Useful or Useless: A dot painted on a frame's top tube to mark BB center

[MattTuck]

Just thought of this as I am trying to make a quick micro adjustment to my saddle in my office...

Seems like a simple and somewhat useful reference point for setting up the bike.

[Hindmost]

Humm...interesting thought. One would still have establish vertical and measure back to a point on the saddle to get setback.

[LegendRider]

My Time VXRS has it. Seems like a good idea - certainly easier to measure saddle setback.

[benb]

I'm wondering if this would allow use of a standard T-square or similar device to precisely measure setback and/or saddle height instead of expensive X-Y type tools or relying on less precise methods.

The idea has merit. Not really helpful for most of us with frames we already have though.

[MattTuck]

I'm wondering if this would allow use of a standard T-square or similar device to precisely measure setback and/or saddle height instead of expensive X-Y type tools or relying on less precise methods.

The idea has merit. Not really helpful for most of us with frames we already have though.

There's always a sharpie, or some white out ;)


I keed. I keed. Yes, ideally it could just be a very small point put on by the painter. Square idea works only if it is a level top tube. But even without a square, eye-balling setback from tip of saddle to top tube is easier than eye-balling it all the way down to the BB.

Interesting that Time has done it. Guess someone else had the same thought.

[bthornt]

I always thought it would be useful for seatposts and stems (and steerer tubes?) to have a dot or bump at their center, and then to have corresponding dots or bumps on the middle of the top tube so you could easily center the cockpit.

[vqdriver]

My Time VXRS has it. Seems like a good idea - certainly easier to measure saddle setback.

my time vx edge also has this. took me a while to figure out what it was, but whether it was bb center or not, it was always useful for making small changes.
you just tape a plumb line to the tip of the saddle to make adjustments fore/aft. I ghetto rigged a string tied to a nail. also works to make changes to tip angle.

[Mikej]

I only works if you have perfect alignment - level floor and lateral side/side. Ask any custom frame builder who has customers measure their current bike if that has ever happened...

[Mark McM]

Such an alignment dot would be very useful.

But I don't trust for one minute that it would be accurately located during manufacturing on a production frame. I think you'd end up having to place your own calibrated alignment dot.

[Lewis Moon]

I've done this for years. You'll see a dot on the top tube of every bike I own.

[soulspinner]

I've done this for years. You'll see a dot on the top tube of every bike I own.

yup. I remove them when set up correctly.:cool:

[benb]

I think I'll try it as I'm going to try a new saddle soon..

[CMiller]

I often put a piece of electrical tape neatly on the top tube directly over bb. I also do electrical tape over seatpost once I figure out my height. I say it's just while I set up the bike but it usually winds up there for a few months haha

[Bob Ross]

I think you'd end up having to place your own calibrated alignment dot.

^^^That's what I did. A little hard to see in this pic, but that green rectangle just in front of the builder's signature on the top tube is a small piece of artist's tape, with a small line drawn by a Sharpie to indicate bottom bracket center.

http://i1070.photobucket.com/albums/u495/bob_ross4/my%20Sachs%204-25-2016_zpsgg13zea1.jpg

I located this using a huge T-square on my hopefully-close-enough-to-level Dining Room floor. Compared to futzing around with a plumb bob this method is so much easier! Highly recommended. So yes Matt, it would indeed be useful.

[wallymann]

i had stickers made up for that very purpose years ago, fitted to every bike i own:

http://brown-snout.com/cycling/tech/bb-center-stickers.jpg

[Clancy]

Maybe I'm missing something and my method is wrong but it's pretty simple.

I lean my bike against a corner wall, the bike up against one wall, the rear tire touching the other wall.

Basically I lean my bike against a wall, rear tire touching other wall.

I then measure from the wall to the bottom bracket. The wall the rear tire is touching.

Measure from wall to the tip of my saddle.

Subtract one from the other - setback.

[Clancy]

But those stickers are freaking cool.

[Louis]

In a related, but completely random comment:

Some propeller driven aircraft have a red line around the fuselage corresponding to the plane of the props. I was once in a small commuter airplane and by chance my seat corresponded exactly with that location, which made the flight extra-interesting.

http://lockheedmartin.com/content/lockheed/us/products/c130/History/_jcr_content/center_content/image_1.img.jpg/1403022302054.jpg

[wallymann]

Maybe I'm missing something and my method is wrong but it's pretty simple.

I lean my bike against a corner wall, the bike up against one wall, the rear tire touching the other wall.

Basically I lean my bike against a wall, rear tire touching other wall.

I then measure from the wall to the bottom bracket. The wall the rear tire is touching.

Measure from wall to the tip of my saddle.

Subtract one from the other - setback.

that certainly seems good enough for gubment work, but it depends on the level of precision one wants to achieve.

i'm pretty persnickety about position and predisposed to +/-1mm accuracy for fit specs.


In a related, but completely random comment: Some propeller driven aircraft have a red line around the fuselage corresponding to the plane of the props. I was once in a small commuter airplane and by chance my seat corresponded exactly with that location, which made the flight extra-interesting.


"CUT HERE"

[cachagua]

I'm not going to argue whether it looks cool. For purposes of fitting, though -- i dunno. A laser level is too easy, too economical, and too accurate to stab around in space over a spot on your frame.

[MattTuck]

In a related, but completely random comment:

Some propeller driven aircraft have a red line around the fuselage corresponding to the plane of the props. I was once in a small commuter airplane and by chance my seat corresponded exactly with that location, which made the flight extra-interesting.

http://lockheedmartin.com/content/lockheed/us/products/c130/History/_jcr_content/center_content/image_1.img.jpg/1403022302054.jpg


There's probably some overly informative acronym for it... the "Propeller Impalement Zone" PIZ

http://onmilwaukee.com/images/articles/ri/richardmatheson/richardmatheson_fullsize_story1.jpg

[Louis]

Obviously that CAN NOT be Capt Kirk.

[Slow Eddie]

Makes sense on s bike like the Time that comes as a module, but swap to a fork with a different A-C and now your dot's in the wrong place.


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[Ray]

I've never found anything that works better than a square sided post. The two basements where I've set up all of my bikes have em and that makes it easy to measure and adjust the setback on every bike. Even if it's not perfectly vertical, as long as you use the same post, it'll always be consistent...

-Ray