unterhausen

anyone that has the capabilities to put the bosses on would have the capability to adapt canti bosses. Paragon Machine Works (among others) sells canti bosses that aren't mitered for the frame, so they could be put anywhere required. These look like they might work well, but you'd have to make a spring plate

WNG

For centerpulls, draw a line from the pivot bolt to the straddle cable's attachment point. When the pads touch the rims, the cable should be at right angle to the line from pivot bolt.

ftwelder

Well done.

Bianchigirll 

I do not have alot of experinece with them, but I think wether or not they are 'powerful' depends on what your want your brakes to do. do you want them to modulate your speed or make you stop on a dime from 30mph on a 10% down grade?

southpawboston

Well, closer to the latter. The modulation is great, but I can bottom out my rear brake lever pull and not get my rear wheel to skid. The fronts are better, but not great. I think I will have to examine the straddle cable geometry. Thanks, WNG!

WNG

IIRC, the MAFAC Racers I had could lock both wheels and nearly did a stoppy once. The levers were the half-hood model. Rims were squared profile Mavics.
When I replaced them with Superbe Pro sidepulls, I was expecting this significant improvement. I was disappointed that it didn't happen. Respect went to MAFAC centerpulls.

miamijim

tuz

I just did that modification (then found the thread). Machined the bushings on a lathe then pressed them in (see pic). Now I need to find very thin washers... probably from another Mafac.

Road Fan

How thin? I'd be surprised if you can't buy a thin spacer from McMaster-Carr. Won't be cheap, but ...

I have a small pile of Mafac calipers at home now. I'd really like to use them with nice new honed bushings.

rootboy 

[QUOTE=tuz;12524312]I just did that modification (then found the thread). Machined the bushings on a lathe then pressed them in (see pic). Now I need to find very thin washers... probably from another Mafac.

great job. What did you use for bushing material? thx.

Road Fan

This doesn't surprise me. Did you have the shoes at the top of the slots or the bottom, with the Mavics? Big difference in mechanical advantage ...

tuz

The washers are about 0.5-0.6 mm thick. McMaster Carr indeed has something like than in the "shims" section. Although the red ones are pretty neat.

I made the bushings out brass or bronze (it was in the scrap pile). I guess they need to be slightly OS or of equal size as the brake arm hole.

noglider 

Has anyone explained the rationale for doing this? I didn't notice, and I don't understand.

GrayJay

Contrary to some of the advise in this thread, for centerpulls, a shorter saddle cable will always result in more mechanical advantage at the caliper. Here is a link to a online brake geometry calculator where you can play with various saddle heights and see the effect on the mechanical advantage. (models both centerpulls and the various cantilever flavors).
https://www.circleacycles.com/cantilevers/

Downside of too much mechanical advantage is that you need to setup the pads very close to the rim so the brakes are more likely to rub sooner with a slightly bent rim. It can also be difficult to get a wide inflated tire past the pads for wheel removal.

Road Fan

You mean for replacing bushings? To eliminate a source of brake caliper play and roughness due to age and wear, with attendant flex and possible chatter when you apply the brakes. And to be able to do this even with the unavailability of Mafac replacement bushings.

More generally, to get more longevity out of good old parts.

miamijim

Why not use reguler cantilever bolt washers? If I remember correctly you can find thin washers at Ace hardware.

WNG

Yes, these ran closer to the top, thus the better power. I was running 27" wheels.

PDXaero

J'arriver
I installed the bronze bushings and mounted them with direct comparison to and original delrin bushed model.
I feel let down that I cannot compare it to a brand new delrin piece, but the change from old plastic to new bronze is very noticable when you are feeling the motion of the brake arms in your hand.
There is no more lateral motion or any wiggle in the brake arm. Still a nice smooth rotation about the center pivot, it was a little tight at first but worked in well and feels great.

i just need some new brake pads and I will throw these into use for a real application testing.

noglider 

I'm quite eager to hear how well they work.

southpawboston

Me too. I wonder if it will help in the modulation of the brakes.

grm1067

"Mcmaster has the bearing for $2.17 ea and the washer $0.40 in bronze, over 1$ in plastic."

I'm very interested in this replacement set of Mafac bushes.
What are the contact details for McMasters?
Have they got a web site?

grm

Grand Bois

Google McMaster-Carr.

grm1067

I've never seen such good replacements, so I'm going for them.
Many thanks, Grand Bois.

noglider 

Wow, now I'm going to spend DAYS reading the McMaster web site. I've never seen anything like it.

PDXaero

It is quite the resource, not great for bike specific parts but amazing little bips and bops.
If you need the line item number for the bearing let me know.
They come with some white surface lining on the inside and the only thing the box says it "follow manufacturers reccomended procedures" the manfacturer is german though so I just resorted to using an x-acto blade to scrape off the lining, otherwise it was too snug.
Also, mcmaster ships quick and pretty cheap ( you don't know the shpping price until you order) but if you buy 4 bushings they will come in a shoebox so combine your order, find some p-clamps and bolts or polishing equipment at the same time and make it worth the effort.

Update on my replacement brake application: awaiting decals for restoration.

Edit: McMaster-carr everything from set screws to train derailers.