Oct 24, 2002 1:51 AM
|well, I finally got my epx built up...it rides nicely but it has a very unusual, IMO, geometry. The Seat tube and head tube angles are fairly vertical, yielding a longish top tube with minimal setback. Once I got my saddle positioned like my Colnago, I had to shorten my stem by 2cm! The bottom line is that for the $450 I paid for it, it is an ok frame. But I much prefer the Colnago geometry every time. My reach is relatively short compared to my inseam, so the shorter top tubes on the Colnagos are more to my liking. If you have the opposite fit issues, longer reach compared to your inseam, then the EPX may be the answer for you.
|re: epx 303||Frith|
Oct 24, 2002 5:50 AM
|Thanks for the report. I managed to hop on one for a little spin a couple weeks back and noticed the same geometry issues. I also have a relatively short torso and found that for sure i would need a shorter stem. I also found the natural flat seat angle to be really ill fitting. I'm sure this bike fits a lot of bodies, not mine unfortunately. What's weird though is that I had ruled out Trek 5x00 for the reason that it's geometry seemed like it was for a longer torso but i hopped on a 58 that same day and was pleasantly surprised at the immediate comfort.|
Oct 24, 2002 6:23 AM
|What I've discovered through this experience is that top tube length itself is not the main determinate of reach, because the saddle position is really determined by the STA and the reach by the HTA. Thus, in my situation, where a 56 Colnago fits me with a 55 cm top tube, a Look 56 (54c-c) which has a 56 top tube would not necessarily require a shorter stem, since the set back is 1.5cm> than the Colnago due to the shallower STA. Thus the saddle position may actually be more forward negating the 1cm increase in TT length. Saddle position is everything.|
Oct 24, 2002 9:56 AM
|What you say seems to be contradictory. If the the Look has more setback, then the saddle position should be more back, not more forward, as you said.
One thing that I think is lost here is that the setback is typically measured along the top tube. However, the setback will vary with the saddle height: the higher the saddle, the greater the setback. How great is determined by the seat tube angle. Once the correct saddle height is determined the setback can be adjusted further by moving the saddle for or aft along the saddle rails.
Once this is set then reach can be determined. This is a function of the head tube angle (a steeper head tube angle effectively lengthens the reach and vice-versa), the stem length, the stem angle, the bars used (some bars have a longer reach to the hoods) and of course the top tube length. However, reach is not the only thing. You need to be concerned with the drop (distance from the saddle to the top of the bars). This is a function of the steerer tube length (determined by the head tube length) and stem angle.
|I didn't explain it very well, sorry.||MXL02|
Oct 24, 2002 2:46 PM
|If a frame has a lot of set back already, then theoretically, given the same saddle height, you will not have to move the seat farther back on the seatpost, like you would if the frame had a steeper STA. Thus, if both bikes have 56 cm TT's, but on one the seat is farther back (the one with the steeper STA), then this steeper frame will actually position the rider further back from the head tube. Believe me, I know this is true: I spent 2 hours last night with my LBS owner/racer who's been doing this for 20 years... If you use the same saddle height and fore/aft position in relation to the KOPS concept, with the same TT length, a steeper STA will actually position the rider further away from the head tube, this is why Colnago uses shallower HTA's and shorter top tubes-so they can make the STA fairly steep, without increasing the reach to the bars, and probably why Eddy Merckx uses a shallower STA, so he can get his riders on stem lengths of 110mm, while maintaining a good KOPS relationship, as has been pointed out in previous posts.|
|The concept of effective top tube length||Kerry|
Oct 24, 2002 4:39 PM
|While some insist that the phrase "effective top tube length" only applies to sloping top tube bikes, it has long been applied to your situation. Assuming that you can get the correct position of the saddle relative to the BB, then changes in seat tube angle will change the effective TT length. Increasing STA increases the effective TTL by about 1 cm per degree. IOW, for two bikes with the same measured TTL, the bike with a 74 degree STA will put the head tube 1 cm farther forward than the bike with a 73.|
Oct 24, 2002 8:13 PM
|Thanks for a more lucid explanation.
|The concept of effective top tube length||chapperal2k|
Oct 26, 2002 11:38 PM
|As I understand it all you are really saying is that on a bike with a steeper STA you simply have to move the saddle further back, which obviously lengthens the reach.|| |