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Moisture 12-12-20 10:58 AM

Comprehensive Frame Fitting Guide
 
As some of you may know, it's been quite a journey for me with regards to frame fitting. I hope that my methods of trial and error as well as research can help guide someone looking for a bike into t he right direction. Please be kind and offer feedback in a constructive manner, if need be.

With the average person being built different from one another, it is imperative to find a riding position which ensures that you are not leaning back or forward too much. You should feel a good centre of gravity by ensuring that you can easily lean forward or backwards without too much of your weight always being fore or aft.

- Skinnier people tend to prefer a more leaning over position to achieve the desired balance versus someone who is top heavy either with fat or muscle.

- Three main frame measurements to consider:

- Stack - make sure you find a bike with a sufficient stack, ideally so that you don't need to add several spacers or a stem riser in order to get your handlebars level with your seat.

- Reach - How close or far away the bottom bracket is from the bars. This will affect your balance, comfort and power trasnfer whilst pedalling out of the saddle.

- Top tube length, or Effective top tube - This is the measurement which determines how comfortable you are while sitting in the saddle. You can make small adjustments by sliding the seat fore or aft to get the best leverage over your cranks, but this is never a solution to a poor fitting frame.

- Standover height should never be used as a basis for a comfortable fitting frame.

- Crank arms should be in direct proportion to your inseam. This mostly a matter of comfort, but will always pay some dividends to overall performance as well as the way the bike is geared.

- Once you have the top tube length and reach set in order, you must make sure that the stem you are using is an ideal length for you. it's better to err on an overly short frame reach because you can always compensate with a longer stem.

- Drop bars vs flat bars- I find that drop bars only work well with a precisely fitting frame. As long as the bar is roughly your shoulder width, you should have an optimal level of manveurability. drop bars tend to decrease precision around twisty or tight turns, but the different hand placements and aerodynamic profile can be highly efficient for power transfer, especially during climbing and descending. flat bars tend to offer better control over the bike, but the rake of your fork and head tube angle also plays a role here.

As a general rule of thumb, if you can just almost touch the ground with your toes while sitting on the saddle, you got the seat height about right. Now, if your handlebars are lower than the saddle, chances are you may want to try out some spacers or a stem which is higher and/or closer to you. If that is not enough to reasonably level your handlebars, this is a solid indication that the frame is not a suitable size for you.

Generally speaking, there are two generic types of frame geometry.

Road or Gravel bike - generally a shorter reach, designed to compensate for the stretched out position of having drop bars and a lengthy stem. Lower bottom bracket. Faster handling.

XC, trail bikes, etc etc - These type of mountain bikes tend to have a pretty long reach. It's not ideal for gravel or road/urban rides.

For example, im really only comfortable on a bike with quite a short reach and top tube length. something you will typically find on an older style road bike, using a pretty short stem. This brings the cranks a bit further in front of the seat for better leverage while helping me bias my weight rearward. I like having my butt hovering over the saddle, so I can easily adapt my power levels by keeping weight off the seat and into the cranks or conserving energy by pedalling in the saddle more. This way, my weight is rear biased. However, being top heavy, this means I don't need extra top tube or stem length to bias my weight forward easily like you always tend to do with a mountain bike.

Cycletography 12-13-20 09:05 AM

And what is the sample size of the population you studied to arrive at these conclusions/recommendations? Was is a random sample that proved to be a representative cross-section of the global population of cyclists?

I ask these questions not to be a PITA, but to point out that one cannot make the assertions you make in the original post without a formal research study based on a random sample of sufficient number that will allow you make general conclusions of the population as a whole (or at least a reference to studies already conducted).

I see nothing wrong with sharing your experience and making it clear what's worked for you. However, for anyone who does not have the proper skills, knowledge, experience and training to prescribe solutions (myself included), sharing personal experience for purposes of information only is probably as far as one should go.

mack_turtle 12-13-20 01:30 PM

There are a few things I agree with in this first post, but most of it is so over-generalized that it's not going to be helpful for most people. Sorry.

philbob57 12-15-20 06:27 PM

What are the bases for your conclusions? How many miles have you ridden? How many different bikes have you ridden and for how long on each? What different styles have you tried out? How many and what different sizes have you ridden of each style?

