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Discussion Starter #1
hi im thinking of buying a new frame my height is 5 8" here is the results i got from calculator fit is it make sense mesurments are correct and was taken a few times
im intrested in the french fit system what is your opinion?


Measurements
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Inseam: 81
Trunk: 64
Forearm: 34
Arm: 72
Thigh: 58.4
Lower Leg: 54
Sternal Notch: 140


The Competitive Fit (cm)
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Seat tube range c-c: 52.4 - 52.9
Seat tube range c-t: 54.1 - 54.6
Top tube length: 56.1 - 56.5
Stem Length: 11.2 - 11.8
BB-Saddle Position: 73.1 - 75.1
Saddle-Handlebar: 54.1 - 54.7
Saddle Setback: 3.9 - 4.3
Seatpost Type: NON-SETBACK


The Eddy Fit (cm)
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Seat tube range c-c: 53.6 - 54.1
Seat tube range c-t: 55.3 - 55.8
Top tube length: 56.1 - 56.5
Stem Length: 10.1 - 10.7
BB-Saddle Position: 72.3 - 74.3
Saddle-Handlebar: 54.9 - 55.5
Saddle Setback: 5.1 - 5.5
Seatpost Type: NON-SETBACK


The French Fit (cm)
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Seat tube range c-c: 55.3 - 55.8
Seat tube range c-t: 57.0 - 57.5
Top tube length: 57.3 - 57.7
Stem Length: 10.3 - 10.9
BB-Saddle Position: 70.6 - 72.6
Saddle-Handlebar: 56.6 - 57.2
Saddle Setback: 4.6 - 5.0
Seatpost Type: SETBACK
 

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It's all in the top tube

There is no ‘right’ or ‘wrong’ when it comes to bike fit. What may be comfortable and efficient for one rider doesn't necessarily hold true for another. I would warn against getting a bike with a top tube that is too long for you. There is nothing you can do about that; if the top tube or seat tube is too short you can always go for a longer seatpost with more set-back and a longer stem. There is nothing you can do with a top tube that is too long for you and that includes fitting a really short stem. I would always err on the side of ‘too short’ than ‘too long’ when it comes to top tube length.
The 'French Fit' measurements that you have quoted seem to be quite long in the top tube area. You asked for opinion and here is mine: be very careful not to get a bike with a top tube that is too long for you.
 

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duh...
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gizzard said:
There is no ‘right’ or ‘wrong’ when it comes to bike fit. What may be comfortable and efficient for one rider doesn't necessarily hold true for another. I would warn against getting a bike with a top tube that is too long for you. There is nothing you can do about that; if the top tube or seat tube is too short you can always go for a longer seatpost with more set-back and a longer stem. There is nothing you can do with a top tube that is too long for you and that includes fitting a really short stem. I would always err on the side of ‘too short’ than ‘too long’ when it comes to top tube length.
The 'French Fit' measurements that you have quoted seem to be quite long in the top tube area. You asked for opinion and here is mine: be very careful not to get a bike with a top tube that is too long for you.

to add, TT gotta be considered with STA. A frame with a longer TT and slack STA could fit exactly the same as a frame with a shorter TT and steep STA. Regarding the "wrong" sized TT, you can get a longer stem to stretch out (albeit while pos affecting handling and weight distribution), but stems only come so long and so short.
 

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Disagree

The example of a long top tube and a slack seat-tube angle being similar in fit to a short top tube and a steep seat-tube angle, is inappropriate. In fact they are diametrically opposed. I think what you meant was: a short top tube with a slack seat-tube angle would be similar in terms of fit to a long top tube and a steep seat-tube angle.
When considering seat tube angles it is also important to consider how far you like to slide your saddle back on its rails and even how much set back your seat post has (compare a record carbon seat post with a Thomson Elite zero setback for example).
Still, all things being equal, if you're too stretched out as a result of a very long top tube you're as good as screwed.
 

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I went through the same thing..

