Why All The "Sky Is Falling" and Double Think About Bike Frame Fitting
#51
working on my sandal tan
Join Date: Aug 2011
Location: CID
Posts: 22,672
Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)
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Hi I am about 6ft and I am looking to do up a racer... Would this frame suit me?
L'eroica Vintage Raleigh Reynolds 531c Frame & Forks | eBay
L'eroica Vintage Raleigh Reynolds 531c Frame & Forks | eBay
#53
~>~
4 cm frame difference, with the same geometry, less than an inch is needed to move the saddle back for the smaller frame. To have the exact same position relative to the pedal, and therefore imposing no compromise to pedaling efficiency, nor any other aspect to pedaling.
On a 52cm Vitus seatposts were not long enough to set my correct seat height.
That certainly compromises pedaling efficiency.
Too small.
On a 60cm Vitus setting seat height correctly is not a problem, however saddle rails are too short to properly set my cleat to pedal axle position.
That certainly compromises pedaling efficiency.
Being unable to comfortably straddle a 60cm frameset presents another aspect that should be obvious as well.
Too tall.
A Goldilocks fit gets everything Just Right, anything else is a kludge.
-Bandera
#54
working on my sandal tan
Join Date: Aug 2011
Location: CID
Posts: 22,672
Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)
Liked 2,606 Times
in
1,595 Posts
To be crystal clear: a 4cm variance from my 56cm properly fit frame either way is unacceptable.
On a 52cm Vitus seatposts were not long enough to set my correct seat height.
That certainly compromises pedaling efficiency.
Too small.
On a 60cm Vitus setting seat height correctly is not a problem, however saddle rails are too short to properly set my cleat to pedal axle position.
That certainly compromises pedaling efficiency.
Being unable to comfortably straddle a 60cm frameset presents another aspect that should be obvious as well.
Too tall.
A Goldilocks fit gets everything Just Right, anything else is a kludge.
-Bandera
On a 52cm Vitus seatposts were not long enough to set my correct seat height.
That certainly compromises pedaling efficiency.
Too small.
On a 60cm Vitus setting seat height correctly is not a problem, however saddle rails are too short to properly set my cleat to pedal axle position.
That certainly compromises pedaling efficiency.
Being unable to comfortably straddle a 60cm frameset presents another aspect that should be obvious as well.
Too tall.
A Goldilocks fit gets everything Just Right, anything else is a kludge.
-Bandera
#55
~>~
Too small and too large are what they are.
Converting to 'brifters, a CF saddle and a power tap would just be so wrong on this beauty as well.
Sometimes the Period Correct Police have it right.
If one desires a Modern Race fit, which I most certainly do not, select a modern frame in the proper size and contemporary component groups instead.
Buying the proper frame size as appropriate for French/Rando, Classic Race and Modern Race is just not that difficult, why kludge around if one is going to be doing high effort/long distance cycling.
-Bandera
Last edited by Bandera; 04-24-15 at 03:49 PM.
#56
Senior Member
Join Date: Apr 2005
Location: Ann Arbor, MI
Posts: 16,985
Bikes: 1980 Masi, 1984 Mondonico, 1984 Trek 610, 1980 Woodrup Giro, 2005 Mondonico Futura Leggera ELOS, 1967 PX10E, 1971 Peugeot UO-8
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I'll offer a contrasting viewpoint. Fit might not be so important for some individuals, particularly if they don't ride very often or very far. However, if you ride a lot of miles, fit becomes more and more important. I started developing all sorts of aches and pains when I went from being an occasional cyclist to riding 7,000+ miles a year. At that point, I had a professional fitting done and got a new bike that fit me much better, and the problems went away.
However, I will concede that a bike fitting is just a starting point. It will get you in the ballpark for what size frame to use, but it takes a certain amount of trial and error for a cyclist to find the right size stem, handlebar height and other fit parameters. And, of course, many cyclists can ride bikes within a certain size range by adjusting stem lengths and saddle heights. My bikes range from 56-58 cm according to manufacturers sizing, but I've got them set up very similar by using different stems, handlebar heights, etc.
Many new cyclists don't have a clue about what size bike to get, and fall prey to the fallacy that you fit a bike by standing over the top tube. That is where a good fitting can make a difference. In my opinion, the most important dimensions are top tube lengths and head tube lengths, and I can fit a range of bikes if those two measurements are within my zone. However, if a bike has a top tube that is too long or a head tube that is too short, I will never be comfortable riding it for very long. Standover is practically useless for fitting bikes, IMHO, yet many people rely on that almost solely.
However, I will concede that a bike fitting is just a starting point. It will get you in the ballpark for what size frame to use, but it takes a certain amount of trial and error for a cyclist to find the right size stem, handlebar height and other fit parameters. And, of course, many cyclists can ride bikes within a certain size range by adjusting stem lengths and saddle heights. My bikes range from 56-58 cm according to manufacturers sizing, but I've got them set up very similar by using different stems, handlebar heights, etc.
