Frame size, new bike fitting, questions

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GT56
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Location: Switzerland

by GT56

i looked at a number of geo tables, but there aren't any with stack heights of 600 that have a reach of less than 395

staying with cervelo (as reference only :)) you could consider going down one size to 56 - stack = 580 reach is 387 so frame reach is 9 mm less. also decrease stem lenght to 110. if you want to keep the handlebar drop the same, you would have to add 25 mm of spacers though......

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Sjoerd
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by Sjoerd

You're absolutely right. Tall bikes naturally come with (a relatively) long reach and that's not what I'm after necessarily. The Rose Xeon RS still looks like a relatively tall and relatively short bike to me, but I'll do some more number-crunching ;)

Regarding the "spacer tower": I feel I could lose at least another centimter in bar-height on my current bike, maybe even 1,5 cm but not much more. I could live with a 1 cm spacer though, or a cone shaped headset-cover.

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stella-azzurra
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by stella-azzurra

Get a frame that is one size smaller that will give you the shorter top tube.
You can adjust the seat height and bar reach with the stem and seat post.
The geometry will be fine.
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Colonia
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by Colonia

Sjoerd wrote:187 cm tall
91 / 92 cm inseam
I ride my saddle at 82 cm with 9,5 cm of setback
I have 10,5 cm of drop between saddle and bars, with a slammed stem and an extra thin headset-cover
The stem is 6 degrees angle and 120 mm long

So, long legs and short torso.

@ultimobici: the Cervelo is tall enough but feels too long. It's more a question of weight distribution than being unable to reach the bars. I'm quite light for my length, in the summer I go down to 60 kg and judging by feeling, most of that weight is on the rear wheel. A longer bike makes cornering harder for me. If you look at the size of the Rose, the bike looks shorter than the Cervelo with a relatively long seat tube, so I thought that it would fit me better. I need the height because of the saddle height, but I don't need the long top tube that ususally comes with it. I've had a 57 cm BMC Pro Machine (57,5 cm toptube, 18,7 cm headtube) which fit me much better than my current bike, but unfortunately I broke two frames and couldn't get a warranty replacement because they weren't being made anymore.


Your saddle is too high. It's higher than what even that old Lemond/Guimard formula recommends for your inseam, and that typically produces a high seat height which requires a long adaptation period for those who can tolerate it, and many can't. For an accurate saddle height do the heel on pedal test in your socks and add in the thickness of your shoe sole to get a starting saddle height. Saddle should be fairly far back in the clamp for this test -- at least at midrail. You should be able to pedal backwards smoothly and without hip rocking with heels on the pedals. With your shoes on and in a normal riding position, you should be able to drop your heel at least 1-2 cm below the horizontal pedal with the leg in the fully stretched position. If you can't then you have almost no bend in your leg when pedaling and are probably dipping your toes to achieve bend, which is inefficient. At your height, you should be on a frame that gives you about a 9cm drop to the bar with the saddle in the correct position. For your size, the top of saddle should be about 18 cm above the seat tube. That will give you a classic stage racing position and a sweet looking set up. Your Cervelo should be very close.

This is an excellent general reference, but you have to get the saddle height right first. I would not go by a static inseam measurement: http://de.scribd.com/doc/93309029/Bike- ... ve-Moulton

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Sjoerd
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by Sjoerd

Thanks for your kind response, I appreciate that! Although I don't have the feeling that my saddle is up too high, out of curiosity I'll check how things are with the heel method you're mentioning.

Colonia
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by Colonia

Sjoerd wrote:Thanks for your kind response, I appreciate that! Although I don't have the feeling that my saddle is up too high, out of curiosity I'll check how things are with the heel method you're mentioning.

Sure. Just a note: On Dave's chart, I would ignore the inseam measurement. Look at the other parameters of height, shoe size, etc. to get your frame size. Inseam measures are rarely taken correctly, and even Dave's method differs slightly from some of the others floating around. What matters is your actual saddle height, as it can throw off everything else if incorrect. Unless you have really wacky proportions, your Cervelo should be close. My guess is that your true saddle height is going to be around 78-79 based on the test.

