Okay, talk to me about riding 'too small' bikes: a geometry discussion!
12-26-23, 10:18 AM
#101
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...it's a me thing though.
For crankset lengths in current drop bar bikes I have 175, 175, 172.5, 170, 180, and 170.
As a result, my saddle height is slightly different between bikes. It's only a +/- 1 or 2mm in most instances, but it's definitely noticeable.
When I slapped the 180mm crank onto a hike that used to have 170mm arms, that was actually pretty significantly different, to the point that I felt my hips roll when pedaling. Ha, that was quickly adjusted.
squirtdad - as he said, saddle height to center of BB is totally separate from frame size, really. This is especially true when it comes to comparing a level top tube bike with a sloping top tube bike, since the sloping top tube bike will have more seatpost showing.
12-26-23, 10:24 AM
#102
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Like you, I think that this might be important, just to have a location of where and how high the start of the seatpost is going to be, because if it is wildly off from where you normally sit, it might very well affect frame sizing, and saddle setback?
Hopefully, I'm going to be picking up today the mysterious bicycle that was the inspiration for this thread. I'm going to try to study this stack/reach chart a little bit more to better understand it, and try to apply that to this new bike, as well as the Novara, which are both close to the same size. We'll see how far we are from some of the bikes that I consider a good fit.
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12-26-23, 10:45 AM
#103
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Of course stack and reach are not the be all end all for fit. They are useful for comparing multiple frames, but they are not the only thing you should use to set up a bike's fit. I don't think anyone is arguing they should be the only measurements though.
It's just a way to compare multiple frames of the same style that have varying geometry. You can then find the one that will work the best for you and set it up with your individual needs for saddle position, bar reach, stem length and angle, etc.
What stack and reach does is narrows and/or clarifies.
Take a size 61 frame, for example.
I have a size 61 gravel frame that has 650mm of stack and 405mm of reach.
The same brand sells the same model with alternative geometry where a size 61 has 612mm of stack and 410mm of reach.
The effective top tube lengths for both are nearly identical- 597mm vs 598mm.
So if someone just looked at seat tube length and top tube length to determine fit, they may end up with a very ill fitting frame- either too upright for what they want or too low and long.
But yeah, stack and reach is not some full fitting approach to setting up a bike. It's just a way to compare frame geometry across multiple bikes to narrow down what would or wouldn't be good for an individual to then set up for proper fit.
It's just a way to compare multiple frames of the same style that have varying geometry. You can then find the one that will work the best for you and set it up with your individual needs for saddle position, bar reach, stem length and angle, etc.
What stack and reach does is narrows and/or clarifies.
Take a size 61 frame, for example.
I have a size 61 gravel frame that has 650mm of stack and 405mm of reach.
The same brand sells the same model with alternative geometry where a size 61 has 612mm of stack and 410mm of reach.
The effective top tube lengths for both are nearly identical- 597mm vs 598mm.
So if someone just looked at seat tube length and top tube length to determine fit, they may end up with a very ill fitting frame- either too upright for what they want or too low and long.
But yeah, stack and reach is not some full fitting approach to setting up a bike. It's just a way to compare frame geometry across multiple bikes to narrow down what would or wouldn't be good for an individual to then set up for proper fit.
12-26-23, 11:46 AM
#104
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I've got to admit I am super curious about how this odd beast is going to feel under. 56 seat tube but 53.5 top tube with that really long head tube. Is it a too small frame, too large, idiotic choice, cycling nirvana, or what? Screw rules, sometimes you just have to play around and see what happens.
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12-26-23, 01:00 PM
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I've got to admit I am super curious about how this odd beast is going to feel under. 56 seat tube but 53.5 top tube with that really long head tube. Is it a too small frame, too large, idiotic choice, cycling nirvana, or what? Screw rules, sometimes you just have to play around and see what happens.
Custom frame?
12-26-23, 01:38 PM
#106
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Of course stack and reach are not the be all end all for fit. They are useful for comparing multiple frames, but they are not the only thing you should use to set up a bike's fit. I don't think anyone is arguing they should be the only measurements though.
It's just a way to compare multiple frames of the same style that have varying geometry. You can then find the one that will work the best for you and set it up with your individual needs for saddle position, bar reach, stem length and angle, etc.
What stack and reach does is narrows and/or clarifies.
Take a size 61 frame, for example.
I have a size 61 gravel frame that has 650mm of stack and 405mm of reach.
The same brand sells the same model with alternative geometry where a size 61 has 612mm of stack and 410mm of reach.
The effective top tube lengths for both are nearly identical- 597mm vs 598mm.
