Centerpull toe in washer
 

Hiya folks,
I'll be setting up some Mafac Racer centre pulls at some point, so I've been researching how to set the toe in.
Apparently strong arming the calipers is an option, I've done that successfully on Weinman side pulls.

But I've discovered that Rene Hearse already solved this problem: https://www.renehersecycles.com/a-be...adjust-toe-in/
Basically they've modified the mounting washer in the "eye-bolt assembly" (456E below) to give a 2.5 degree toe in.They did this for their Compass brakes but also sold the washers for use in Mafacs via CompassCycles.
Unfortunately Compass Cycles doesn't seem to exist any more.


https://cimg0.ibsrv.net/gimg/bikefor...ab1ceac892.jpg

So my question is: has anybody tried these washers, or found some for sale, or maybe made their own.
It seems to me I could take a file to some original Mafac Racer washers, or something similar.

Compass Cycles is Rene Herse, same parts, same products, just different name

you can buy these washers, or make your own using a rat-tail file and Mafac parts. All you need to do is bevel the washer.

While you're at it, be sure to get the RH (compass) brass bushing kit for the brakes. it is a super upgrade and will give you much more positive braking "feel"

/markp

https://cimg1.ibsrv.net/gimg/bikefor...196f92e701.jpg

Here's the current link for the part: https://www.renehersecycles.com/shop...e-washer-pair/

Doh, I should have been able to find that.
I was fooled by the broken link in the Rene Herse page.

Toe-in washers (pair) $9.00 https://www.renehersecycles.com/shop...e-washer-pair/
Toe-in washers kit $19.00 https://www.renehersecycles.com/shop...hers-and-nuts/
Brass bushings $24.00 https://www.renehersecycles.com/shop...erpull-brakes/

Shipping for 2 washers $18.90 :(
Don't seem to be available in the UK via Ebay etc.

I may have to try making my own.

Just measured those Mafac washers:

OD 16mm
ID 11.7mm
max thickness 3.23mm
min thickness 2.96mm

So to get 2.5 degrees one side needs to be reduced by 0.699mm (2.96 one side, 2.26 the other).

Smaller toe-in might also work
Measured Mafac 4dot brake pads as 46.23mm long.

1 degree, washer diff 0.279, brake pad diff 0.81
1.5 degree, washer diff 0.419, brake pad diff 1.21
2 degree, washer diff 0.559, brake pad diff 1.62
2.5 degree, washer diff 0.699, brake pad diff 2.02

Measured credit card as 0.81mm thick.

So for front of brake pad 0.81mm closer to rim than back of brake pad 1 degree toe-in works

Mafacs don't bend as easily as Weinmanns. They break. Get a rat tail file for 9 bucks.

Yep, the geometry is different so it looked quite dodgy trying to bend Mafac.
The Washer Kit from RH includes 2 washers without toe-in so if I screw it up I can just order from RH.
I've also got plenty of files so it's basically free.

don't forget those brass bushings.

they are the shiznit.

Most "competitions" had brass bushings but the Racers had those red plastic things which are now close to 50 years old ?

/markp

Yep, I'd heard of the brass bushings.
The Racers I've just got look fairly unused though (they're 1977 so very late) - the red plastic is unworn - so I'll give them a try before trying brass.

I have RAIDs on my Monti Special (with brazed on posts and bras/bronze bushings). Very nice.

I got some old Dural Forge Racers from a friend for my Automoto. They have bronze bushings as well, so my thinking is MAFAC started with them, but then cheaped out somewhere (bikes boom?) and switched to plastic.

yes I agree, cost reduction. The plastic deteriorates over time and by now these brakes are 40-50 years old

the improvement in braking feel that the brass bushings provide is significant ! they are well worth the trouble.

But what do I know ?

/markp

My experience with toe-in tells me not to buy (waste money on) those washers.

Over time, pads wear-in and lose their toed-in shape.

Toe-in has to be periodically restored by re-shaping the pad, removing a tiny bit of material from the rear of the pad to allow the front to touch down first on the rim.

Anyone considering brass bushing upgrades should be aware that tolerances were loose on the Mafac arms, and pressing in the bushings often compresses them enough that they need to be reamed to fit properly on the posts. Not too hard to do, but the reamer costs more than the bushings do, so if this is the only set of brakes you're ever going to ream, this becomes a more expensive upgrade.

The first set I upgraded wouldn't go on the posts without a ream. I bought a fixed-size 8 mm reamer and found it took off more than I like; the brakes worked fine but I would prefer less slop. So I boutght a small adjustable reamer. A fixed reamer a couple thousandths smaller would have done the trick also, but considering the posts vary in size also, I like being able to custom-ream each brake to fit the post it is going on.

I guess you could also ream the brake before pressing in the bushing, to prevent this compression, but what with the tolerance stack, I think reaming the brass after pressing it in is better.

Mark you are talking about the fit of the bushing into the arm?

I think I pressed the bushing in using a C-clamp and then the installation tool

The only problem I had was the bushing once pressed into the arm would not go on the post

so I just used some 320 emery paper to "polish" the post

Spence in fact did polish all mafac brake posts because that made them operate smoothly.

it's worth the trouble even if you have to do some amateur gunsmithing to get it to work well.