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Sjoerd
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by Sjoerd

Can't access that chart since I am at work, but I'll look into it tonight.

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elviento
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by elviento

Maybe a custom frame? Or move saddle forward slightly for weight distribution and see how that feels?
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kgt
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by kgt

With most modern frames having 4-6 sizes it is not that easy to find a really good fit. Colnago still has 12 or something sizes for that reason. A custom frame is another option.

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Sjoerd
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by Sjoerd

Wish I could afford a C59, but unfortunately that's not going to happen. Same goes for custom. And I would never go down that route without a proper fitting proces. Problem is, you read so many different stories on bike fitting and good / bad fitters. Steve Hogg mentions on his website he deals with clients that have been "professionally" fitted three times before they come to him. So that raises the question: when is a fitter a good fitter? And will I benefit from it?

Let's not forget that I'm able to ride my current bike without any (big) problems. In fact, I've ridden tons of miles (two Marmottes, two Maratone dles Dolomites, five Trois Ballons) on bikes that I consider a bit too large. They were fine but they never felt perfect. I just kept getting the feeling a smaller bike would suit me better. Maybe with roughly the same reach, but with my weight more on the front wheel.

My dad lent me his Orbea Orca (size 57) this week and although I had the feeling it would be too small, it fits very nicely! It has a 57 cm toptube and a 18,5 cm headtube (with a 1 cm spacer). It's given me enough confidence to order the Rose Xeon RS in size 59. If it doesn't fit well I'll let you guys know and you can all shout at me :lol:

DaleRider
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by DaleRider

I'm in need of a quick sanity check here before I have my LBS order up a new SLR01 frameset.

I'm 172.5 CM tall which puts me at the large end of the 50cm frame and the small end of the 53cm frame. Currently my favorite frame and best fitting frame is my old 54CM CAAD8 R1000 circa 2004 or 05. Based on my hack job measurements, the CAAD8 has a stack of 540mm and a reach of about 585mm. I'm running a 100mm, -6* stem that sits on the 1cm FSA headset cap with no extra spacers.

Based on my backwards math, I'm thinking that the 50cm SLR01 with a 110mm stem and a 10-15 mm of spacers on top of the headset cap should put my bars in almost the exact same spot as my CAAD8. If I go with the 53 SLR01, I think that I'd need a 90mm stem that would be slammed on top of the head tube to get the 110mm of saddle to bar drop that I run.

Sadly the local shop doesn't have a 50 or a 53 to test out to see what would work best.

Any thoughts???

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Elrey
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by Elrey

I would go for the 53
They don't feel that long. So you could use a 100mm. stem, just as well.

DaleRider
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by DaleRider

I managed to stumble across this while looking at some other stuff this morning.

Image

These measurements line up with what I was getting on my frame. The original CAAD8 had a shorter head tube and a longer seat tube, and less of a slope to the top tube than the newer one. This would put my stack and reach numbers close to what I believe they are.

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bikerjulio
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by bikerjulio

looking at the 2 geometry charts, and the key measurements, the 53cm BMC is closer, slightly bigger.

STA is the same at 73.5 deg.

ETT is 55cm for BMC vs 54.5 for the CAAD

HT is 15.3 for BMC vs 14.6 for CAAD.

both measurements are 1cm smaller than CAAD for the 50cm BMC.

So if you need a more aggressive position, get the 50cm. Otherwise it's the 53.
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DaleRider
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by DaleRider

bikerjulio wrote:
So if you need a more aggressive position, get the 50cm. Otherwise it's the 53.


Never thought if it that way. I don't need a more aggressive position, in fact, I don't think I can get more aggressive with my position.

I did however decide to get scientific about the whole thing. I built a simple calculator in Excel and based off the measurements in Cannondale's chart I get these nubmers:

Stack= 556
Reach= 379

Very close to the newer CAAD8 surprisingly.

So it looks like I'll be going with the 53cm frame.

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