Changing threaded fork with un-threaded fork- Mtbr.com
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  1. #1
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    Changing threaded fork with un-threaded fork

    Guys -- I'm fixing up an old hybrid bike that has on old flimsy suspension fork with a threaded steerer tube. I would love to replace this with a rigid fork and disc brake. Am I correct in thinking that I can purchase a fork with an un-threaded steerer tube to install if I replace the stem as well?

    I would love to hear your thoughts and share any experience you can pass my way.

    Thanks!

  2. #2
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    If it's a threaded steerer there's a good chance it's 1" instead of 1 1/8".

    And there wasn't a lot of overlap between 1" forks and disk brake forks, a year or two at most in 1996-1997. Could be a challenge to find something like that.
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  3. #3
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    You'd need a new headset, too.

  4. #4
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    It is a 1" steerer tube. That sucks. Looks like I may be stuck with cantilever brakes. Better than no brakes I guess.

    It may not be a bad Idea to replace my headset while I'm at it. Its the really old kind where I can see the ball-bearings. I have not cleaned them up yet so I don't know if they are really bad and pitted up or not. I will find out this weekend.

  5. #5
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    Plenty of 1" headsets out there, and 1" stems too. Found a 1" disc brake fork, but it's for cyclocross tires. Probably has some width limits. It'll also has a short axle-to-crown length. Might be ok if you're putting it on a 26" bike, not so fine for a 700c hybrid. there were also some review comments about problems with different disc hubs, so you'll want to check them out too.
    Nashbar Carbon Cyclocross Fork
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  6. #6
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    Quote Originally Posted by p08757 View Post
    It is a 1" steerer tube. That sucks. Looks like I may be stuck with cantilever brakes. Better than no brakes I guess.

    It may not be a bad Idea to replace my headset while I'm at it. Its the really old kind where I can see the ball-bearings. I have not cleaned them up yet so I don't know if they are really bad and pitted up or not. I will find out this weekend.
    If you're looking for a replacement fork (I'm assuming because yours is shot?) measure from the axle mounting point to the crown race. Take that number, and if you have any local co-ops, give them a call looking for a rigid fork within 10-15mm of that number (this is called, unsurprisingly, the axle-to-crown measurement).

    Your chances of finding a 1" threaded steerer that also has IS51 disc brake mounts are very low, so if you're looking for sealed braking, look into a Sturmey Archer drum brake. The 70mm is more than enough for a general use bike, the 90mm is overkill.

    You may have some measure of luck by looking for (beach) cruiser forks. Until fairly recently, most manufacturers were still using 1" threaded forks. Distributors such as Action Bicycle or KHS (which many shops will have an account for one or the other) still sell threaded 1" forks. Ebay is also a good source, if you don't mind buying 'sight unseen'.

  7. #7
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    Update: I took the fork into my LBS and it did have a 1 1/8 steerer tube. I ended up ordering a Surly Disc Trucker fork to replace the flimsy shock fork that was on there before. I will pick out a new stem and have a new headset installed as well. I should be good to go in no time at all.

    The project I'm working on is converting an old bike into an E-Bike. (Don't Judge) The 500 watt motor was not recommended for installation on a suspension fork. Thus the replacement.

    The bike is for my wife to use so she can keep up on group bike rides. The conversion kit was ordered on Kick Starter last fall and will ship out in a few weeks. I hope to have the bike ready by sometime in March.

  8. #8
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    Quote Originally Posted by p08757 View Post
    The project I'm working on is converting an old bike into an E-Bike. (Don't Judge)
    oh, we're judging.

    Lot of different e-bike designs. Is this a front wheel, rear wheel, or crankset drive? sounds like it's a front wheel motor if it mentions "front shocks not recommended". Have to be careful with those, they can get away and yank out the front end easier than ones mounted on the rear. For casual hybrid riding, a lot less weight over the front wheel than the back, so a lot less traction.
    "a hundred travel books isn't worth one real trip"

  9. #9
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    Quote Originally Posted by watts888 View Post
    oh, we're judging.

    Lot of different e-bike designs. Is this a front wheel, rear wheel, or crankset drive? sounds like it's a front wheel motor if it mentions "front shocks not recommended". Have to be careful with those, they can get away and yank out the front end easier than ones mounted on the rear. For casual hybrid riding, a lot less weight over the front wheel than the back, so a lot less traction.
    This is a front wheel design with pedal assist. Their lower wattage kits received great reviews. When they announced the 500 watt kits on Kick-Starter for less than $700.00, I immediately jumped on it and pulled the trigger.

    This will be used on MUP's and side roads. No dirt trails.

    Here is a link to their 500 watt kits. LEED USA Electric Bike Conversion Kits | Shop 500 Watt E-Bike Kits

  10. #10
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    Was this a 26" wheel bike? 700?