/markp
https://cimg3.ibsrv.net/gimg/bikefor...5cd728697d.jpg

Yes, either reducing the post OD or increasing the bushing ID will work. I like the latter because it's a tad more conservative, "non-destructive" in a way. Also the arms, after being reamed to spec, can be moved to another bike with braze-ons that might be to spec, or to another etrier, and/or this etrier used with other arms later, that might be to spec. Either of those is an unlikely scenario I guess, but I'm a fan of interchangeable parts. A preference, but not one to get too worked up over, I admit. Plus I already mentioned using an adjustable reamer to 'tune' the bushing to fit the post it's going on, proof that I don't follow my own advice all the time. Interchangeable is over-rated!

But also for slightly better precision in some cases. On the first ones I had to ream, they needed enough removed that taking the posts down that much would be beyond what I'd call "polishing". Sorry I don't remember the number, but it would have been a lot to do with an inherently imprecise method like hand-sanding. Plus, once you own the reamer, it's faster and easier to ream than to hand-fit by sanding. And I like owning tools, to a fault I know. I have so many tools I'll use once or twice if I'm lucky.

Bottom line, use a reamer if you're a tool fetishist like me or want the very best possible precision fit. But if not,sanding the posts is fine, as Mark P's experience shows. Don't let perfect be the enemy of good.

Mark B

I've now got some Kool Stop replacement pads and fitted them.

Turns out somebody had already bent the caliper arms to give about 2mm toe-in - ie quite a lot.
Rotated the pad holders round to even out the toe-in and went for a short ride - no squeal.
I'm thinking that probably means they''re ok, in my (limited) experience wear usually reduces squeal.

Something slightly interesting was the labelling on the Kool Stop pads:

https://cimg8.ibsrv.net/gimg/bikefor...b21383eeab.jpg
https://cimg9.ibsrv.net/gimg/bikefor...d47b0b9e9c.jpg

I'm guessing most of us think Kool Stop probably known what they're talking about :)
They say 1mm toe-in, which is 1.24 degrees.

I have always set the Mafacs up with about the same toe in that Rene Herse recommends and machines their washers for….a little over 2 mm. I think the Koolstop recommendation of 1 mm maybe fine in some cases, but some rims, especially newer ones with a shiny anodized brake track, might cause some squeal with that small of a toe in figure.

CLB washers have a set of slots that allow angle adjustment; plus they are thicker; filing the Mafac ones may be problematic - I have several such washers that have broken at the points where the stud pinched them.

I wish it was common knowledge that you could just file the washers back when Mafacs were coming on new bikes. I don't think I have ever seen a filed set that I didn't file myself.

I found the proper size brass tube for the round part of the bushing. I haven't gotten around to making any yet though.

I was checking my list of parts I could buy and did a search for Mafac Racer brass bushings.
Found nothing except the Rene Herse offering https://www.renehersecycles.com/shop...erpull-brakes/
Which is out of stock, however it does give the specifications:So I had a look on Amazon and found this: https://www.amazon.co.uk/sourcing-ma...FJ5/ref=sr_1_7Seems to be quite a lot of entries under "sleeve bearings"For £5.49 it could well be worth a try :)

I tried.

Don't bother.

https://www.bikeforums.net/22805585-post5.html

If your not picky about vintage correct you could just buy a set of kool stop eagle claw post pads which have a slight toe-in set for center pull, cantilever brakes work great pretty easy.
https://www.google.com/search?client...top+eagle+claw

Cheers, I should have guessed somebody would have tried them :)

Something to research during the long winter months probably, since Rene Herse is still out of stock.

All of the bits with grooves to effect toe-in have an engineering flaw.

They depend on a sloppy fit somewhere; tightening the fixing nut either cants the eyebolt in the slot, or the eye holds the post on one end.

If you want toe-in, angle the pads.

That engineering flaw doesn't prevent the brakes from working perfectly though. I can live with flaws like that.

To whoever said bending a Mafac will break it: I worked in a very large high volume shop all through the early '70s and I can't imagine how many Mafac arms we bent to toe them in. It's like a 5 second job and pretty effective. You don't even take the pad holder out. No other method comes close, for speed efficiency.

Of those hundreds (thousands?) of Mafacs we bent, number that broke = zero... that I know of. Someone's brake could have broken later, and they for some reason chose not to tell us. Seems unlikely though.

Even more severe bends from crashing, we'd just bend it back.

If anyone has evidence of a Mafac that broke after being bent, like preferably photos, please do speak up.

Note I'm not saying bending the arms is the best way, just saying it's the fastest.

I like an angled alloy ring, not with a groove filed in it with a rat-tail file, I mean the whole top face ground to an angle like a wedge. Then you can rotate the ring to get a range of toe-in angles, from zero when the wedge is clocked at 12 or 6 o'clock, to a maximum with it clocked at 3 or 9 o'clock. When you tighten it, the post makes an indent in the ring, so it doesn't slip or rotate in use, but it means it isn't infinitely adjustable in practice, you have to move it far enough that it's not falling into the existing indent. One downside is the wedge angle is slight, can be hard to see. The next mechanic who works on the brake probably won't notice it. Not a problem for me since no one else touches my brakes.

Anyway, lots of ways to pet a cat. Each cat can have his favorite way, doesn't make the other ways wrong.

Mark B