Mafac Racer questions!!

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Tom Norton

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Nov 23, 2019, 8:38:05 PM11/23/19
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This is a "late in the game" thing..
I am going to take frame building course with Doug Fattic and will be building a Randoneur style frame and fork. I had been planning to use my Paul Touring Cantilever brakes on this build. But...
Now I am really contemplating braze-on center pulls. But I have a fe questions.
Are there more than 1 size when it comes to reach?
I plan to use VO 52mm wide fenders. Will they work in this application?
I see them on eBay and the "conversion kit" is available through René Herse. But not sure which braze-ons to get.
Any help would be great!!
Thanks!
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Etan Heller

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Nov 23, 2019, 9:00:43 PM11/23/19
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Hi Tom. Good timing as I just started a database for braze-on brake measurements to help out tasks just like yours:
https://docs.google.com/spreadsheets/d/1ze6QFPgZFbBQmgM8ATWDE5JStRur-Q3-Mmr4hMtclRg/edit#gid=812153980

See the "Direct mount centerpull" sheet in the link above for measurements and specifications for MAFAC centerpulls. The information that's in there, although incomplete, is directly from MAFAC catalogues.

MAFAC made two versions of the Racer brake reach-wise: short reach and long reach. Measured from the central mounting bolt to the minimum and maximum points of the brake post mounting slot, the two versions have the following specs:

Short reach:
Min: 48.5mm
Max: 63mm

Long reach:
Min: 53.5m
Max: 68mm

I don't yet have the reach measurements from the brake pivot points, which is more relevant to you than from the central mounting bolt (which you won't be using). If someone with a Racer brake in hand can measure and add to my spreadsheet that would be appreciated :D

Measuring the brake in hand, you will see that the pivots on a Racer are 62mm apart. In the MAFAC catalog, MAFAC recommends for builders that the mounting bosses be placed with 60mm-64mm apart when using the Racer as a braze-on brake. I would shoot for placing the bosses 62mm apart on the nose (CTC).

Regarding hardware and bosses, centerpull braze-on bosses are different from cantilever bosses. Cantilever bosses are 8mm in diameter, with a 16.5mm length and use an M6 bolt. Various centerpulls will need different bosses depending on the internal diameter of the pivots. MAFAC centerpull braze-ons are also 8mm in diameter and use an M6 bolt, but are 10mm long instead of 16.5mm. You can cut down a canti boss, or find a genuine MAFAC centerpull boss online. The stock springs on the Racer should work for a braze-on setup. Just make sure you have a spring stop installed on your bosses for it.

Chris Cullum

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Nov 23, 2019, 9:04:51 PM11/23/19
to Etan Heller, 650b
On Sat, Nov 23, 2019, 17:52 Etan Heller, <helle...@gmail.com> wrote:
Hi Tom. Good timing as I just started a database for braze-on brake measurements to help out tasks just like yours:

https://docs.google.com/spreadsheets/d/1ze6QFPgZFbBQmgM8ATWDE5JStRur-Q3-Mmr4hMtclRg/edit#gid=812153980

See the "Direct mount centerpull" sheet in the link above for measurements and specifications for MAFAC centerpulls. The information that's in there, although incomplete, is directly from MAFAC catalogues.

MAFAC made two versions of the Racer brake reach-wise: short reach and long reach. Measured from the pivots to the minimum and maximum points of the brake post mounting slot, the two versions have the following specs:


Short reach:
Min: 48.5mm
Max: 63mm

Long reach:
Min: 53.5m
Max: 68mm

This is true but I'm pretty sure the arms are exactly the same forging. The reach is just varried by the placement of the centre mount posts. So if you are mounting them on braze on posts this is irrelevant. It will be determined by the placement of the posts (within the range of adjustability).

 

Measuring the brake in hand, you will see that the pivots on a Racer are 62mm apart. In the MAFAC catalog, MAFAC recommends for builders that the mounting bosses be placed with 60mm-64mm apart when using the Racer as a braze-on brake. I would shoot for placing the bosses 62mm apart on the nose (CTC).

Regarding hardware and bosses, centerpull braze-on bosses are different from cantilever bosses. Cantilever bosses are 8mm in diameter, with a 16.5mm length. Various centerpulls will need different bosses depending on the internal diameter of the pivots. You might be able to find MAFAC-made centerpull bosses on ebay. Try ebay France as well. Dia Compe also makes centerpull bosses for their brakes - I'm not sure if they fit MAFACs but it's worth looking into.

Rene Herse sells the braze on posts in their framebuilding section of the website. I think there is more information and specs there too.

What width of tires are you using? The Racer is OK for up to about 38mm but wider like 42mm you should go to the Raid, especially if you're planning on fenders.


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Etan Heller

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Nov 23, 2019, 9:09:35 PM11/23/19
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A couple of additional points:

-Dia Compe makes centerpull bosses, as well as spring+stop kits for converting their centerpull brakes from central mounting to braze-on. If finding a Racer and making/finding MAFAC centerpull bosses is annoying, consider just buying one of the various Dia Compe centerpulls, bosses, and springs/stops all at once. They have a variety of very nice centerpulls, some forged and some CNC-machined.

