# 585 reach measurement



## wayne (Aug 3, 2006)

Does anyone know what the 'reach" measurement of the large 585 optimum would be?
The imaginary line from the center of the bottom bracket to the center of the top of the head tube.


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## C-40 (Feb 4, 2004)

*info...*

If you're trying to compare a 585 to some other brand, forget about reach and stack measurements. A reach measurement can be misleading if the stack heights are not the same. 

Compare the TT lengths of the two frames and add 1cm per degree to the TT length of the frame with the steeper STA. If the STAs are the same, then just compare the TT lengths. The reach measurement is no more valuable.

If you need more help, post the frame(s) under comparison.


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## uscsig51 (May 7, 2006)

*Look 585 (XL) Stack & Reach*

Any idea what the stack and reach of a Look 585 (XL) might be? Trying to compare to Cervelo R3-SL and Trek Madone 6.9 stack & reach measurements.


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## mds (Dec 16, 2008)

You can calculate those measurements given data from the tables on the web site and in the catalog.

stack = A1*sin(J)
reach = B-A1*cos(J)

For the 585 XL Origin and Ultra, stack = 545mm and reach = 408mm, measured from the BB center to the intersection of the centerlines of the top and head tubes. These calculations won't necessarily be perfectly accurate, but they should be pretty close. On my size L bike, these calculations are very close.

uscsig51, these 3 bikes have quite a different feel, handling and ride. Test ride them all.


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## uscsig51 (May 7, 2006)

Thanks. 

However, when I measure with a tape from centerline of bottom bracket to top of top tube, I get approx. 565 mm (56.50 cm) stack vs. 570 x .956 (sine of 73*) = 54.5 cm? So with the 545mm (54.5 cm) measurement what are they measuring to, centerline of top tube? 

From the geometry chart if you take the top tube measurement of 575 mm and subtract the setback of 167 mm the reach equals 408mm (40.8 cm).


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## mds (Dec 16, 2008)

I think E = A1*cos(J), so I think you are correct: reach = B - E.

The measurement is to the centerline. That may account for your measurement difference.

By the way, the point where stack/reach are measured to (intersection of centerlines of top and head tubes) is about 48mm below the top edge of the headset, measured along the head tube centerline. So actual stack height is stem stack plus spacer stack plus 48mm above this stack/reach point.


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## C-40 (Feb 4, 2004)

uscsig51 said:


> Thanks.
> 
> However, when I measure with a tape from centerline of bottom bracket to top of top tube, I get approx. 565 mm (56.50 cm) stack vs. 570 x .956 (sine of 73*) = 54.5 cm? So with the 545mm (54.5 cm) measurement what are they measuring to, centerline of top tube?
> 
> From the geometry chart if you take the top tube measurement of 575 mm and subtract the setback of 167 mm the reach equals 408mm (40.8 cm).



I guess you don't believe that comparing the TT length with corrections for STA is just as accurate?

What leads to mistakes is comparing reach values that are not taken at the same stack height. Reach is not some magical number that allows a comparison of any size frame to another.

In this case, starting with the LOOK 585 in the XL as the base line, the R3 should have about 5mm more reach, and the 60cm Trek should be about 9mm longer.


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## uscsig51 (May 7, 2006)

So what is the stack for the LOOK 585 (XL)? Centerline of bottom bracket to the centerline of the top of head tube along a horizontal axis (which is how I believe Cervelo measures)?


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