frame geometry question??

[BlackTiBob]

Hi,
I'm looking to find out the effective seat tube length on a bike with sloping top tube.
If the Horiz TT length is 55.0 cm with a 7 degree slope and the ST length is
49 cm, what is the effective seat tube length??

Any more dimensions needed?

Thanks

[Mikej]

tt actual or effective?

[Mikej]

if tt is effective 55 cm, then st = +6.7531 cm to 49 cm, tt actual = 55.413 cm

if the tt is actual 55 cm, then st = + 6.7028 cm to 49 cm.

All dimensions would be c-c

[Pete Serotta]

The length of effective TT means that if there was a level TT from seat point to HT center. That is the length that is important for fitting for riding

With a sloping tt length - it does not have much of a bearing for fitting onto a road bike.

A sloping TT allows the Head tube to in effect be higher so the stem upward slant can less or level. For some companies it means that can have stock bikes that will get more folks by just changing slope of stem and length.


With Serotta it can be custom and working with a good fitter you can have a slope or not have a slope in many cases.

Many folks like slope and need to know the effective TT length so that can understand the tt length to bars from seat for selecting stem length

[Dave]

As already noted, the term "effective" really means horizontal. If a frame has a horizontal TT length of 55cm, the the seat tube length (c-c) would be 55 times the sine of 7 degress times 55cm, plus 49cm. That would be 55.7cm. The seat tube length plays no part in the fit of a bike. If you want to get some idea of the vertical size of the bike, you should look at the head tube length and the standover height, if you've got short legs.