Weak Ass Brakes

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by massdrive, Nov 9, 2013.

  1. massdrive

    massdrive New Member

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    I installed a front drum brake on one of my bikes and a front disc brake on the other. I expected the drum brake to be weaker than the disc brake, but didn't expect both of them to be just plain ass weak... So I decide that rear brakes are absolutely necessary. I had previously removed the rear coaster brakes because the brake arms interfered with the rear sprocket adaptor sprockets. I revisited my decision to not use the coaster brakes. Fortunately I saved all he brake parts.

    I also didn't use the motor mounts that came with the engine kit and as always I saved them too. I used one of the mounting clamps to modify the coaster brake arms for both bikes by cutting 10mm strips out of the clamp to extend the brake arms out past the rear sprocket and simply cut the brake arms and welded in the strips and secured the arms to the frames with the brake arm brackets just as they were to begin with. This is what I came up with.
     

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  2. maniac57

    maniac57 Old, Fat, and still faster than you

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    I STRONGLY suggest you test the modified brake arms by stomping the brakes REAL hard a few times before you take off on a ride.
    If it lets go in a panic stop, bad things can happen.
    I had a customer bring me a wasted bike for fork and rim replacement caused by the coaster brake arm breaking where he welded it when he had to stop to avoid a pedestrian walking out to the mailbox. Lots of broken parts and road rash was the result.
     
  3. massdrive

    massdrive New Member

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    Point well taken maniac. I gave them both a hardy stress test... I have the flat spots on my tires to prove it. I'm confident.
    dance1
     
  4. maniac57

    maniac57 Old, Fat, and still faster than you

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    Good job!
    I'm ashamed to admit I have had modified brake arms fail before.
    It's kinda hard to get good welds with a HF buzzbox sometimes...
     
  5. SuperDave

    SuperDave New Member

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    [​IMG]I use a front disc brake and rear coaster. Had to cut the sprocket using a dremel as well as slightly tweek the coaster arm to clear the rag joint bolts. Dual brakes should be manditory for anything capable of 20 mph or more, stopping is more important than going. I'm not gonna trust a rim clamp brake if my bike hits 30, not tomention your grip power diminishes a lot when they get wet, such as hitting a puddle or driving thru a sprinkler.
     
  6. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    Enlarging sprocket holes with a dremel is going to burn it up.

    A hole saw in a drill and a simple jig is a better way to enlarge sprocket holes.

    I am guessing that you don't own a drill or don't want to pay for a hole saw? :)

    Your front brake does about 70% of the stopping!

    Your front brake does about 70% of the stopping!

    Your front brake does about 70% of the stopping!

    V rim brakes with salmon pads work great for 30ish speeds and will do stoppies.
     
    #6 MotorBicycleRacing, Nov 10, 2013
    Last edited: Nov 10, 2013
  7. 2door

    2door Moderator
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    My question would be why the disc you installed on the front was "weak"? Properly sized, installed and adjusted disc brakes are the best choice for front brakes. Even the small 160mm rotors are good enough to lock up a front wheel if you really romp on them.
    Maybe a picture of your installation would help us tell you why yours didn't perform for you.

    Tom
     
  8. SuperDave

    SuperDave New Member

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    Burn up what? The dremel, the bit, or the sprocket? Look again at the pic I posted, I used a carbide wheel mounted on a mandril, both of which come with a dremel accessory kit, not to mention lots of other bits which are useful for porting & polishing. A worthy investment for a China Girl, not to mention much more useful than a hole saw.
    [​IMG]
    There's more than one way to skin a cat, just as there are more ways to enlarge an axle hole on a sprocket to provide clearance for the coaster brake arm than using an expensive dedicated single purpose tool.
    .spr.

    Yes I have a drill & hole saw, but it's designed for wood, not chrome steel. Using it for this task would ruin it.

    No, I don't own or have access to a jig or a drill press. Not everyone has access to a fully equipped machine shop. I'm willing to bet a whole dollar that most of us who visit these forums who own, ride, or are interested in motorized bikes are like me, looking to achieve cheap transportation to stretch their meager earnings, folks with limited funds & tools who desire a vehicle capable of 100 miles per gallon. These forums were set up not just to showcase our creations and skills, but to share our knowledge, successes & failures. I am sharing how I was able to modify my drive sprocket so that others could see how it was done and duplicate it themselves.
     
  9. massdrive

    massdrive New Member

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    Yes this is my under standing too. However even though I went through great effort to properly alien and adjust the brake (Origin 8 disc brake) it just doesn't grab like I anticipated it would, should... I have check and rechecked and everything looks good.
     
  10. wheelbender6

    wheelbender6 Active Member

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    My front disk brake became very weak on my pedal bike. I cleaned the rotor and pads with alcohol, hit them with some fine sand paper and recleaned them. Braking power returned to normal.
     
  11. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    No drill press or expensive anything needed.
    The jig is a piece of plywood and a couple of screws.........

    Screw the sprocket to a piece of scrap 3/4" plywood around a center pilot hole.

    Use hole in plywood to center hole saw on the sprocket and drill away.

    Much faster and quicker than using an underpowered dremel.

    A Milwaukee 2" bi-metal hole saw is $10.97 at Home Depot.

    How long does it take to make all those cuts with your dremel.
     
  12. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    And then there is my way of enlarging rear sprocket holes. A drill press, a 1/16" drill bit and a hammer. Drill holes tightly in the circle size desired and then knock it out with the hammer. File to fit if needed. It's pretty quick too.

    I don't skin cats :D

    dnut
     
  13. massdrive

    massdrive New Member

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    Yep very confident that my welds would hold... The brake arm twisted but my weld held. :-||
     

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    #13 massdrive, Nov 10, 2013
    Last edited: Nov 10, 2013
  14. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I concur!! Disc brakes are the best kind of brake out there!! That's why you see them on the front of every modern (quality) vehicle! (^)

    That's a very good point!! (Brake cleaner works better)! ;)
     
  15. massdrive

    massdrive New Member

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    The brake is a newly installed Origin 8. I put a lot of effort into aliening the rotor and caliper, and adjusting the pads and cable.
     

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  16. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    Here's another little tip... use a 'shifter' cable on it; they're a lot more rigid & don't feel as 'squishy' when you pull the lever. ;)
     
  17. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    Go hydraulic disc and don't look back...

    .wee.
     
  18. dodge dude94

    dodge dude94 New Member

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    Did you scuff your rotor and sand your pads or bed them?

    My lil' ol' 160mm rotor on my cheap ass front disc on my mtn bike will flat out PULL my wheel out of the fork if I lay on it too hard.
     
  19. 2door

    2door Moderator
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    That should be able to stand you on your nose, Mass. I agree with some of the other advice; maybe dirty/oily rotor or pads? Cable stretch? Sumpin' ain't right. Rider weight can play into it. I'm a lighweight but my neighbor and I switch off bikes occasionally and he weighs in at 180. I have two bikes with 203 rotors in front and one with a little 160. Even the small one brings him to a stop, pronto.

    Pads also need to be broken in a little. Disc brakes get better with age. How new is your disc setup? How many miles?


    Tom
     
  20. Scootmeister

    Scootmeister Member

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    I have a box of brand X calipers that I could not get to work properly. I finally wised up and went to Avid Juicy calipers and they stop on a dime, plus they are easy to adjust. I also swapped out the stretchy bicycle cables for heavy scooter cables that don[t seem to stretch as much. I was shocked at how much difference these two changes made. Finally, I swapped the smaller 160mm discs for 205mm and the difference was even more profound. It all boils down to physics, the heavier the bite, the quicker the stop!!
     

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