Great Article on Bike Fit

[Dave]

I'd disagree that you can ALWAYS put the saddle where you want it. The most common seat posts range from zero setback to 32mm, the last time I looked. I know how much seat post setback I need for a range of seat tube angles, but I want something that comes close to centering the saddle rails over the clamp. My new bike came with an unacceptable zero setback model, so I got a 25mm setback model. Some frames have proprietary posts with no setback options.

There are so many misconceptions posted above that I won't bother to comment further. Simply put, if you have the stack, reach and STA you have everything you need to ensure that the frame you bought will fit. It can also help to understand the impact of limited stem angles on your desired stack. Some bikes only have one stem angle available.

ETT adds nothing.

[Likes2ridefar]

Originally Posted by rothwem

I don't really think this is true. Having longer legs makes you look taller though, so I suspect that you just notice them more.

People with long legs typically have long arms though, and that makes their "effective torso" longer. The people that are extra f'ed are the "t-rex" types with long legs and short arms.

I also read something interesting in another fitting blog where it mentioned that if you look at two people that have identical torso lengths but different length legs, the person with the longer legs typically has smaller feet than the person with the shorter legs, so the saddle height and setback tend to even out somewhat.

People are crazy, right?

Im one of the extra f’ed. my legs (or hip height to ground) are out of proportion with my arms. I’m all legs as they say.

[Alistair]

Originally Posted by rothwem

People are crazy, right?

The Air Force figured that out in the 50s, after building fighters to match “average” dimensions for a few decades and having atrocious accidents rates.

https://www.thestar.com/news/insight...e52d60bd9.html

[rothwem]

Originally Posted by Alistair

The Air Force figured that out in the 50s, after building fighters to match “average” dimensions for a few decades and having atrocious accidents rates.

https://www.thestar.com/news/insight...e52d60bd9.html

Fascinating article, confirms a lot of what I’ve empirically noticed from just looking at people.

That Norma was a babe though amiright?

[spoonrobot]

editing

[benb]

Originally Posted by Dave

I'd disagree that you can ALWAYS put the saddle where you want it. The most common seat posts range from zero setback to 32mm, the last time I looked. I know how much seat post setback I need for a range of seat tube angles, but I want something that comes close to centering the saddle rails over the clamp. My new bike came with an unacceptable zero setback model, so I got a 25mm setback model. Some frames have proprietary posts with no setback options.

There are so many misconceptions posted above that I won't bother to comment further. Simply put, if you have the stack, reach and STA you have everything you need to ensure that the frame you bought will fit. It can also help to understand the impact of limited stem angles on your desired stack. Some bikes only have one stem angle available.

You are thinking in that framework of conventional/historic road bike frame designs and seatposts.

The seatpost being straight is not a requirement. The seatpost intersecting the BB centerlien is not a requirement. Traditional off the shelf seatposts are not a requirement. Those kinds of bikes end up having 4 numbers around the seat tube angle and top tube angle. They have effective top tube, actual top tube, effective seat tube angle, and actual seat tube angle.

The modern bike sizing #s work whether or not the frame has conventional/historic seat tube & seatpost configuration.

A lot of mountain bikes already have an effective and actual STA that are different. There is absolutely no reason they couldn't do a road bike that way too, but it would probably end up not requiring an offset seatpost and roadies love offset seatposts.

[ridethecliche]

Originally Posted by rothwem

Fascinating article, confirms a lot of what I’ve empirically noticed from just looking at people.

That Norma was a babe though amiright?

Kinda creeps me out that a OBGYN collected measurements on so many young women and compiled them to create the 'average' form like that.

Different era etc... but oof.

[dgauthier]

Originally Posted by rothwem

Fascinating article, confirms a lot of what I’ve empirically noticed from just looking at people.

That Norma was a babe though amiright?

I'd give her a "5".

[Dave]

Originally Posted by benb

You are thinking in that framework of conventional/historic road bike frame designs and seatposts.

