Fitting Your Bike Are you confused about how you should fit a bike to your particular body dimensions? Have you been reading, found the terms Merxx or French Fit, and don’t know what you need? Every style of riding is different- in how you fit the bike to you, and the sizing of the bike itself. It’s more than just measuring your height, reach and inseam. With the help of Bike Fitting, you’ll be able to find the right fit for your frame size, style of riding, and your particular dimensions. Here ya’ go…..the location for everything fit related.

Conflicting fit advice

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Old 04-14-18, 10:09 PM
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DianetS
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Conflicting fit advice

I am 5' 8 1/2', 200 pounds - female. I'm shopping for a new bike and decided to get fitted first. The fitter says I need a 51cm bike. I rode 3 (Cannonade Synapse, BMC Gran Fondo, and Giant Avail) and thought they were OK. Then I took out a BMC Roadmachine 54cm and loved it - but my neck/shoulders hurt and he said it couldn't be adjusted to make the pain go away and I would have to order a 51cm bike. I decided to hold off. Have since been to two other bike stores and they both insist I should be on "at least" a 54cm bike.

Did the Roadmachine feel great because it was a 54? Maybe I didn't love those other bikes because they were too small? If I test road the Roadmachine in a 51 I wonder how I would have felt about it.

I don't know who's telling me the truth! I wanted to get a fitting to do this the right way, and now I'm wondering if I just threw away $250.

Any advice would be appreciated. Thanks.
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Old 04-15-18, 12:28 AM
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You're 5"8, unless you're not telling us something about your inseam, you should be able to ride a 52 or 54. A 54 will be less aggressive, you will ride with less bend in your back, and particularly at your weight it will be more comfortable.

Go to see another bike shop and talk to them about fitment to confirm or deny what I am saying. At 90kg which is fairly heavy for a woman you should feel more comfortable on a bike with a longer top tube and a lower seat position. Unless of course you are sitting on the absolute maximum point of insertion for your seat tube which runs a risk of cracking the seat tube, or you have really short arms I don't see a problem.

Like I said, go and speak to someone else.
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Old 04-15-18, 12:55 AM
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You got a fit, and then you got an offhand opinion based on your height. And when you tested the fit of the 54, it was uncomfortable - probably because of the longer reach to the handlebar. Maybe that's a good indicator that the fitter, who spent more time with you, knows what he's talking about.

When you rode the Roadmachine, you were uncomfortable but also loved it. What did you love?


The problem with the bikes you're comparing is that the BMC Gran Fondo is taller at the handlebar for a given frame size than the Roadmachine. So while a 51 in a Gran Fondo might have a good combination of height and reach, the Roadmachine might be too low in a 51 or too long in a 54.

That said, there is usually a combination of stem and bar that will make either the 51 or 54 Roadmachine fit just like the 51 bikes the fitter had you on. Ask the fitter which Roadmachine size would adapt best to your fit. With a fit sheet it is relatively easy to pick a size from looking at the geometry chart, and your fitter should be able to do that in minutes.


So I don't see a conflict. You just need to have the data you paid for applied to the bike you enjoyed.
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Old 04-15-18, 04:33 AM
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Fitting from a fit chart is a terribly pessimistic and narrow way of looking at things. At best with some brands they will give you 2 or 3 frame sizes that will fit a person in the modern McDonalds bike sense (small, medium or large and would you like fries with that) but then there are some manufacturers that still measure accurately per centimeter (using the metric system). This is why bike shops have professional fitters and no its not really a personal thing either if you want to do it properly. A good fitter will be able to fit you within the sizes that suit your body. Of course there are nuances in the human body that are specific to each person. These must be taken into account by the fitter if they're doing their job properly.

But then maybe its just your American thing. In a nation that still has to measure in quarters and thirds of whatever in some measurement I've never heard of you don't really wonder where this kind of thinking comes from. But the majority of the world uses the metric system and if given the right set of opportunities then a fitter can measure your body down to the millimeter.

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Old 04-15-18, 07:48 AM
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Originally Posted by Kontact View Post
When you rode the Roadmachine, you were uncomfortable but also loved it. What did you love?

The problem with the bikes you're comparing is that the BMC Gran Fondo is taller at the handlebar for a given frame size than the Roadmachine. So while a 51 in a Gran Fondo might have a good combination of height and reach, the Roadmachine might be too low in a 51 or too long in a 54.