So if someone just looked at seat tube length and top tube length to determine fit, they may end up with a very ill fitting frame- either too upright for what they want or too low and long.
But yeah, stack and reach is not some full fitting approach to setting up a bike. It's just a way to compare frame geometry across multiple bikes to narrow down what would or wouldn't be good for an individual to then set up for proper fit.
It's just a way to compare multiple frames of the same style that have varying geometry. You can then find the one that will work the best for you and set it up with your individual needs for saddle position, bar reach, stem length and angle, etc.
What stack and reach does is narrows and/or clarifies.
Take a size 61 frame, for example.
I have a size 61 gravel frame that has 650mm of stack and 405mm of reach.
The same brand sells the same model with alternative geometry where a size 61 has 612mm of stack and 410mm of reach.
The effective top tube lengths for both are nearly identical- 597mm vs 598mm.
So if someone just looked at seat tube length and top tube length to determine fit, they may end up with a very ill fitting frame- either too upright for what they want or too low and long.
But yeah, stack and reach is not some full fitting approach to setting up a bike. It's just a way to compare frame geometry across multiple bikes to narrow down what would or wouldn't be good for an individual to then set up for proper fit.
I have noticed on this forum that way too many bikes in my assessment have the saddle WAY too far forward. I hammered that as this will reduce pedaling efficiency ( keeping in mind that farther forward from 50 years ago is a thing).
add in that many ride with no toe clips…
I do not know what they are doing and many do not know either.
A forward saddle will alter handling too.
most often, not in a good way.
12-26-23, 01:47 PM
#107
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I’m back. Here’s what we have:
Upon cursory examination and measuring…it’s even smaller than I thought
A hair under 49cm on the top tube, and an about 21” or 53.5cm for the top tube.
Upon cursory examination and measuring…it’s even smaller than I thought
A hair under 49cm on the top tube, and an about 21” or 53.5cm for the top tube.
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12-26-23, 02:08 PM
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12-26-23, 02:16 PM
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I've got to admit I am super curious about how this odd beast is going to feel under. 56 seat tube but 53.5 top tube with that really long head tube. Is it a too small frame, too large, idiotic choice, cycling nirvana, or what? Screw rules, sometimes you just have to play around and see what happens.
It was derived from 2 bikes I already had, 60ish cm. Gordon and the 66cm. Merz.
The Merz was the first big frame I acquired that fit correctly, the Gordon is very smallish but rides very well for me.
So here it is again, we sort of split the difference and added a big pinch of Dave's magic/expertise so it can literally carry me to the end of the line.
And yes again, I realize its a bit jarring to look at but here we are, rides fantastic in the best way for me.
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12-26-23, 02:42 PM
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12-26-23, 02:54 PM
#111
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Preface: I ride about a 56cm. I may be picking up a 'too small' bike (looks around 50cm give or take) which is obviously too small, right? However. I've been on a quest the last year or so to try to find my 'correct' size. It turns out 'correct' can mean a lot of things, and it seems like there is quite the willy-nilly approach to sizing, given the application - French fit, race fit, and what not. What initially got me thinking about this was a couple years ago when I picked up this little Novara Randonee which is probably about a 52cm. Again, obviously too small. But the bike had a tall stem, and the saddle raised up high enough for me. It was actually really comfortable. I stopped riding it because I got a weird feeling in my knee when I rode it.
However, I've been playing around with geometry and adjustments a lot recently (via the Guerciotti and Huffente in the other thread), and just for kicks, I took a look at the Randonee again. Re-adjusted the saddle, and have been riding it. No knee pain (which makes sense, if the saddle/crank relationship is identical to other bikes I ride). So it got me thinking...just what is 'too small'?
I sort of get the feeling that seat tube length means nothing, apart from standover. You can simply adjust the seatpost higher, and it adjusts along the same angular plane of the seat tube angle, so if that was taller, it wouldn't change a thing. Where it seems like it matters a lot more is in top-tube length, and overall wheelbase length, where a shorter wheelbase would create more toe overlap, and a shorter top tube would necessitate a longer stem, which changes steering.
Case in point: I've been looking up bike pictures recently, and here are a few that I've found that are interesting:
Both of these are Miyata 1000s. Probably both around 50cm. Look at the saddle, and then look at the stem. There are plenty of people that would look at these two bikes and say 'too small!' for the rider. But these people are riding these bikes. Are they wrong? Are these bikes too small for the rider? Is there too much toe overlap? Is steering negatively affected? Is having a shorter top tube somewhat looked more favorably on a touring bike, where it may be considered a less aggressive position?