Moisture, I find your dogmatism and lack of evidence annoying. I mean that as feedback, not as criticism. I really wish you'd change your posting style.

Road Fan 12-16-20 08:06 AM

@Moisture, I also think that what you wrote is not a comprehensive point of view. But your title set the expectation that it is applicable to all riders on all machines. For example, riders of Raleigh 3-speeds in original config. Something like "Comprehensive summary of my experience self-fitting and assisting friends and family."

I often try to help people by telling them what I think they should do. BF'ers have been kind enough not to call me out on that, but I'm lately trying harder to say "this is what I do" or "this is what I have done in your situation, if I understand it correctly."

As far as specifics:

You don't need evidence, you need a less directive tone. To describe your own experience is enough. To generalize broadly from that, is too much. If you are and experience

To be balanced on the saddle, I move the saddle forward or backward. This can end up limiting the choice or saddle, seat post, and even frame design in terms of stack. Then I go on to set the saddle-bar drop, and reach to the brifters (or Ergopowers). Again this can constrain choice of TTlenght or reach, stem angle and extension, and handlebar design. Even on the randonneur I like to pedal in the drops without my knees hitting my elbows. This all negates COPS.

This is for my road bikes and for my randonneur. I set my wife's this way as well, and she is not shy about expressing her concerns.

It's important that the bicycle+rider is a system, or a set of systems. For example the stem length or extension is not something that is perfect for the rider, its something that helps to set how high and how far forward the hand contact points will be. That position needs to be perfect for the rider. Different combinations of extension, bar reach, and brifter length (for a road, cross, or rando bike) may be used to achieve this position, as the primary goal. You may also have goals in terms of handling and handlebar response, but these get into frame reach, head angle, tire choice and pressure, and fork design. You could say the cockpit subsystem is a subsystem of the vehicle control subsystem.

As far as touching the ground with your toes, there is another theory for that. The saddle height must be set only based on quality of pedaling, and my experience here is limited to road, urban, and distance riding. For me this includes 60 mile days on pavement and as yet a few rides on our local unpaved. At least in this realm you need to pedal with good leg extension. Failure to do this can result in knee injury (yes, really). There are a lot of methods to set this up - heel on pedal, measurements based on pubic bone height, fitter measurements based on knee angle, and fitter measurements based on video and analysis of the recorded leg motion. A rider needs to learn to mount and dismount the bike when stopping, not to depend on their feet reaching the ground. You can have both with a bike with high setback, such as an Electra, but usually not much ground contact can be achieved on a 700c or 650b road bike with a flat top tube.

For the same reason it's not safe to have inadequate standover clearance, which depends on stack, head tube design, BB drop, rim diameter and tire size. It's safest to stand straddling the frame when stopped, but there is a possibility of contact with the top tube. Whether this is tolerable is a matter of opinion, but that contact could be painful or even harmful. But it's not safe to set saddle height strictly for the purpose of foot contact. You should dismount the saddle when stopping, have adequate stopped frame clearance, and have efficient, sustainable pedaling when riding, based on leg extension.

There's so much here, I could go on. But in my view there are established concepts for bike fitting for performance riding (speed, distance, power, or competition), and they are based on goals of efficiency, rider health, pedaling effectiveness, safe handling and braking and considering rider preferences. Within this framework a frame first needs to be built with components that enable a bicycle to be ridden with safe and effective equipment, perform initial adjustment to suit the body of a specific rider for effectiveness and safety, and finally to optimize stem length versus handlebar reach, handlebar height versus total rider reach to the bars, and other fine points.