I encountered the same problem when I decided to to buy a bike that fit 4 years ago. Each online site I visited provided me with a different frame size. I got fitted professionally (for free) with the stipulation that I could swap out stems. However by the time I got everything tweaked in, two years had passed and it was way past the time to ask for a stem exchange. For me, my body went through a lot of changes as I had not ridden for several years and it was a matter of finding the right saddle position (and the "right" saddle). I did go to a longer stem as I found I needed to be more stretched out. One thing that helped me is that the owner of my LBS guaranteed that I would like my new rig or I could ask for a refund. I don't think you can find that kind of deal on the internet. It also shows the advantage of being a loyal customer.

Getting professionally fitted by someone who knows what they are doing is a step in the right direction. I know what fits me now, but I had no clue before

In my own humble little know nothing opinion, unless you are absolutely sure of what frame size/geometry to go with, I'd take the time to get fitted and be leery of the online fit guides. Two different riders can have the same body proportions, but ride different size bikes. A lot of it comes down to preference and what works for you.
 

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You may disagree, but you're totally wrong

gizzard said:
In fact they are diametrically opposed. I think what you meant was: a short top tube with a slack seat-tube angle would be similar in terms of fit to a long top tube and a steep seat-tube angle.
You are, in fact, 100% wrong. A steep seat tube angle means that, with the rider in the same position relative to the BB, the top tube "starts" from a position in space that is farther forward compared to a frame with a slack seat tube angle. Therefore, to have the head tube in the same place relative to the rider, a frame with a steeper seat tube angle will need a shorter top tube. For every degree of steeper seat tube angle, the top tube needs to be roughly 1 cm shorter to keep the head tubethe same distance forward from the rider.

It's one thing to be wrong about such things, but to be simultaneously so sure of yourself is something else again :)
 

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duh...
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gizzard said:
The example of a long top tube and a slack seat-tube angle being similar in fit to a short top tube and a steep seat-tube angle, is inappropriate. In fact they are diametrically opposed.
you sure?


gizzard said:
I think what you meant was: a short top tube with a slack seat-tube angle would be similar in terms of fit to a long top tube and a steep seat-tube angle.
No, I meant what I wrote and wrote what I meant.
 

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Semantics

I think we're saying the same thing, although I' m pretty sure you're going to disagree. Generally, shallow seat angles tend to produce longer top tubes. Can we at least agree on that? The corollary of that statement is that steep seat angles – like those typical of tri-specific bikes – tend to produce short top tubes, although that does not necessarily hold true for all tri bike manufacturers. Another example is the typical geometry of a track bike; steep seat angle and short-ish top tube. No so?
 

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Discussion Starter #9
well what should i do?

thank you all just went to rivendaals site where the man tells you to take bigger sizes of frames by 2-5 cm above your current frame due to wrong frame sizes sell by bikes shops
what do you say?
and i quate from rivendalol web site

"When you come to us already owning two or three or half a dozen or more bikes, and I recommend a size two to five centimeters bigger than the bikes you already own and have spent lots of money on, your brain tries to reconcile what you have (and have spent lots of money on) with what I’ve just recommended."

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http://www.rivendellbicycles.com/html/bikes_framesize.html
 

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naranjito
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gizzard said:
I think we're saying the same thing, although I' m pretty sure you're going to disagree. Generally, shallow seat angles tend to produce longer top tubes. Can we at least agree on that? The corollary of that statement is that steep seat angles – like those typical of tri-specific bikes – tend to produce short top tubes, although that does not necessarily hold true for all tri bike manufacturers. Another example is the typical geometry of a track bike; steep seat angle and short-ish top tube. No so?
You are definitely not saying the same thing! (you weren´t the first time anyway, this time you are saying the opposite to what you first said...) Forget about where the saddle is and think about the horizontal distance from the BB to the TT/headtube intersection (commonly known as 'reach'), which is what TT length is all about. For a bike with a shallower seat angle (73*, for example), you will need a longer TT to put the TT/HT intersection at the same place as on a bike with a steeper ST (for example 73.5*). All the while assuming that the TT on each bike is horizontal and they are both the same vertical height above the BB.
It´s not that shallower or steeper ST angles "produce" longer or shorter TT, it´s more a case of when changing the ST angle you need to adjust the TT length accordingly to provide the same reach, if that´s what you want.

foz
 

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Samantics

Foz

Which is why I mentioned semantics. You're right, 'produce' is an inappropriate term to use; I should have used the term 'require'. But basically you're explaining my most recent post.
Perhaps my initial reply to FatTireFred was ill explained, but try to get your head around this statement: “A frame with a longer TT and slack STA could fit exactly the same as a frame with a shorter TT and steep STA”.
I responded to FatTireFred’s assertion because it simply isn’t true. Like I said those two scenarios he cited are diametrically opposed. Before you disagree with me read it again: “A frame with a longer TT and slack STA could fit exactly the same as a frame with a shorter TT and steep STA”.
 