I'm going to try to make this 50cm bike work. If it doesn't, it is an easy pass to one of my kids, or potential trading material in the 'frame doesn't fit pass-around game' thread.
I'm also paging campfire as his Bianchi Grizzly is setup the same way - small frame, higher seatpost and stem -
If anyone else rides a bike in this configuration, with a small frame/shorter top tube, and higher saddle and stem, I'd be interested in your thoughts.
However, I've been playing around with geometry and adjustments a lot recently (via the Guerciotti and Huffente in the other thread), and just for kicks, I took a look at the Randonee again. Re-adjusted the saddle, and have been riding it. No knee pain (which makes sense, if the saddle/crank relationship is identical to other bikes I ride). So it got me thinking...just what is 'too small'?
I sort of get the feeling that seat tube length means nothing, apart from standover. You can simply adjust the seatpost higher, and it adjusts along the same angular plane of the seat tube angle, so if that was taller, it wouldn't change a thing. Where it seems like it matters a lot more is in top-tube length, and overall wheelbase length, where a shorter wheelbase would create more toe overlap, and a shorter top tube would necessitate a longer stem, which changes steering.
Case in point: I've been looking up bike pictures recently, and here are a few that I've found that are interesting:
Both of these are Miyata 1000s. Probably both around 50cm. Look at the saddle, and then look at the stem. There are plenty of people that would look at these two bikes and say 'too small!' for the rider. But these people are riding these bikes. Are they wrong? Are these bikes too small for the rider? Is there too much toe overlap? Is steering negatively affected? Is having a shorter top tube somewhat looked more favorably on a touring bike, where it may be considered a less aggressive position?
I'm going to try to make this 50cm bike work. If it doesn't, it is an easy pass to one of my kids, or potential trading material in the 'frame doesn't fit pass-around game' thread.
I'm also paging campfire as his Bianchi Grizzly is setup the same way - small frame, higher seatpost and stem -
If anyone else rides a bike in this configuration, with a small frame/shorter top tube, and higher saddle and stem, I'd be interested in your thoughts.
12-26-23, 08:46 PM
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12-26-23, 09:19 PM
#114
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12-26-23, 11:04 PM
#115
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Frame too small?
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12-27-23, 06:31 AM
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I used to set up the reach on all my bikes with a tip of saddle to centerline of handlebars measurement. This all changed when I bought my 56cm Specialized Tarmac Pro - I normally ride 51-52cm so how could I possibly ride this ginormous beast?! (BTW, bought it because it was nearly a giveaway deal from a neighbor). I set it up using all my standard dimensions and it met all of those dimensions but the fit was horrible. WTH?? I soon realized the handlebars had way too much reach and width (42mm) and that the brake hood design was much longer than my other bikes. I now measure tip of saddle to the hoods. Finding a measurement point on the hoods can be frustrating because they're all different. I use the top 'point' of the hoods (where the brake cable would've entered on traditional vintage brakes). I went thru and re-fitted all my bikes using this method and the fit is far more consistent throughout the stable now. I was surprised how much handlebar width affects overall fit on a bike and I'm now acutely conscious of that dimension on all bikes.
As it turned out, the 56cm Tarmac has a surprisingly great fit (maybe the best of the bunch) thanks in part to a sloping top tube, my short legs/long torso, saddle positioning, and a change to a shorter stem and 38mm compact handlebars. Still need to change the 172.5 crank arms to 165. Also, the relatively tall stack height puts me in a slightly more upright position which seems to be more comfortable at this stage of my cycling 'career'. With a traditonal C&V frame, I would only be able to ride a 56 with the saddle slammed all the way down, and then just barely.
Apologies for the highly offensive photo of this plastic fantastic in the C&V section, but wanted to show the resulting setup and prove that, yes, someone who rides 51/52 can ride a 56! Well, and the bike is 17 years old (a classic in its own rite).
As it turned out, the 56cm Tarmac has a surprisingly great fit (maybe the best of the bunch) thanks in part to a sloping top tube, my short legs/long torso, saddle positioning, and a change to a shorter stem and 38mm compact handlebars. Still need to change the 172.5 crank arms to 165. Also, the relatively tall stack height puts me in a slightly more upright position which seems to be more comfortable at this stage of my cycling 'career'.
With a traditonal C&V frame, I would only be able to ride a 56 with the saddle slammed all the way down, and then just barely.Apologies for the highly offensive photo of this plastic fantastic in the C&V section, but wanted to show the resulting setup and prove that, yes, someone who rides 51/52 can ride a 56! Well, and the bike is 17 years old (a classic in its own rite).