Many new cyclists don't have a clue about what size bike to get, and fall prey to the fallacy that you fit a bike by standing over the top tube. That is where a good fitting can make a difference. In my opinion, the most important dimensions are top tube lengths and head tube lengths, and I can fit a range of bikes if those two measurements are within my zone. However, if a bike has a top tube that is too long or a head tube that is too short, I will never be comfortable riding it for very long. Standover is practically useless for fitting bikes, IMHO, yet many people rely on that almost solely.
Unless you are totally constrained to use a new bike exactly as you bought it, fitting and size selection are different steps in the process of getting a bike that fits well for you use.
Once you get helped with a fitting, you go out in the real world. There your body moves around as you deal with bumps, road gratings, cars, hills, live animals, dead animals, junk on the road surface, weather, fatigue, and lighting. You butt might not want to be in that perfect location all the time, or you might have a clothing malfunction that makes you change your position. Then you have adjustments to make. The fitting is just a starting point, even if it is perfect when you leave the store. But if you don't have a good sizing, the adjustments you can make to your fitting could be limited.
#57
Senior Member
Join Date: Apr 2005
Location: Ann Arbor, MI
Posts: 16,985
Bikes: 1980 Masi, 1984 Mondonico, 1984 Trek 610, 1980 Woodrup Giro, 2005 Mondonico Futura Leggera ELOS, 1967 PX10E, 1971 Peugeot UO-8
Liked 689 Times
in
527 Posts
To be crystal clear: a 4cm variance from my 56cm properly fit frame either way is unacceptable.
On a 52cm Vitus seatposts were not long enough to set my correct seat height.
That certainly compromises pedaling efficiency.
Too small.
On a 60cm Vitus setting seat height correctly is not a problem, however saddle rails are too short to properly set my cleat to pedal axle position.
That certainly compromises pedaling efficiency.
Being unable to comfortably straddle a 60cm frameset presents another aspect that should be obvious as well.
Too tall.
A Goldilocks fit gets everything Just Right, anything else is a kludge.
-Bandera
On a 52cm Vitus seatposts were not long enough to set my correct seat height.
That certainly compromises pedaling efficiency.
Too small.
On a 60cm Vitus setting seat height correctly is not a problem, however saddle rails are too short to properly set my cleat to pedal axle position.
That certainly compromises pedaling efficiency.
Being unable to comfortably straddle a 60cm frameset presents another aspect that should be obvious as well.
Too tall.
A Goldilocks fit gets everything Just Right, anything else is a kludge.
-Bandera
If you have a 52 cm frame with a 73 degree seat tube angle and a 56 cm frame with a 73 degree seat angle, and you set your saddle height the same on both, the horizontal distance from the saddle rail clamp to the BB will be the same. Same for a 60 cm frame with that same angle. Hence there is no need in those three cases to change the saddle position on the seatpost. It's just trigonometry. As long as your preferred height can be achieved on all three bikes (you might be too tall for a short post on the 52 or too short to achieve target height on the 60), you pedaling should be the same on all three bikes.
If the 60 cm Vitus has a different seat tube angle, you could run out of "slide range" on a saddle.
#58
~>~
Fitting a rider on bike properly assures that they are as comfortable, efficient and in control as possible.
Having the correct frame size matters in the process, which is tested on real hills for real hours by real riders on actual hardware not a spreadsheet.
Once more, the seatposts of the design era are Too Short to get the saddle height correct on a 52cm frame, it is simply Too Small.
Try finding a 25mm OD seatpost long enough for the suggested kludge ( good luck), if found the drop would be 9cm, not the 5cm required for a Classic Race fit as pictured.
That puts it into Modern Race fit, which I am not adapted to or interested in with decades on this very fine Guimard/LeMond system fit.
With the Classic Race fit I run DT controls, which is part of the fit design requirement for confident convenient shifting in a peloton of the era.
Try that with an extra 4cm of drop, no thanks that's Way below where I could operate. Too small, even if kludged.
Quill stems will not allow a taller position, it is what it is.
Control placement and operation is reflected in frame design for each generation of components.
The fit and sizing of the 1940', 1980's and 2000's takes into consideration control operation.
Modern Race fit relies on the 'brifter system ( with considerable seat time and adaptation),re-designed "cockpit" components and saddles to achieve the extremely aero position top riders use today.
If we still ran the Bianchi's '40's tech we'd still use a similar frame sizing from that era.
A 4cm frame size variance up/down today would be just as unacceptable as in my Classic Fit era. Ask in '33 if you are curious.
If the 60 cm Vitus has a different seat tube angle, you could run out of "slide range" on a saddle
The Turbo on my 56 is slammed back to max to get the correct cleat to pedal spindle, a 25mm seat post did not come w/ set back: Too Big and a big wobbly pig as well.
Rule #1 in getting a proper fit for whatever high effort/long distance cycling one does has been to get the Proper Size frame and have the components selected correctly on it.
If you think that kluding around on framesets that Just Do Not Fit is worth the time, effort and $$$$ have at it.
I wear shoes that fit and ride bikes that do too, not so great for comfort or efficiency to cut holes in the toes or shove wadded up newspaper in one's sneakers.....
-Bandera
Last edited by Bandera; 04-25-15 at 03:52 PM.