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Well..

amirt62 said:
thank you all just went to rivendaals site where the man tells you to take bigger sizes of frames by 2-5 cm above your current frame due to wrong frame sizes sell by bikes shops
what do you say?
and i quate from rivendalol web site

"When you come to us already owning two or three or half a dozen or more bikes, and I recommend a size two to five centimeters bigger than the bikes you already own and have spent lots of money on, your brain tries to reconcile what you have (and have spent lots of money on) with what I’ve just recommended."

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http://www.rivendellbicycles.com/html/bikes_framesize.html
Well, I just own two bikes. Different brands, different geometries. One is a 59, the other a 61.

I can probably ride anything between a 58-60, it's just a matter of moving the saddle around and have the right stem length. However I put about 6,400 miles a year on the bike that fits me the best (the 59) and about 1,000 on the 61. If I ride the 61 a lot, my back will bother me.

You might want to try and find a pro bike shop and sit down and talk to someone. I talked to the owner of my LBS before hours and a lot of questions he asked was about the type of riding I did and what I did not like about my current ride.

I used a book a lot for reference "Training For Cycling", Davis Phinney/Connie Carpenter.
They have a good chapter about the process of of equipment and setup. The best way to learn is from the experience of others. I discovered this book way after I bought my new bike and it helped me set it up right.

Take your time and don't rush into anything.
 

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duh...
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Nope, can't blame semantics or samantics, this is what you wrote:

gizzard said:
a short top tube with a slack seat-tube angle would be similar in terms of fit to a long top tube and a steep seat-tube angle
No, THIS is "diametrically opposed". And before you disagree, read it again... then think about it and read it again if you have to.

I wrote "A frame with a longer TT and slack STA could fit exactly the same as a frame with a shorter TT and steep STA". How is this any different than your statement that "shallow seat angles tend to produce [require] longer top tubes"???
 

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naranjito
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gizzard,

In your first reply to FatTireFred you stated "The example of a long top tube and a slack seat-tube angle being similar in fit to a short top tube and a steep seat-tube angle, is inappropriate. In fact they are diametrically opposed. I think what you meant was: a short top tube with a slack seat-tube angle would be similar in terms of fit to a long top tube and a steep seat-tube angle" FTF knew what he meant, and Kerry Irons and I know what he meant too. I think you got confused between long and short and steep and shallow.

Later you stated that "I think we're saying the same thing, although I' m pretty sure you're going to disagree. Generally, shallow seat angles tend to produce longer top tubes. Can we at least agree on that? The corollary of that statement is that steep seat angles – like those typical of tri-specific bikes – tend to produce short top tubes" This is the opposite to what you said the first time, and is correct.

Basically for the same reach you need a long TT and shallow ST angle, or short TT and steep ST angle. Saddle setback from the BB is not related to the reach of a frame, and can be made the same on frames with different ST angles by sliding the saddle on the rails or using a seatpost with more or less setback.

foz
 

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Call me a Fred
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I size my frames the old fashion way, I go to a LBS and test ride various sizes and by the one that seems to fit the best. It's the same way I buy shoes. When I leave, I have a product that fits. No measuring necessary.

It hasn't failed me yet.
 

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I would agree that the "effective top tube" measurement or "cockpit length" (i.e. level measurement from center of seat post to hand position) is the best starting point. I've found that the cockpit length on all of my bikes is nearly identical , whether mountain bike, cyclocross, or road bike. For bikes with drop handlebars, I measure the cockpit length to a hand position on the hoods, so the reach to the tops or drops varies from there of course.