Last edited by cegerer; 12-27-23 at 06:48 AM.
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12-27-23, 07:58 AM
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I used to set up the reach on all my bikes with a tip of saddle to centerline of handlebars measurement. This all changed when I bought my 56cm Specialized Tarmac Pro - I normally ride 51-52cm so how could I possibly ride this ginormous beast?! (BTW, bought it because it was nearly a giveaway deal from a neighbor). I set it up using all my standard dimensions and it met all of those dimensions but the fit was horrible. WTH?? I soon realized the handlebars had way too much reach and width (42mm) and that the brake hood design was much longer than my other bikes. I now measure tip of saddle to the hoods. Finding a measurement point on the hoods can be frustrating because they're all different. I use the top 'point' of the hoods (where the brake cable would've entered on traditional vintage brakes). I went thru and re-fitted all my bikes using this method and the fit is far more consistent throughout the stable now. I was surprised how much handlebar width affects overall fit on a bike and I'm now acutely conscious of that dimension on all bikes.
As it turned out, the 56cm Tarmac has a surprisingly great fit (maybe the best of the bunch) thanks in part to a sloping top tube, my short legs/long torso, saddle positioning, and a change to a shorter stem and 38mm compact handlebars. Still need to change the 172.5 crank arms to 165. Also, the relatively tall stack height puts me in a slightly more upright position which seems to be more comfortable at this stage of my cycling 'career'. With a traditonal C&V frame, I would only be able to ride a 56 with the saddle slammed all the way down, and then just barely.
Apologies for the highly offensive photo of this plastic fantastic in the C&V section, but wanted to show the resulting setup and prove that, yes, someone who rides 51/52 can ride a 56! Well, and the bike is 17 years old (a classic in its own rite).
As it turned out, the 56cm Tarmac has a surprisingly great fit (maybe the best of the bunch) thanks in part to a sloping top tube, my short legs/long torso, saddle positioning, and a change to a shorter stem and 38mm compact handlebars. Still need to change the 172.5 crank arms to 165. Also, the relatively tall stack height puts me in a slightly more upright position which seems to be more comfortable at this stage of my cycling 'career'.
With a traditonal C&V frame, I would only be able to ride a 56 with the saddle slammed all the way down, and then just barely.Apologies for the highly offensive photo of this plastic fantastic in the C&V section, but wanted to show the resulting setup and prove that, yes, someone who rides 51/52 can ride a 56! Well, and the bike is 17 years old (a classic in its own rite).
A 52 generally has a 54cm TT, and a 56 generally has a 56.5TT, so it isn't crazy to think that a short stem will make a bike two sizes too large rideable.
12-27-23, 08:55 AM
#118
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My take-away after 5 pages of pictures and squak = I will not be making frame size decisions based on member input. Tall-tall stems, 66cm front-center, extended headtubes, etc. Brings me back to post #2 = Why ride the wrong size? Or more productively - Get a fit!
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12-27-23, 09:37 AM
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Strangely, even though I am 5'11-1/2" tall this little bike that has like a 13cm headtube does not cause neck or back pain for me. I can also ride the drops fine on this bike.
Last edited by masi61; 12-27-23 at 11:17 AM.
12-27-23, 10:55 AM
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You can get a fit all you want but if you're 171.5 cm tall with an 82.5cm inseam riding a classic steel bike with a horizontal top tube and happen to be comfortable with the tops level with the saddle, you're gonna be on a 54cm bike with the stem raised quite high, and the stem will have to be stubby (unless you have long arms). It's why custom bikes are a thing. Or maybe you meant to type Get a fit AND a custom frame.
12-27-23, 11:11 AM
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I like to stay within the 2-3 cm range but will do a lot of playing with a tandem.
Since I have only a reluctant stoker I don't get many miles on this but still love it.
Since I have only a reluctant stoker I don't get many miles on this but still love it.
12-27-23, 12:00 PM
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This is an interesting thread. It seems at the limits of bike sizing (some of) the questions are:
What happens when the stem is too short/long?
What happens when the front tire is too close to the pedals/foot?
The geometry of very long seatpost and very high stem interaction
At what point does handling degrade? To the casual rider? To the enthusiast? To the point is becomes unsafe?
Are there more questions or potential issues?
What happens when the stem is too short/long?
What happens when the front tire is too close to the pedals/foot?
The geometry of very long seatpost and very high stem interaction
At what point does handling degrade? To the casual rider? To the enthusiast? To the point is becomes unsafe?
Are there more questions or potential issues?
