Classic & Vintage - Mafac racer bushing upgrade

CAN IT BE DONE

http://i52.tinypic.com/egttw4.jpg

Apparently the bronze sleeve bearing is supposed to be 10mmOD 8mmID and 9.8mm length
the plastic thrust washer is supposed to be 15mmOD 8mmID and 1/16in thick

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

A. Should I go for it?
B. Is it worth it or only appreciable to the snooty retrogrouch?
C. Plastic or Bronze on the thrust washer?

And before you tell me to spend $12 on better brakes.... NO.:twitchy:

Its only money....go for it.

I have 4 sets of titanium crank bolts and titanium Campy threaded axles sitting in a box.....it was only money.

I would just make sure it's not the bore that is worn. I say go for it. If the parts don't work, send them to me. I have a huge stash of odd bearings/bushings.

I say try it and while your at it order me a set too.

Put it all in a bag and remarket it on ebay for $40 bucks a set.

Put it all in a bag and remarket it on ebay for $40 bucks a set.

Now that's clever!

I'm curious to hear how they work in your brakes. I'm glad we have so many Mafac fans here!

I just pulled the pair that I had apart that looked like they were on Davy Jones' bike(no not the Monkees' Davy Jones either). Got some aluminum polish and steel wood and went to town. Then just lightly sanded and greased the studs and bushings and they were smooth as butter. What about trying delrin instead of brass bushings?

Do the Racers have the same dimensions as the Competitions?

Bookmarking this thread in case I have a need when I get to that point.

I just pulled the pair that I had apart that looked like they were on Davy Jones' bike(no not the Monkees' Davy Jones either). Got some aluminum polish and steel wood and went to town. Then just lightly sanded and greased the studs and bushings and they were smooth as butter. What about trying delrin instead of brass bushings?

Yeah, I rebuilt mine pretty much the same way-- polished up the aluminum parts and studs, degreased the plastic bushings, applied fresh grease, and they're smooth as anything... but honestly, they're not very powerful centerpulls to begin with... what's all the hubbub about them?

I thought that racers had a plastic bushing?

I thought that racers had a plastic bushing?

Correct. I was under the assumption the OP wanted to "upgrade" to brass. But I guess now that you mention it, a bushing of 2mm thick brass won't fit.

the bronze bushings are not a bad idea. I think I might go for a flanged bearing. 5448T3 has a 16mm flange, although the outside of the bushing area is 12mm. You could cut that down on a lathe or ream the arms.

Some racers had bronze bushings. There are a lot of racers out there in a lot of iterations.
To clarify, the brakes I have are the red plastic sleeve.
I pulled them and cleaned them but just got to thinking about how much of a difference bronze would make. Target bike is a 69 PX10 and that predates the mafac competition brakes, but still, Racers were some of the best brakes anywhere in the 60s.
Also brazed pivots (a la PY10) are not out of the question but I can't find them for the life of me.

I never saw a Peugeot with brazed pivots before. There was a framebuilder making them a while back, I don't think he has them any more. I am part way through making some, but I'm a little conflicted about permanently sticking racers on a frame; they are unique and you are stuck with them once you put the bosses on.

The ones on the PY10 pictures I saw look very much like Mafac cantilever bosses. The issue with using cantilever bosses is that they are longer, but it seems like they could be modified.

... but honestly, they're not very powerful centerpulls to begin with... what's all the hubbub about them?

??? IME, MAFACs are the most powerful centerpulls out there, smooth and great modulation to boot. Is your straddle cable too long maybe? Then again, maybe they are junk. Send 'em to me and I'll dispose of them for you.

SP
Bend, OR

??? IME, MAFACs are the most powerful centerpulls out there, smooth and great modulation to boot. Is your straddle cable too long maybe? Then again, maybe they are junk. Send 'em to me and I'll dispose of them for you.

SP
Bend, OR

Ha! You know, maybe I have them set up totally wrong. Also, maybe the problem is with the brake levers (Tektro inverted). Lastly, maybe the problem is with the pads (VO salmon). They just feel very mushy, and don't have the best stopping power. They're also prone to squealing. I can try shortening the straddle wire to decrease the mechanical advantage.

I've posted this before but I'll say it again. The MAFACs on my UO8 will stop a freight train. They are better than the Weinmanns on my Raleigh. But then, I don't usually go as fast as a freight train.

If they're mushy, the straddle cable is likely to be too short, from too much leverage. If they're stiff but don't stop, the straddle cable is too long.

Set them up right and you'll love them. It takes time and patience, but they're easier than cantilevers to set up.

If they're mushy, the straddle cable is likely to be too short, from too much leverage. If they're stiff but don't stop, the straddle cable is too long.

Set them up right and you'll love them. It takes time and patience, but they're easier than cantilevers to set up.