I find I have to revise my bike setup at the beginning of each season, and then refine it as my distances increase. What works for 10 mile rides does not always work for 25!

cubewheels 12-17-20 05:23 AM


Originally Posted by Road Fan (Post 21835119)
@MoistureAs far as touching the ground with your toes, there is another theory for that. The saddle height must be set only based on quality of pedaling, and my experience here is limited to road, urban, and distance riding. For me this includes 60 mile days on pavement and as yet a few rides on our local unpaved. At least in this realm you need to pedal with good leg extension. Failure to do this can result in knee injury (yes, really). There are a lot of methods to set this up - heel on pedal, measurements based on pubic bone height, fitter measurements based on knee angle, and fitter measurements based on video and analysis of the recorded leg motion. A rider needs to learn to mount and dismount the bike when stopping, not to depend on their feet reaching the ground. You can have both with a bike with high setback, such as an Electra, but usually not much ground contact can be achieved on a 700c or 650b road bike with a flat top tube.

I'm a huge "heel dropper" so my saddle is lower than baseline fit. In addition to a large setback (to remove pressure on my hands in a slammed down aero position), my feet can easily reach the ground while sitting on the saddle. Although in practice, I always get off from the saddle and into the top tube when stopping as it's still easier to be on the top tube while stopped than on the saddle.

And because my saddle is low, I also needed a lower stack (to take advantage of the fact, I can get more aero with lower saddle if I can get the dropbar lower too) which suggests a frame few sizes smaller. It's how I ended up. A two sizes smaller frame, with longer angled-down stem with the drops almost as low as the top of the front tire making it look like a racing setup. Considerable deviation from baseline fit....But perfectly comfortable for me! Fits me so well, including the saddle choice I don't even need to wear gloves nor padded shorts.

Many reasons come into play where one can deviate a large degree from the baseline / standard fit.

Even a change in riding technique may have a large effect on fit. There's not really just one rule per aspect of fit but many and the rest is up to extensive testing (trial and error)

Moisture 12-17-20 07:52 AM


Originally Posted by mack_turtle (Post 21830878)
There are a few things I agree with in this first post, but most of it is so over-generalized that it's not going to be helpful for most people. Sorry.

Thats totally understandable.


Originally Posted by philbob57 (Post 21834560)
What are the bases for your conclusions? How many miles have you ridden? How many different bikes have you ridden and for how long on each? What different styles have you tried out? How many and what different sizes have you ridden of each style?

Moisture, I find your dogmatism and lack of evidence annoying. I mean that as feedback, not as criticism. I really wish you'd change your posting style.

I do appreciate the feedback. Ive sort of eased down with the posting in general.


Originally Posted by cubewheels (Post 21836734)
I'm a huge "heel dropper" so my saddle is lower than baseline fit. In addition to a large setback (to remove pressure on my hands in a slammed down aero position), my feet can easily reach the ground while sitting on the saddle. Although in practice, I always get off from the saddle and into the top tube when stopping as it's still easier to be on the top tube while stopped than on the saddle.

And because my saddle is low, I also needed a lower stack (to take advantage of the fact, I can get more aero with lower saddle if I can get the dropbar lower too) which suggests a frame few sizes smaller. It's how I ended up. A two sizes smaller frame, with longer angled-down stem with the drops almost as low as the top of the front tire making it look like a racing setup. Considerable deviation from baseline fit....But perfectly comfortable for me! Fits me so well, including the saddle choice I don't even need to wear gloves nor padded shorts.

Many reasons come into play where one can deviate a large degree from the baseline / standard fit.

Even a change in riding technique may have a large effect on fit. There's not really just one rule per aspect of fit but many and the rest is up to extensive testing (trial and error)

Further proof of your completely nonsensical fit right here. You should be able to *almost* fully extend your knee at the very bottom of each pedal stroke, but not quite, so that you don't need to roll your hips to compensate for the stroke. You can go slightly lower than this, but once you can start to touch the ground with even just your toes, that will begin to limit your power output and tends to put quite a lot of impingement stress on your knees.

I understand that you think you have your frame fit setup correctly, but all it takes is one quite glance at the picture of your bike, and scanning over your ideas to easily determine that whatever you're riding is NOT the right size for you, even though you genuinely do think it works well for you. If you dont even have the saddle set to baseline, this is just further proof of that.

cubewheels 12-17-20 09:07 PM


Originally Posted by Moisture (Post 21836818)
Further proof of your completely nonsensical fit right here. You should be able to *almost* fully extend your knee at the very bottom of each pedal stroke, but not quite, so that you don't need to roll your hips to compensate for the stroke. You can go slightly lower than this, but once you can start to touch the ground with even just your toes, that will begin to limit your power output and tends to put quite a lot of impingement stress on your knees.