12-27-23, 01:33 PM
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You can get a fit all you want but if you're 171.5 cm tall with an 82.5cm inseam riding a classic steel bike with a horizontal top tube and happen to be comfortable with the tops level with the saddle, you're gonna be on a 54cm bike with the stem raised quite high, and the stem will have to be stubby (unless you have long arms). It's why custom bikes are a thing. Or maybe you meant to type Get a fit AND a custom frame.
12-27-23, 03:01 PM
#124
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I'm not tagging the multi-quote button, comments forward body position. Though wish to highlight some practices in body position on a bike, mostly for those into running as well.
When one rides a smaller frame, they trend to utilize seat setback, long railed saddles and get rearward. It may (or may not) reduce aero drag, a key advantage to reduce frontal area. But if you're an avid runner and then go riding, it feels a bit unnatural, more work is on the quads. In contrast, moving the saddle forward effectively changes the seat tube angle, the hip extensors / hamstrings feels more inline to muscle memory from the running.
So what, you say? Well then you're now figuring where or what is your priority; comfort or performance or... how to get that balance.
Leading into aero bars and forearm support. That thingy considered a modern bike innovation, which then affected saddle position and shunned by roadies. But the runners and other cyclist may like getting that upper body closer to being over the crank.
Solution- Somewhere in a bin I still have a clever device for old school triathlon bikes. Its called a 'seat shifter'. Ugly device that fits between the saddle rails and the seat post cradle (actually, the seat post clamp is tossed aside). It has a cable and remote lever from a BMX brake. Spring loaded horizontal bolt action. Ideal for standard road bikes and when using add-on aero bars, though its pretty cool using without aero bars. Big climb days seated or just to relax or vary hip and leg muscle groups.
When one rides a smaller frame, they trend to utilize seat setback, long railed saddles and get rearward. It may (or may not) reduce aero drag, a key advantage to reduce frontal area. But if you're an avid runner and then go riding, it feels a bit unnatural, more work is on the quads. In contrast, moving the saddle forward effectively changes the seat tube angle, the hip extensors / hamstrings feels more inline to muscle memory from the running.
So what, you say? Well then you're now figuring where or what is your priority; comfort or performance or... how to get that balance.
Leading into aero bars and forearm support. That thingy considered a modern bike innovation, which then affected saddle position and shunned by roadies. But the runners and other cyclist may like getting that upper body closer to being over the crank.
Solution- Somewhere in a bin I still have a clever device for old school triathlon bikes. Its called a 'seat shifter'. Ugly device that fits between the saddle rails and the seat post cradle (actually, the seat post clamp is tossed aside). It has a cable and remote lever from a BMX brake. Spring loaded horizontal bolt action. Ideal for standard road bikes and when using add-on aero bars, though its pretty cool using without aero bars. Big climb days seated or just to relax or vary hip and leg muscle groups.
12-27-23, 03:10 PM
#125
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Location: Weston-super-Mare, Somerset, UK
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Bikes: Gitane Course, Paris Sport, Peugeot AO8, Peugeot Bretagne, Peugeot Premiere 85, Peugeot Premiere 86, Peugeot ANC Halfords Team Replica, Peugeot Festina Team Replica, Motobecane Grand Sport, Motobecane Super 15, Raleigh Pro Race, Raleigh Stratos, BSA
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Just my tuppence worth here, but the great thing about old bikes is the fact that the quill stem gives us a whole lot more to work with than a bike with an Ahead steerer that's been cut to size. Seat adjustment's pretty much the same, but the fact you can easily fit a quill stem with a longer or shorter height AND reach makes a huge difference.
Case in point, I've a Raleigh Record Sprint in 25 inch size, and a Gitane Course that's about 22 inches. I'll very happily ride both over 200km, both are comfortable as only a steel bike can be and feel "right" for me, although if I'm honest the Raleigh's towards the edge and I couldn't ride anything bigger for long. The difference is that the Gitane's got a lot of post on show, and a stem with a lot of height and reach, while the Raleigh's got next to no extension of the seatpost and the stem is shorter and sat right down in the steerer.
I may just be oddly proportioned of course...
Case in point, I've a Raleigh Record Sprint in 25 inch size, and a Gitane Course that's about 22 inches. I'll very happily ride both over 200km, both are comfortable as only a steel bike can be and feel "right" for me, although if I'm honest the Raleigh's towards the edge and I couldn't ride anything bigger for long. The difference is that the Gitane's got a lot of post on show, and a stem with a lot of height and reach, while the Raleigh's got next to no extension of the seatpost and the stem is shorter and sat right down in the steerer.
I may just be oddly proportioned of course...