The seatpost being straight is not a requirement. The seatpost intersecting the BB centerlien is not a requirement. Traditional off the shelf seatposts are not a requirement. Those kinds of bikes end up having 4 numbers around the seat tube angle and top tube angle. They have effective top tube, actual top tube, effective seat tube angle, and actual seat tube angle.

The modern bike sizing #s work whether or not the frame has conventional/historic seat tube & seatpost configuration.

A lot of mountain bikes already have an effective and actual STA that are different. There is absolutely no reason they couldn't do a road bike that way too, but it would probably end up not requiring an offset seatpost and roadies love offset seatposts.

If you want to buy a bike, someone has to build the frame first, then you select a seat post to fit it. What's possible to build is irrelevant. What I described is reality, not conjecture. There's nothing unusual or wrong about a design with an effective STA, but the effective length needs to be included

Cervelo moved a straight seat tube forward about 20 years ago, then published a seat tube angle that was apparently the angle between the center of the BB and some point higher that might have been an average saddle rail height. They have a similar situation with their S5 frame with inadequate description of where the seat post is located.

Here's an example of inadequate definition. https://www.cervelo.com/en-US/bikes/s5

[charliedid]

I sort of agree about size offerings and smaller (really small) could still benefit from smaller wheels. Let's be real it is economics that drives these decisions and that will be a tough one to crack for many (most) of these companies. It would be a great move though.

Endurance/all-road bikes have (almost) always existed in the time most of the people here have been riding, we just called them sport-touring bikes. There was a period of time when moving into the 90's where these were harder to find as we sold racing bikes in larger numbers.

All that said, what this article seems to be asking for is bikes that are even further skewed to a less fit rider "real people" who are uninterested in any sort of work required to ride bikes that are...dare I say way more fun to ride. You don't need to race bikes (very few do) to own and really enjoy riding them. This is how the industry ended up "designing" probably via focus-groups the comfort hybrid. It's a horrid thing and we should have just stuck to the up-right swept back bar bikes of decades past.

So it goes.

[rmhurley]

T-rex here.. most bikes I have ever owned and enjoyed riding were either sized down with the bars as high as they can be; or sized up to the point of just being able to throw a leg over. I will say, as far as steel steerer tubes go, its much easier to make things fit when you can simply raise up the quill stem or stack up spacers as high as necessary, aesthetics be damned.

It becomes more of an issue when introducing a carbon steerer which generally allows only 40mm of spacers below the stem, which also, cannot have the pinch bolts located below the horizontal part. This essentially eliminates the possibility of any tall stack stems.

[NHAero]

Originally Posted by rmhurley

T-rex here.. most bikes I have ever owned and enjoyed riding were either sized down with the bars as high as they can be; or sized up to the point of just being able to throw a leg over. I will say, as far as steel steerer tubes go, its much easier to make things fit when you can simply raise up the quill stem or stack up spacers as high as necessary, aesthetics be damned.

It becomes more of an issue when introducing a carbon steerer which generally allows only 40mm of spacers below the stem, which also, cannot have the pinch bolts located below the horizontal part. This essentially eliminates the possibility of any tall stack stems.

An upturned stem works in this case to get the bars higher.

[rmhurley]

Originally Posted by NHAero

An upturned stem works in this case to get the bars higher.

Definitely does. I have tried a wide variety of stem configurations. I suppose for some that will get the bars just high enough, but even that little bit is unlikely to put some of the more aggressive fits in range for me.

My personal fit dilemma has always been longish legs, longish torso with proportionally short arms. Leg-wise, a 57cm or 58 fit well but anything over a 90mm stem starts to feel too long on most of those if the reach is on the longer side too.

Maybe the ease of adjusting handlebar height is why I would likely never give up completely on threaded stems and steerers, even though I have come to prefer many common modern build features.

[tomato coupe]

Originally Posted by Dave

They have a similar situation with their S5 frame with inadequate description of where the seat post is located.

Here's an example of inadequate definition. https://www.cervelo.com/en-US/bikes/s5

All the necessary information is in their table and the associated diagram.

[P K]

Originally Posted by benb

It has never seemed like taller people trend towards shorter legs & longer torsos... it seems like it's the opposite.

This!