Funny, because I've never had problems getting cantis "just right".

Really? too short? I thought it's when the straddle cable is too long (yoke is high) that you get mushiness, and when the cable is too short (yoke is low) they feel stiff. Do I have it backwards? Mine are definitely mushy, like something is flexing a lot.

Here are pics, tell me if you think they're too long/short:

http://farm5.static.flickr.com/4021/4636662969_0848d8e25a_z.jpg

http://farm5.static.flickr.com/4046/4637311518_138959bcdb_z.jpg

I always imagined an equilateral triangle formed by the straddle cable and the anchor points was the ideal.

The ones on the PY10 pictures I saw look very much like Mafac cantilever bosses. The issue with using cantilever bosses is that they are longer, but it seems like they could be modified.

unfortunatly not. Here in the right frame is the Racer hanger on a fork to give you appropriate location and the MAFAC canti bosses, they are made to sit out side of the fork blade to give a better angle for the canti brake.
In the left frame you can see the actual centerpull bosses, almost straight bosses for the front and slightly inside for the rear, also as you mentioned, shorter.
http://i52.tinypic.com/2u53tki.jpg


Correct. I was under the assumption the OP wanted to "upgrade" to brass. But I guess now that you mention it, a bushing of 2mm thick brass won't fit.

But it will!
the plastic (delrin) bushings are the same size as the bornze bushings that were in some models.
http://i54.tinypic.com/2iv1q4z.jpg


the bronze bushings are not a bad idea. I think I might go for a flanged bearing. 5448T3 has a 16mm flange, although the outside of the bushing area is 12mm. You could cut that down on a lathe or ream the arms.

Too much machining for me. I no longer have a lathe other wise I would try to make the CP boss braze-ons.
The flanged bushing you mention would require me to thin the OD, flange thickness, and flange width.
The ones I have found thus far would only require me to overbore the ID of the thrust bearing, easy enough to do with a drill press.

I really need to get some parts shipped out today but assuming I order parts this week I will buy two full sets, firstly in case of some failure of adaptation, but also, if it works I will send the second set to another member (bianchiGirl already voiced interest) for an impartial review.
Hopefully its not just hype. There has to be some reason that bronze bushings were installed on nicer models.

But it will!
the plastic (delrin) bushings are the same size as the bornze bushings that were in some models.


I stand corrected! It does look like it would work.

But is the canti stud that you have propped on the fork leg inverted 180 degrees? The spring retainer hole should be facing in. Would flipping it change the position of the post?

I stand corrected! It does look like it would work.

But is the canti stud that you have propped on the fork leg inverted 180 degrees? The spring retainer hole should be facing in. Would flipping it change the position of the post?
It is flipped around, that was my trying to position it as closely to the racer pivot as I could by mounting it backwards.
Not mounted, just balanced with the use of one of the rear pivots underneath... :sneaky:

I'm not sure what's ideal. I could be wrong but I'm pretty sure longer decreases leverage. When I shortened mine. I got more stopping power.

If the straddle wire is too short, the caliper arm will flex first. If the straddle wire is too long, the brake wire will flex first. You are correct Tom.

Another thing to consider is the amount of cable movement for blade movement. If it pulls less wire, it pulls with greater force.

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 (http://www.paragonmachineworks.com/storename/paragonmachineworks/dept/261299/ItemDetail-10685054.aspx) look like they might work well, but you'd have to make a spring plate

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.

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.

Well done.

... but honestly, they're not very powerful centerpulls to begin with... what's all the hubbub about them?


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?

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?

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!

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.

I never saw a Peugeot with brazed pivots before. There was a framebuilder making them a while back, I don't think he has them any more. I am part way through making some, but I'm a little conflicted about permanently sticking racers on a frame; they are unique and you are stuck with them once you put the bosses on.

The ones on the PY10 pictures I saw look very much like Mafac cantilever bosses. The issue with using cantilever bosses is that they are longer, but it seems like they could be modified.



http://i495.photobucket.com/albums/rr314/jimr2527/bf%20stuff/8fd2_1_sbl.jpg

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.

198425

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.

[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.

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.

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 ...

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.

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

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).
http://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.

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

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.

Now I need to find very thin washers... probably from another Mafac

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

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 ...

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

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.
https://lh6.googleusercontent.com/_eyxn8SPSTwU/TbdeA6N325I/AAAAAAAAAfY/qGihayRfV2U/s640/IMG_20110426_150344.jpg
i just need some new brake pads and I will throw these into use for a real application testing.

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

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

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

"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

"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

Google McMaster-Carr.

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

Wow, now I'm going to spend DAYS reading the McMaster web site (http://www.mcmaster.com/). I've never seen anything like it.

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.