Never heard this plumb bob measurement before. I have a lot of Scandahovian in me and my last name is Norwegian. I ended up at 6'5" so most of the bikes that this site adores are way, way too small. However I'm going to try the plumb bob on my present rides which are all very comfortable both in seat position and handlebar placement. 1980-81 Schwinn Sports Tourer with 27" wheels and a 27" frame. This bike gets used a lot on dirt roads and does just fine. The picture of the kids under the desk was me in the late 50's early 60's preparing to kiss our butts goodby if the big one dropped on us.I tell ya what, you sleep for a second on this build off and you slide right back on that slippery slope to Page 2 Slackerdom !
Had an interesting conversation about body positioning on a bike last night with a couple of our esteemed members here on RRB. I know we don't often talk a lot about the actual 'riding' of the bike in these build offs, but there are a few tips I have learned over the last 34 yrs of making happy customers through a good bicycle 'fit', that might be helpful here for those that ride their 'rolling art creations', aka Build Off bikes!
We talk here about the 'go' and the 'show' positions of our saddles. This discussion is mostly related to the 'go' position, but if you plan and scale your build you can have a decent 'show' position with these tips as well.
For those of us that are probably 5'10" and taller, we will never have a full leg extension on a vintage cruiser framed bicycle. But we can have a comfortable fit, and feel good riding the bike, even if we don't have the required leg extension for full power to the pedals. The frames simply weren't manufactured with tall people in mind, and the average height in 1950 is almost the same for today, 5'9" in the USA. Now those of you with Scandinavian ancestors will scoff at this, as the average height for those of us with that heritage is nearly 6' tall, 3" taller than the average American male. But size isn't what matters here, bicycle fit is.
During our conversation last night, I went out to the BACK40, grabbed my tape measure, and confirmed what I already knew to be true. The relative position of my saddle fore and aft, no matter what the height of the saddle was, in regard to my pedal position was nearly exactly the same on all my bikes in the stable. And, the distance from my center seated position to my hand position on the bars, was also nearly spot on. Even though my bikes aren't in a perfectly straight line here, for storage purposes, you can kind of get the idea.
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Those two factors, in that order, can make for a comfortable and fairly efficient pedaling position on the bike.
A common mistake is trying to adjust distance from the bars by altering saddle position – usually by moving it forward. Saddle should be positioned relative to the pedals, regardless of the bars position. For our purposes, because we use different types of saddles and saddle mounts, this measurement should be taken from the center of your seated position on the saddle, with your pedals at the 3 and 9 o'clock position. The plumb bob, a string or fish line with a heavy washer or nut on the end, held off the front of your knee cap, should line up with the pedal axle with the widest part of your foot over the axle. This photo shows it well.
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Again, this measurement isn't relative to saddle height, but rather the fore and aft position of the saddle.
Only after the saddle is positioned correctly, the bar should be set in the desired position. Placing the bars closer and higher results in a more upright riding position and vice-versa – placing the bars further and/or lower, results in a more leaned position. As shown in this diagram, you can see the saddle to pedal position is the same, even though the upper body position changes.
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Over the years I have found that every bike I have no matter if it's a laid back 'nanner equipped big boy muscle bike, a klunker build fit for off-road, or a vintage cruiser build; they all share the same saddle to pedal fit and within fractions of the same centered seated to hands on the bars distance fit.
If you are like me, the laid back seat post is a necessity to achieve this on our build off bikes using vintage frames. Thanks to Chad @ChopShopCustomz for all those seat posts that have made it possible! The only bike I don't have that fits well yet is my current build Silver King Unchained ! Because I had to use a quill style BACK40 Kustom post, I am still figuring on how to get it back about 2" for my optimal position.