That said, there is usually a combination of stem and bar that will make either the 51 or 54 Roadmachine fit just like the 51 bikes the fitter had you on. Ask the fitter which Roadmachine size would adapt best to your fit. With a fit sheet it is relatively easy to pick a size from looking at the geometry chart, and your fitter should be able to do that in minutes.
My inseam is 32.

I wish I could tell you exactly what I loved about the Roadmachine. The second I started pedaling it just felt right - responsive - fun - I didn't want to get off. But then after 10 - 15 minutes that old familiar ache between my shoulder blades set in.

I'm glad I didn't order it in the 51 - I just don't want to spend the money without actually giving it a test ride. And thanks for the info about the way the different bikes fit. I'm trying to make an educated decision and I guess this is part of the process.
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Old 04-15-18, 10:46 AM
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Originally Posted by 1500SLR View Post
Fitting from a fit chart is a terribly pessimistic and narrow way of looking at things. At best with some brands they will give you 2 or 3 frame sizes that will fit a person in the modern McDonalds bike sense (small, medium or large and would you like fries with that) but then there are some manufacturers that still measure accurately per centimeter (using the metric system). This is why bike shops have professional fitters and no its not really a personal thing either if you want to do it properly. A good fitter will be able to fit you within the sizes that suit your body. Of course there are nuances in the human body that are specific to each person. These must be taken into account by the fitter if they're doing their job properly.

But then maybe its just your American thing. In a nation that still has to measure in quarters and thirds of whatever in some measurement I've never heard of you don't really wonder where this kind of thinking comes from. But the majority of the world uses the metric system and if given the right set of opportunities then a fitter can measure your body down to the millimeter.
I'm not sure what you're talking about. After someone has completed a fitting, that fitting should produce a set of geometric points in space that can be compared to any available geometry. It isn't "pessimistic", it's arithmetic. And a good fitter will see which of the sizes that could be made to work involves the fewest compromises. And that's what I suggested the OP should go ask her fitter for.

Originally Posted by DianetS View Post
My inseam is 32.

I wish I could tell you exactly what I loved about the Roadmachine. The second I started pedaling it just felt right - responsive - fun - I didn't want to get off. But then after 10 - 15 minutes that old familiar ache between my shoulder blades set in.

I'm glad I didn't order it in the 51 - I just don't want to spend the money without actually giving it a test ride. And thanks for the info about the way the different bikes fit. I'm trying to make an educated decision and I guess this is part of the process.
Since the 54 Roadmachine might not be the "wrong" size for you, you should find out what sort of saddle adjustment and stem length would put it close to your fit numbers for a better test ride and give it a try again with the right set up. (I would hope a shop looking to sell a bike wouldn't find this to be too much trouble.) Even if the 51 would be the most ideal size, riding the 54 with the correct stem in it would tell you something about the bike in general that would apply to the 51 as well.


It isn't that 51 is right and 54 is wrong, 51 is just "more right" in many models. So please do not regard a test ride on a bike one size up as trying out a completely different beast. I usually ride 50 or 51s, but it is really no big deal for me to hop on a 52 with a shorter stem. The jump isn't that large. So if you had a pleasant ride on a 54 with the reach corrected, you should know whether you like the model well enough to order whatever the optimum size is.



And just in case it is an issue for you - fitters should be relatively agnostic about your bike purchase. So don't be afraid to ask your fitter to help you size a bike his shop doesn't carry. You paid for a fit that is supposed to apply to any bike you decide to buy, not just the ones the fitter sells.
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Old 04-15-18, 10:49 AM
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Hi DianetS. I'm 5'7" with an inseam measurement of 30.75" so you are leggier than me and that is typical of females. I ride a specialized Secteur with stated size of 54mm. It happens that the top tube, the usually more important dimension, is also 54mm. At present, I'm using a stem length of 75mm but during summer riding months when I'm riding many more miles and thus fitter, I like to be stretched out more and will switch to a 90mm or 100mm stem. As you can see, the most comfortable position is closely related to physical conditioning. My guess is that a top tube length of 53 or 54 would work fine for you. However, be aware that your most comfortable position will be a moving target as your fitness changes.

