Top Tube question

[nscrbug]

Could they be measuring them differently? Just a thought...

Well, it appears they all use the "horizontal" or effective TT length...so I would assume that they are all measuring the same way. But I suppose it's always a possibility that they aren't.

[indysteel]

Eh, I've talked to any number of LBS sales people over the years to know that some of them don't know their product lines very well. A few weeks ago, someone tried to convince me that a particular company's WSD FS bikes had short top tubes/standover than their unisex counterparts. No, actually they don't but thanks for the helpful salespitch.

Now, don't get me wrong; it's hard to commit that stuff to memory year and year. I get it to some degree, but I think they should be careful in making geometry generalizations.

[Becky]

Eh, I've talked to any number of LBS sales people over the years to know that some of them don't know their product lines very well. A few weeks ago, someone tried to convince me that a particular company's WSD FS bikes had short top tubes/standover than their unisex counterparts. No, actually they don't but thanks for the helpful salespitch.

Indy, so true! My only "WSD" bike has identical geometry to the company's unisex "comfort carbon" geometry....and a girly paint job

[laura*]

Well, it appears they all use the "horizontal" or effective TT length...so I would assume that they are all measuring the same way. But I suppose it's always a possibility that they aren't.

They may all be "measuring the same way", but that doesn't mean they are measuring equivalent lengths.

Imagine a bike with a very vertical seat tube. To set up a proper saddle to crank relation, this bike would use a seat post with a large setback. Now imagine a bike with a very tilted back seat tube. This bike might have a seat post with no setback. With identical saddle to handlebar length, the second bike will have a much longer (effective) top tube.

[OakLeaf]

The weird thing is that my 50 cm '07 Synapse Feminine has a 50.5 ETT. It does have a pretty steep STA though. Unfortunately they took the archived specs down and I didn't save a copy, but I want to say mine is 75° vs. your 74°. Wasn't somebody just talking about trigonometry - will 1° of difference over say 70 cm of seat tube, seatpost and saddle make a 1.5 cm difference in the reach??

[Becky]

A little bit of reading on the subject:

http://www.billbostoncycles.com/seat_tube_angle.htm

http://www.velofitter.com/storage/Ro...lines.4.10.pdf (page 4)

The rule of thumb is that, for every degree that the STA increases, the effective top tube increases 1 cm.