Bicycle geometry is driving me NUTS!!!

[Catagory6]

on paper, my Look 585 and 2016 De Rosa Protos look to be almost identical. although there is some info missing from both geometry charts.

same saddle, same stem, same bars.
ST angle is only 0.1 degree difference (74.49 protos, 74.5 look)
the eTT is 0.49 mm difference (53.49 protos, 53 look)
the distance from BB to fork dropout is 0.01mm difference (57.99 protos, 59 look)
the distance from the nose of the saddle to the "crotch" of the shifters (campy 11 vs campy 10) is identical
distance from nose of saddle to center of handle bar clamp is 5mm shorter for the protos.

however the saddle setback (nose of saddle from the center of BB) is WILDLY off.
the Protos is 32mm set back. the Look is 50mm set back

the De Rosa HT angle, and BB-drop are missing from the chart, and unknown to me. but considering all the other measurements, the HT angle shouldn't be too far off. certainly not so far off as to have to put the saddle 18mm further forward.
and measuring saddle height from the floor to the top of the saddle is identical. so that would suggest they have identical BB-drop as well.
obviously the center of BB to top of saddle is identical

[MrCurrieinahurry]

Some pics please... Only cos I love both bikes,

[jlok]

Don't be surprised if the geometry chart is a bit off. Do you think they could be that accurate up to 0.01?

[Catagory6]

Don't be surprised if the geometry chart is a bit off. Do you think they could be that accurate up to 0.01?

i'll take the Protos out for a ride tomorrow and get some good photos

[Catagory6]

Don't be surprised if the geometry chart is a bit off. Do you think they could be that accurate up to 0.01?

that did cross my mind.
but for an 18mm difference, i would think there's something that's pretty far off in the geo chart

[synchronicity]

I am no expert but I don't think you should be looking at measurements of both bikes with the parts attached. Too many variables.
I suggest that you first look at the geometry of the frames alone, and then look at the geometry of individual parts like seatposts, stems, and handlebars (comparing those to each other).

[jasjas]

i ve a look 585 and a 595, both L, i put the same finishing kit on the 595 inc groupset, as i liked what i had on the 585.... the measurements were different, saddle to bar, set back, drop - all around 5mm off.

However, i couldn't really tell the difference, so who cares, recently added a TCR in a M/L and thats way different again, but within a few rides i don't notice.

I think the LOOK charts are way off or their QA is terrible.

[ghostinthemachine]

Should have built them to the same fit then.

[jasjas]

Should have built them to the same fit then.

Why? it caused me no issues!
i could go to 10 different bike fitters and end up with 10 different fits, who is to say the original fit was correct?

My point was that Geo charts may not be accurate.

[ghostinthemachine]

Why? it caused me no issues!

I was answering the OP.

i could go to 10 different bike fitters and end up with 10 different fits, who is to say the original fit was correct?

Correct or Not Correct is pretty much irrelevant. Consistent is important. (obviously 5mm variation is not inconsistent to you, 18mm on saddle setback (OP) is)

My point was that Geo charts may not be accurate.

Geo charts are a long way from the most important thing about a bike fit. Most of the fit dimensions are adjusted by saddle and bar position. As long as the frame is broadly in the right ball park, most things can be made confortable and efficient.

[Karvalo]

on paper, my Look 585 and 2016 De Rosa Protos look to be almost identical. although there is some info missing from both geometry charts.

same saddle, same stem, same bars.
ST angle is only 0.1 degree difference (74.49 protos, 74.5 look)
the eTT is 0.49 mm difference (53.49 protos, 53 look)
the distance from BB to fork dropout is 0.01mm difference (57.99 protos, 59 look)

Please learn to use decimal points properly

the distance from the nose of the saddle to the "crotch" of the shifters (campy 11 vs campy 10) is identical
distance from nose of saddle to center of handle bar clamp is 5mm shorter for the protos.

however the saddle setback (nose of saddle from the center of BB) is WILDLY off.
the Protos is 32mm set back. the Look is 50mm set back

the De Rosa HT angle, and BB-drop are missing from the chart, and unknown to me. but considering all the other measurements, the HT angle shouldn't be too far off. certainly not so far off as to have to put the saddle 18mm further forward.
and measuring saddle height from the floor to the top of the saddle is identical. so that would suggest they have identical BB-drop as well.
obviously the center of BB to top of saddle is identical

WHat's the stack and reach?