Unfortunately, advertised frame sizes are based mostly on seat tube measurements, which results in a lot of variations between different manufacturers. Ideally, I'd look first for the frame size that gives me my desired cockpit length, using about a 100mm stem length. Thus, I can make small adjustments to stem if I need to, without adversely affecting the handling (as too short or too long of stems can do).

For instance I'd generally fit a 53cm for Lemond, Look, or Merckx. I'd fit a 54cm for Trek or Colnago. I'd fit a 55cm for Bianchi. Beyond finding the right cockpit length, it's all about getting the right feel in stability and handling. Things like seat tube angle, head tube angle, fork rake, stiffness, seat-to-handlebar drop, are all going to affect the overall handling. I don't think there is any magic fit formula for this. Also, I don't quite get these fit systems, because they seem to be based on sitting in a static position on the bike, when what's really important is how it feels when you're riding it.

There really is a big difference between how different frames feel. I love the fit and feel of a Colnago, and hate the fit and feel of a Lemond. But that's just me. So, find the right effective TT length for you and then take some bikes for some test spins.
 

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gizzard said:
Which is why I mentioned semantics.
You sound like a bunch of Anti-Semantics to me. For shame.

OP should call Rivendell and have them build him a custom. Most folks will think it's way too big for him, which will add to the bike's mistique. He can play with the various fit calculators for two years while his order languishes on the Riv wait list.

TTFN,

FBB
 

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re. Rivendell

amirt62 said:
thank you all just went to rivendaals site where the man tells you to take bigger sizes of frames by 2-5 cm above your current frame due to wrong frame sizes sell by bikes shops
what do you say?

Keep in mind that the information posted on the Rivendell website is generally Grant's opinion. Some folks agree with him, some don't. A lot of it depends on what you want to do with the bike.
As far as different fit systems or philosophies giving you different recommendations for frame sizes I would say just use the fitting numbers as a range to work with. There is no one system that can determine perfect fit everyone on the planet. Find some bikes that fall in between the extremes of the recommendations and ride them.
 

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Still can't agree with you on the 'fit' thing

Hi Fred
I'm afraid I still can't agree with you on the ‘fit’ thing, and I promise you I am not arguing with you for the sake of it; I merely find it interesting that there are a number of views on this issue and I’d like to get more information on the ‘fit’ thing so that I can better appreciate yours.
You stated: A frame with a longer TT and slack STA could fit exactly the same as a frame with a shorter TT and steep STA. I’m battling to reconcile those two geometries (configurations might be a more appropriate term). A frame with a long TT and slack STA, like an old-style European ‘climbing’ or stage-race frameset like a Casati, would have a large ‘cockpit’ relative to a frame with a short TT and a steep STA, like those typical of track frames. That I think is fairly universally accepted. How then could the fit be exactly the same? The only thing I can think of that may be causing the confusion is our different interpretation of the term ‘fit’. I assume you’re referring to the position of the rider, position of the saddle (all things being equal), and maybe position of the bars, given the same stem length. In my opinion, they would be hugely different and therefore the fit would be different.
That is all that I am saying.
 

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naranjito
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gizzard,

I´m not arguing just for sake of it either, so please don´t think I am...

Have a look at this diagram. Hopefully it is clear how the BB, saddle and bar position are not dependent on the frame geo (within reason!). The drawing is not to scale, but the calculations are.
Assume a frame with 56cm c-c ST, ST angle of 73* and TT of 56cm. The TT length of 56cm can be broken down into two distinct parts - setback and reach - these two dimensions being the amount of TT on either side of a vertical line drawn upwards from the BB. In the case of this frame, the setback would be 16.4 cm and the reach would be 39.6cm.
Now, imagine a second frame with 56cm ST, and 74* ST angle. the setback for this frame would be 15.4cm (cos 74 x 56). this is exactly 1cm less then for the first frame, so with a TT 1cm shorter than the first frame (55cm), the reach would be exactly the same.

The saddle setback from the BB can be kept the same either by sliding it forward or back on the seatpost or by using a setpost with more setback on the frame with 74* ST.
If the same stem setup is used on each bike then the bars will also be in the same position relative to the BB and also the saddle. The fit is the same for both bikes, even though one of them has a longer TT and shallower ST angle than the other. The same rider could achieve the exact same position on these two bikes with absolutely no problems.

foz
 
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