I'm a "heel dropper" so none of the things you said there applies to me.


I understand that you think you have your frame fit setup correctly, but all it takes is one quite glance at the picture of your bike, and scanning over your ideas to easily determine that whatever you're riding is NOT the right size for you, even though you genuinely do think it works well for you. If you dont even have the saddle set to baseline, this is just further proof of that.
This is why you got many replies where they didn't find your guide useful. Not everyone wants endurance-oriented fit (racing fit will often be few sizes smaller). Not everyone has the same pedaling style. Indeed, pedaling style will have a considerable influence in bike fit.

Moisture 12-31-20 09:38 PM

What is important for you in a bike, considering you got the fit aspect right?

- fairly steep head tube angle, increased fork rake for combination of stability and response .

- pretty slack seat tube for better rear biased weight distribution and better hill climbing abilities

- frame should offer a good balance between compliance and stiffness

- compatibility with different wheel sizes

- recessed drive side chainstay for better crankset compatibility

- nice tall stack, super short reach,.short top tube length,

mack_turtle 01-05-21 08:17 AM


Originally Posted by Moisture (Post 21857304)
What is important for you in a bike, considering you got the fit aspect right?

- fairly steep head tube angle, increased fork rake for combination of stability and response .

- pretty slack seat tube for better rear biased weight distribution and better hill climbing abilities

- frame should offer a good balance between compliance and stiffness

- compatibility with different wheel sizes

- recessed drive side chainstay for better crankset compatibility

- nice tall stack, super short reach,.short top tube length,

those are all subjective aspects of a bike. those might be good to have on a bike ... if that's how you want the bike to fit and handle. some people will want a slack head tube angle and less fork rake, depending on the type of terrain they are riding. bike attributes like angles, dimensions, wheel sizes, etc depend on how and where the rider wants to use it. if you shared preferences like that in the context of "for a rider with ___ physical abilities riding on ___ terrain, these are good attributes," this list might make some sense. unless you are able to provide those specifics, your suggestions are too subjective to be useful.

for whom, riding where, are your suggestions useful? or are you saying this is what YOU look for in a bike? if so, why call this "comprehensive frame fitting guide" if it is a specific fitting guide for you, which makes it the opposite of comprehensive? are you basing this on science and fitting hundreds of paying customers on bikes, or just a cursory reading of general tidbits you picked up while riding this forum?

Moisture 01-09-21 05:33 AM


Originally Posted by mack_turtle (Post 21863263)
those are all subjective aspects of a bike. those might be good to have on a bike ... if that's how you want the bike to fit and handle. some people will want a slack head tube angle and less fork rake, depending on the type of terrain they are riding. bike attributes like angles, dimensions, wheel sizes, etc depend on how and where the rider wants to use it. if you shared preferences like that in the context of "for a rider with ___ physical abilities riding on ___ terrain, these are good attributes," this list might make some sense. unless you are able to provide those specifics, your suggestions are too subjective to be useful.

for whom, riding where, are your suggestions useful? or are you saying this is what YOU look for in a bike? if so, why call this "comprehensive frame fitting guide" if it is a specific fitting guide for you, which makes it the opposite of comprehensive? are you basing this on science and fitting hundreds of paying customers on bikes, or just a cursory reading of general tidbits you picked up while riding this forum?

you bring up some good points Mack.

First of all, I believe that my ideas in the original post here can cater to a fair percentage of people reading this. But this is not up to me to decide . For this "guide" to be comprehensive, only Way would be to get other people to chime in and detail what works for them, and what they had to do to achieve an ideal fit. FWIW, I just changed out the stem on my bike from my old 60mm riser quill stem to one that is 40mm with a 30 degree riser. It made enough of a difference by moving the handlebars closer toward me to get an absolutely perfect reach for my needs.

as for my ideas with head tube angles and what not, this is based off a 200+lb rider who tends to ride mostly pavement and some gravel sprints. My bike is classified as a sport touring model, meaning its designed to get you around quickly when carrying a light load. The angles make a lot more sense when carrying 35lb of groceries. However, I tend to spend most of my time riding at relatively lower speeds where the extra stability from the long fork rake and slack head tube perhaps makes the handling just a touch less responsive than what I would prefer.. however, considering that this bike is clearly designed around a somewhat different purpose from how I usually use it, its understandable.

