# Look Geometries completely confusing!!!



## elviento (Mar 24, 2002)

Been looking at a Look frame lately and I checked out the geometries at the following link.

http://www.lookcycle.com/v2/anglais/catalogue/2006/geom.php

Here is my puzzle. 

1. Between a 51 and 53 (for 585), the seattube lenght is 4.5cm different even though their virtual seattube length is 2cm apart. OK, then I notice the 51 toptube has a greater slope at 6cm instead of 3.5cm. So maybe that's why. The idea might be that the shorter guy needs more clearance so make it a bit more sloping (kinda like Giant TCR). 

OK, but why does a 49 frame have less slope than a 51 (at 5cm)? And why does a 55 have more slope than a 53? In fact the 57 has no slope at all. Up to 59, it starts to have a little bit of slope again. So as the size increases, the slope situation is as followings: 5cm, 6cm, 3.5cm, 4.5cm, 0cm, 0.7cm. Seems extremely arbitrary to me. 

2. Now in terms of headtube length, the 51 is 12.5cm and the 53 is 14.8cm. The 51 headtube is 2.3cm shorter. That's strange too, because the 51 has a steeper seat angle and a slacker head angle, both of which should result in a slightly longer toptube (check Colnago's sizes and you will know what I mean) so the 51 headtube should be roughly only 1.5cm shorter than the 53. I can't figure out how it ended up 2.3cm shorter. Note at this point we don't really care about the slope or seattube length, since we are going off the virtual seattube here. 

I am between sizes, but since I ride a 53 Colnago (which is really 51cm c-c), the 51 Look seems more logical but I may have a little trouble getting used to the dramatic slope it has.


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## C-40 (Feb 4, 2004)

*geometry chart error...*

I copied all the realvent comments I posted on the bikes,frames and forks forum and posted it here:

I just happened to measure the actual seat tube length on my 51cm 585 and found that it is 1cm longer than listed on the LOOK geometry chart. The total length, is 48.6cm, not 47.6cm and the c-c ST is 46cm, not 45cm. That makes the slope 5cm, not the 6cm listed on the chart. The standover is also larger than listed. Who knows how many other errors might be in the chart.

http://www.lookcycle.com/v2/anglais/.../2006/geom.php


The only thing I pay attention to when figuring out if a sloping TT frame will fit is the TT length, the STA and the head tube length with the headset installed. The TT and STA will give me the frame's reach (TT minus setback), so I can figure out the stem length difference between a new frame and my current ride. The head tube length, with the headset, tells me how much spacer I might need. Rarely, you might find a frame with a BB drop that differs significantly from the standard 7cm. If so, then this will affect your HT length requirement.

As for being in-between a 51cm and a 53cm, that seems kind of unlikely, considering the HT difference is only 2.3cm and the actual reach only differs by 1cm, after taking into account the change in the reach caused by the STA difference. The smaller size will require some combination of greater stem rise or spacers to make up 2.3 cm and one size longer stem.

The reach of the 51cm LOOK and the 53cm Colnago are basically the same. The LOOK has a .5 degree steeper STA, but a 5mm shorter TT, which offset each other. The LOOK will have a total HT length of 140mm, with the headset, which should be virtually identical to your Colnago, depending on the model year. Colnago increased the HT length by 7mm across the board a few years ago. It does not seem that you are in-between sizes at all, unless the Colnago doesn't fit.


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