putting longer bolt into caliper brakes

Discussion in 'Cycling Equipment' started by urge2kill, Feb 6, 2014.

  1. urge2kill

    urge2kill Member

    Joined:
    Aug 13, 2013
    Messages:
    448
    Likes Received:
    10
    The nut that screws onto the bolt wont fit through the fork's hole. It's not just excess coating on the hole, the nut is clearly too wide.

    The old caliper brakes had a long bolt that went through the whole fork. Could I put that bolt into the Shimano BR-5700 brakes?

    It's a chromoly fork.
     
    Tags:


  2. alfeng

    alfeng Well-Known Member

    Joined:
    Jul 23, 2005
    Messages:
    6,723
    Likes Received:
    126
    Probably NOT because I would guess that the bolt for your vintage brake caliper does NOT have a flat bolt head which would nest in the recess of the Shimano BR-5700 brake's yoke ...

    BUT, with a "chromoly fork" you simply need to enlarge the rear-facing hole with a 5/16" drill bit so that it can accept the brake caliper's recessed nut.
     
  3. urge2kill

    urge2kill Member

    Joined:
    Aug 13, 2013
    Messages:
    448
    Likes Received:
    10
    Thanks, I'll give it a shot. I hope the fork doesn't lose its integrity and ultimately collapse. It's a "Dure Forte custom tube set" fork.
     
  4. alfeng

    alfeng Well-Known Member

    Joined:
    Jul 23, 2005
    Messages:
    6,723
    Likes Received:
    126
    FWIW. IMO, you should not be overly concerned about enlarging the hole on the backside of the fork's SHOULDER by such a small amount ...

    Unless it is a "uni-crown" style fork, the fork's shoulder is typically cast & it is fairly robust OTHERWISE the fork's legs would have already collapsed ...

    YOU simply need the appropriate size drill bit + an electric drill (a variable speed drill is recommended ... do they even make drills which are not, now?) ... and, know how to use it ...

    The ONLY (?) caveat is that once the hole is drilled, you will (probably) always need to use a brake caliper designed to use a recessed nut OR ...

    1. alternatively (when using the "original" or a vintage brakeset), use a caliper with a shorter (rear) bolt + [SIZE=small]the recessed nut[/SIZE]
    2. OR, install a bushing/collar to re-fill the hole to the appropriate diameter & then use a standard nut(-and-washer)

    ... the threading for the nut is a standard metric size ... on some calipers, it is possible to replace the bolt with one which you may be able to buy at an auto supply store and subsequently file the head of the bolt so that the bolt's head will be flush inside the yoke (if one with the correct head type isn't available) ... I suppose you could try to do THAT with the bolt from your "original" front brake caliper ... BUT, on some other calipers (e.g., Shimano) there is some variability in the diameter of the unthreaded portion of the bolt and/or other threading in the assembly which may present a greater nuisance than simply enlarging the hole on the backside of the fork.

    FYI. Over the years, I have "updated" about a half dozen forks to accept a recessed brake nut ...

    • when I have updated a fork to accept a recessed brake nut, I happened to do it with the fork OFF the bike ...
    • I do NOT know if THAT is necessary ... but, it is probably a good idea,

    BTW. I have also enlarged the forward facing hole on the REAR brake bridge to accept a recessed brake nut. THAT can be a bit more difficult due to the space ... depending on the frame, EITHER a non-power tool OR a drill with a 90º chuck may be needed.
     
  5. urge2kill

    urge2kill Member

    Joined:
    Aug 13, 2013
    Messages:
    448
    Likes Received:
    10
    Actually, it is a uni-crown. The blades curve 90 degrees and weld to the steerer. There is no crown intermediary.


    [​IMG] I got a titanium 5/16" drill bit, but no drill or drill extension will ever get between the seat tube and stays with that bulky 5/16" bit on it. There is 3 inches or less of room.

    What are my options regarding non-power tools?

    I don't know what you just said, but I think I could drill from the other side of the seat stays, expanding both holes, then correct the near hole with that procedure!
     
  6. alfeng

    alfeng Well-Known Member

    Joined:
    Jul 23, 2005
    Messages:
    6,723
    Likes Received:
    126
    Not to worry ...

