you choose to go over, lessening the stiffening effect a lot. Under the rim is a nice clean short span but spoke interference might get a little old. (But it can be your best stopping wall hanger.)

Edit: To the topic - I've got two winter/rain/city bikes with Mafac RACER front brakes and a bunch of 1/4" 6061 aluminum plate lying around. I could just go to Ace Hardware, find bolts 1/4" longer, drill, cut and shape. And for those hole centers - I wonder if I could just shorten a nail and find the right sleeve where it would sit centered in the boss. Drill one side, put on, tap down onto the nail and now other side is ready to drill! Or I could just look at that table on the previous page, set my calipers to that measure the brakes. Sounds way less interesting.

(These bikes have Weinmann centerpull rears for more stiffness, less power. Front and rear feel identical and panic stops are incredible! But rain and lack of attention means that the lever hitting the bars can be an issue. This bridge would help that.)

79pmooney

In my mind, feasible IFyou can remove the bosses. IF you have to drill them out, it might be tricky to keep the drill bit from wandering from the presumably harder boss into the softer aluminum. Or, thinking as he types so wear your helmet as you read... drill with a bit just clearing the bolt size down through boss, using it as your centering device. Go clear through. Cut and file the boss flush on the outside (front). I'd only attempt this with a drill press but then I've got one and my hand drill skills are so-so.

top506

I did this many moons ago on a set of Weinnmanns:



Didn't seem to make much difference.

Top

Road Fan

As well, toeing-in increases pressure at the front of the brake pad, increasing wear rate at the front even without any wiggliness or flex in the caliper. This should tend to eliminate the toe effect, by itself.

gugie 

Spacer?

cudak888 

Part of me thinks that these Mafac-specific brake boosters don't really stiffen the brake at all, but provide a place for the forward arm to rest upon during braking - a job that would be lost with a spacer pushing it forward. Stiffness might even be affected depending on how much of the bushing is contacted by the spacer.

-Kurt

Charles Wahl

Does this help, Kurt?

The original, that would probably be at higher resolution, is here:
https://ruedatropical.wordpress.com/...l-brake-specs/

cudak888 

Yes, perfect. I forgot that Rueda Tropical had that picture; I remember discussing these at length with Mike way back when.

Nevertheless, I'm not going to have a set of RAID stiffeners made until I see what I get with the Racer/Competition variation.

-Kurt

oneclick 

If by adjustable stirrup is meant these ones:



then I can confirm:

79pmooney

That looks to me to be too thin. Especially if that is aluminum. Steel, maybe. I'm thinking beefy 1/4 aluminum plate to make it as rigid as possible. And yes, I'd have to get new, longer bolts.

capnjonny 

I'm loving all the imput from you all about this. I often use Mafac racers when I need to use 700 c wheels on an old 27" frame. We have 10 times as many 700c wheels as 27"s at the Bike Exchange. Since we are on the subject, I have another couple questions. Where can I find the Brass bushings mentioned, and where can I get stradle cables for mafac competition brakes. I have a set but have only one straddle cable.

The bike Exchange had a parking lot sale today. It rained on and off all morning but we still sold quite a few bikes. Interestingly, the bikes sold were almost all mountain bikes. No interest in the road bikes. Too bad because we had some very nice ones, including a PDG Paramount, and a couple of Bianchis. we will most likely have another sale once the weather clears up.

chain_whipped

Without spoiling the party, and budget bargain MAFAC centerpull's though with all this over thinking, extra machining parts, aftermarket expense booster whatever...

Spend it on a pair of GB Courier 66 brakes. Ingenious main support casting with wrap around pivot bearing for the individual arms. Superior design over MAFAC. Done.

79pmooney

But ... just going to the Velobase website (1st hit when I duck-duck'd GB Courier 66) I saw several posters talk of missing springs. (2015. I doubt springs have spent the past 8 years crawling out of the woodwork.) Yes, I had spring issues with my first pair - from the bike I bought when I was 13, used for 22,000 miles then on my next bike. Blame the ham fisted teenager. And one pair I bought used and abused need a little spring work to get the calipers equal and cable roughly centered on the straddle. But never a chronic issue on a brake I am guessing cost considerably less than the Courier.

chain_whipped

Indeed the first version (early 1960's) had potential losing the arm return springs. That type had a small hole drilled into the pivot mount end to hold the end of the spring. If set with too much relaxed or weak tension, its possible to lose the spring. If you were lucky in not losing it, they could rust and seize in that small hole. Also, because of individual brake tension differential, that would cause a bit of a hassle in centering with 'centerpull'... (if that makes any sense).

Version two of the later 1960's is the one to have. No way could one lose that return spring. More comparable to Weinmann or Dia compe and with a looped end that hooks around the lower brake arms. Easy setup, too. Awesome vintage brake.

Believe there was a third version, however I've never had one. Not sure if it was based on the first or second type but it did have the GB logo cast into the sides of that main carrier.