How to fit a bicycle...



biker7

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Oct 15, 2004
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Wanted to share one of the best written articles on bike fit I have read out on the web and I have read as others have conservatively hundreds of sometimes conflicting articles and can spout fit formulas ad nasseum. Being analytical by nature, it is easy to get caught up in the theoretical abyss for fit but at the end of the day, formulas or even a so called bullet proof bike shop fitting systems are spurious as the brilliant writer Peter White of the following article understands and explains.
I am going through tuning the fit on my new bike and therefore thought I
would post Mr. White's refreshing commentary which dispells many myths believed as fact on the subject:

http://www.peterwhitecycles.com/fitting.htm

Enjoy,
George
 

boudreaux

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Oct 16, 2003
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biker7 said:
..... it is easy to get caught up in the theoretical abyss for fit but at the end of the day, formulas or even a so called bullet proof bike shop fitting systems are spurious as the brilliant writer Peter White .....
Brilliant as in genius like you know who Georgie?
 

dhk

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Sep 1, 2003
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biker7 said:
Wanted to share one of the best written articles on bike fit I have read out on the web and I have read as others have conservatively hundreds of sometimes conflicting articles and can spout fit formulas ad nasseum. Being analytical by nature, it is easy to get caught up in the theoretical abyss for fit but at the end of the day, formulas or even a so called bullet proof bike shop fitting systems are spurious as the brilliant writer Peter White of the following article understands and explains.
I am going through tuning the fit on my new bike and therefore thought I
would post Mr. White's refreshing commentary which dispells many myths believed as fact on the subject:

http://www.peterwhitecycles.com/fitting.htm

Enjoy,
George
The message I get from the article is that fit on the bike should be comfortable and not be slave to what any formulas say. Can't argue with the premise. Not sure whether that message is brilliant or a BFO...."blinding flash of the obvious."

To me, the article doesn't seem to provide much specific guidance to a new rider trying to size or set up a bike. The author asserts that the fits provided by the standard formulas aren't right for the "average" rider, but he doesn't say why. Besides, isn't any position sitting on a bike is going to feel strange and uncomfortable until you get used to it by actually riding on the road? Position needs to feel right on the road, not when just sitting on the bike.

The test about sliding the saddle forward until you can support yourself without using your hands seems confusing. I can sit up and ride with fingers touching the bar, with no weight on my hands at all....but what does that prove about my seat position? Having weight on the hands on a road bike provides for good weight distribution and a power platform for pushing and seated climbing. The old knee-over-pedal position works fine for me here.

Certainly an experienced rider should be free to fine-tune things the way he wants, but I'd say someone new to road cycling needs a bit more specific help to get it right.
 

biker7

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Oct 15, 2004
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I thought the premise of the writer's treatise on bike fit was obvious. As always, the beauty of what the author had to say was in its refreshing simplicity. A fit formula which is basically a parametric analysis of dimensions does not take into account the athleticism or type of rider involved...only his "spec's". Racers are inherently more flexible and set their bikes up more aggressively than most recreational riders. Climbers like their bars lower and closer in for leverage. Tri-bikes are set up with their seat's more forward...on and on. Even the same riders set up their bikes differently based on their intended use. A formula, and formulas exist for every body and frame measurement, does not address not only how the bike is going to be ridden but the natural tendency of the rider.
One of the best articles I have read but your mileage may vary ;)

Curious dhk...while on the subject...what size bike do you ride relative to your biking inseam and where do you fit on Lemond's formula for seat height relative to crank length?

George
 

53-11

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Mar 21, 2005
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biker7 said:
I thought the premise of the writer's treatise on bike fit was obvious. As always, the beauty of what the author had to say was in its refreshing simplicity. A fit formula which is basically a parametric analysis of dimensions does not take into account the athleticism or type of rider involved...only his "spec's". Racers are inherently more flexible and set their bikes up more aggressively than most recreational riders. Climbers like their bars lower and closer in for leverage. Tri-bikes are set up with their seat's more forward...on and on. Even the same riders set up their bikes differently based on their intended use. A formula, and formulas exist for every body and frame measurement, does not address not only how the bike is going to be ridden but the natural tendency of the rider.
One of the best articles I have read but your mileage may vary ;)

Curious dhk...while on the subject...what size bike do you ride relative to your biking inseam and where do you fit on Lemond's formula for seat height relative to crank length?

George
Formulas are great, but everyone has individual preferences on how they like to ride. I thought the cranklength and seat position part of the article was nice.

IF it feels good and you are fast....you are riding the right way.
 

boudreaux

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Oct 16, 2003
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dhk said:
Certainly an experienced rider should be free to fine-tune things the way he wants, but I'd say someone new to road cycling needs a bit more specific help to get it right.
Absolutely, and that is where some measurement and standard fit guidelines come into play as a place to start. A good fitter goes from there.AFWIW, how do you think custom builders do it?? Try sending a n00b off to a bike shop with PWs 'brilliant' masterpiece,and see where he ends up.....LOL....Not that he couldn't end up on the wrong barge if the 'fitter' happened to be a nose picker and a$$ scratcher. ;)
 

biker7

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Oct 15, 2004
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Exactly 53. Speaking of formulas which I think are good to butress native tendencies...I like the following article on seat height.
Gives better perspective to Lemond's .883 X biking inseam or 1.09 X biking inseam for low crank position relative to seat height.
I like mine about 1.07 for a combination of power and comfort.

