Shimano Sora Brake in old Peugeot frame

[treeno]

Hi all,

My friend has an old Peugeot road bike and has recently acquired a new Shimano Sora front brake. She asked me to install it but I found that the bolt is not long enough to reach through the frame (new frames apparently have a recess to use a recessed nut with). This appears to be a common problem and the usual advice is to drill into the frame to make space. I haven't done this before and wouldn't feel confident doing so, however I was wondering if it would be possible to just get a longer bolt and fit it to the brake. I took the brake apart and the current bolt changes thread width part way along its length. It screws through the first section of the brake rather than just sliding through like a normal bolt. I haven't been able to find a longer bolt with the same thread width change, so I was wondering if I could just get an M6 bolt that was long enough (the thinnest part of the current bolt is M6) and use that instead. There doesn't seem to be any obvious reason why the bolt needs to change width, so as long as it is tightened up correctly would this do the trick?

Thanks

 

[alfeng]

FYI. While the thread on SOME (as in VERY FEW) central bolts of some Road brake calipers will have a continuous size throughout its length, most will NOT ...

AND, you will need either a bolt with a rather shallow head or need to file/grind it down so that it fits flush inside the assembly ...

Regardless, on most-if-not-all Shimano brake calipers, the NUT which keeps everything together is a different size than the one onto which the recessed nut is secured.

IMO, it is SO MUCH EASIER to simply drill out the backside of a front fork to accommodate the diameter of the recessed nut (~5/16" is the size which comes to mind ... ~8mm).

BTW. Are you certain that the REACH of the SORA brake caliper is long enough to use with your friend's Peugeot fork?

 

[treeno]

Thanks for the info. Is this a fairly easy task then? I have decent experience with a drill... Yes the reach is enough.

 

[alfeng]

Originally Posted by treeno

Thanks for the info. Is this a fairly easy task then? I have decent experience with a drill... Yes the reach is enough.

If you have a variable speed (hand) drill or access to a drill press (the latter will require removing the fork from the bike), then if you have the correct size drill bit (compare it to the barrel of the recessed nut before drilling), then figure that it takes between 5 seconds & 1 minute to enlarge the rear hole (total!) after you put the bit in the drill's chuck ...

Set the tip "against" the hole ...

Depending on how sharp-or-dull the bit is, slowly ramp up the speed as the bit actually engages the fork ...

The actual drilling will be done before you know it ...

Clean any burrs ...

DONE!

Although 'I' typically have enlarged the hole while the fork was not attached to the bike, THAT was only a matter of happenstance because I have probably been concurrently re-packing the headset bearings AND you can certainly enlarge the backside of the brake mounting hole while the fork is attached to the bike.

 

[90535i]

I just finished a full rebuild/restoration of my 1984 Peugeot PGN-10. I dealt with the same brake issue but refused to do any destructive construction. I found Tektro R-539 brakes can be found in the nutted version, not needing the recessed nut you described. If you have 700 wheels the pad adjustment should center in the caliper arms. These brakes are excellent, true to original design form, with dual pivots for greater pad pressure. If you have question, send a line.