The short stem noticeably quickened up the handling in the front end, so now i have a pretty good balance between speed and stability.

Furthermore, in the future i think I would prefer sticking to 26" rims with slightly wider tires, since they seem to provide better handling as well as acceleration response at speeds i am usually riding at without any real penalty when I do reach higher speeds going down a hill.

For personal reference, I would like a specific balance between slightly increased head tube angle, as well as slightly less fork rake and maybe slightly shorter chainstays while maintaining the same seat tube angle for my own needs in the future. My theory that the slightly shorter wheelbase along with smaller diameter rims will help incrrase steering response at speeds which I most frequently ride without impacting stability while riding loaded.

cubewheels 01-11-21 01:30 AM


Originally Posted by Moisture (Post 21869514)
For this "guide" to be comprehensive, only Way would be to get other people to chime in and detail what works for them, and what they had to do to achieve an ideal fit.

I was one of them and you just keep on dismissing what I have to say even if my different fit works perfectly for my needs.

Moisture 01-11-21 08:30 AM


Originally Posted by cubewheels (Post 21872261)
I was one of them and you just keep on dismissing what I have to say even if my different fit works perfectly for my needs.

I can clearly see that I am not the only person who disagreed, but until we see you riding your bike, I won't make any further comments.

cubewheels 01-11-21 08:32 PM


Originally Posted by Moisture (Post 21872482)
I can clearly see that I am not the only person who disagreed, but until we see you riding your bike, I won't make any further comments.

https://cimg8.ibsrv.net/gimg/bikefor...7090f2a64e.gif

UncleG 02-12-21 06:06 AM

Panasonics rule!!!
 
Remember back in the late 80s early 90s Panasonic came out with a bicycle where you went into a shop, they put you on a machine which was like a slide rule and when you're all dialed in on this machine... hit "enter" and the measurements went to the factory in Japan ( I assume), and within a few weeks you received a Panasonic bicycle at your doorstep that was custom fit to your measurements that we're taken on their customized sizing apparatus.

I always thought it was a really cool idea, I think the press at the time did too but it never really took off among the general public and Panasonic still might be in business but I haven't seen a shop and years so I'm not really certain what their business model looks like today.

If you recall in the late 80s early 90s is when a lot of organizations and corporations and the government and the military all started really looking at quality management and this is one of the examples I recall hearing about denoting efficiency and quality management.

Rage 02-12-21 07:35 AM

Where’d you go, Drippy D?!

Iride01 02-12-21 08:48 AM


Originally Posted by Rage (Post 21920816)
Where’d you go, Drippy D?!

The OP? He was given a forced holiday. Won't be back till about March 7.

Rage 02-12-21 08:58 AM

Jeeze, I only saw that now.
I thought it was weird he just vanished like that.

Rage 02-12-21 09:08 AM

Double jeeze, it seems...

StanSeven 02-12-21 09:23 AM


Originally Posted by UncleG (Post 21920758)
Remember back in the late 80s early 90s Panasonic came out with a bicycle where you went into a shop, they put you on a machine which was like a slide rule and when you're all dialed in on this machine... hit "enter" and the measurements went to the factory in Japan ( I assume), and within a few weeks you received a Panasonic bicycle at your doorstep that was custom fit to your measurements that we're taken on their customized sizing apparatus.

I always thought it was a really cool idea, I think the press at the time did too but it never really took off among the general public and Panasonic still might be in business but I haven't seen a shop and years so I'm not really certain what their business model looks like today.

If you recall in the late 80s early 90s is when a lot of organizations and corporations and the government and the military all started really looking at quality management and this is one of the examples I recall hearing about denoting efficiency and quality management.

Fit systems are around and there are lots. Just like everything else, they evolved with technology
Google them

cb400bill 02-12-21 10:09 AM

Thread closed


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