-Paul also makes two varieties of centerpull, the Racer, and the Racer Medium (less reach and less tire clearance). You can buy these as braze-on ready straight from Paul. They use standard cantilever bosses, instead of special centerpull bosses, which makes things slightly easier.

-Ditto the above for Rene Herse. You can get their centerpulls braze-on ready, along with all necessary hardware and bosses, straight from the source.

-Check out this old blog post. It has some useful info from a guy who got a bike from Waterford with braze-on post and did some research into it. https://ruedatropical.wordpress.com/2009/01/07/mafac-brake-bosses-v-canti-bosses/

Tom Norton

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Nov 23, 2019, 9:10:24 PM11/23/19
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Etan,
You dá man!!!
I have some messages out to eBay seller's right now. And I appreciate what you have told me!!
Because I was planning to use Paul Touring Cantilever I bought SS cantilever posts with the 3 hole plate. So it sounds like I can cut these down.
Tomorrow I will check the dimensions and compare it to my current bike,Soma Grand Randoneur, which will be similar to the build.

Etan Heller

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Nov 23, 2019, 9:13:29 PM11/23/19
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Good point about tire clearance with the Racer, Chris C. I deleted my initial post which you quoted in order to correct some mistakes: I mistakenly said those reach specs above were from the pivots, instead of the central mounting bolt, like you pointed out. I also added more detail about centerpull bosses in my replacement post. Thanks for the corrections.

Brad

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Nov 24, 2019, 7:33:46 PM11/24/19
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I believe spring placement may be different between Mafac Racers and Weinmann/ Dia Compe.   My understanding is that the Paul's use the same boss as canti brakes.
Additionally, I have read about people desoldering the posts from a Mafac Racer back plate and then brazing those same posts to the frame.  I think they had to fabricate the piece that the spring connects to.

Chris Cullum

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Nov 24, 2019, 8:07:03 PM11/24/19
to Bradford, 650b


On Sun, Nov 24, 2019, 16:33 Brad, <riendeau...@gmail.com> wrote:
I believe spring placement may be different between Mafac Racers and Weinmann/ Dia Compe.   My understanding is that the Paul's use the same boss as canti brakes.
Additionally, I have read about people desoldering the posts from a Mafac Racer back plate and then brazing those same posts to the frame. 

Those posts aren't soldered in place. They are steel that's press fit into the aluminum centre mount piece. You'd have to cut them out somehow. And you would need to fabricated the spring holder because the hole is in the aluminum part.

It seems like a lot of work when you can just buy these:


I think they had to fabricate the piece that the spring connects to.

On Saturday, November 23, 2019 at 9:13:29 PM UTC-5, Etan Heller wrote:
Good point about tire clearance with the Racer, Chris C. I deleted my initial post which you quoted in order to correct some mistakes: I mistakenly said those reach specs above were from the pivots, instead of the central mounting bolt, like you pointed out. I also added more detail about centerpull bosses in my replacement post. Thanks for the corrections.

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David Parsons

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Nov 24, 2019, 8:35:10 PM11/24/19
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On Sunday, November 24, 2019 at 5:07:03 PM UTC-8, Chris Cullum wrote:
Those posts aren't soldered in place. They are steel that's press fit into the aluminum centre mount piece. You'd have to cut them out somehow. And you would need to fabricated the spring holder because the hole is in the aluminum part.

If they are press fit, you can push them out with a drift  (on the Racer's I've got they are riveted into place;  I use my drill press and a suitably-sized drill bit to cut off the flared off ends, then just push the posts out.    When I braze them onto a fork or frame I'll shape a section of steel plate to set them in & while I'm shaping it I also drill a spring retaining hole;  this could also be done with a press-fit post, of course!)

-david parsons

Tom Norton

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Nov 24, 2019, 8:42:19 PM11/24/19
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Well after doing more and more reading and research it app that Racers will not fit with the fenders and tire size I want to go with. So I am going to go with the Paul Touring Cantilever brakes.
I would need the Reid? model which time does not permit finding. Or the René Herse ones who I really don't want to go to that expense.

Chris Cullum

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Nov 24, 2019, 8:54:48 PM11/24/19
to David Parsons, 650b


On Sun, Nov 24, 2019, 17:35 David Parsons, <grr.g...@gmail.com> wrote:


On Sunday, November 24, 2019 at 5:07:03 PM UTC-8, Chris Cullum wrote:
Those posts aren't soldered in place. They are steel that's press fit into the aluminum centre mount piece. You'd have to cut them out somehow. And you would need to fabricated the spring holder because the hole is in the aluminum part.

If they are press fit, you can push them out with a drift  (on the Racer's I've got they are riveted into place;  I use my drill press and a suitably-sized drill bit to cut off the flared off ends, then just push the posts out.  

Yes more correctly riveted than pressfit.

  When I braze them onto a fork or frame I'll shape a section of steel plate to set them in & while I'm shaping it I also drill a spring retaining hole;  this could also be done with a press-fit post, of course!)

