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Old 05-13-19, 12:17 PM
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79pmooney
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Join Date: Oct 2014
Location: Portland, OR
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Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

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My take? If the contact points (seat and bars) are right and your weight is well placed between the wheels, frame size matters little save the top tube contacting your leg in different places and bie bike "feel" being different due largely to the (presumably) different wheelbase. I've ridden (and got the fit right for) 62 cm frames, 59 and 58 (my "best), 56 and probably a 53. The 53 is an old Raleigh Competition. I have a 140 stem set not very high. Feels perfect.

Oh, a word on my sloped line reach theory. For me - any location of handlebar tops on a line that has a "slope" of 1 cm steerer spacers and 2 cm of horizontal reach is equal comfort and speed. In other words, I can have the bars so low ans close I hit them with my knees climbing or nearly up at seat level but much further forward and be equally comfortable. That line is an approximation of the arc my hands would swing through with my most comfortable lean forward and elbow bend.

I came up with this theory when I picked up that 62 cm frame. It was a laid back touring frame. I always felt cramped climbing on it with a slammed 130 stem. Drew it and my custom on the same paper, sharing the BB location. Sketched in where my shoulders would be. Swung the arc through my custom's bars. Saw where it hit the much higher stem height for that big frame. (All my bikes have old-school horizontal stems.) Measured the distance steerer to intersection. 7" Went to a local framebuilder and had a 7" stem made. (178 mm) Worked! Really well! I rode 20,000 miles on that bike and stem until it died a violent death. Later I set up a 56 cm fix gear with a near slammed 130. Other end of that line. Knee contact was happened. A hot, fun custom pure $105 race bike! Loved it!

So, when I look at a potential bike, I measure it up to see where the stem is relative to the BB. Go home and sketch it up. Lay my "line" over the drawing. Now, what stem height and reach is required to place the bars on that line? Is that stem reasonable and available? Do I want this bike to have bars (say) that low and close or far and high?

I also look at where my weight is. Years ago I weighed the front and rear wheels of one of my bikes with me on it. (Phone books under the other wheel so the bike was level.) Did the math and computed where my weight was located relative to the bottom bracket. So I look at whether that location works well with where the wheels are on this prospective bike.

The bike that doesn't meet those two criteria is a bike I won't go back and buy. If it does (and it is a bike I really want), the frame size is not a consideration. (Well, I like horizontal top tubes and ones that might be life altering, I stay away from.)

Edit: This may have already come across in this post. I am perfectly willing to use unusual stems and seatposts to nail the fit. My last two customs have steep seat angles (for optimum rear wheel placement weight-wise on one and for a very long dropout on another) and custom seatposts with huge setbacks. (60 mm) I've had stems made of 178, 180, 175 and 155 mm. Love the Nitto Pearl 13s that actually measure 140 mm.

Ben

Last edited by 79pmooney; 05-13-19 at 12:26 PM.
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