[Catagory6]

on paper, my Look 585 and 2016 De Rosa Protos look to be almost identical. although there is some info missing from both geometry charts.

same saddle, same stem, same bars.
ST angle is only 0.01 degree difference (74.49 protos, 74.5 look)
the eTT is 0.51 mm difference (53.49 protos, 53 look)
the distance from BB to fork dropout is 0.01mm difference (57.99 protos, 59 look)

Please learn to use decimal points properly

the distance from the nose of the saddle to the "crotch" of the shifters (campy 11 vs campy 10) is identical
distance from nose of saddle to center of handle bar clamp is 5mm shorter for the protos.

however the saddle setback (nose of saddle from the center of BB) is WILDLY off.
the Protos is 32mm set back. the Look is 50mm set back

the De Rosa HT angle, and BB-drop are missing from the chart, and unknown to me. but considering all the other measurements, the HT angle shouldn't be too far off. certainly not so far off as to have to put the saddle 18mm further forward.
and measuring saddle height from the floor to the top of the saddle is identical. so that would suggest they have identical BB-drop as well.
obviously the center of BB to top of saddle is identical

WHat's the stack and reach?

math is a little off, and stack and reach are missing from both charts

measuring along the sloping TT, reach for the Look is 385, Protos looks to be 390, which would reflect the 5mm difference in eTT

[Karvalo]

ST angle is only 0.01 degree difference (74.49 protos, 74.5 look)
the eTT is 0.51 mm difference (53.49 protos, 53 look)
the distance from BB to fork dropout is 0.01mm difference (57.99 protos, 59 look)
....
math is a little off

It still is.

0.01 degrees
4.9mm
10.1mm

[flying]

the distance from BB to fork dropout is 0.01mm difference (57.99 protos, 59 look)
the distance from the nose of the saddle to the "crotch" of the shifters (campy 11 vs campy 10) is identical
distance from nose of saddle to center of handle bar clamp is 5mm shorter for the protos.

however the saddle setback (nose of saddle from the center of BB) is WILDLY off.
the Protos is 32mm set back. the Look is 50mm set back

If what your trying to do is match nose of saddle behind BB/setback the same on both try this

touching rear wheel to wall
A-measure distance from wall to nose of saddle
B-measure distance from wall to center of BB
C- subtract nose measurement from BB measurement this is setback....which setback do you want? Protos or Look? Make them the same....done

Do not confuse this with front to bars measurements etc It has not to do with that nor stack/reach yada yada yada
Not that those things aren't important

[Catagory6]

ST angle is only 0.01 degree difference (74.49 protos, 74.5 look)
the eTT is 0.51 mm difference (53.49 protos, 53 look)
the distance from BB to fork dropout is 0.01mm difference (57.99 protos, 59 look)
....
math is a little off

It still is.

0.01 degrees
4.9mm
10.1mm

well thank you dr. smarty-pants

anyway, i found the reach on the protos. 385mm

floor is horizontal. bar is horizontal. plumb line bisects BB







the green tape indicates the center point of the heat tube:




gotta do the Look now... measuring from the top of the TT at the center of the HT, like i did on the Protos, reach is also 385

Protos HTa is 72-deg, which is what the Look is

this is getting more confusing with each measurement. by all measurements, these 2 bikes are almost identical

edit: persistence beats resistance, but boy do i feel stupid. at least i now know all the measurements!