Retro Grouch 

I'm in the process of converting a bike from Magura rim brakes to linear pulls. My question has to do with the hole for the return spring. My fork doesn't have any.
Instead it has a pair of 20 mm diameter, 5 mm thick (aluminum?) washers that are secured with set screws. The 2 mm return spring hole would have to be drilled 2.5 mm from the edge of the washer. I think that would be beyond my expertise. My low tech solution is to saw a kerf on one edge of the washer to retain the return spring nub.

My machinist son says "Bad idea." He's afraid the saw kerf might break out and I'd find myself coasting downhill on a rocky trail someday with no brakes. I'm thinking all the return spring nub does is to push the brake arm back when you release the brake. There is so little force involved it would be unlikely to break out and, even if it did, all that would happen is the brake would rub.

My son said he would machine me a proper pair of replacements but his time frame for doing (free) jobs like can be a LOT different than mine.

Are proper replacement parts get-able? If not, is my plan likely to cause me bodily harm?

HillRider

How deep would the kerf have to be and how close to the center hole of the washer would it come? Based on the diameter of those washers (20 mm you said) I think there will be plenty of metal to support that thin notch. I agree with your analysis that the return spring just retracts the shoes and its loss won't cause brake failure, just a bit of drag.

fietsbob

Build a drum brake hub wheel and the bosses can be ignored.

Best solution since, minus pictures, I cannot see a Damn thing , and I have 1 bike with HS33 brakes .

and another with S-A Drum brakes.


add , I could change the HS33 for disc brakes , frame and forks have the mounts,

but they work so well There would be little gain..
My BiFri came with discs and It is another use it as Is.. N+1

drum brakes are on my iced up roads snow -studded tire bike.. at the ready for 20 years .

I vote to just leave the Magura's on they dont need a spring anchor at all .

Though .. Pauls V brakes dont use the frame boss holes either

..https://www.paulcomp.com/motolite.html| https://www.paulcomp.com/motobmx.html

Hopslam

Once again I learn something here about something I have & have thought of changeing . I too have the hyd.Magura rim brakes on one of my tandems . Question did your brakes cause you grief? Mine have been flawless for 8 yrs now , no adjustments what so ever. They have a large distance of travel
I can't bring myself to change them,if a ain't broke
& you guys cost me money as I just ordered a FD 443 for my flat bar

Thanks & Cheers

Retro Grouch 

When I took the Maguras off of the mountain bike with the intention of installing them on another frame I discovered a broken casting. I've been using Avid single Digit 7's on some other bikes and liked them so I decided to use them on this rebuild too.

fietsbob

Quote:

When I took the Maguras off of the mountain bike with the intention of installing them on another frame I discovered a >broken casting<. I've been using Avid single Digit 7's on some other bikes and liked them so I decided to use them on this rebuild too.

Which Parts?
Magura USA ships spare parts (they're Much better at it than Shimano) out of Olney Ill..

OK but it reads like the frame boss lacks the spring anchor hole..
Want to have new Bosses installed by a framebuilder?

{of course, as usual, Im running off blind guesses without seeing the job, in person )