    While I think that the steerer on MOST uni-crown forks extends all way through the shoulders & thereby bolsters the shoulder/etc, even if it doesn't on your fork, if you look at it, the amount of steel that you see should be fairly substantial.

    • If in doubt, partially flatten a tin can & drill through it ...
    with one of the two holes large enough to accept the recessed nut ...
    • mount your brake caliper onto the tin can ...
    • you should see that even a comparatively flimsy tin can will present a formidable platform onto which you can mount your brake caliper.

    FWIW. Here is a fork whose brake hole I moved UP after removing the what 'I' deemed to be excess material on the underside of the shoulder ...
    [​IMG]

    The "normal" 39-49 calipers are too short, but the fork will accommodate a 700x32 tire, now ...

    [​IMG]

    Here is a long reach (49-59) caliper mounted to the rear after enlarging forward hole normally used to mount a fender or other accessory on a MTB frame (!?!) whose cantilever brake mounting bosses were removed from the seat stays ...

    [​IMG]
    Quote:
    [​IMG] I got a titanium 5/16" drill bit, but no drill or drill extension will ever get between the seat tube and stays with that bulky 5/16" bit on it. There is 3 inches or less of room.

    What are my options regarding non-power tools?




    You can fabricate the necessary "tool" by taking a FLAT BLADE, "stubby" screwdriver whose blade you will modify by grinding its taper down to a suitable width which varies between 1/4" (or, slightly under) to 5/16" (or, just over AS LONG AS YOU KNOW TO STOP & CHECK the hole BEFORE reaching the wide end of the taper!!!) ...

    The crisper the edges on the taper, the better it will "cut"/(ream) the hole as you slowly turn the DIY tool in the hole ...

    • MOST "flat" files are often fairly brittle, but if you have a set of CHEAPER files, then it may be soft enough to bend the TANG (the end which goes into the handle) 90º and thereby create a tool with more leverage ...

    Obviously, the wide end of the tang will need to be 5/16" of an inch, or more, to make this a viable option.

    An aluminum brake bridge will be COMPARATIVELY QUICK & EASY to enlarge ...

    A steel brake bridge will take more time & patience ... the quality of the edge on your DIY tool will dictate how quickly you can complete the task.

    Quote:

    I don't know what you just said, but I think I could drill from the other side of the seat stays, expanding both holes, then correct the near hole with that procedure!


    I have NOT tried this (however, I probably will the next time I want to enlarge the forward facing hole on a rear brake bridge to accept a recessed nut), yet ...

    BUT, if you want to enlarge the front facing hole on the rear brake bridge from the rear with the aid of a power drill, then you may want to use a smaller diameter bit (< 1/4"), wrap the shaft some tape where it would otherwise contact the hole, and then wallow out the forward facing hole ...

    Steel is actually incredibly soft, so CHECK OFTEN (!!!) so that you don't over enlarge the forward facing hole AND to ensure it is as close to ROUND as possible!

    If you STOP wallowing out the hole with the drill bit before you achieve the necessary 5/16" hole, then you can square & "clean up" the forward facing hole with the fore mentioned, modified stubby screwdriver.
     
  7. urge2kill

    urge2kill Member

    Joined:
    Aug 13, 2013
    Messages:
    448
    Likes Received:
    10
    I got some bushings with 6mm bore and 8mm outside diameter (OD). Is cast bronze okay?

    The 8mm OD is a perfect match for the recessed nuts that came with my Shimano BR-5700.

    The 6mm bore slides along the bolt easily. There is wiggle room, but very little. Maybe a 5.5mm bore could fit better, but a 5.0mm bore would be too narrow.
     
  8. CAMPYBOB

    CAMPYBOB Well-Known Member

    Joined:
    Sep 12, 2005
    Messages:
    11,945
    Likes Received:
    1,038
    Make a tool? Are you insane???[​IMG]

    Manly men know the correct tool already exists and more importantly BUY said tool to add to their manly tool collection.! Just kidding, Alf! I applaud all home shop toolmaking skills, whether it be from a sharpened/ground file, screwdriver of jack knife!

