converting to disc brakes-- mounting adapters for my road fork
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  1. #1

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    converting to disc brakes-- mounting adapters for my road fork

    Hi, I'm converting my old Fuji Special Road racer frame into a winter fixed gear machine. Its been gathering dust for too long, and I'm afraid to lock up my shiny new track bike outside. I'm building it with the rear wheel brakeless, but since I'll be using it in snow and ice through downtown traffic, I want to put a disc brake on the front wheel. I've managed to find a 700c front wheel with a 160mm disc brake rotor and a small shimano deore hydraulic disc brake and lever. What I need to figure out is what mounting adapter(s) I need to connect the disc brake to my fork.

    My fork has an eyelet for fenders, like this fork: https://parts.spicercycles.com/site/...odl/FK0801.jpg

    and I would like to make it like this: https://www.fixedgeargallery.com/2004/c/olsson2.jpg

    Any help is greatly appeciated!

  2. #2
    RoadBikeReview Member
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    Fork not made for it

    Consider this: your fork was made to handle the weight of the rider, lateral forces between the dropouts and the fork crown, and rearward pushing forces from impacts, through the dropouts to the crown. Now you want to put full braking forces into one leg of the fork pushing forward. The fork was never designed to do it. It may be OK, and it may not. Strongly consider using the bike as designed, with front and rear rim brakes.

  3. #3
    DY
    DY is offline

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    I wouldn't attempt it.......

    Do a search for similar people that have tried this. There was a link to a web site posted a year or so ago here that talked about failures when trying this with road bike forks.

    I new road fork designed for this is one thing but taking a fork designed for rim brakes is totally another.........

    If you insist on doing it make sure your health insurance is up to date.

  4. #4
    First one home gets beer
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    Don't do it

    ...with the original fork. Buy a cyclocross/touring fork designed for discs. Winwood, Interloc, Kelly, Independent Fab, maybe a few others. The new fork costs way less than the hospital bill when the old one shears at the crown.

  5. #5

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    I ended up buying a dimension 700c threadless rigid steel disc fork. Unfortunately its black and doesn't look nearly as cool as my last fork (no chromed fork crown or two tone painting). My last fork was threaded too meaning I needed to get a new headset and stem as well. I do however plan on putting this bike through a fair amount of abuse, so in the end safety and durability are the the most important. It should still look pretty sweet regardless though! I'll post a picture once I have everything assembled.

  6. #6
    chica cyclista
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    physics issues

    There are other physics issues related to discs besides fork shear that roadie equipment is not built to deal with.

    1) Windup. The windup on your spokes when braking with a disc system is extreme compared to that with rim brakes, due to the leverage generated on the spokes by brake forces being generated at the hub, not the rim. I'm sure the engineering geeks here can expound on this but in short, what this means is you'd better build the hell out of those wheels or else you're constantly going to be retruing / breaking spokes.

    2) Dropout ejection. Again, this is due to the physics of disc braking force, and why most disc brake specific bikes are now being built with full-clamp (i.e. closed) dropouts, rear facing dropouts, etc. The downward force on the wheel under hard disc braking can and will exceed the clamp force of your quick release. What this means is that if you don't have burly lawyer tabs on (and I recently saw one instance where discs on a cross bike partially sheared the lawyer tabs off AND cracked the fork crown) and/or if you have vertical dropouts on the rear, be prepared to have your rear wheel jack out of the dropouts in hard braking situations. It goes without saying that you should use steel Q/Rs and tighten the hell out of 'em.

    Still convinced you need discs on the roadie?
    Grandpa LFR: "Kid, don't wrestle with pigs; you'll just get covered in crap, and the pig enjoys it."

    /Grandpa LFR

  7. #7

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    Yes, I am prepared.

    This is pretty much a project bike and I've always thought a winter fixed gear bike with a disc brake would be a whole bunch of fun; I like the fact that both the front and rear wheels brake at the hub too (half hydraulic/half muscle).

    Considering I am getting a disc specific steel fork and a disc hub wheel built up with 3x laced double guage spokes, I think I should be relatively safe as far as mechanical failure goes. I'm not doing downhill on this after all, maybe just the occasional curb hop or pothole as I go through the city.

  8. #8

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    Quote Originally Posted by Shiznaz
    Hi, I'm converting my old Fuji Special Road racer frame into a winter fixed gear machine. Its been gathering dust for too long, and I'm afraid to lock up my shiny new track bike outside. I'm building it with the rear wheel brakeless, but since I'll be using it in snow and ice through downtown traffic, I want to put a disc brake on the front wheel. I've managed to find a 700c front wheel with a 160mm disc brake rotor and a small shimano deore hydraulic disc brake and lever. What I need to figure out is what mounting adapter(s) I need to connect the disc brake to my fork.