I would add that quite a bit can be accomplished to improve comfort and bike fit with stems of various lengths and angle of rise as well as seat posts with different setbacks that support the saddle further forward or back. This helps get your center of gravity located in the most comfortable location in relation to the pedals. Good luck.
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Old 04-15-18, 11:03 AM
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After rereading your original post where you say you had discomfort between shoulder blades, one reason might be too much weight on the hands. Another reason might be simply getting used to sitting on a bike which time will cure. Also there is a sort of method to sitting on a bike in the same way there is method to sitting on a horse. On a horse, one sits with a relaxed posture but still erect and stable when the stirrups are the right length. On the bike there is an analogous position that when it is correct, people can ride hundreds of miles.
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Old 04-15-18, 11:12 AM
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Handlebar width is the usual culprit for sore shoulders your handlebars need to be straight out in front of your arms. A proper fitter will measure your shoulder blades to get your handlebar width but as a rough guide your handlebars should be directly in front of your arms when they are reached out in front of you.

The other factor that affects this is stem length. Your shoulder blades should be neutral you should not be reaching forward to grab the bars or having to bend your arms back either.

A good fitter should be able to fit you on a 54 given what the other poster has said here. All of the other factors suck as stem length and handlebars are interchangeable. It may cost you some money but these are the first things you should get right.

If you're hurting yourself every time you ride your bike it's a crap fit to begin with.
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Old 04-15-18, 11:26 AM
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I haven't checked specifically but 51 vs 54cm would have about 3cm reach difference. So your hands are about 3 cm closer on the 51 frame. Apply the sniff test: would moving your hands an inch back really prevent your neck and shoulder muscle pain? Is that truly an insurmountable obstacle on that bike?

One thing to bear in mind is that your whole position, the configuration of your upper body, is surely going to be different on the 54cm bike than on a 51. Bars are likely higher (longer head tube), you're stretched out more and probably with straighter arms which would put your back higher, which feels more comfortable. At least at the start. It's a different kind of bike fit.

Often we can get that neck pain from simply riding in a different, perhaps lower, position than we're accustomed to. The down-to-a millimeter bike fit, in that case, is just a smokescreen. But personally, having spent $250 on the fit, I would want to test ride bikes the size that was recommended. If you throw it away and get a 54cm bike, and then adjust it to your comfort with a different kind of fit, then yeah you did throw away the $250. At least give it a chance and see what it's like.
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Old 04-15-18, 11:36 AM
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Originally Posted by wphamilton View Post
I haven't checked specifically but 51 vs 54cm would have about 3cm reach difference. So your hands are about 3 cm closer on the 51 frame. Apply the sniff test: would moving your hands an inch back really prevent your neck and shoulder muscle pain? Is that truly an insurmountable obstacle on that bike?
This is generally not the case. While frame sizes may go in 2 or 3cm increments, top tube increments are much smaller. This is because 50cm bikes have the equivalent of 53cm top tubes and 60cm frames have more like 59cm top tubes. So in that 10cm of frame size range the TTs only changed by 6cm.

Specifically to the Roadmachine, the difference in TT length between the 51 and 54 is only 1.4cm, not 3cm.
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Old 04-15-18, 11:37 AM
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Originally Posted by 1500SLR View Post

But then maybe its just your American thing. In a nation that still has to measure in quarters and thirds of whatever in some measurement I've never heard of you don't really wonder where this kind of thinking comes from. But the majority of the world uses the metric system and if given the right set of opportunities then a fitter can measure your body down to the millimeter.
I really don't think that has anything to do with the situation. Basically every fitter I know uses the metric system in the US. In case you didn't know, there are smaller fractions than quarters, so your comment has no merit.

I use both. Sometimes I will measure in inches, but convert. That being said, either work equally well, it just depends on the person doing the measuring.

Now, back to the subject at hand.
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Old 04-15-18, 11:41 AM
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Originally Posted by phughes View Post
I really don't think that has anything to do with the situation. Basically every fitter I know uses the metric system in the US. In case you didn't know, there are smaller fractions than quarters, so your comment has no merit.

I use both. Sometimes I will measure in inches, but convert. That being said, either work equally well, it just depends on the person doing the measuring.

Now, back to the subject at hand.
My basic point is the metric system is far more accurate. Every time I have to think in imperial units I wonder why I do it. Yes I'm aware that this is primarily a US based forum
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Old 04-15-18, 11:44 AM
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Originally Posted by 1500SLR View Post
My basic point is the metric system is far more accurate. Every time I have to think in imperial units I wonder why I do it. Yes I'm aware that this is primarily a US based forum
No, it isn't more accurate, I have a micrometer that says you are wrong. Either is as accurate as the other. It simply depends on the scale you decide to use. If you choose to measure in the thousandths of an inch, you will be more accurate than using a 1/4 inch scale. Sadly, you have no idea what you are talking about.
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Old 04-15-18, 11:48 AM
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Originally Posted by phughes View Post
No, it isn't more accurate, I have a micrometer that says you are wrong. Either is as accurate as the other. It simply depends on the scale you decide to use. If you choose to measure in the thousandths of an inch, you will be more accurate than using a 1/4 inch scale. Sadly, you have no idea what you are talking about.
I realise that there are greater percentages. It's just ridiculous none the less. A millimetre is a millimetre is a millimetre and then that is 1000th of a metre if you want that also. Get a set of Cali ores out and you know what a millimetre is straight away. It's also base 100 to save you any confusion. None of this nonsense about 3/8ths of an inch or quarter drive.