http://www.pponline.co.uk/encyc/cycling-biomechanics.html

George
 

boudreaux

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Oct 16, 2003
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biker7 said:
Exactly 53. Speaking of formulas which I think are good to butress native tendencies...I like the following article on seat height.
Gives better perspective to Lemond's .883 X biking inseam or 1.09 X biking inseam for low crank position relative to seat height.
I like mine about 1.07 for a combination of power and comfort.

http://www.pponline.co.uk/encyc/cycling-biomechanics.html

George
And another point in his brillaint masterpiece that can be taken exception to is the notion that one can choose from several sizes and still get a good fit. Having been there on both larger and smaller sizes, sure you can cob a fit. It was a happy day when I got rid of all the cobbed wrong size stuff and and started riding what worked best with an approximate 56.75 TT.Again, prooving you can sell a n00b almost anything. If you know straight up it doesn't fly so well.
 

53-11

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Mar 21, 2005
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boudreaux said:
And another point in his brillaint masterpiece that can be taken exception to is the notion that one can choose from several sizes and still get a good fit. Having been there on both larger and smaller sizes, sure you can cob a fit. It was a happy day when I got rid of all the cobbed wrong size stuff and and started riding what worked best with an approximate 56.75 TT.Again, prooving you can sell a n00b almost anything. If you know straight up it doesn't fly so well.
nothing worse than using a funky length stem to make the wrong TT work. Or worse yet, slamming your seat forward (on slack STA) with aftermentioned wrong TT length. Screws up the balance of the bike. Better for me just to get something with the right geometry.

Nice Sydney, I like how you put double zeros whenever you write n00b.
 

boudreaux

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Oct 16, 2003
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53-11 said:
Nice Sydney, I like how you put double zeros whenever you write n00b.
Learnt it from the master. Any old dog can learn a new trick. Doesn''t even have to be a genius... ;)
 

dhk

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Sep 1, 2003
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biker7 said:
I thought the premise of the writer's treatise on bike fit was obvious. As always, the beauty of what the author had to say was in its refreshing simplicity. A fit formula which is basically a parametric analysis of dimensions does not take into account the athleticism or type of rider involved...only his "spec's". Racers are inherently more flexible and set their bikes up more aggressively than most recreational riders. Climbers like their bars lower and closer in for leverage. Tri-bikes are set up with their seat's more forward...on and on. Even the same riders set up their bikes differently based on their intended use. A formula, and formulas exist for every body and frame measurement, does not address not only how the bike is going to be ridden but the natural tendency of the rider.
One of the best articles I have read but your mileage may vary ;)

Curious dhk...while on the subject...what size bike do you ride relative to your biking inseam and where do you fit on Lemond's formula for seat height relative to crank length?

George
Seat height, is at 76.5cm with a 86 cm inseam....LeMond says 75.9. Of course, height of the shoes/cleats will vary and affect the measurement you like.

I'm on a 58cm frame, with 57.5 top tube measurement. My previous bike, which I got to try crit racing in the early 90's, was a 56. I had the seat tube all the way to the limit mark, with a good 10 cm drop to the bars. I knew I wanted something a little bigger now for less drop to bars and more room when standing for climbing.

I went to the local builder knowing the dimensions I wanted, and it turned out his stock geometry 58 cm frame fit the bill perfectly for me.

Sounds like we're all pretty close here on seat height. Tells me that the formulas can be useful to provide a starting point, and that's all they need to be used for.
 

biker7

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Oct 15, 2004
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agree...we are on the same page dhk. Issue with .883 which I think is a pretty good number BTW is it doesn't crunch crank length which the 1.09 number does.
With an 88.9 cm inseam I ride 175mm cranks so the 1.09 works better for me than the .883 coefficient.
I find the .67 coef. to be a pretty good ballpark gage for seat post/frame size as well if not a bit shy of what I ride which is typical for taller riders. I like the generally longer wheel base and taller steerer tube height of a biggish frame and like to spread out a bit so I error on the high side of frame geometry relative to my measurements. Standover for my bike is 32.5" which is full 2.5" below my biking inseam to my PB....rule of thumb being 1-2 inches. Wouldn't want to go up any in frame size as my 61cm frame virtual top tube length of 586mm is at the high side of what I like.
My bike came with a 130mm Deda stem that "will change" however :)...can see too much front hub behind my bars.
George
 

mgagnonlv

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Sep 25, 2003
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Formulae are good starting points, but suffer from a few flaws.

1. The usual "bike fitting theories" are based on maximum performance, usually at the expense of comfort. The needs of a racer, randonneur and bicycle tourist are totally different. As a bicycle tourist, my main concerns are seeing the road and the landscape and being comfortable for 8-10 hours.

2. Formulae don't consider riding style or preferences. Isn't it strange that most formulae consider that one will ride on the drops about or at least half the time, yet most riders don't ride on the drops? Maybe they shouldn't be fitted according to formulae? Or maybe formulae would need to be tweaked to their age and agility?

3. Peter White covers some of the basics of bike fitting. Beyond formulae are important factors such as :
- saddle height ;
- fore-to-aft balance.

In the same vein, Rivendell and to a lesser point Heron also cover bike fitting basics with a no-nonsense viewpoint.