    You may want to switch that fork to an Instigator 1.0 (26") or Karate Monkey (700) if it's not too late. Hub motors put out a lot of torque into the dropout, best to have a beefy fork.

  11. #11
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    Quote Originally Posted by wschruba View Post
    Was this a 26" wheel bike? 700?

    You may want to switch that fork to an Instigator 1.0 (26") or Karate Monkey (700) if it's not too late. Hub motors put out a lot of torque into the dropout, best to have a beefy fork.
    Its a 700c. According to the documentation just about any CroMo fork should work. There is a small bar that will connect to the fork arm and distribute the force across about 4 or 5 inches

  12. #12
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    This just sounds all sorts of dangerous. Strong fork will win every time.
    "a hundred travel books isn't worth one real trip"

  13. #13
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    Quote Originally Posted by p08757 View Post
    Its a 700c. According to the documentation just about any CroMo fork should work. There is a small bar that will connect to the fork arm and distribute the force across about 4 or 5 inches
    Just a piece of friendly advice from someone who has cobbled stuff together outside of original intent: Go for the simplest shape possible--which happens to be the two straight-legged forks above, the Karate Monkey in particular, for the 700 wheel. If you have a straight reaction arm that rests against the fork leg (I'm assuming it will be bolted down with a strap, though), it will be better if it isn't hitting the fork on a tangent; ie: the fork leg would contact in only one spot, since road touring forks (like the DT's) are traditionally curved.

    I have no experience with this particular mod, but can say that straight leg forks don't get noodly with large drum brakes...curved ones tend to.

  14. #14
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    kona still makes the p1 in 1" threadless i think. But i dont if they offer a disc version.

  15. #15
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    I received the e-bike conversion kit last Friday and installed it Saturday morning. The only real issue I had was the stock 160mm rotor did not allow enough clearance for the BB7 caliper. Luckily I had a 20mm spacer and an extra 180mm rotor and the front wheel/motor fit like a champ.

    I showed the finished project to my wife and she seemed satisfied that it didn't look too much like an e-bike. We made plans for a short 6 mile round trip test ride to get some food for lunch. She ended up enjoying the ride so much we passed on the close place for lunch and went an additional 4 miles for a 14 mile round trip up some steep hills. I can now ride a bike with my wife again without having to plan a route without hills.

    I chose not to install the thumb throttle, and oped for only installing the pedal assist. I figure if she is gong to ride a bike, I'm going to make her pedal.

    On Sunday, I took it for a quick 20 mile ride to see what it was like and shake out any potential problems. I found that I could still get somewhat of a good workout while riding it. The only difference was that I could ride at a much faster pace. I could easily manage a 21+ MPH pace with only getting my HR up into the cardio zone. If I were to attempt to keep that pace without the electric motor I would max out my HR and and slow down after about 5 minutes or so.

    I'm glad I got the conversion kit for my wife. I know some people are against e-bikes, but in my case my wife really needed the boost to keep on riding. This week I will post some photos of the project.

  16. #16
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    Quote Originally Posted by p08757 View Post
    I chose not to install the thumb throttle, and oped for only installing the pedal assist. I figure if she is gong to ride a bike, I'm going to make her pedal.
    It still has a switch near the handlebar to shut off pedal assist, right? A friend of mind has an e-bike that he commutes with. Wet asphalt got him on pedal assist. Luckily, he was able to disengage quickly. I don't know if it was a "push to engage" pedal assist switch, but if I had an option, that's what I'd want it to be. Easier to turn it off.
    "a hundred travel books isn't worth one real trip"

  17. #17
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    Quote Originally Posted by p08757 View Post
    I showed the finished project to my wife and she seemed satisfied that it didn't look too much like an e-bike. We made plans for a short 6 mile round trip test ride to get some food for lunch. She ended up enjoying the ride so much we passed on the close place for lunch and went an additional 4 miles for a 14 mile round trip up some steep hills. I can now ride a bike with my wife again without having to plan a route without hills.
    Winner, winner, chicken dinner!
    Recalculating....

  18. #18
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    Quote Originally Posted by watts888 View Post
    It still has a switch near the handlebar to shut off pedal assist, right? A friend of mind has an e-bike that he commutes with. Wet asphalt got him on pedal assist. Luckily, he was able to disengage quickly. I don't know if it was a "push to engage" pedal assist switch, but if I had an option, that's what I'd want it to be. Easier to turn it off.
    There is a control unit on the handle bars where she can change the assist level and turn on and off the electric system.

  19. #19
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    Quote Originally Posted by p08757 View Post
    I can now ride a bike with my wife again without having to plan a route without hills.
    Excellent. Glad you got a good result. Enjoy your rides!
    2018 commutes - 26 days, 542 miles

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