The first thing I do with imperial sockets and wrenches is throw them out the window.

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Old 04-15-18, 11:50 AM
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Originally Posted by 1500SLR View Post
I realise that there are greater percentages. It's just ridiculous none the less. An inch is an inch is an inch and then that is a 36th of a yard if you want that also. Get a set of Cali ores out and you know what an inch is straight away.
Math.
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Old 04-15-18, 11:53 AM
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Originally Posted by 1500SLR View Post
I realise that there are greater percentages. It's just ridiculous none the less. A millimetre is a millimetre is a millimetre and then that is 1000th of a metre if you want that also. Get a set of Cali ores out and you know what a millimetre is straight away.
Exactly. SO what is your point? Most all tape measures have marks for 1/16th inch, which is approximately 1.58mm. There is no way you will measure any part of the body, so precisely to be within .5mm, so measuring in the metric system or in inches won't make a difference. Now, if you remove the femur from the body, and use calipers, maybe, but if my fitter suggests that, I'm going to a different fitter.

Once again, your point is moot. Both are as precise, depending on the scale used. They are simply different. And as I said, most all fitters I know in the US, use the metric system, or a combination of both. Then again, if the fitter only relies on mathematic formulas to determine fit, I would go to a different fitter.
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Old 04-15-18, 12:00 PM
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Yes of course if your fitter is measuring you only by calipers and tape and can't see visually what you're doing or not doing you need a new fitter. The thing is I can't see the person in question so I can only suggest rudimentary guidelines.
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Old 04-15-18, 12:02 PM
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Originally Posted by Kontact View Post
This is generally not the case. While frame sizes may go in 2 or 3cm increments, top tube increments are much smaller. This is because 50cm bikes have the equivalent of 53cm top tubes and 60cm frames have more like 59cm top tubes. So in that 10cm of frame size range the TTs only changed by 6cm.

Specifically to the Roadmachine, the difference in TT length between the 51 and 54 is only 1.4cm, not 3cm.
So even less of "sniff test" pass, and my comments apply even more strongly.
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Old 04-15-18, 12:14 PM
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Originally Posted by wphamilton View Post
So even less of "sniff test" pass, and my comments apply even more strongly.
What I thought your comments were getting at is this:

One thing to bear in mind is that your whole position, the configuration of your upper body, is surely going to be different on the 54cm bike than on a 51. Bars are likely higher (longer head tube), you're stretched out more and probably with straighter arms which would put your back higher, which feels more comfortable. At least at the start. It's a different kind of bike fit.

Given that the fit difference between the 51 and 54 is only 1.4cm of top tube and 1.6cm of head tube, the fit could be made identical between them by selecting two different stems. Why are you characterizing such a small change that can be had with a stem change as a "different kind of bike fit"?

https://www.bmc-switzerland.com/us-e...achine-02-one/


The tone of some of the comments on this thread make it sound like fit numbers are not just coordinates but have some sort of mystical quality. But they really are just points on a grid that are either compatible with a given size or not.
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Old 04-15-18, 12:57 PM
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Thank you all for the great advice and information. I'm going to put a little more faith in the fit I received - but go armed with a little more knowledge to ask the right questions and maybe not take "no" for an answer. Comments about riding position and posture do make me think. During the fitting, he was correcting my posture - so even though I was trying to be conscious of it during the test ride - perhaps I got lazy and returned to bad habits.

I'm not a speedster, but I do ride long distances. I've never been able to do more than 65 in a day because I'm completely spent by that time (and I'm also a runner so cardio isn't the problem - I just ache all over by that time). My current bike is a 10 year old entry-level Trek that I just walked into the bike store, rode in a circle in the parking lot, and bought. It has served me well but it's time for an upgrade.