    What is needed to counterbore a limited clearance rear brake bridge in a tool known as a 'reverse counterbore' or a 'back counterbore'.

    These tools might be found at McMaster-Carr, MSC Supply, Reid Tool, Grainger or other quality tool supply or machine shop supply house.

    They may look something like the ones I'll link below and can be of a one-piece design or multi-piece, consisting of a cutter and an arbor. The tool would be inserted from the seat post side of the hole and then chucked into a drill motor and 'pulled' as it is spun...using a cutting oil, of course.

    http://www.mscdirect.com/browse/tn/Holemaking/Counterbores-Porting-Tools/Reverse-Counterbores-Spot-Facers/?008=-99&pcrid=37185984544&007=Search&006=37185984544&005=49010881984&004=11325471064&002=2167139&mkwid=s913bZiMp%7Cdc&cid=ppc-google-Product+-+Holemaking+RLSA_s913bZiMp_reverse+counterbore+tools_e_37185984544_c_S&026=-99&025=c&navid=12106110#navid=12106110+4288176765

    http://www.t-yamakatsu.co.jp/en/en-information/cutters/ei_zaguri.html

    There are many styles, types, cutter materials and applications of these cutters, but $25-$50 would probably be in the range of what a single 5/16" counterbore would run. Note: match your arbor size to your existing hole in your brake bridge or bush to it if necessary.
     
  9. urge2kill

    urge2kill Member

    Joined:
    Aug 13, 2013
    Messages:
    448
    Likes Received:
    10
    Could I put a back/reverse counterbore onto a drill piece thin enough to pass through a <6mm hole?

    [​IMG]
     
  10. CAMPYBOB

    CAMPYBOB Well-Known Member

    Joined:
    Sep 12, 2005
    Messages:
    11,945
    Likes Received:
    1,038
    Yes, 'depending' on the workpiece and tool.

    There are metric series and sets of tools to do this and for back counterboring a bike's brake bridge...definitely you can. Like Alf suggested, it 'could' be done without even using power tools given sufficient time and elbow grease. And there are applications...such as renovating a classic and somewhat valuable (or at least well valued!) frame where doing a job by hand will be safer and potentially less damaging than an amatuer home machinist breaking out a power drill motor.

    We have a saying in the world of firearms: More $2,000 guns have been turned into $200 guns by the Dremel Tool than have been damaged by rust, kabooms and liberal politicians combined.
     
  11. alfeng

    alfeng Well-Known Member

    Joined:
    Jul 23, 2005
    Messages:
    6,723
    Likes Received:
    126
    HMmmmm ....

    I've got to say that ALL subsequent suggestions (counterboring, etc.) may ultimately be better than the expedience of DIY hand tools, but NASA tolerances are not necessary ...

    Regardless, because the brake bolt is NOT supposed to be rotating once tightened in place, the recessed nut will certainly serve the same function of load distribution which a bushing-or-collet would ...

    I'm thinking that with a hand tool that it is only about a 5-to-10 minute job to hand ream the hole to a suitable diameter in a steel rear brake bridge with a DIY tool ... the actual DIY tool & user's motivation will determine how long it actually takes ... allow for a significantly longer time to enlarge a fork's shoulder by hand due to how thick the "casting" or steerer column's extension may be.

    BTW. If the head of the recessed nut pressing against the hole (as pictured above) in the simple hole in the back of the fork is a concern, then a simple washer will probably suffice to bolster the back of the fork OR of the forward side of the rear brake bridge ...
     
  12. urge2kill

    urge2kill Member

    Joined:
    Aug 13, 2013
    Messages:
    448
    Likes Received:
    10
    If the recessed nut alone isn't enough to keep the bolt from spinning, it will be allowed to spin insdie the bushing. Is that okay?
     
  13. alfeng

    alfeng Well-Known Member

    Joined:
    Jul 23, 2005
    Messages:
    6,723
    Likes Received:
    126
    FYI. You can get some (that is, "a small bag of ...") appropriately sized STAR WASHERS from HOME DEPOT, LOWE'S, ACE HARDWARE, etc. to mount on the caliper side of the bolt to ensure that the brake caliper doesn't rotate once the recessed nut is tightened.
     
Loading...
Loading...