PDXaero

CAN IT BE DONE



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.

miamijim

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.

ftwelder

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.

Bianchigirll 

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

triplebutted

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

noglider 

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!

Henry III

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?

treebound 

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.

southpawboston

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?

unterhausen

I thought that racers had a plastic bushing?

southpawboston

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.

unterhausen

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.

PDXaero

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.

unterhausen

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.

bobbycorno

??? 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

southpawboston

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.

jimmuller 

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.

noglider 

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.

southpawboston

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:

BluesDaddy

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

PDXaero

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.


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


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.

southpawboston

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?

PDXaero

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:

noglider 

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.

ftwelder

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.