It's a bit of work for something that's available a ready made part fairly cheaply. I applaud your industriousness. My first randonneur frame used cut down canti posts and it worked ok. They lack the step of the Mafac style post where the coil spring sits which slightly suboptimal. They were also still a tiny bit long which created a bit of slop. I filed them down just enough to slide a thin brass washer over the post between the arm and the bolt head. That worked out pretty well.


-david parsons

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Chris Cullum

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Nov 24, 2019, 8:56:04 PM11/24/19
to Tom Norton, 650b


On Sun, Nov 24, 2019, 17:42 Tom Norton, <tnort...@gmail.com> wrote:
Well after doing more and more reading and research it app that Racers will not fit with the fenders and tire size I want to go with. So I am going to go with the Paul Touring Cantilever brakes.

Paul Touring brakes are really nice!

I would need the Reid? model which time does not permit finding. Or the René Herse ones who I really don't want to go to that expense.

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Mark Bulgier

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Nov 24, 2019, 9:58:01 PM11/24/19
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Chris Cullum wrote:
I wonder if Amir Avitzur still has any for sale?  He made his from very strong steel (not too strong though -- you can still miter them with files), and with superior precision and finish.  I don't think he is a member of this group, but he's active on CR.  I can ask him if you're interested.

After a little more research it looks like that was over 10 years ago, so probably no more available from that channel.  Here's a pic though: https://www.flickr.com/photos/mafac_brakes/4102259031/
As you can see, the spring holder was aluminum, placed on the stud after the frame is painted, just held in place by the brake.  That seems fine to me.  Singer and Herse used to braze a tiny little tube to the top of the pivot post to hold the tail of the spring, but that seems super fiddly.  Nothing wrong with it, but Amir's version is easier.

Singer version:

Singer centerpull boss.jpg



Check out the rest of Amir's "mafac_brakes" Flickr is you have an hour or two to kill -- amazing amount of info there.  Watch him manufacture modern reproductions of MaxiCar hubs for example.

-Mark

 

David Parsons

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Nov 25, 2019, 12:32:05 AM11/25/19
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On Sunday, November 24, 2019 at 5:54:48 PM UTC-8, Chris Cullum wrote:
It's a bit of work for something that's available a ready made part fairly cheaply.

 It depends on what tools you've got floating around.  $17 + shipping from rent-a-herse isn't awful, but it's only about 30 minutes to drill out a bikes worth of posts, then cut, drill, and shape the steel spring retainers if you have the right collection of tools.  Not worth the effort if you have to go out and buy the tools, yes, but if you're a framebuilder you may already have them lying around (and if you're not Sasha White, eRichie, or a handful of other big-name & big-dollar builders, that's $17 that doesn't come out of your pocket) so why not?

-david parsons
 

Dave Cain

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Nov 25, 2019, 10:18:12 AM11/25/19
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A quick search on eBay turns up a few sets of Raids for under $100.
Tom Matchak built my wife's frame around a vintage set of Raids and they've been great. It's also handy that Herse has since come out with their reproductions in case we ever need to repair or replace.
Cheers,
Dave


www.waxwingbagco.com
www.dockittm.com

Hahn Rossman

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Nov 25, 2019, 11:24:37 AM11/25/19
to Dave Cain, 650b
Tom-
The rene herse bosses also come in a  premitered version to fit the kaisei (or reynolds) blades which you may be planning to use as well. I'm totally biased since I helped design these parts, but the reason they exist is because I got sick of messing around each time I built a bike. There is only so much time you can spend on it and I would rather use it to shape and thin lugs than to replicate an off the shelf part.
While we are on the subject of me saying "just buy the solution I already made for you" ...you should also get the chainstays I bend for Rene Herse which allow for 650x42 tires and 52mm fenders to work great with road cranks!
And I would also add this gauge to your order which helps check what you are doing along the way in the build:
Have fun at the class and post some pictures!
Hahn Rossman 

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Sean PNW

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Nov 25, 2019, 11:31:16 AM11/25/19
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Brian Chapman posted this video recently demonstrating how he makes the mounts used on his builds by mating modified canti bases to the posts removed from original Mafac backing plates.


It's pretty ingenious and elegant to my eye.

Thompson Custom Bicycles

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Nov 25, 2019, 11:35:33 AM11/25/19
to Hahn Rossman, 650b
I'll add my hearty endorsement to everything Hahn said- these items are major time savers and make life a lot easier!

-Corey Thompson
Thompson Custom Bicycles

Tom Norton

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Nov 25, 2019, 5:12:34 PM11/25/19
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Hahn,
I did buy the fork crown and blades from René Herse!!

Hahn Rossman

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Nov 25, 2019, 6:00:38 PM11/25/19
to Tom Norton, 650b
Tom-
I think you will be pleased! You can struggle a lot or just get "the Kit" essentially for the bikes that Corey and I make. There is still a lot of effort needed to get from the frame and fork with good clearances to the kind of bikes that people showed up with at the concours de machines this summer at PBP. It's a fun project and you have a good head start.
Hahn

On Mon, Nov 25, 2019 at 2:12 PM Tom Norton <tnort...@gmail.com> wrote:
Hahn,
I did buy the fork crown and blades from René Herse!!

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