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  1. #1
    Uncle
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    Measure my current frame angles?

    This might be working in reverse from frame building, but hopefully someone here can provide a good answer. I tried searching this but didn't get what I was looking for.

    Is there a fairly simple yet accurate way to measure my current bike's ST and HT angles? I know the iPhone has an angle finder app, but I don't know how accurate it is. I'm using the term "accurate" pretty loosely here -- within say, .1 or even .2 degrees. I'm trying to compare two older frames I have.

    Thanks for any help.
    josh
    Eat, ride, eat, rest, repeat.

  2. #2
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    Yes

    My guess is that the iphone app is not very accurate, but you could easily check that if you want to go that route (ie, get a regular old carpenter's level, see if the Iphone agrees with it, then flip 90 degrees and see if they still match up).

    If you don't want to do the iphone route, or spend any money on an angle finder/torpedo level, you can still measure the angles with a plumb bob, a ruler, and some basic trigonometry, to a pretty high degree of precision if you're careful.

    -Walt

    Quote Originally Posted by Entrenador
    This might be working in reverse from frame building, but hopefully someone here can provide a good answer. I tried searching this but didn't get what I was looking for.

    Is there a fairly simple yet accurate way to measure my current bike's ST and HT angles? I know the iPhone has an angle finder app, but I don't know how accurate it is. I'm using the term "accurate" pretty loosely here -- within say, .1 or even .2 degrees. I'm trying to compare two older frames I have.

    Thanks for any help.
    josh
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  3. #3
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    Use an angle finder... but if you have an iPhone and the app, that should be sufficient. Otherwise you can use a plumb bob, a small square, and trigonometry.

  4. #4
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    This is what I use. You should be able to find one used on CL for a reasonable price. I pulled this pic from an ebay auction at $20. They often come in a set with a square and a center finder and a 12" beam.

    Put the bike on level ground and turn the dial until the bubble is level and read the number. Very accurate.


  5. #5
    Uncle
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    Thanks for the information, folks.

    I might start with the iPhone app, test it like Walt suggests, and then do 10 measurements and take the average? IIRC, it goes to 10ths, so that might get it done if the numbers aren't too rangy. Will keep the angle finder suggestion in mind in case the big apple lets me down.
    Eat, ride, eat, rest, repeat.

  6. #6
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    As long as you calibrate the Iphone on a known level surface(as you should any angle finder) it is incredibly accurate. It matches up with all of my digital and analog stuff.

  7. #7
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    This is what I use. It's a Craftsman and really affordable, under $40.



    These are the advertised specs on the Strowler....



    The first step is to put the bike on a flat surface. In this case we'll use my workbench. You must have the same tires on the front and the rear to get an accurate angle reading or else you'll be off.



    The next step is to put the digital protractor on the bench and zero it in. This makes sure that the relative angle of the surface the bike is on is correct to start.



    Now let's measure the seat tube angle. Because the protractor won't fit in between the top tube and the downtube we'll just measure the seatpost. As long as the seatpost is not bent, the angle will read the same. The advertised spec is 70 degrees and that is exactly what it reads!



    Now let's check the head tube angle. Same deal here, the best place to measure this is at the fork and if it's not bent, the angle will read the same as the head tube. 74.5 degrees is what's advertised and it's dead nuts again.



    The tool is magnetic so it stays where you put it. Unless you try to put it on an aluminum seatpost.



    So there you have it. A great tool to check the angles of your frames and a pretty well built Hoffman product as well.

  8. #8
    Uncle
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    Brilliant!

    Neither my suspension fork nor my seat post are steel, but I'm fine with holding this thing in place. Hopefully my tool collective buddies will be interested in going in on one. Thanks for the detailed pics and description.
    Eat, ride, eat, rest, repeat.

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