    My fork has an eyelet for fenders, like this fork: https://parts.spicercycles.com/site/...odl/FK0801.jpg

    and I would like to make it like this: https://www.fixedgeargallery.com/2004/c/olsson2.jpg

    Any help is greatly appeciated!

    I think it will be ok, since you're using a fork designed for discs and a disc wheel. The spoke issue and dropout ejection I think are more relevant to mountain bikes where you can frequently make jolting stops that torque and un-torque the hub in the wheel. The additional traction you get from fat knobbies on dirt also allows you to get more useable power out of the brakes. A road tire with far less contact area will put a greater limit on how much total stopping power you will get out of the brake (meaning if you grab too much lever, your tire will lose traction and slide out). That's one thing to be careful with, the grabbiness of the brake. That's also the nice thing about discs, the increase in power equals less handforce for given brake power output. In addition you get consistency in wet weather, longer pad life, no rim damage and much better cooling on long decents, all useful traits for a winter bike. So I would recommend it.


    Get a feel for the brake before you ride it in the rain, because it will feel a lot more grabby than a rim brake. I would recommend a bigger tire for the front as well to increase your braking traction. A "treaded" tire is up to you. If your riding purely road, then you want as much contact area as possible, so a full on "slick" tire will actually give you the best traction because it maximizes contact area. A bicycle tire simply cannot hydroplane unless you ride your bike at insanely high (and mostly impossible) speeds. Sheldon Brown's website talks about this. A lightly treaded tire such as a hybrid tire might be more useful if you frequently ride through patches of debris, gravel, etc. or take some off-road shortcuts. Hope that info is useful.


    -Ryan


  9. #9

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    Okay guys, after way too long, I finally have this bike done. Since I finished it in the nick of time for Halloween, and because of the necromantic, schizofrenic and pieced together nature of the bike, I have decided to dub her 'Fujenstein'.

    I had numerous stumbling blocks on the way to building this bike, it being the first one I have put together all on my own. I bought a threadless disc fork for the bike thinking I could convert it to aheadset, but unfortunately the steerer was about an inch too short to attach a stem to the top of (70's tall people road frames have HUGE headtubes!), so rather than risk the stem popping off, I got the fork threaded at a bike shop. This however meant that I ended up paying more in labour to thread the fork than it cost for the fork in the first place. Plus the guy managed to scratch the paint a fair bit, but that would have happened on its own. I also now have an extra aheadset and threadless stem, but I didn't pay too much for them so I'm not too concerned.

    Parts that are original are the frame, cranks/chainrings, stem and saddle, all the rest I got on ebay, from Gene at Spicer Cycles, and from the LBS.

    I had the outer ring on the crank machined down by my friend's dad (a machinist); he did such a pro job I had the guy at the LBS ask me where I bought it!

    I haven't been able to use this in the snow yet but its a blast to ride, eats up bumps and potholes like cheerios and I can see it holding up nicely all winter.

    When I remember the rest of what I was going to say I will post that too. Anyhow, Happy Halloween! Fujenstein says 'urggghhhh!!'
    Attached Images Attached Images

  10. #10
    Climbin' Clyde
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    Nice work

    I love wrenching on bikes, and when I finish a creation I'm stoked. My friends shrug their shoulders and have a look on their faces that says, "Geez- I don't see any Dura Ace or carbon fiber... what's the big deal?" Have fun with it.

  11. #11
    Say "nuke-u-lar"
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    Pretty ride, I like it!

    Just a question about the rim..is it disc specific also? It's recommended on mountain bike rims and would assume that would hold true for a 700c too. I suppose as it's a fixie your braking duties are lighter, but...
    Suum quique.

  12. #12
    A wheelist
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    Great stuff! The final touch would be to take the fork to a plating shop and have them chrome or nickle plate it.
    .

  13. #13

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    What a beautiful winter beater! Sugino Maxi crankset - I haven't seen one of those in a while. I think that other than replaceing parts like tires, a Sugino Maxi crankset is the first bike component that I ever bought. Mega-points for machining down the teeth on the big chainring to make a pants guard. Nice work.

  14. #14
    NeoRetroGrouch
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    Absolutely beautiful. There is nothing more satisfying than a "project". - TF
    "Don't those guys know they're old?!!"
    Me, off the back, at my first 50+ road race.

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