Measuring a sloping top tube

[cnighbor1]

I just bought this small Caylor frame. and when I added some wheels noticed it was a sloping top tube frame design. I know the builder Gunnar Caylor and have asked him about measuring a sloping top tube and if had the built sheet from the 1970's
till his reply how do you Measure a sloping top tube frame. Use a level to get what a level top tube would be at and measure along seat tube to level?
Gunnar I hope will take it to the Oregon bike show along with newly built Caylor's. Yes he is building again! after that has it is too small I post FS on Paceline
Notice the great details on this Caylor, Gunnar is sure a great builder of bicycle frames
Thanks for any help
Charles

[Mikej]

Use your iphone app? 1970 ? Nice ! That's a real tool.

[rePhil]

GCN is your friend:

https://www.youtube.com/watch?v=B7mPbF0U270

[Peter P.]

You're looking to measure the Effective Top Tube Length.

1. Place a piece of masking tape along the length of the headtube on the side. Using a tape measure, measure straight up from the ground to the intersection of the centerlines of the head tube and top tube. Place a dot where they intersect.

2. Next, stick a seatpost in the frame and apply a strip of masking tape along the side of it.

3. Now, remember the measurement you got from #1 above? Measure the same distance from the ground straight up to the seatpost and place a dot on the masking tape.

4. Connect your 2 dots which are pretty much in a horizontal line, and you'll have your Effective Top Tube Length.

[redir]

I just put a piece of masking tape on the seat post and use a long level and place a dot on the center of seat post. Then measured from the center of the head tube to the dot would give you your effective TT length center to center, or at least close enough.

BTW nice bike you got there.

[Scooper]

Maybe this will help you visualize what folks are describing.

[cnighbor1]

Originally Posted by Scooper

Maybe this will help you visualize what folks are describing.

Great that works I get 52cm TT CTC and 53cm ST CTT
I thought I had a very small frame but it much larger size
Thanks
Charles Nighbor

[carpediemracing]

That BB shell looks low. It might be the picture angle and lens distortion but it seems lower than normal. If that's the case then the frame stand over will be low for a given seat tube length. This would make such a frame seem shorter than the seat tube length might indicate.

In the opposite way I have a bike like that. It's a track bike, it's a 51 cm, but the head tube looks like a 53-54 cm head tube. I liked it partially because it looked taller than it was. At some point I realized the BB was really high, hence the tall head tube (since everything got pushed up a bit).

My Riggio 51 cm. Note how the chainstays look like they don't drop at all, meaning the BB is pretty high. This forces the top tube higher since the seat tube is positioned higher off the ground at its base. This leads to a very high seat binder bolt area - it's much higher than the frame in the first picture. Note the head tube length, which, for me, was a long head tube. The fork isn't bent, that's a distortion thing.

[Joachim]

Are you not an architect?