Thank you all again. I feel a little less confused and a little better informed.
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Old 04-15-18, 03:10 PM
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Originally Posted by Kontact View Post
]Given that the fit difference between the 51 and 54 is only 1.4cm of top tube and 1.6cm of head tube, the fit could be made identical between them by selecting two different stems. Why are you characterizing such a small change that can be had with a stem change as a "different kind of bike fit"?
Because that's what it is. Basically, you're sitting differently on the two bikes. French fit vs racing fit for example. Sure, you can bend down more and get aero with a fit with more reach, and some do. But my experience and what I've observed, people ride the more stretched out higher handlebar configuration in a more upright and relaxed stance.

Think of it this way. If the difference in frame sizes don't by themselves account for the way OP feels, and it's not how she positions on the bike (the "fit"), then what?

Yeah it gets pretty mystical when people start talking mm adjustments and "perfect" fits improving "power transfer" and so on. I get more variation than they propose simply by changing my grip slightly and moving my weary bottom over a smidgen. But I think that different "fits" induce people to sit differently, and I think that more than likely accounts for OP feeling comfortable on the 54cm frame and getting a sore neck after a while. She might very well be better off on a 51 frame, and should try it.
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Old 04-15-18, 03:20 PM
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Originally Posted by wphamilton View Post
Because that's what it is. Basically, you're sitting differently on the two bikes. French fit vs racing fit for example. Sure, you can bend down more and get aero with a fit with more reach, and some do. But my experience and what I've observed, people ride the more stretched out higher handlebar configuration in a more upright and relaxed stance.

Think of it this way. If the difference in frame sizes don't by themselves account for the way OP feels, and it's not how she positions on the bike (the "fit"), then what?

Yeah it gets pretty mystical when people start talking mm adjustments and "perfect" fits improving "power transfer" and so on. I get more variation than they propose simply by changing my grip slightly and moving my weary bottom over a smidgen. But I think that different "fits" induce people to sit differently, and I think that more than likely accounts for OP feeling comfortable on the 54cm frame and getting a sore neck after a while. She might very well be better off on a 51 frame, and should try it.
But you're not sitting differently.

If I have two bikes with all the same angles, and one is 1cm taller and 1cm longer, and then I use a stem on that bike that is 1cm lower and 1cm shorter than the other, the fit is now identical between them. How could I possibly be sitting differently if the location of the saddle, pedal and handlebar are identical?
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Old 04-15-18, 03:50 PM
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Originally Posted by Kontact View Post
But you're not sitting differently.

If I have two bikes with all the same angles, and one is 1cm taller and 1cm longer, and then I use a stem on that bike that is 1cm lower and 1cm shorter than the other, the fit is now identical between them. How could I possibly be sitting differently if the location of the saddle, pedal and handlebar are identical?
51 to 54 is more than 1cm. Frame reach and stack gets a little funny on small bikes because the HT stops shrinking. But it does move the bars relative to saddle height. Regardless, I didn't get the impression that anyone changed the stems and handlebars for OP's test ride.

If you believe that 51 and 54 sized bikes are identical, then there's not much left to discuss. I can tell you though that between my 54 and 56, there is a huge difference in the way I sit, and it's mainly because of the setup, differences of less than 2 inches.
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Old 04-15-18, 04:15 PM
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Originally Posted by wphamilton View Post
51 to 54 is more than 1cm. Frame reach and stack gets a little funny on small bikes because the HT stops shrinking. But it does move the bars relative to saddle height. Regardless, I didn't get the impression that anyone changed the stems and handlebars for OP's test ride.

If you believe that 51 and 54 sized bikes are identical, then there's not much left to discuss. I can tell you though that between my 54 and 56, there is a huge difference in the way I sit, and it's mainly because of the setup, differences of less than 2 inches.
the standard variables between stems that do and don't make a difference in the way your bike handles is about 40mm. Between 90mm and 130mm its all what we could call for this intent and purpose the same enough that most people wouldn't complain about the difference. 51 to 54cm is 30mm which is well within the tolerance of it being "nothing much different."

Of course when you make that much of a change you may also have to pay for a new stem and likewise if you go from 44 to 38cm handlebars you may also have to pay for those also. This comes into the bike shops mind with how much you want to spend and what you want to achieve. It might be that the 51 is the most economical option. In all of this sense a 51 can be made to fit like a 55 and a 55 can be made to fit like a 51 and any other size there in between can also fit. Although, our friend may not have standover clearance on a 55. If she is insistent she wants a 54 then push the question as to why not...

I have my spidey senses its because "women shouldn't ride big bikes." But given you've got more inseam than most men do I don't see why not if it makes you more comfortable.

Last edited by 1500SLR; 04-15-18 at 04:25 PM.
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